Download Peripheral Nervous System

Chapter 9
Nervous System
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Introduction:
A. The nervous system is composed of neurons and
neuroglia.
1. Neurons are typically divided into:
a) cell body
b) axon
c) dendrites
2. Neurons transmit nerve impulses along nerve
fibers to other neurons.
3. Neuroglia carry out a variety of functions to aid
and protect components of the nervous system.
4. Nerves are made up of bundles of nerve fibers.
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B. Organs of the nervous system can be divided into
1. Central nervous system (CNS)
a) Brain
b) Spinal cord
2. Peripheral nervous system (PNS)
a) Peripheral nerves
b) Connect the CNS to the rest of the body
C. The nervous system provides
1. Sensory
2. Integrative
3. Motor functions
a) Somatic nervous system - consciously controlled
b) Autonomic system - unconscious
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General Functions of the Nervous System
A. Sensory receptors
1. At the ends of peripheral nerves
2. Gather information
3. Convert it into nerve impulses
B. Sensory impulses are integrated in the brain as
perceptions (integrative function)
C. Conscious or subconscious decisions follow
D. Lead to motor functions via effectors
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Supporting cells
A. Function of Neuroglial Cells
1. Fill spaces
2. Support neurons
3. Provide structural frameworks
4. Produce myelin
5. Carry on phagocytosis
B. Classification of Neuroglial Cells
1. Four are in the CNS and the last in the PNS
2. Microglial cells
a) Small
b) Phagocytize bacterial cells and cellular debris
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3. Oligodendrocytes
a) Form myelin in the brain and spinal cord
4. Astrocytes
a) Near blood vessels and support structures
b) Aid in metabolism
c) Respond to brain injury by filling in spaces.
5. Ependyma
a) Cover the inside of ventricles
b) Form choroid plexuses within the ventricles.
6. Schwann cells
a) Peripheral nervous system only
b) Produce myelin
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Neuron Structure
A. Nerve fibers include:
1. Numerous dendrites
a) Branching
b) Carry impulses from other neurons (or from
receptors) toward the cell body
2. A solitary axon
a) Transmits the impulse away from the axonal
hillock of the cell body
b) May give off side branches
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3. Larger axons are enclosed by sheaths of myelin
a) Provided by Schwann cells
b) Outer layer of myelin surrounded by a
neurilemma (neurilemmal sheath) made up of
the cytoplasm and nuclei of the Schwann cell.
c) Narrow gaps in the myelin sheath between
Schwann cells are called nodes of Ranvier.
4. The smallest axons lack a myelin sheath and so
are called unmyelinated fibers.
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3. White matter in the CNS is due to myelin sheaths in
this area
4. Unmyelinated nerve tissue in the CNS comprise the
gray matter.
5. Peripheral neurons are able to regenerate because of
the neurilemma
6. CNS axons are myelinated by oligodendrocytes thus
lacking neurilemma and usually do not regenerate
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Classification of Neurons
A. Neurons can be grouped in two ways:
1. Structural differences
a) Bipolar neurons
1) found in the eyes, nose, and ears
2) have a single axon and a single dendrite extending
from opposite sides of the cell body.
b) Unipolar neurons
1) found in ganglia outside the CNS
2) have an axon and a dendrite arising from a single
short fiber extending from the cell body
c) Multipolar neurons
1) found in the brain and spinal cord
2) have many nerve fibers arising from their cell bodies
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2. Functional differences
a) Sensory neurons (afferent neurons)
1) usually unipolar
2) some bipolar
3) conduct impulses from peripheral receptors to the CNS
b) Interneurons
1) multipolar neurons
2) within the CNS
3) form links between other neurons
c) Motor neurons
1) multipolar neurons
2) conduct impulses from the CNS to effectors
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Cell Membrane Potential
A. A cell membrane is usually polarized
1. Excess of negative charges on the inside of the
membrane
2. Polarization is important to the conduction of
nerve impulses
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B. Distribution of Ions
1. Distribution of ions is determined by the membrane
channel proteins
2. MCPs selective for certain ions
3. Potassium ions (K+) pass through the membrane
more readily than do sodium ions (Na+)
4. Potassium ions a major contributor to membrane
polarization
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C. Resting Potential
1. Due to active transport
a) Cells maintain a greater concentration of sodium ions
outside
b) Greater concentration of potassium ions inside the
membrane
2. Inside the membrane - excess negative charge
3. Outside - excess positive charge
4. This separation of charge, or potential
difference, is called the resting potential
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D. Potential Changes
1. Stimulation of a membrane can locally affect its
resting potential
2. When the membrane potential becomes less
negative, the membrane is depolarized
3. If sufficiently strong depolarization occurs, a
threshold potential is achieved as ion channels open
4. At threshold, an action potential is reached
5. Action potentials may be reached when a series of
subthreshold stimuli combine to reach threshold
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E. Action Potential
1. At threshold potential
a) Na+ channels open
b) Membrane permeability to Na+ quickly changes in the
region of stimulation.
c) Na+ rushes in
d) Membrane potential changes and becomes depolarized.
e) K+ channels open allowing K+ to leave the cell
f) The membrane becomes repolarized
g) Resting potential is reestablished.
2. This rapid sequence of events is the action potential.
3. Active transport mechanisms then restore the original
concentrations of Na+ and K+
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Flash x2
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Nerve Impulse
A. A nerve impulse is conducted as an action
potential is reached at the trigger zone.
B. This spreads by a local current flowing down the
fiber, and adjacent areas of the membrane reach
action potential.
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C. Impulse Conduction
1. Unmyelinated fibers conduct impulses over their
entire membrane surface.
2. Myelinated fibers conduct impulses from one
Node of Ranvier to the next (saltatory conduction)
3. Saltatory conduction is many times faster
conduction over the complete membrane surface
D. All-or-None Response
1. Nerve fibers respond to a stimulus completely by
conducting an impulse or not at all
2. Greater intensity of stimulation triggers more
impulses per second, not stronger impulses.
Flash
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The Synapse
A. Nerve impulses travel from neuron to neuron along
complex nerve pathways.
B. The junction between two communicating neurons is
called a synapse
C. A synaptic cleft is the space between them across which
the impulse must be conveyed.
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D. Synaptic Transmission
1. When an impulse reaches the synaptic knobs of an
axon, synaptic vesicles release a neurotransmitter into
the synaptic cleft
2. The neurotransmitter from the presynaptic neuron
reacts with specific receptors on the postsynaptic
membrane
3. This process by which the impulse in the presynaptic
neuron is transmitted across the synaptic cleft to the
postsynaptic neuron is called synaptic transmission
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Flash
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E. Excitatory and Inhibitory Actions
1. Neurotransmitters that increase postsynaptic
membrane permeability to Na+ may trigger
impulses and are thus excitatory
2. Other neurotransmitters may decrease
membrane permeability to Na+, reducing the
chance that it will reach threshold, and are thus
inhibitory
3. The effect on the postsynaptic neuron depends
on which presynaptic knobs are activated
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F. Neurotransmitters
1. 50+ different neurotransmitters are produced by
the nervous system
a) most are synthesized in the cytoplasm of synaptic knobs
b) stored in synaptic vesicles.
