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Chapter 7
The Nervous System
Lecture Presentation by
Patty Bostwick-Taylor
Florence-Darlington Technical College
© 2015 Pearson Education, Inc.
Functions of the Nervous System
1. Sensory input—gathering information
 To monitor changes occurring inside and outside the
body
 Changes  stimuli
2. Integration
 To process and interpret sensory input and decide
whether action is needed
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Functions of the Nervous System
3. Motor output
 A response to integrated stimuli
 The response activates muscles or glands
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Figure 7.1 The nervous system’s functions.
Sensory input
Sensory receptor
Motor output
Brain and spinal cord
Effector
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Organization of the Nervous System
 Nervous system is classified based on:
 Structures (structural classification)
 Activities (functional classification)
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Structural Classification of the Nervous
System
 Central nervous system (CNS)
 Organs
 Brain
 Spinal cord
 Function
 Integration; command center
 Interpret incoming sensory information
 Issues outgoing instructions
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Structural Classification of the Nervous
System
 Peripheral nervous system (PNS)
 Nerves extending from the brain and spinal cord
 Spinal nerves—carry impulses to and from the spinal
cord
 Cranial nerves—carry impulses to and from the brain
 Functions
 Serve as communication lines among sensory organs,
the brain and spinal cord, and glands or muscles
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Figure 7.2 Organization of the nervous system.
Central Nervous System
(brain and spinal cord)
Peripheral Nervous System
(cranial and spinal nerves)
Sensory
(afferent)
Sense
organs
Motor
(efferent)
Somatic
(voluntary)
Autonomic
(involuntary)
Skeletal
muscles
Cardiac and
smooth muscle,
glands
Parasympathetic
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Sympathetic
Functional Classification of the Peripheral
Nervous System
 Sensory (afferent) division
 Nerve fibers that carry information to the central
nervous system
 Somatic sensory fibers carry information from the
skin, skeletal muscles, and joints
 Visceral sensory fibers carry information from visceral
organs
 Motor (efferent) division
 Nerve fibers that carry impulses away from the
central nervous system organs
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Figure 7.2 Organization of the nervous system.
Central Nervous System
(brain and spinal cord)
Peripheral Nervous System
(cranial and spinal nerves)
Sensory
(afferent)
Sense
organs
Motor
(efferent)
Somatic
(voluntary)
Autonomic
(involuntary)
Skeletal
muscles
Cardiac and
smooth muscle,
glands
Parasympathetic
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Sympathetic
Functional Classification of the Peripheral
Nervous System
 Motor (efferent) division (continued)
 Two subdivisions
 Somatic nervous system  voluntary
 Consciously controls skeletal muscles
 Autonomic nervous system  involuntary
 Automatically controls smooth and cardiac muscles
and glands
 Further divided into the sympathetic and
parasympathetic nervous systems
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Nervous Tissue: Support Cells
 Support cells in the CNS are grouped together as
neuroglia
 General functions
 Support
 Insulate
 Protect neurons
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Nervous Tissue: Support Cells
 CNS glial cells: astrocytes
 Abundant, star-shaped cells
 Brace neurons
 Form barrier between capillaries and neurons
 Control the chemical environment of
the brain
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Figure 7.3a Supporting (glial) cells of nervous tissue.
Capillary
Neuron
Astrocyte
(a) Astrocytes are the most abundant
and versatile neuroglia.
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Nervous Tissue: Support Cells
 CNS glial cells: microglia
 Spiderlike phagocytes
 Dispose of debris
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Figure 7.3b Supporting (glial) cells of nervous tissue.
Neuron
Microglial
cell
(b) Microglial cells are phagocytes that
defend CNS cells.
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Nervous Tissue: Support Cells
 CNS glial cells: ependymal cells
 Line cavities of the brain and spinal cord
 Cilia assist with circulation of cerebrospinal fluid
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Figure 7.3c Supporting (glial) cells of nervous tissue.
Fluid-filled cavity
Ependymal
cells
Brain or
spinal cord
tissue
(c) Ependymal cells line cerebrospinal
fluid-filled cavities.
