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Chapter # 9
Nervous System
A. Introduction
1. The nervous system is the control center
and communication network within the
It monitors the sate of the body,
processes the information, and initiates
a response.
_________ function – monitor
___________ function – ability to
process the information
_________ function – initiating a
B. Divisions of the Nervous system
• 1. Central Nervous System (CNS)
– ___________ and spinal cord
– Located along midline of body
– All sensory impulses go to______, all motor
impulses _______________ from the CNS
• 2. Peripheral Nervous System (PNS)
– Include the nerves____________ the CNS
• Cranial nerves – originate from the brain to supply
head and neck
• Spinal nerves – originate from the spinal cord to
supply body below the head
– a. ___________ System – voluntary (conscious) nervous
– b. _____________System – involuntary (unconscious)
nervous system
» Sympathetic - “fight or flight" response
» Parasympathetic – “rest-repose”
C. Nerve Tissue
• Nerve tissues primary function is to
conduct impulses.
• There are two categories of cells
– Neuroglia and neurons
1. Neuroglia
• Cells that help __________and maintain
the neurons.
• These cells make up ____ of the brain and
spinal cord.
– Astrocytes
– Ependymal cells
– Microglia
– Oligodendrocytes
– Schwann cells
Supporting cells
A. Classification of Neuroglial Cells
Neuroglial cells ____spaces, ______
neurons, provide structural frameworks,
produce myelin, and carry on
phagocytosis. Four are in the CNS and
the last in the PNS.
Microglial cells are small cells that
_____________ bacterial cells and cellular
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
3. Oligodendrocytes form _______ in the
brain and spinal cord.
Astrocytes are near blood vessels and
support structures, aid in metabolism,
and respond to brain injury by filling in
Ependyma cover the inside of
ventricles and form choroid plexuses
within the ventricles.
Schwann cells are the _______
producing neuroglia of the peripheral
nervous system.
2. Neurons
• The structural and
functional units of the
nerve tissue.
• a. Structure:
– ___________ – contains
nucleus and cytoplasm
– ______________ – thin
branching extensions of
the cell body
– _____ – carries impulses
away from the cell body.
Also called a nerve fiber
– 1. Myelinated vs unmyelinated
• myelin sheath created by the
_________ cells form a
protective covering around the
axon. This creates white matter
• _____________________ – gap
between myelin sheath
• Unmyelinated lacks the schwann
cells and creates gray matter
b. Types of Neurons
• 1. Structural differences
– ___________ – many dendrites
arising from the cell body, and a
single axon.
– CNS to muscle
– _________ – single dendrite and
single axon from cell body in
opposite directions.
– Eyes, ears, nose.
– ___________– single nerve fiber
extending from the cell body
branching to spinal cord and other
to periphery. Skin to spinal cord
• 2. Functional differences
– ___________neurons – (afferent neurons)
carry nerve impulses from a peripheral part of
the body to the CNS. unipolar
– ____________ neurons – (interneurons)
located within the CNS. They form a link
between neurons. Multipolar
– ________ neurons – (efferent neurons) carry
nerve impulses from CNS to parts of the
body. Multipolar
c. Function
• A nerve impulse is similar to the flow of
electricity through an insulated wire
• 1. _______ Potential – at rest
a neuron has an uneven
distribution of ions across its
– It has a higher concentration of
_________ outside the
membrane than inside.
Making the inside more
– The sodium-potassium pump
will pump Na+ out and K+ in.
– A neuron that has a resting
potential is called __________.
2. Action Potential
• Neurons have excitability (respond to
change in environment)
• A stimulus great enough to alter the resting
membrane potential will cause the
membrane to change and become
permeable to Na+.
• _______ will move into the membrane and
cause the charge to become more positive.
• This is called _________________.
• Immediately after
the depolarization,
the K+ flow out of
the axon to
repolarize the
• This is called an
or nerve impulse.