2. When an action potential reaches the synaptic knob
a) calcium ions rush inward
b) in response some synaptic vesicles fuse with the
membrane releasing their contents to the synaptic cleft
3. Synaptic cleft and on postsynaptic membrane
enzymes rapidly decompose the neurotransmitters
4. Removal of the neurotransmitter prevents
continuous stimulation of the postsynaptic neuron
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Impulse Processing
A. How impulses are processed is dependent upon how
neurons are organized in the brain and spinal cord.
B. Neuronal Pools
1. Neurons within the CNS are organized into
neuronal pools with varying numbers of cells.
2. Each pool receives input from afferent nerves and
processes the information according to the special
characteristics of the pool.
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C. Facilitation
1. A particular neuron of a pool may receive excitatory
or inhibitory stimulation
2. If the net effect is excitatory but subthreshold, the
neuron becomes more excitable to incoming
stimulation (facilitation).
D. Convergence
1. A single neuron within a pool may receive impulses
from two or more fibers (convergence)
2. Makes it possible for the neuron to summate
(combine) impulses from different sources.
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E. Divergence
1. Impulses leaving a neuron in a pool may be
passed into several output fibers (divergence)
2. This pattern serves to amplify an impulse.
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Convergence
Divergence
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Types of Nerves
A. A nerve is a bundle of nerve fibers held together
by layers of connective tissue.
B. Nerves can be:
1. Sensory
2. Motor
3. Mixed, carrying both sensory and motor fibers.
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Nerve Pathways
A. The routes nerve impulses travel are called
pathways, the simplest of which is a reflex arc.
B. Reflex Arcs include:
1. Sensory receptors
2. Sensory neurons
3. Interneurons in the spinal cord
4. Motor neurons
5. Effectors
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C. Reflex Behavior
1. Reflexes are automatic subconscious responses to
stimuli
2. Help maintain homeostasis (heart rate, blood
pressure, etc.)
3. Carry out automatic responses (vomiting, sneezing,
swallowing, etc.)
4. The knee-jerk reflex (patellar tendon reflex) is an
example of a monosynaptic reflex (no interneuron)
5. The withdrawal reflex involves
a)
b)
c)
d)
Sensory neurons
Interneurons
Motor neurons
Simultaneously the antagonistic extensor muscles are
inhibited
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Meninges
A. The brain and spinal cord are surrounded by
membranes called meninges
B. Meninges lie between the bone and the soft tissues.
C. Dura mater
1. Outermost meninx
2. Tough, white dense connective tissue
3. Contains many blood vessels
4. Forms the inner periosteum of the skull bones.
5. Forms partitions between lobes of the brain
6. Forms dural sinuses.
7. The sheath around the spinal cord is separated
from the vertebrae by an epidural space.
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D. Arachnoid mater
1. The middle meninx
2. Thin and lacks blood vessels
3. Does not follow the convolutions of the brain
4. Subarachnoid space
a) Between the arachnoid and pia mater
b) Contains cerebrospinal fluid
E. Pia mater
1. Innermost
2. Thin and contains many blood vessels and nerves
3. Attached to the surface of the brain and spinal
cord
4. Follows the contours of the brain and spinal cord
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C. Functions of the Spinal Cord
1. The spinal cord has two major functions:
a) to transmit impulses to and from the brain
b) to house spinal reflexes
2. Nerve tracts are identified by the origin and
termination of the fibers in the tract
3. Ascending tracts tracts carry sensory information
to the brain
4. Descending tracts carry motor information from
the brain
5. Many spinal reflexes also pass through the spinal
cord.
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Brain
A. The brain is the largest most complex portion of the
nervous system
B. Contains 100 billion multipolar neurons
C. Can be divided into the:
1. Cerebrum
a) largest portion
b) associated with higher mental functions
2. Diencephalon - processes sensory input
3. Cerebellum - coordinates muscular activity
4. Brain stem - coordinates and regulates visceral
activities
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D. Structure of the Cerebrum
1. Largest portion of the mature brain
2. Consists of two cerebral hemispheres.
3. The corpus callosum, a deep ridge of nerve fibers,
connects the hemispheres.
4. The surface of the brain is marked by convolutions,
sulci, and fissures.
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6. The cerebral cortex
a) A thin layer of gray matter
b) Lies on the outside of the cerebrum
c) Contains 75% of the cell bodies in the nervous system
7. Beneath the cortex lies a mass of white matter
a) Made up of myelinated nerve fibers
b) Connects the cell bodies of the cortex with the rest of
the nervous system
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E. Functions of the Cerebrum - higher brain functions
1. Interpretation of sensory input
2. Initiating voluntary muscular movements
3. Memory
4. Integrating information for reasoning
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G. Hemisphere Dominance
1. Both cerebral hemispheres function in receiving
and analyzing sensory input and sending motor
impulses to the opposite side of the body.
2. Most people exhibit hemisphere dominance for the
language-related activities of speech, writing, and
reading.
3. The left hemisphere is dominant in 90% of the
population
4. The non-dominant hemisphere specializes in
nonverbal functions and controls emotions and
intuitive thinking
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I.
Diencephalon
1. Lies above the brain stem
2. Composed of the:
a) Thalamus
b) hypothalamus
c) optic tracts
d) optic chiasma
e) infundibulum (attachment for the pituitary)
f) posterior pituitary
g) mammillary bodies
h) pineal gland
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3. The thalamus
a) functions in sorting and directing sensory information
arriving from other parts of the nervous system
b) performing the services of both messenger and editor
4. The hypothalamus
a) maintains homeostasis by regulating a wide variety of
visceral activities including:
1)
2)
3)
4)
5)
6)
7)
heart rate and arterial blood pressure
body temperature
water and electrolyte balance
hunger and body weight
movements and secretions of the digestive tract
growth and reproduction
sleep and wakefulness
b) Links the endocrine system with the nervous system
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5. The limbic system
a) In the area of the diencephalon
b) Controls emotional experience and expression
c) Generates pleasant or unpleasant feelings about
experiences
d) Guides behavior that may enhance the chance of
survival using these feelings
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J.
Brain Stem
1. Lies at the base of the cerebrum
2. Connects the brain to the spinal cord
3. Consists of the:
a) Midbrain
b) Pons
c) Medulla oblongata
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4. Midbrain
a) Located between the diencephalon and pons
b) Contains bundles of myelinated axons that convey
impulses to and from higher parts of the brain
c) Masses of gray matter that serve as reflex centers,
including centers for auditory and visual reflexes.
5. Pons
a) lies between the midbrain and medulla oblongata
b) transmits impulses between the brain and spinal cord
c) contains centers that regulate the rate and depth of
breathing
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5. Medulla Oblongata
a) transmits all ascending and descending impulses
between the brain and spinal cord
b) houses nuclei that control visceral functions, including
1) the cardiac center that controls heart rate
2) the vasomotor center for blood pressure control
3) the respiratory center that works, along with the
pons, to control the rate and depth of breathing
4) Other nuclei associated with coughing, sneezing,
swallowing, and vomiting
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6. Reticular Formation
a) Throughout the brain stem, hypothalamus,
cerebrum, cerebellum, and basal ganglia, is a
complex network of nerve fibers connecting tiny
islands of gray matter; this network is the reticular
formation.
b) Decreased activity in the reticular formation results
in sleep; increased activity results in wakefulness.
c) The reticular formation filters incoming sensory
impulses
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K. Cerebellum
1. Two hemispheres connected by a vermis
2. The cerebellar cortex is a thin layer of gray matter
that lies outside a core of white matter
3. Communicates with other parts of the CNS via
cerebellar peduncles
4. Integrates sensory information about the position
of body parts
5. Coordinates skeletal muscle activity and maintains
posture
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Peripheral Nervous System
A. The peripheral nervous system (PNS) consists of the
cranial and spinal nerves that arise from the central
nervous system and travel to the remainder of the
body.