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Nervous Tissue: Support Cells
 CNS glial cells: oligodendrocytes
 Wrap around nerve fibers in the central nervous
system
 Produce myelin sheaths
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Figure 7.3d Supporting (glial) cells of nervous tissue.
Myelin sheath
Process of
oligodendrocyte
Nerve
fibers
(d) Oligodendrocytes have processes that form
myelin sheaths around CNS nerve fibers.
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Nervous Tissue: Support Cells
 PNS glial cells
 Satellite cells
 Protect neuron cell bodies
 Schwann cells
 Form myelin sheath in the peripheral nervous system
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Figure 7.3e Supporting (glial) cells of nervous tissue.
Satellite
cells
Cell body of neuron
Schwann cells
(forming myelin sheath)
Nerve fiber
(e) Satellite cells and Schwann cells (which
form myelin) surround neurons in the PNS.
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Nervous Tissue: Neurons
 Neurons  nerve cells
 Cells specialized to transmit messages
 Major regions of neurons
 Cell body—nucleus and metabolic center of the cell
 Processes—fibers that extend from the cell body
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Nervous Tissue: Neurons
 Cell body
 Nissl bodies
 Specialized rough endoplasmic reticulum
 Neurofibrils
 Intermediate cytoskeleton
 Maintains cell shape
 Nucleus with large nucleolus
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Figure 7.4a Structure of a typical motor neuron.
Mitochondrion
Dendrite
Cell body
Nissl substance
Axon hillock
Axon
Neurofibrils
Nucleus
Collateral
branch
One Schwann cell
Axon
terminal
(a)
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Node of Ranvier
Schwann cells,
forming the myelin
sheath on axon
Figure 7.4b Structure of a typical motor neuron.
Neuron
cell body
Dendrite
(b)
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Nervous Tissue: Neurons
 Processes outside the cell body
 Dendrites—conduct impulses toward the cell body
 Neurons may have hundreds of dendrites
 Axons—conduct impulses away from the cell body
 Neurons have only one axon arising from the cell
body at the axon hillock
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Figure 7.4a Structure of a typical motor neuron.
Mitochondrion
Dendrite
Cell body
Nissl substance
Axon hillock
Axon
Neurofibrils
Nucleus
Collateral
branch
One Schwann cell
Axon
terminal
(a)
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Node of Ranvier
Schwann cells,
forming the myelin
sheath on axon
Nervous Tissue: Neurons
 Axons
 End in axon terminals
 Axon terminals contain vesicles with
neurotransmitters
 Axon terminals are separated from the next neuron
by a gap
 Synaptic cleft—gap between adjacent neurons
 Synapse—junction between nerves
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Nervous Tissue: Neurons
 Myelin sheath—whitish, fatty material covering
axons
 Schwann cells—produce myelin sheaths in jelly roll–
like fashion around axons (PNS)
 Nodes of Ranvier—gaps in myelin sheath along the
axon
 Oligodendrocytes—produce myelin sheaths around
axons of the CNS
 Myelin sheaths speed the nerve impulse
transmission
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Figure 7.5 Relationship of Schwann cells to axons in the peripheral nervous system.
Schwann cell
cytoplasm
Axon
Schwann cell
plasma membrane
(a)
Schwann cell
nucleus
(b)
Neurilemma
Myelin
sheath
(c)
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Neuron Cell Body Location
 Most neuron cell bodies are found in the central
nervous system
 Gray matter—cell bodies and unmyelinated fibers
 Nuclei—clusters of cell bodies within the white
matter of the central nervous system
 Ganglia—collections of cell bodies outside the
central nervous system
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Neuron Cell Body Location
 Tracts—bundles of nerve fibers in the CNS
 Nerves—bundles of nerve fibers in the PNS
 White matter—collections of myelinated fibers
(tracts)
 Gray matter—collections of mostly unmyelinated
fibers and cell bodies
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Functional Classification of Neurons
 Sensory (afferent) neurons
 Carry impulses from the sensory receptors to the
CNS
 Cutaneous sense organs
 Proprioceptors—detect stretch or tension
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Figure 7.6 Neurons classified by function.