3. Conduction of Nerve Impulse
• The action potential spreads from one points
along the length of the neuron.
• The speed of a nerve impulse is extremely rapid
(1/1000 second) and does not vary in
• _______ conduction is found in myelinated fiber.
The impulse jumps from one ______________
to the next
4. All or None Response
• If a stimulus is strong enough to cause an
action potential the nerve will conduct the
__________________ of the nerve fiber.
• ___________stimulus – minimum strength
required to initiate an action potential.
– Increasing the strength of the stimulus has no
effect on action potential.
– Sub-threshold stimuli cannot initiate an
impulse but can have a cumulative affect
called summation.
5. Transmission of Impulses from
cell to cell
• Junction between neurons is called a
– ______________neuron – neuron that sends
the impulse to the synapse
– __________ neuron – neuron that receives
the impulse.
– The presynaptic neuron ends with a synaptic
end bulb, which contain synaptic vesicles
which contain __________________.
– The neurotransmitters cross the synaptic cleft
to the post synaptic neuron
Figure 9.08 Synaptic Transmission at a Chemical Synapse
6. Excitatory vs. Inhibitory
• A transmission involving neurotransmitters
that increase the postsynaptic membrane
permeability to Na+ is called an ________
– Examples: Acetylcholine and Norepinephrine
• A transmission that decreases the
permeability to Na+ is called an ________
– Examples: Endorphins and GABA
7. Processing at the synapse
• A post synaptic neuron may have
thousands of presynaptic neurons
affecting it. The overall effect on the
postsynaptic membrane is determined by
the sum of the effects from excitatory and
inhibitory neurotransmitters
• Chemicals and their influence
– Stimulants
– Depressants
– Antidepressants
– Psychedelic drugs
– Analgesics
D. The Central Nervous System
• Contains the brain and spinal cord
1. The Spinal Cord
• The spinal cord is a long bundle of nerves
that extended from the base of the brain to
about the ___________ lumbar vertebra
• It provides the connection between the
brain and peripheral nerves
a. Protective Coverings
• The spinal cord is protected by the:
– Vertebral Column – ___________
– ____________fluid (CSF) – liquid cushion that
provides for shock absorption
– Meninges – 3 layers of membranes around
• ___________ – outer layer
• Arachnoid – middle layer
• __________ – inner layer
– The space between the arachnoid and pia mater is filled
with CSF
b. Structure
• The cord consists of _____ segments, and
each contain a pair of spinal nerves
• Its cross section contains white and gray
– 1. Gray matter distribution – contains
unmyelinated fibers and neuron bodies.
– It occupies the center of the cord in the shape
of an ______.
– It consists of the posterior gray horns
(sensory) and the anterior gray horns (motor)
– 2. White matter
distribution –
___________ fibers
and surrounds the
gray matter
c. Function
• 1. Conduction pathways – descending
(motor) and ascending (sensory) tracts
• 2. Reflex center – A spinal reflex is a rapid
signal the bypasses the higher brain
centers for reduced response time.
– a. ____________ – involves a sensory
receptor, sensory neuron, reflex center in
spinal cord and motor neuron
– b. Somatic – stimulate skeletal muscle
– Visceral – stimulate or inhibit visceral
organs (heart rate, breathing, vomiting,
sneezing, coughing)
2. The Brain
• Divided into 3 regions
– __________ –
Cerebrum and
– __________– smallest
– ___________ – pons,
medulla oblongata,
and cerebellum
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
 Brain
A. The brain is the largest, most complex
portion of the nervous system,
containing 100 billion multipolar
B. The brain can be divided into the
________ (largest portion and associated with
higher mental functions), the diencephalon
(processes sensory input), the ___________
(coordinates muscular activity), and the
____________ (coordinates and regulates
visceral activities).