B. Includes two components
1. The somatic nervous system that oversees
voluntary activities
2. The autonomic nervous system that controls
involuntary activities.
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5. The main branches of some spinal nerves form
plexuses.
a) Cervical plexuses
1) Lie on either side of the neck
2) Supply muscles and skin of the neck
b) Brachial plexuses
1) Arise from lower cervical and upper thoracic nerves
2) Lead to the upper limbs
c) Lumbrosacral plexuses
1) arise from the lower spinal cord
2) Lead to the lower abdomen, external genitalia,
buttocks, and legs
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Autonomic Nervous System
A. The autonomic nervous system (ANS) maintains
the homeostasis of visceral activities without
conscious effort
B. General Characteristics
1. Motor pathways include two fiber types:
a) preganglionic fibers leave the CNS
b) postganglionic fibers innervate the effectors
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2. Includes two divisions exerting opposing effects on
target organs:
a) sympathetic
1) operates under conditions of stress or emergency
2) Fibers arise from the thoracic and lumbar regions of
the spinal cord
3) synapse in paravertebral ganglia close to the vertebral
column
4) Postganglionic axons lead to an effector organ
b) Parasympathetic
1) operates under normal conditions
2) Fibers arise from the brainstem and sacral region of
the spinal cord
3) synapse in ganglia close to the effector organ
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Sympathetic
Parasympathetic
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3. Autonomic Neurotransmitters
a) Preganglionic fibers of both sympathetic and
parasympathetic divisions release acetylcholine.
b) Parasympathetic postganglionic fibers are
cholinergic fibers and release acetylcholine
c) Sympathetic postganglionic fibers are adrenergic
and release norepinephrine
d) The effects of these two divisions are generally
antagonistic due to the effects of releasing
different neurotransmitters to the effector
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4. Control of Autonomic Activity
a) largely controlled by reflex centers in the
brain and spinal cord
b) The limbic system and cerebral cortex alter
the reactions of the autonomic nervous
system through emotional influence
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Chapter 10
Somatic and
Special Senses
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Introduction
A. Sensory receptors detect changes in the environment
B. Stimulate neurons to send nerve impulses to the brain.
C. Sensations are formed based on the sensory input
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Receptors and Sensations
A. Each receptor is more sensitive to a specific kind of
environmental change and less sensitive to others
B. Types of Receptors
1. Five general types:
a)
b)
c)
d)
Chemoreceptors detect changes in chemical concentration
Pain receptors detect tissue damage
Thermoreceptors detect temperature differences
Mechanoreceptors detect changes in pressure or
movement
e) Photoreceptors
1) In the eyes
2) Detect light energy
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C. Sensations
1. Sensations are feelings that occur when the brain
interprets sensory impulses.
2. Projection sends the sensation from the CNS to its
point of origin
a) Simultaneous to sensation formation
b) Allows pinpointing of area of stimulation
D. Sensory Adaptation
1. When stimuli are constant sensory impulses are sent
at rates decreasing to zero
2. Prevents sensory overload from static ‘background’
stimuli
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Somatic Senses
A. Receptors associated with the skin, muscles, joints,
and viscera make up the somatic senses.
B. Temperature Senses
1. Warm receptors
a) Work best within a range of temperatures
b) Adapt quickly
c) Temperatures near 45o C stimulate pain receptors
2. Cold receptors
a) Work best within a range of temperatures
b) Adapt quickly
c) Temperatures below 10o C stimulate pain receptors and
produce a freezing sensation
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D. Sense of Pain
1. Pain receptors consist of free nerve endings that are
stimulated when tissues are damaged
2. Little or no adaptation
3. Many stimuli affect pain receptors such as chemicals
and oxygen deprivation
4. Visceral pain receptors are the only receptors in the
viscera that produce sensations
a) Respond differently than surface tissues
b) Referred pain can occur because of the common nerve
pathways leading from skin and internal organs
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4. Pain Nerve Fibers
a) Acute pain fibers
1) Thin, myelinated fibers
2) Carry impulses rapidly to CNS
3) Cease when the stimulus stops.
b) Chronic pain fibers
1) Thin, unmyelinated fibers
2) Conduct impulses slowly
3) Continue sending impulses after the stimulus stops
c) Impulses processed in the gray matter of the dorsal horn
of the spinal cord
d) Impulses are conducted to the
1) Thalamus
2) Hypothalamus
3) cerebral cortex
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5. Regulation of Pain Impulses
a) Awareness of pain begins with the impulse reaching the
thalamus
b) The cerebral cortex judges the intensity and location of
the pain and determines emotional and motor response
c) Areas of gray matter in the brain stem regulate the flow
of pain impulses from the spinal cord
d) The brain stem can trigger the release of enkephalins and
serotonin, which inhibit the release of pain impulses in the
spinal cord
e) Endorphins released by the hypothalamus and pituitary
provide naturally suppress pain (similar to morphine)
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Special Senses
A. The special senses are associated with relatively large
and complex structures located in the head
B. These include:
1. Smell
2. Taste
3. Hearing
4. Static equilibrium
5. Dynamic equilibrium
6. Sight
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Sense of Smell
A. Olfactory Receptors
1. Olfactory receptors are chemoreceptors
2. The senses of smell and taste operate together to aid
in food selection
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B. Olfactory Organs
1. Olfactory organs
a) located in the upper nasal cavity
b) olfactory receptors
c) epithelial supporting cells
2. Receptor cells
a) bipolar neurons
b) hair-like cilia covering the dendrites project into the nasal
cavity
3. Chemicals that enter the nasal cavity must dissolve
into the watery fluid surrounding the cilia to be
detected
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C. Olfactory Nerve Pathways
1. When olfactory receptors are stimulated, their fibers
synapse with neurons in the olfactory bulbs lying on
either side of the crista galli.