Central process (axon)
Sensory
Spinal cord
Cell neuron
(central nervous system)
body
Ganglion
Dendrites
Peripheral
process (axon)
Afferent
transmission
Interneuron
(association
neuron)
Peripheral
nervous system
Receptors
Efferent transmission
Motor neuron
To effectors
(muscles and glands)
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Figure 7.7a Types of sensory receptors.
(a) Free nerve endings (pain
and temperature receptors)
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Figure 7.7b Types of sensory receptors.
(b) Meissner’s corpuscle
(touch receptor)
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Figure 7.7c Types of sensory receptors.
(c) Lamellar corpuscle (deep
pressure receptor)
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Figure 7.7d Types of sensory receptors.
(d) Golgi tendon organ
(proprioceptor)
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Figure 7.7e Types of sensory receptors.
(e) Muscle spindle
(proprioceptor)
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Functional Classification of Neurons
 Motor (efferent) neurons
 Carry impulses from the central nervous system to
viscera, muscles, or glands
 Interneurons (association neurons)
 Found in neural pathways in the central nervous
system
 Connect sensory and motor neurons
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Figure 7.6 Neurons classified by function.
Central process (axon)
Sensory
Spinal cord
Cell neuron
(central nervous system)
body
Ganglion
Dendrites
Peripheral
process (axon)
Afferent
transmission
Interneuron
(association
neuron)
Peripheral
nervous system
Receptors
Efferent transmission
Motor neuron
To effectors
(muscles and glands)
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Structural Classification of Neurons
 Structural classification is based on number of
processes extending from the cell body
 Multipolar neurons—many extensions from the cell
body
 All motor and interneurons are multipolar
 Most common structure
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Figure 7.8a Classification of neurons on the basis of structure.
Cell body
Axon
Dendrites
(a) Multipolar neuron
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Structural Classification of Neurons
 Bipolar neurons—one axon and one dendrite
 Located in special sense organs, such as nose and
eye
 Rare in adults
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Figure 7.8b Classification of neurons on the basis of structure.
Cell body
Dendrite
(b) Bipolar neuron
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Axon
Structural Classification of Neurons
 Unipolar neurons—have a short single process
leaving the cell body
 Sensory neurons found in PNS ganglia
 Conduct impulses both toward and away from the
cell body
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Figure 7.8c Classification of neurons on the basis of structure.
Dendrites
Cell body
Short single
process
Axon
Peripheral
process
(c) Unipolar neuron
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Central
process
Functional Properties of Neurons
 Irritability
 Ability to respond to a stimulus and convert it to a
nerve impulse
 Conductivity
 Ability to transmit the impulse to other neurons,
muscles, or glands
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Nerve Impulses
 Resting neuron
 The plasma membrane at rest is polarized
 As long as inside is more negative than outside, the
cell stays at rest
 Fewer positive ions are inside the cell than outside
the cell
 K is the major positive ion inside the cell
 Na is the major positive ion outside the cell
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Figure 7.9 The nerve impulse.
Slide 2
[Na+]
[K+]
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1 Resting membrane is polarized. In the resting state, the
external face of the membrane is slightly positive; its internal
face is slightly negative. The chief extracellular ion is sodium
(Na+), whereas the chief intracellular ion is potassium (K+).
The membrane is relatively impermeable to both ions.
Nerve Impulses
 Action potential initiation and generation
 A stimulus depolarizes the neuron’s membrane
 The membrane is now permeable to sodium as
sodium channels open
 A depolarized membrane allows sodium (Na) to flow
inside the membrane
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Figure 7.9 The nerve impulse.
Na+
Na+
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Slide 3
2 Stimulus initiates local depolarization. A Stimulus
changes the permeability of a local “patch” of the membrane,
and sodium ions diffuse rapidly into the cell. This changes the
polarity of the membrane (the inside becomes more positive;
the outside becomes more negative) at that site.