a. Protective covering
– Cranium – bone
– CSF – fluid around brain
– Meninges – membranes around brain and
spinal cord ( pia mater, arachnoid and dura
Cerebrospinal fluid and
ventricles of the brain
– 1. _______________ - cavities in the brain
that produce CSF
– 2. CSF production and circulation - fluid
flows within arachnoid space and then
returned to blood stream
c. Cerebrum
• Largest structure of the brain
• Contains _____________
attached by the corpus
• External region is called the
cerebral _______ (gray
matter), underlying is white
• Function: controls complex
thought, voluntary movement,
language, reasoning and
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
The lobes of the brain are named
according to the bones they
underlie and include the frontal
lobe, parietal lobe, temporal lobe,
occipital lobe, and insula.
A thin layer of gray matter, the
cerebral cortex, lies on the
outside of the cerebrum and
contains 75% of the cell bodies in
the nervous system.
d. Diencephalon
• Contains the
• Located inferior
to the corpus
• This together
with the
cerebrum make
up the forebrain
1. Thalamus
• Largest portion of the diencephalon
• Acts as a relay station for most sensory
impulses on their way to the cerebral
cortex and voluntary motor impulses
traveling out
2. Hypothalamus
• Located below the
• Controls the
__________ nervous
– Body temperature
– Emotions
– Hunger
– Thirst
e. Midbrain
• -Above the pons
between the hindbrain
and forebrain
• ___________ sensory
information from the
spinal cord to the
– Relay for rapid eye, head
and trunk movements
f. Pons
• Bridge between
spinal cord and brain
g. Medulla Oblongata
• At the top of the
• Controls breathing, heart
rate, and blood pressure.
• Brainstem –
– midbrain
– Pons
– medulla
h. Cerebellum
• At the lower rear
• Divided into 2
• Controls movement,
__________, posture
• “automatic pilot” for
the motor responses,
keeps muscle
movements smooth
E. The Peripheral Nervous System
• The peripheral nervous system provides a
________________________ pathway for
impulses traveling between the CNS and
the other parts of the body.
• It consists of nerves, ganglia, and sensory
1. Organs of the PNS
• a. Nerves and ganglia – a nerve is a true organ,
composed of many tissues. ( nerve vs. nerve
– _____________ – carry impulses to CNS
– __________ – carry impulses away from the CNS
– Mixed – contain fibers from both sensory and motor
• Ganglia – cluster of neuron cell bodies located
outside the CNS
• b. ___________________ – structures that are
specialized to respond to stimuli.
– Simple (touch, pain, temperature) to complex ( eyes,
2. Cranial Nerves
• Nerves attached directly to the brain
• There are 12 pair of cranial nerves that
extend through the cranium to supply head
and neck.
• See page 265
Cranial Nerve
Brain Region
Major Functions
Cerebral Cortex
Limbic System
Eyelid & eyeball
pupil dilation
Control downward & lateral
eye movement
Chewing; sensation of face &
Control lateral eye movement
Control most facial
expressions; secretion of tears & saliva; taste; ear sensation
Hearing; balance
Glossopharyngeal 9“
Taste; swallowing; sensation from
tongue, tonsil, pharynx, carotid blood pressure
Sensory, motor and
autonomic functions of viscera - glands, digestion, heart rate, breathing rate, aortic
blood pressure
Spinal Accessory 11“
Controls muscles used in head
Controls tongue movements
3. Spinal Nerves
• There are 31
pair that
attach directly
to the spinal
cord, one pair
each segment.
4. Somatic System
• Part of the PNS that controls
________________ activities.
• The sensory component receives
information from skin organs and sensory
• The motor neuron always terminate in
___________, which are skeletal muscle.
5. Autonomic System
• Part of the PNS that is under
________________ control.
• Sensory pathway leads to hypothalamus,
brain stem or spinal cord.
• Motor neurons are complex.
a. Sympathetic division
• Processes that uses energy.
• Called the ___________________system
b. Parasympathetic division
• Processes that conserve energy.
• Called the ___________________ system