2. Sensory impulses are first analyzed in the olfactory
bulbs
3. Then travel along olfactory tracts to the limbic
system
4. Then finally to the olfactory cortex within the
temporal lobes
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D. Olfactory Stimulation
1. Scientists are uncertain of how olfactory reception
operates
2. It is thought that each odor stimulates a set of
specific protein receptors in cell membranes
3. The brain interprets different receptor
combinations as an olfactory code
4. Olfactory receptors adapt quickly but selectively
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Sense of Taste
A. Taste buds are the organs of taste
B. located within papillae of the tongue and scattered
throughout the mouth and pharynx
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C. Taste Receptors
1. Taste cells (gustatory cells)
a) Modified epithelial cells that function as receptors
b) Contain taste hairs
1) Protrude from openings called taste pores
2) Sensitive to taste
2. Chemicals must be dissolved in water (saliva) in
order to be tasted
3. Taste probably involves specific membrane protein
receptors that bind with specific chemicals in food
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4. Five types of taste cells:
a) Sweet receptors plentiful near the tip of the tongue
b) Sour receptors occurring along the lateral edges of the
tongue
c) Salt receptors abundant in the tip and upper portion of
the tongue
d) Bitter receptors are at the back of the tongue
e) Umami receptors responds to certain amino acid
derivatives such as monosodium glutamate (MSG)
5. Taste buds may be responsive to at least two taste
sensations but one is likely to dominate
6. Taste receptors adapt rapidly
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Sense of Hearing
A. The ear has external, middle, and inner sections
B. Provides the senses of hearing and equilibrium
C. External Ear
1. The auricle collects sound
2. Sound travels down the external auditory meatus
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D. Middle Ear
1. Begins with the tympanic membrane
2. Tympanic cavity (an air-filled space) houses the
auditory ossicles
a) Malleus
b) Incus
c) Stapes
3. The tympanic membrane vibrates the malleus, which
vibrates the incus, then the stapes
4. The stapes vibrates the fluid inside the oval window
of the inner ear
5. Auditory ossicles both transmit and amplify sound
waves
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Sense of Equilibrium
A. Static equilibrium
1. Maintains stability when the head and body are still
2. Organs located
a) Within the vestibule (a bony chamber) of the inner ear
b) Inside the utricle and saccule (expansions of the
membranous labyrinth).
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3. A macula, consisting of hair cells and supporting
cells, lies inside the utricle and saccule
4. Hair cells contact gelatinous material holding
otoliths
5. Gravity causes the gelatin and otoliths to shift,
bending hair cells generating a nerve impulse
6. Impulses travel to the brain via the vestibular branch
of the vestibulocochlear nerve, indicating the position of
the head
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B. Dynamic Equilibrium
1. Maintains balance when the head and body suddenly
move and rotate
2. The three semicircular canals
a) Detect motion of the head
b) Aid in balance during sudden movement
c) Canals lie at right angles to each other
3. Cristae ampullaris
a) Located in the ampulla of each semicircular canal
b) Hair cells extend into a dome-shaped gelatinous cupula
c) Rapid turning of the head or body generates impulses as
the cupula and hair cells bend
4. Propriopceptors (Mechanoreceptors) associated with
joints and changes detected by the eyes aid in
maintaining equilibrium
76

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Sense of Sight
A. Visual Accessory Organs
1. The eyelid
a) Protects the eye from foreign objects
b) Made up of the thinnest skin of the body
c) Lined with conjunctiva
2. The lacrimal apparatus
a) Produces tears
1) lubricate and cleanse the eye
2) contain an antibacterial enzyme
b) Two small ducts drain tears into the nasal cavity
3. The extrinsic muscles
a) attach to the sclera
b) move the eye in all directions
77
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B. Structure of the Eye
1. The eye is a fluid-filled hollow sphere with three
distinct layers, or tunics.
2. The Outer Tunic
a)
b)
c)
d)
Fibrous
Transparent cornea at the front of the eye
White sclera of the anterior eye
The optic nerve and blood vessels pierce the sclera at the
posterior of the eye
78
3. The Middle Tunic
a) The vascular tunic includes:
1) The choroid coat
a. vascular and darkly pigmented
b. Nourishes other tissues of the eye
c. Keeps the inside of the eye dark
2) The ciliary body
a. forms a ring around the front of the eye
b. contains ciliary muscles and suspensory ligaments
c. hold the lens in position and change its shape
(focus)
d. The ability of the lens to adjust shape to facilitate
focusing is called accommodation
79
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3) The iris
1) a thin, smooth muscle
2) has a circular set of and a radial set of muscle
fibers
3) hole in its center
4) adjusts the amount of light entering the pupil
4) The anterior cavity
1) The anterior chamber (between the cornea and iris)
2) the posterior chamber (between the iris and vitreous
body and housing the lens)
3) Filled with aqueous humor
4) The aqueous humor circulates from one chamber
to the other through the pupil
80
4. The Inner Tunic
a) Covers the back side of the eye to the ciliary body
b) Consists of the retina which contains photoreceptors
c) In the center of the retina is the macula lutea
1) the fovea centralis in its center
2) the point of sharpest vision in the retina
d) the optic disk
1) Medial to the fovea centralis
2) where nerve fibers leave the eye
3) a blind spot
e) The large cavity of the eye is filled with vitreous humor
81
D. Visual Receptors
1. Rods
a)
b)
c)
d)
Elongated
Function in dim light
More sensitive to light
Produce colorless vision
82
2. Cones
a)
b)
c)
d)
e)
Blunt cone-shaped
Function in bright light
Provide sharp images
Enable color vision
The fovea centralis
1) contains the highest concentration of cones
2) proportion of cones decreases with distance from
fovea centralis
3) To see something in detail, a person moves the eyes
so the image falls on the fovea centralis
83
Chapter 11
Endocrine System
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Introduction
A. The body has two kinds of glands:
1. Endocrine - secrete products into body fluids
2. Exocrine - secretes products into ducts
B. The function of the endocrine system is to
communicate with cells using hormones
C. The cells, tissues, and organs of the endocrine system
secrete hormones into body fluids
D. Hormones diffuse into the bloodstream to act on
specific target cells elsewhere in the body
85
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E. Endocrine glands and their hormones regulate a number
of metabolic processes within cells, tissues, and organs
F. Their actions are precise, they only affect specific target
cells
G. Endocrine glands include the:
1. Pituitary gland
2. Thyroid gland
3. Parathyroid glands
4. Adrenal glands
5. Pancreas
6. and other hormone-secreting glands and tissues
86
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Hormone Action
A. Hormones are:
1. Steroids
2. Amines
3. Peptides
4. Proteins
5. Glycoproteins
B. They can influence target cells even if they are present
only in minute concentrations
87
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C. Steroid Hormones
1. Steroid hormones are lipid-soluble and so can
pass through cell membranes
2. Receptors for steroid hormones are located in the
targeted cell’s nucleus
3. The hormone-receptor complex:
1. Binds with target cell DNA
2. Activates specific genes
3. Genes direct the synthesis of specific proteins
88
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D. Nonsteroid Hormones
1. Nonsteroid hormones combine with receptors in
target cell membranes
2. Receptors have a binding site and an activity site
3. The hormone-receptor complex (as first messenger)
triggers a cascade of biological activity
4. The hormone-receptor complex generally
activates a G protein
5. G protein then activates the enzyme adenylate cyclase
that is bound to the inner cell membrane
89
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6. This enzyme removes two phosphates from ATP
to produce cyclic AMP (the second messenger)
7. cAMP in turn activates protein enzymes that
activate proteins
8. These activated proteins induce changes in the cell
9. Not all nonsteroid hormones use cAMP
10. Others use diacylglycerol (DAG) or inositol
triphosphate
90
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Control of Hormonal Secretions
A. Hormone levels are very precisely regulated.
B. Control Mechanisms:
1. Release of tropic hormones from the
hypothalamus controls secretions of the anterior
pituitary
2. The nervous system influences certain endocrine
glands directly
3. Other glands respond directly to changes in the
internal fluid composition
91
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C. Negative Feedback Systems
1. Commonly, negative feedback mechanisms control
hormonal releases
2. In a negative feedback system, a gland is sensitive
to the concentration of the substance it regulates
or which regulates it
3. When the concentration of the regulated
substance reaches a certain level (high or low), it
inhibits the gland from secreting more hormone
until the concentration returns to normal
Flash
92
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Pituitary Gland
A. The pituitary gland is attached to the base of the
brain
B. Has an anterior lobe (anterior pituitary) and a
posterior lobe (posterior pituitary).