Nerve Impulses
 Action potential initiation and generation
 A stimulus leads to the movement of ions, which
initiates an action potential in the neuron
 A graded potential (localized depolarization) exists
where the inside of the membrane is more positive
and the outside is less positive
 If the stimulus is strong enough and sodium influx
great enough, local depolarization activates the
neuron to conduct an action potential (nerve
impulse)
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Figure 7.9 The nerve impulse.
Na+
Na+
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Slide 4
3 Depolarization and generation of an action potential.
If the stimulus is strong enough, depolarization causes
membrane polarity to be completely reversed and an action
potential is initiated.
Nerve Impulses
 Propagation of the action potential
 If enough sodium enters the cell, the action potential
(nerve impulse) starts and is propagated over the
entire axon
 All-or-none response means the nerve impulse either
is propagated or is not
 Fibers with myelin sheaths conduct nerve impulses
more quickly
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Figure 7.9 The nerve impulse.
Slide 5
4 Propagation of the action potential. Depolarization of
the first membrane patch causes permeability changes in the
adjacent membrane, and the events described in step 2 are
repeated. Thus, the action potential propagates rapidly along
the entire length of the membrane.
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Nerve Impulses
 Repolarization
 Potassium ions rush out of the neuron after sodium
ions rush in, repolarizing the membrane
 Repolarization involves restoring the inside of the
membrane to a negative charge and the outer
surface to a positive charge
 Until repolarization is complete, a neuron cannot
conduct another nerve impulse
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Figure 7.9 The nerve impulse.
K+
K+
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Slide 6
5 Repolarization. Potassium ions diffuse out of the cell as
the membrane permeability changes again, restoring the
negative charge on the inside of the membrane and the
positive charge on the outside surface. Repolarization occurs
in the same direction as depolarization.
Nerve Impulses
 Repolarization
 Initial ionic conditions are restored using the sodiumpotassium pump
 This pump, using ATP, restores the original
configuration
 Three sodium ions are ejected from the cell while
two potassium ions are returned to the cell
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Figure 7.9 The nerve impulse.
Na+
Na+
Na+
Na+ Diffusion
K+ Diffusion
Cell
exterior
Slide 7
Cell
interior
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K+
K+
K+
K+
Na+ – K+
pump
6 Initial ionic conditions restored. The ionic conditions
of the resting state are restored later by the activity of the
Plasma
membrane sodium-potassium pump. Three sodium ions are ejected for
every two potassium ions carried back into the cell.
Transmission of a Signal at Synapses
 When the action potential reaches the axon
terminal, the electrical charge opens calcium
channels
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Figure 7.10 How neurons communicate at chemical synapses.
Slide 2
Axon of
transmitting
neuron
Receiving
neuron
1 Action
Dendrite
Axon terminal
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potential
arrives.
Vesicles
Synaptic
cleft
Transmission of a Signal at Synapses
 Calcium, in turn, causes the tiny vesicles containing
the neurotransmitter chemical to fuse with the
axonal membrane
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Figure 7.10 How neurons communicate at chemical synapses.
Slide 3
2 Vesicle Transmitting neuron
fuses with
plasma
membrane.
Synaptic
cleft
Ion
channels
Receiving neuron
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Neurotransmitter
molecules
Transmission of a Signal at Synapses
 The entry of calcium into the axon terminal causes
porelike openings to form, releasing the transmitter
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Figure 7.10 How neurons communicate at chemical synapses.
Slide 4
2 Vesicle Transmitting neuron
fuses with
plasma
membrane.
3 Neurotrans-
mitter is
released into
synaptic cleft.
Synaptic
cleft
Ion
channels
Receiving neuron
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Neurotransmitter
molecules
Transmission of a Signal at Synapses
 The neurotransmitter molecules diffuse across the
synapse and bind to receptors on the membrane of
the next neuron
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Figure 7.10 How neurons communicate at chemical synapses.