94
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B. The brain controls the activity of the pituitary
gland
1. Releasing hormones from the hypothalamus
control the secretions of the anterior pituitary
2. The releasing hormones are carried in the
bloodstream directly to the anterior pituitary by
hypophyseal portal veins
3. The posterior pituitary releases hormones into
the bloodstream in response to nerve impulses
from the hypothalamus
95
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C. Anterior Pituitary Hormones
1. Growth hormone (GH)
a) Stimulates body cells to grow and reproduce
b) Speeds the rate at which cells use carbohydrates
and fats
c) Growth hormone-releasing hormone from the
hypothalamus increases the amount of GH
released
d) GH release-inhibiting hormone inhibits its release
e) Nutritional status affects the release of GH; more
is released when nutrients are insufficient.
96
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2. Prolactin (PRL)
a) Promotes milk production following the birth
of an infant
b) The effect of PRL in males is less-well
understood, although it may cause a deficiency
of male sex hormones
97
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3. Thyroid-stimulating hormone (TSH)
1. Controls the secretion of hormones from the
thyroid gland
2. Thyrotropin-releasing hormone (TRH) from the
hypothalamus regulates the release of TSH
3. As blood concentrations of thyroid hormones
increases, secretions of TRH and TSH decrease
98
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5. Adrenocorticotropic hormone (ACTH)
a) Controls secretion of hormones from the
adrenal cortex
b) Regulated by corticotropin-releasing hormone from
the hypothalamus
c) Stress can also increase its release
100
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6. Follicle-stimulating hormone (FSH) and
luteinizing hormone (LH) are gonadotropins
affecting the male and female sex organs.
101
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D. Posterior Pituitary Hormones
1. The posterior lobe consists of nerve fibers and
neuroglial cells
2. Supports nerve fibers arising in the hypothalamus
3. Neurons in the hypothalamus produce
a) Antidiuretic hormone (ADH)
1) Produces its effect by causing the kidneys to conserve
water
2) hypothalamus regulates the secretion of ADH based
on the amount of water in body fluids
3) Stored in the posterior pituitary
102
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b) Oxytocin
1) Plays a role in childbirth by contracting muscles in the
uterine wall
2) Forces milk into ducts from the milk glands
3) Stretching of the uterus in the latter stages of
pregnancy stimulates release of oxytocin
4) Suckling of an infant at the breast stimulates release of
oxytocin after childbirth
103
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Thyroid Gland
A. The thyroid gland is located below the larynx and
consists of two broad lobes connected by an isthmus
B. The thyroid consists of secretory parts called follicles
filled with hormone-storing colloid
104
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C. Thyroid Hormones
1. The hypothalamus and pituitary gland control release
of thyroid hormones
105
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2. Follicular cells produce two iodine-containing
hormones:
a) Thyroxine (T4 ) (tetraiodothyronine)
b) Triiodothyronine (T3)
c) Essential for normal growth and development
d) Together regulate energy metabolism
1) Increase the rate at which cells release energy from
carbohydrates
2) Enhance protein synthesis
3) Stimulate the breakdown and mobilization of lipids
106
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3. Extrafollicular cells of the thyroid secrete
calcitonin
a) Lowers blood levels of calcium and
phosphate ions when they are too high
b) Increases the rate at which calcium is stored
in bones and excreted in the urine
c) Secretion is regulated by negative feedback
involving blood concentrations of calcium
107
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Parathyroid Glands
A. The four, tiny parathyroids are located on the
posterior of the thyroid
B. Parathyroid glands consist of tightly
packed
secretory cells covered by a thin capsule of
connective tissue
108
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C. Parathyroid Hormone
1. Parathyroid hormone (PTH) increases blood calcium ion
concentration
2. Decreases phosphate ion concentration
3. PTH stimulates bone resorption by osteoclasts, which
releases calcium into the blood
4. PTH also influences the kidneys to conserve calcium and
causes increased absorption of calcium in the intestines
5. A negative feedback mechanism involving blood calcium
levels regulates release of PTH
D. Calcitonin and PTH exert opposite effects in regulating
calcium ion levels in the blood
109
110
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Adrenal Glands
A. The adrenal glands sit atop the kidneys enclosed in a
layer of fat
B. The pyramid-shaped glands consist of
1. Inner adrenal medulla
a) Made up of modified postganglionic neurons
b) Connected to the sympathetic nervous system
2. Outer adrenal cortex
a) Makes up most of the adrenal glands
b) Consists of epithelial cells in three layers
1) Outer zone
2) Middle zone
3) Inner zone
111
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C. Hormones of the Adrenal Medulla
1. The adrenal medulla secretes epinephrine and
norepinephrine into the blood stream
2. The effects of these hormones resemble those of
the sympathetic division neurotransmitters of the
same name
3. They last up to 10 times longer when they are
secreted as hormones
4. Used in times of stress and for “fight or flight”
5. Release of medullary hormones is regulated by
nervous impulses from the central nervous system
113
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D. Hormones of the Adrenal Cortex
1. The cells of the adrenal cortex produce over 30
different steroids
2. Some are vital to survival
3. Most important are
a) Aldosterone
1) A mineralocorticoid
2) Causes the kidneys to conserve sodium ions and thus
water
3) Causes the kidneys to excrete potassium ions
4) secreted in response to decreasing blood volume and
blood pressure as a result of changes in the kidney
114
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b) Cortisol
1) a glucocorticoid
2) influences the metabolism of glucose, protein,
and fat
3) response to conditions that stress the body and
require a greater supply of energy in the
bloodstream
4) A negative feedback mechanism involving CRH
from the hypothalamus and ACTH from the
anterior pituitary controls the release of cortisol
5) Stress, injury, or disease can also trigger
increased release of cortisol
115
116
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Pancreas
A. Elongated organ posterior to the stomach
B. The pancreas secretes digestive juices to the digestive
tract as an exocrine gland
C. Secretes hormones as an endocrine gland
D. Islets of Langerhans, its endocrine portions, include
two cell types:
1. Alpha cells that secrete glucagon
2. Beta cells that secrete insulin
117
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E. Hormones of the Islets of Langerhans
1. Glucagon
a) Increases the blood levels of glucose by
stimulating the breakdown of glycogen and
the conversion of noncarbohydrates into
glucose
b) Release is controlled by a negative feedback
system involving low blood glucose levels
118
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2. Insulin
a) Decreases the blood levels of glucose by stimulating
the liver to form glycogen
b) Increasing protein synthesis, and stimulating adipose
cells to store fat
c) The release of insulin is controlled by a negative
feedback system involving high blood glucose levels
3. Insulin and glucagon coordinate to maintain a
relatively stable blood glucose concentration
Flash
119
120
121
Chapter 12
Blood
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Introduction
A. Blood is a connective tissue
B. A complex mixture of cells, chemicals, and fluid
C. Transports substances throughout the body
D. Helps to maintain a stable internal environment
E. Includes:
1. Red blood cells
2. White blood cells
3. Platelets
4. Plasma
123
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Blood Cells
A. Red Blood Cells
1. Erythrocytes
a) Biconcave disks
b) Discard their nuclei during development so:
1) Cannot reproduce
2) Cannot produce proteins
c) Contain one-third hemoglobin by volume
1) Hemoglobin carries O2
2) When combined with O2 oxyhemoglobin results
(bright red)
3) Deoxygenated blood (deoxyhemoglobin) is darker
124
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3. Red Blood Cell Production and Control
a) In the embryo and fetus RBC production occurs in
1) Yolk sac
2) Liver
3) Spleen
b) After birth RBC production in red bone marrow
c) Average life span of RBCs is 120 days
d) The total number of RBCs remains relatively constant
due to a negative feedback mechanism
1) Detection of low O2 in blood
2) Erythropoietin is released from the kidneys and liver
3) More RBCs produced
4) O2 carrying capacity of blood increases
125
126
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4. Dietary Factors Affecting RBC Production
a) Vitamins B12 and folic acid are needed for DNA
synthesis, so are necessary for the reproduction
of all body cells
b) Iron is needed for hemoglobin synthesis
c) Deficiency in RBCs or quantity or hemoglobin is
anemia
127
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5. Destruction of Red Blood Cells
a) With age RBCs
1) Become increasingly fragile
2) Are damaged by passing through narrow capillaries
b) Macrophages in the liver and spleen
phagocytize damaged red blood cells
c) Hemoglobin is then converted into:
1) Heme - an iron carrying porphyrin ring
2) Globin - its protein carrier
d) Heme is decomposed into
1) Iron which is stored or recycled
2) Biliverdin and bilirubin which are excreted in bile
Flash
128
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B. White Blood Cells
1. Leukocytes help defend the body against disease
2. Formed from hemocytoblasts (hematopoietic stem cells)
3. Five types of WBCs are in circulating blood
a) Distinguished by:
a)
b)
c)
d)
Size
Granular appearance of the cytoplasm
Shape of the nucleus
Staining characteristics
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b) Granular
1) Neutrophils
a. Red-staining fine cytoplasmic granules
b. Multi-lobed nucleus
c. 54-62% of leukocytes
2) Eosinophils
a. Coarse granules that stain deep red
b. Bilobed nucleus
c. 1-3% of circulating leukocytes
3) Basophils
a. Fewer granules that stain blue
b. < 1% of leukocytes
130
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c) Agranular
1. Monocytes
a. Largest blood cells
b. Variably-shaped nuclei
c. 3-9% of circulating leukocytes
2. Lymphocytes
a. Long-lived
b. Large round nucleus
c. 25-33% of circulating leukocytes
131
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4. Functions of White Blood Cells
a) Leukocytes can squeeze between cells lining
walls of blood vessels by diapedesis
b) Attack and remove bacteria and debris
1) Neutrophils
a. Phagocytic
2) Eosinophils
a. Moderate allergic reactions
b. Defend against parasitic infections
3) Basophils
a. Migrate to damaged tissues
b. Release histamine to promote inflammation
c. Release heparin to inhibit blood clotting
132
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4) Monocytes
1) phagocytic
2) engulf the larger particles
5) Lymphocytes
a. major players in specific immune reactions
b. Some produce antibodies
133
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C. Blood Platelets
1. Blood platelets are fragments of megakaryocytes
2. Help repair damaged blood vessels by adhering to
their broken edges
3. Normal counts vary from 130,000 to 360,000
platelets per mm3
134
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Blood Plasma
A. Plasma
1. Clear, straw-colored fluid portion of the blood
2. Mostly water (~90%)
3. Contains a variety of substances
4. Transports
a) Nutrients
b) Gases
5. Regulates fluid and electrolyte balance
6. Maintains a favorable pH
135
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B. Plasma Proteins
1. Most abundant dissolved substances in plasma (~7%)
2. Not used for energy
137
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3. Fall into three groups:
a) Albumins
1) ~ 60% of plasma proteins
2) help maintain osmotic pressure of the blood
b) Globulins
1) ~ 36% of plasma proteins
2) Designated as alpha, beta, and gamma globulins
a. Alpha and beta globulins function in transporting
lipids and fat-soluble vitamins
b. Gamma globulins are a type of antibody
c) Fibrinogen
1) ~ 4% of plasma proteins
2) plays a primary role in blood coagulation
138
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C. Nutrients and Gases
1. The most important blood gases are
a) Oxygen (O2)
b) Carbon dioxide (CO2)
2. Plasma nutrients include
a) Amino acids
b) Monosaccharides
c) Nucleotides
d) Lipids
1) Not soluble in the water of the plasma
2) Surrounded by protein molecules for transport
through the bloodstream as lipoproteins
139
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e) Lipoproteins are classified based on their
densities
1) Density reflects composition
2) Types of lipoproteins include:
a. HDL – high density
b. LDL – low density
c. VLDL – very low density
d. Chylomicrons
140
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D. Nonprotein Nitrogenous Substances
1. generally include amino acids, urea, and uric acid
a) Urea and uric acid are the by-products of protein
and nucleic acid catabolism
141
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E. Plasma Electrolytes
1. Are absorbed by the intestines or are by-products
of cellular metabolism
2. Include
a)
b)
c)
d)
e)
f)
g)
h)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Phosphate
Sulfate
(Na+)
(K+)
(Ca2+)
(Mg2+)
(Cl-)
(HCO3-)
(PO43-)
(SO42-)
3. Some are important in maintaining
a) Osmotic pressure
b) pH
142
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Hemostasis
A. Hemostasis
1. Stoppage of bleeding
2. Follows injury to a vessel
3. Three steps:
a) Blood vessel spasm
1) Cutting a blood vessel causes the muscle in its
walls to contract in a reflex (vasospasm)
2) Lasts only a few minutes
3) Long enough to initiate the second and third steps
of hemostasis
143
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b) Platelet plug formation
1) Platelets stick to the exposed edges of damaged
blood vessels, forming a net with spiny processes
protruding from their membranes
2) A platelet plug is most effective on a small vessel
144
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c) Blood coagulation
1)
2)
3)
4)
5)
6)
7)
8)
Most effective means of hemostasis
Very complex process involving clotting factors
Damaged tissues release tissue thromboplastin
Thromboplastin activates the first in a series of
factors
Leads to production of prothrombin activator
Prothrombin activator converts prothrombin in the
plasma into thrombin
Thrombin catalyzes a reaction that converts
soluble fibrinogen into net-like insoluble fibrin
Fibrin causes the blood cells to catch
146
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9) The amount of prothrombin activator
formed is proportional to the amount of
tissue damage
10) Once a blood clot forms, it promotes still more
clotting through a positive feedback system
11) After a clot forms fibroblasts invade the area and
produce fibers throughout the clots
12) A clot that forms abnormally in a vessel is a
thrombus
13) A thrombus that dislodges is an embolus
147
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Blood Groups and Transfusions
A. After mixed success with transfusions, scientists
determined that blood
1. was of different types
2. only certain combinations were compatible
149
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B. Antigens and Antibodies
1. Clumping of red blood cells following transfusion is
called agglutination
2. Agglutination is due to the interaction of antigens
on the surfaces of RBCs with antibodies carried in
the plasma
3. Only a few of the antigens on RBCs produce
transfusion reactions
1. ABO group
2. Rh group
150