Slide 5
2 Vesicle Transmitting neuron
4 Neurotransfuses with
3 Neurotrans- mitter binds
plasma
membrane.
mitter is
released into
synaptic cleft.
Synaptic
cleft
Ion
channels
Receiving neuron
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to receptor
on receiving
neuron’s
membrane.
Neurotransmitter
molecules
Transmission of a Signal at Synapses
 If enough neurotransmitter is released, graded
potential will be generated
 Eventually an action potential (nerve impulse) will
occur in the neuron beyond the synapse
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Figure 7.10 How neurons communicate at chemical synapses.
Slide 6
Neurotransmitter
Receptor
Na+
5 Ion channel opens.
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Transmission of a Signal at Synapses
 The electrical changes prompted by
neurotransmitter binding are brief
 The neurotransmitter is quickly removed from the
synapse by either:
 Reuptake
 Enzymatic activity
 Transmission of an impulse is electrochemical
 Transmission down neuron is electrical
 Transmission to next neuron is chemical
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Figure 7.10 How neurons communicate at chemical synapses.
Slide 7
Neurotransmitter
is broken down
and released.
Na+
6 Ion channel closes.
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The Reflex Arc
 Reflexes are:
 Rapid
 Predictable
 Involuntary responses to a stimulus
 Reflexes occur over neural pathways called reflex
arcs
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Figure 7.11a Simple reflex arcs.
Stimulus at distal
end of neuron
1
2
Receptor
5
Effector
(a) Five basic elements of reflex arc
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Spinal cord
(in cross section)
Skin
Sensory
neuron
4
Motor neuron
3
Integration
center
Interneuron
The Reflex Arc
 Somatic reflexes
 Reflexes that stimulate the skeletal muscles
 Example: pulling your hand away from a hot object
 Autonomic reflexes
 Regulate the activity of smooth muscles, the heart,
and glands
 Example: regulation of smooth muscles, heart and
blood pressure, glands, digestive system
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The Reflex Arc
 Five elements of a reflex:
1. Sensory receptor—reacts to a stimulus
2. Sensory neuron—carries message to the
integration center
3. Integration center (CNS)—processes information
and directs motor output
4. Motor neuron—carries message to an effector
5. Effector organ—is the muscle or gland to be
stimulated
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Figure 7.11a Simple reflex arcs.
Slide 6
Stimulus at distal
end of neuron
1
2
Receptor
5
Effector
(a) Five basic elements of reflex arc
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Spinal cord
(in cross section)
Skin
Sensory
neuron
4
Motor neuron
3
Integration
center
Interneuron
Two-Neuron Reflex Arc
 Two-neuron reflex arcs
 Simplest type
 Example: patellar (knee-jerk) reflex
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Figure 7.11b Simple reflex arcs.
Slide 1
1 Sensory (stretch) receptor
2 Sensory (afferent)
neuron
3
4 Motor (efferent) neuron
5 Effector organ
(b) Two neuron reflex arc
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Three-Neuron Reflex Arc
 Three-neuron reflex arcs
 Consists of five elements: receptor, sensory neuron,
interneuron, motor neuron, and effector
 Example: flexor (withdrawal) reflex
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Figure 7.11c Simple reflex arcs.
1
Slide 1
Sensory receptor
2
Sensory (afferent)
neuron
3
4
5
(c) Three-neuron reflex arc
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Motor (efferent) neuron
Effector organ
Interneuron
Central Nervous System (CNS)
 CNS develops from the embryonic neural tube
 The neural tube becomes the brain and spinal cord
 The opening of the neural tube becomes the
ventricles
 Four chambers within the brain
 Filled with cerebrospinal fluid
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Figure 7.12a Development and regions of the human brain.
(a) 13 weeks
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Cerebral
hemisphere
Outline of
diencephalon
Midbrain
Cerebellum
Brain stem
Figure 7.18a Ventricles and location of the cerebrospinal fluid.