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C. ABO Blood Group
1. Type A blood
a) A antigens on RBCs
b) anti-B antibodies in the plasma
2. Type B blood
a) B antigens on RBCs
b) anti-A antibodies in the plasma
3. Type AB blood
a) Both A and B antigens on RBCs
b) No antibodies in the plasma
151
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4. Type O blood
a) Neither antigen
b) Both antibodies in the plasma
5. Adverse transfusion reactions
a) Due to the agglutination of RBCs
b) Avoided by preventing the mixing of blood
that contains matching antigens and antibodies
Flash
152
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D. Rh Blood Group
1. Named after the rhesus monkey
2. Rh factor surface protein
a)
b)
c)
d)
Present on RBCs then blood is Rh positive
Absent on RBCs then blood is Rh negative
No corresponding antibodies in the plasma
If a person with Rh-negative blood is transfused with
Rh-positive antibodies for the Rh factor will develop in
the plasma
3. Erythroblastosis fetalis
a) develops in Rh-positive fetuses of Rh-negative mothers
b) can now be prevented
154
Chapter 13
Cardiovascular System
155
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Introduction
A. The cardiovascular system consists of
1. Heart
2. Blood vessels
a) Arteries
b) capillaries
c) veins
B. Supplies oxygen and nutrients to tissues
C. Removes wastes from tissues
D. The pulmonary circuit carries deoxygenated blood
to the lungs
E. The systemic circuit sends oxygenated blood to all
body cells
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E. Heart Chambers and Valves
1. The heart has four internal chambers:
a) Two atria on top
1) receive blood returning to the heart
2) thin walls
3) ear-like auricles projecting from their exterior
b) Two ventricles below
1) The thick-muscled
2) Pumps blood to the body
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2. A septum divides the atrium and ventricle on each
side
3. Each also has an atrioventricular (A-V) valve to
ensure one way flow of blood
a) Right A-V valve (tricuspid)
b) Left A-V valve (bicuspid or mitral valve)
c) Have cusps to which chordae tendinae attach
d) Chordae tendinae attach to papillary muscles in
the inner heart wall
1) Contract during ventricular contraction
2) Prevent the backflow of blood through the A-V valves
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4. The superior and inferior vena cavae bring blood
from the body to the right atrium
5. The right ventricle has a thinner wall than does the
left ventricle because it must pump blood only as far
as the lungs rather than the entire body
6. Pulmonary valve
a) At the base of the pulmonary trunk leading to the lungs
b) Prevents a return flow of blood to the ventricle
7. The left atrium receives blood from 4 pulmonary veins
8. The left ventricle
a) Pumps blood into the entire body through the aorta
b) Guarded by the aortic valve
c) Prevents backflow of blood into the ventricle
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G. Path of Blood through the Heart
1. Blood low in oxygen returns to the right atrium via
a) Venae cavae
b) Coronary sinus
2. The right atrium contracts
3. Blood forced through the tricuspid valve into the
right ventricle
4. The right ventricle contracts, closing the tricuspid
valve
5. Blood forced through the pulmonary valve into the
pulmonary trunk and arteries
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6. Pulmonary arteries carry blood to the lungs where it:
a) Rids itself of excess carbon dioxide
b) Picks up a new supply of oxygen
7. Freshly oxygenated blood is returned to the left
atrium of the heart through the pulmonary veins
8. The left atrium contracts
9. Blood forced through the left bicuspid valve into the
left ventricle
10. The left ventricle contracts closing the bicuspid valve
11. Aortic valve is forced open
12. Blood enters the aorta for distribution to the body
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H. Blood Supply to the Heart
1. The first branches off of the aorta
a) Right and left coronary arteries
b) Feed the heart muscle itself
c) Carry freshly oxygenated blood
2. Branches of the coronary arteries feed capillaries of
the myocardium
3. Heart requires a continuous supply of freshly
oxygenated blood
4. Smaller branches of arteries often have anastomoses as
alternate pathways for blood
5. Cardiac veins
a) Drain blood from the heart muscle
b) Carry it to the coronary sinus
c) Coronary sinus empties into the right atrium
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Heart Actions
A. Cardiac cycle consists of
1. Atria beating in unison (atrial systole)
2. Followed by the contraction of both ventricles,
(ventricular systole)
3. Then the entire heart relaxes for a brief moment
(diastole)
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B. Cardiac Cycle
1. Pressure within the heart chambers rises and falls
with contraction and relaxation of atria and
ventricles
2. When atria fill pressure in the atria is greater than
that of the ventricles forcing the A-V valves open
3. Pressure inside atria rises further as they contract
forcing the remaining blood into the ventricles
4. When ventricles contract pressure inside them
increases sharply
a) A-V valves forced closed
b) aortic and pulmonary valves forced open
c) papillary muscles contract pulling on chordae tendinae and
prevent the backflow of blood through the A-V valves
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D. Cardiac Muscle Fibers
1. A mass of merging fibers that act as a unit is
called a functional syncytium
2. One exists in the atria (atrial syncytium)
3. One in the ventricles (ventricular syncytium)
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E. Cardiac Conduction System
1. Specialized cardiac muscle tissue conducting
impulses throughout the myocardium
2. A self-exciting mass of specialized cardiac muscle
called the sinoatrial node (S-A node or pacemaker)
is located on the posterior right atrium
3. S-A node generates the impulses for the heartbeat
4. Impulses spread next to the atrial syncytium and it
contracts
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5. Impulses travel to the junctional fibers
a) Junctional fibers are small
b) Lead to atrioventricular node (A-V node) in the
septum
c) Allow the atria to contract before the impulse
spreads rapidly over the ventricles
6. Branches of the A-V bundle give rise to Purkinje
fibers leading to papillary muscles
7. These fibers stimulate contraction of the papillary
muscles at the same time the ventricles contract
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F. Electrocardiogram
1. Record of the electrical changes that occur during a
cardiac cycle
2. The first wave, the P wave, corresponds to the
depolarization of the atria
3. The QRS complex corresponds to the depolarization
of ventricles and hides the repolarization of atria
4. T waves end the ECG pattern and corresponds to
ventricular repolarization
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G. Regulation of the Cardiac Cycle
1. The amount of blood pumped at any one time
must adjust to the current needs of the body
(more is needed during strenuous exercise)
2. The S-A node is innervated by branches of the
sympathetic and parasympathetic divisions
a) CNS controls heart rate
b) Sympathetic impulses increase heart rate
c) Parasympathetic impulses decrease heart rate
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3. Baroreceptors detect changes in blood pressure and
signal medulla oblongata
4. The cardiac control center of the medulla
oblongata maintains a balance between the
sympathetic and parasympathetic divisions
5. Impulses from the cerebrum or hypothalamus
may also influence heart rate
6. Body temperature and the concentrations of
certain ions may influence heart rate as well
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Blood Vessels
A. Form a closed tube
B. Carry blood away from the heart, to the cells, and
back again
C. Consist of
1. Arteries
2. Arterioles
3. Capillaries
4. Venules
5. Veins
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D. Arteries and Arterioles
1.
Arteries
a) Strong, elastic vessels
b) Adapted for carrying high-pressure blood
2. Arteries become smaller as they
divide and give rise
to arterioles
3. The wall of an artery consists of
a) Endothelium
b) Tunica media (smooth muscle)
c) Tunica externa (connective tissue)
4. Vasoconstriction directed by the sympathetic
impulses
5. Vasodilation results when impulses are inhibited
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E. Capillaries
1. Capillaries are the smallest vessels
2. Consist of only of a layer of endothelium
through which substances are exchanged with
tissue cells
3. Capillary permeability varies from one tissue to
the next
a) Generally more permeability in:
1) Liver
2) Intestines
3) certain glands
b) Less permeability in:
1) Muscles
2) Brain (blood-brain barrier)
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4. The pattern of capillary density also varies from
one body part to the next.
5. Areas with a great deal of metabolic activity have
higher densities of capillaries
6. Precapillary sphincters
a) Controlled by oxygen concentration in the area
b) Regulate the amount of blood entering a
capillary bed
c) If blood is needed elsewhere in the body the
capillary beds in less important areas are shut
down
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F. Exchanges in the Capillaries
1. Blood entering capillaries contain:
a) High concentrations of oxygen and nutrients
b) Diffuse through capillary walls into the tissues
c) Diffusion driven by hydrostatic pressure
2. Plasma proteins remain in the blood due to their
large size
3. Osmotic pressure of the blood causes much of the
tissue fluid to return to venules
4. Lymphatic vessels collect excess tissue fluid and
return it to circulation
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G. Venules and Veins
1. Venules leading from capillaries merge to form veins
that return blood to the heart.
2. Veins
a) Do not carry high-pressure blood
b) Thinner and less muscular than arteries
c) Have the same three layers as arteries
1) Endothelium
2) Tunica media (smooth muscle)
3) Tunica externa (connective tissue)
d) Flap-like valves prevent backflow of blood
e) Function as blood reservoirs
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Blood Pressure
A. Blood pressure is the force of blood against the
inner walls of blood vessels
B. The term "blood pressure" usually refers to arterial
pressure
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C. Arterial Blood Pressure
1. Arterial blood pressure rises and falls following a
pattern established by the cardiac cycle
a) During ventricular contraction, arterial pressure
is at its highest (systolic pressure)
b) When ventricles are relaxing, arterial pressure is
at its lowest (diastolic pressure)
2. The surge of blood that occurs with ventricular
contraction can be felt as a pulse
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D. Factors that Influence Arterial Blood Pressure
1. Heart action
a) Dependent upon Stroke volume and heart rate (together
called cardiac output)
b) Increased cardiac output increases → increased blood
pressure
2. Blood volume
a) Normally directly proportional to blood pressure
b) Varies with age, body size, and gender
3. Resistance to flow
a) Friction between blood and walls of blood vessels is
peripheral resistance
b) Peripheral resistance increases → blood pressure increases
4. Blood viscosity
a) Greater the viscosity → greater resistance
b) Greater resistance → higher blood pressure
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E. Control of Blood Pressure
1. Blood pressure is determined by cardiac output
and peripheral resistance
2. The body maintains normal blood pressure by
adjusting cardiac output and peripheral resistance
3. Cardiac output depends on
a) stroke volume and heart rate
b) a number of factors can affect these actions
4. Blood volume entering the right atrium ~ the
volume leaving the left ventricle
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5. The cardiac center of the medulla oblongata
responds to arterial blood pressure
a) Arterial pressure increases → parasympathetic
impulses to slow heart rate are sent
b) Arterial pressure drops → sympathetic impulses
to increase heart rate are sent
6. Emotional upset, exercise, and increased
temperature can result in increased cardiac output
and increased blood pressure
7. The vasomotor center of the medulla oblongata
can adjust the sympathetic impulses to smooth
muscles in arteriole walls, adjusting blood pressure
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5. CO2, O2, and H+ can affect peripheral resistance
6. Venous Blood Flow
a) Partially the result of heart action
b) Contractions of skeletal muscle squeeze blood
back up veins one valve at a time
c) Breathing movements and vasoconstriction of
veins
d) Differences in thoracic and abdominal
pressures draw blood back up the veins
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Paths of Circulation
A. Pulmonary circuit
1. Blood from the right ventricle to the pulmonary
arteries
2. To the lungs and alveolar capillaries
3. Pulmonary veins lead from the lungs to the left
atrium
B. Systemic circuit
1. The aorta and its branches lead to all body tissues
2. Veins return blood to the right atrium
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Arterial System
A. The aorta is the largest artery
B. Principal Branches of the Aorta
1. Ascending aorta
a) Right and left coronary arteries
b) Lead to heart
2. Principal branches of the aortic arch
a) Brachiocephalic
b) Left common carotid
c) Left subclavian arteries
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Venous System
A. Veins return blood to the heart after exchange of
substances in the tissues
B. Venous Pathways
1. Larger veins parallel the courses of arteries and are
named accordingly
2. Smaller veins take irregular pathways and are
unnamed
3. Veins from the head and upper torso drain into the
superior vena cava
4. Veins from the lower body drain into the inferior
vena cava
5. The vena cavae merge to join the right atrium
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Describe each of the five types of neuroglial cells.
Describe the groupings of neurons by structural differences and by functional differences.
Compare and contrast resting potential and action potential.
How does a nerve impulse travel the length of a nerve? How is this process different in myelenated fibers vs unmyelinated fibers?
Describe the process of synaptic transmission.
Compare and contrast exitatory and inhibitory actions by neurons.
What are neurotransmitters? Where are they synthesized and stored? How do they act?
Compare and contrast facilitatation, convergence, and divergence.
What is a reflex arc? List the steps involved.
What are meninges? Describe the three types found in the skull.
Compare and contrast white matter and gray matter.
Describe each of the functional divisions of the brain.
What is hemisphere dominance? What functions are performed by the dominant hemisphere? by the non-dominant hemisphere?
Compare and contrast the sympathetic and parasympathetic nervous systems.
List the 5 general types of receptors and state what each detects.
What is sensory adaptation and why is it important?
What is referred pain and why does it occur?
Compare and contrast acute and chronic pain.
Compare and contrast the olfactory and taste senses.
Describe the process of hearing a sound beginning with the sound entering the external auditory meatus.
Compare and contrast static and dynamic equilibrium.
Compare and contrast rods and cones.
Compare and contrast steroid and non-steroid hormones.
Give a detailed example of a negative feedback mechanism involving hormones.
Describe the three basic types of blood cells.
What is hemoglobin? How is it broken down?
What are the 5 types of leukocytes and how are they characterized?
Describe blood plasma and list its major constituents.
Describe the stages of hemostasis.
Why is AB blood the universal acceptor? Why is O blood the universal donor?
What would happen if AB type blood were transfused into a patient with type O blood? (be specific)
Compare and contrast the pulmonary circuit and systemic circuit.
Explain the steps of the cardiac cycle.
What is an electrocardiogram and what does each point in the graph represent?
Compare and contrast arteries, capillaries, and veins.
Describe the exchange of substances between capillaries and surrounding tissues.
195
Describe the factors that effect arterial blood pressure.