Lateral ventricle
Anterior horn
Septum
pellucidum
Interventricular
foramen
Inferior
horn
Third ventricle
Cerebral aqueduct
Fourth ventricle
Lateral
aperture
Central canal
(a) Anterior view
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Regions of the Brain
 Cerebral hemispheres (cerebrum)
 Diencephalon
 Brain stem
 Cerebellum
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Figure 7.12b Development and regions of the human brain.
Cerebral
hemisphere
Diencephalon
Cerebellum
(b) Adult brain
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Brain stem
Table 7.1 Functions of Major Brain Regions (1 of 2)
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Table 7.1 Functions of Major Brain Regions (2 of 2)
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Regions of the Brain: Cerebrum
 Cerebral hemispheres are paired (left & right)
superior parts of the brain
 Includes more than half of the brain mass
 The surface is made of ridges (gyri) and grooves
(sulci)
 Three main regions of cerebral hemisphere
1. Cortex (gray matter)
2. White matter
3. Basal nuclei (deep pockets of gray matter)
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Figure 7.13a Left lateral view of the brain.
Precentral
gyrus
Central sulcus
Postcentral gyrus
Parietal lobe
Parieto-occipital
sulcus (deep)
Frontal lobe
Lateral sulcus
Occipital lobe
Temporal lobe
Cerebellum
Pons
Cerebral cortex
(gray matter)
Gyrus
Sulcus
Fissure
(a) (a deep sulcus)
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Cerebral
white
matter
Medulla
oblongata
Spinal
cord
Regions of the Brain: Cerebrum
 Lobes of the cerebrum
 Fissures (deep grooves) divide the cerebrum into
lobes
 Surface lobes of the cerebrum
 Frontal lobe
 Parietal lobe
 Occipital lobe
 Temporal lobe
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Figure 7.13b Left lateral view of the brain.
Parietal lobe
Left cerebral
hemisphere
Frontal
lobe
Occipital
lobe
Temporal
lobe
Cephalad
(b)
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Caudal
Brain
stem
Cerebellum
Regions of the Brain: Cerebrum
 Specialized areas of the cerebrum
 Primary somatic sensory area
 Receives impulses from the body’s sensory receptors
 Pain, temperature, light touch
 Located in parietal lobe posterior to central sulcus
 Sensory homunculus is a spatial map
 Left side of the primary somatic sensory area receives
impulses from right side (and vice versa)
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Figure 7.13c Left lateral view of the brain.
Primary motor area
Premotor area
Speech/language
(outlined by dashes)
Posterior
association
area
• Problem
solving
• Language
comprehension
Broca’s area
(motor speech)
Olfactory
area
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Primary somatic
sensory area
Gustatory area
(taste)
Anterior
association area
• Working
memory and
judgment
(c)
Central sulcus
Visual area
Auditory area
Regions of the Brain: Cerebrum
 Cerebral areas involved in special senses
 Visual area (occipital lobe)
 Auditory area (temporal lobe)
 Olfactory area (temporal lobe)
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Regions of the Brain: Cerebrum
 Specialized areas of the cerebrum
 Primary motor area
 Sends impulses to skeletal muscles
 Located in frontal lobe
 Motor neurons form corticospinal (pyramidal) tract,
which descends to spinal cord
 Motor homunculus is a spatial map
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Regions of the Brain: Cerebrum
 Broca’s area
 Involved in our ability to speak
 Usually in left hemisphere
 Other specialized areas
 Anterior and posterior association areas
 Speech area
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Regions of the Brain: Cerebrum
 Layers of the cerebrum
 Gray matter—outer layer in the cerebral cortex;
composed mostly of neuron cell bodies
 White matter—fiber tracts deep to the gray matter
 Corpus callosum connects hemispheres
 Basal nuclei (ganglia)—islands of gray matter
buried within the white matter
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Figure 7.13a Left lateral view of the brain.
Precentral
gyrus
Central sulcus
Postcentral gyrus
Parietal lobe
Parieto-occipital
sulcus (deep)
Frontal lobe
Lateral sulcus
Occipital lobe
Temporal lobe
Cerebellum
Pons
Cerebral cortex
(gray matter)
Gyrus
Sulcus
Fissure
(a) (a deep sulcus)
© 2015 Pearson Education, Inc.
Cerebral
white
matter
Medulla
oblongata
Spinal
cord
Figure 7.15 Frontal section of the brain showing commissural, association, and projection fibers running through the cerebrum and the lower CNS.
Longitudinal fissure
Lateral
ventricle
Basal nuclei
(basal
ganglia)
Superior
Association fibers
Commissural fibers
(corpus callosum)
Corona
radiata
Fornix
Thalamus
Internal
capsule
Third
ventricle
Pons
Medulla oblongata
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Projection
fibers
Regions of the Brain: Diencephalon
 Sits on top of the brain stem
 Enclosed by the cerebral hemispheres
 Made of three parts:
1. Thalamus
2. Hypothalamus
3. Epithalamus
© 2015 Pearson Education, Inc.
Figure 7.12b Development and regions of the human brain.
Cerebral
hemisphere
Diencephalon
Cerebellum
(b) Adult brain
© 2015 Pearson Education, Inc.
Brain stem
Figure 7.16a Diencephalon and brain stem structures.
Cerebral hemisphere
Corpus callosum
Third ventricle
Choroid plexus of third
ventricle
Occipital lobe of
cerebral hemisphere
Thalamus
(encloses third ventricle)
Pineal gland
(part of epithalamus)
Anterior
commissure
Hypothalamus
Corpora quadrigemina
Optic chiasma
Cerebral aqueduct
Pituitary gland
Cerebral peduncle
(a)
Mammillary body
Pons
Medulla oblongata
Spinal cord
© 2015 Pearson Education, Inc.
Fourth ventricle
Choroid plexus
Cerebellum
Midbrain
Figure 7.16b Diencephalon and brain stem structures.
Radiations
to cerebral
cortex
Visual impulses
Reticular formation
Ascending general sensory
tracts (touch, pain, temperature)
(b)
© 2015 Pearson Education, Inc.
Auditory
impulses
Descending
motor projections
to spinal cord
Regions of the Brain: Diencephalon
 Thalamus
 Surrounds the third ventricle
 The relay station for sensory impulses
 Transfers impulses to the correct part of the cortex
for localization and interpretation
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Regions of the Brain: Diencephalon
 Hypothalamus
 Under the thalamus
 Important autonomic nervous system center
 Helps regulate body temperature
 Controls water balance
 Regulates metabolism
 Houses the limbic center for emotions
 Regulates the nearby pituitary gland
 Houses mammillary bodies for olfaction (smell)
© 2015 Pearson Education, Inc.
Regions of the Brain: Diencephalon
 Epithalamus
 Forms the roof of the third ventricle
 Houses the pineal body (an endocrine gland)
 Includes the choroid plexus—forms cerebrospinal
fluid
© 2015 Pearson Education, Inc.
Regions of the Brain: Brain Stem
 Attaches to the spinal cord
 Parts of the brain stem
 Midbrain
 Pons
 Medulla oblongata
© 2015 Pearson Education, Inc.
Figure 7.16a Diencephalon and brain stem structures.
Cerebral hemisphere
Corpus callosum
Third ventricle
Choroid plexus of third
ventricle
Occipital lobe of
cerebral hemisphere
Thalamus
(encloses third ventricle)
Pineal gland
(part of epithalamus)
Anterior
commissure
Hypothalamus
Corpora quadrigemina
Optic chiasma
Cerebral aqueduct
Pituitary gland
Cerebral peduncle
(a)
Mammillary body
Pons
Medulla oblongata
Spinal cord
© 2015 Pearson Education, Inc.
Fourth ventricle
Choroid plexus
Cerebellum
Midbrain
Regions of the Brain: Brain Stem
 Midbrain
 Composed mostly of tracts of nerve fibers
 Two bulging fiber tracts, cerebral peduncles, convey
ascending and descending impulses
 Four rounded protrusions, corpora quadrigemina,
visual and auditory reflex centers
© 2015 Pearson Education, Inc.
Regions of the Brain: Brain Stem
 Pons
 The bulging center part of the brain stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of breathing
© 2015 Pearson Education, Inc.
Regions of the Brain: Brain Stem
 Medulla oblongata
 The lowest part of the brain stem
 Merges into the spinal cord
 Includes important fiber tracts
 Contains important control centers
 Heart rate control
 Blood pressure regulation
 Breathing
 Swallowing
 Vomiting
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Regions of the Brain: Brain Stem
 Reticular formation
 Diffuse mass of gray matter along the brain stem
 Involved in motor control of visceral organs
 Reticular activating system (RAS)
 Plays a role in awake/sleep cycles and consciousness
 Filter for incoming sensory information
© 2015 Pearson Education, Inc.
Figure 7.16b Diencephalon and brain stem structures.
Radiations
to cerebral
cortex
Visual impulses
Reticular formation
Ascending general sensory
tracts (touch, pain, temperature)
(b)
© 2015 Pearson Education, Inc.
Auditory
impulses
Descending
motor projections
to spinal cord
Regions of the Brain: Cerebellum
 Two hemispheres with convoluted surfaces
 Controls balance and equilibrium
 Provides precise timing for skeletal muscle activity
and coordination of body movements
© 2015 Pearson Education, Inc.
Figure 7.16a Diencephalon and brain stem structures.
Cerebral hemisphere
Corpus callosum
Third ventricle
Choroid plexus of third
ventricle
Occipital lobe of
cerebral hemisphere
Thalamus
(encloses third ventricle)
Pineal gland
(part of epithalamus)
Anterior
commissure
Hypothalamus
Corpora quadrigemina
Optic chiasma
Cerebral aqueduct
Pituitary gland
Cerebral peduncle
(a)
Mammillary body
Pons
Medulla oblongata
Spinal cord
© 2015 Pearson Education, Inc.
Fourth ventricle
Choroid plexus
Cerebellum
Midbrain
Protection of the Central Nervous System
 Scalp and skin
 Skull and vertebral column
 Meninges
 Cerebrospinal fluid (CSF)
 Blood-brain barrier
© 2015 Pearson Education, Inc.
Figure 7.17a Meninges of the brain.
Skin of scalp
Periosteum
Bone of skull
Superior
sagittal sinus
Subdural
space
Subarachnoid
space
(a)
© 2015 Pearson Education, Inc.
Periosteal
Meningeal
Dura
mater
Arachnoid mater
Pia mater
Arachnoid villus
Blood
vessel
Falx cerebri
(in longitudinal
fissure only)
Meninges
 Dura mater
 Tough outermost layer
 Double-layered external covering
 Periosteum—attached to inner surface of the skull
 Meningeal layer—outer covering of the brain
 Folds inward in several areas
 Falx cerebri
 Tentorium cerebelli
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Meninges
 Arachnoid layer
 Middle layer
 Weblike extensions span the subarachnoid space
 Arachnoid villi reabsorb cerebrospinal fluid
 Pia mater
 Internal layer
 Clings to the surface of the brain
© 2015 Pearson Education, Inc.
Figure 7.17b Meninges of the brain.
Skull
Scalp
Occipital lobe
Tentorium
cerebelli
Cerebellum
(b)
Arachnoid mater
over medulla
oblongata
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Superior
sagittal sinus
Dura mater
Transverse
sinus
Temporal
bone
Cerebrospinal Fluid (CSF)
 Similar to blood plasma composition
 Formed by the choroid plexus
 Choroid plexuses–capillaries in the ventricles of the
brain
 Forms a watery cushion to protect the brain
 Circulated in arachnoid space, ventricles, and
central canal of the spinal cord
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Cerebrospinal Fluid (CSF) Pathway of Flow
1. CSF is produced by the choroid plexus of each
ventricle.
2. CSF flows through the ventricles and into the
subarachnoid space via the median and lateral
apertures. Some CSF flows through the central
canal of the spinal cord.
3. CSF flows through the subarachnoid space.
4. CSF is absorbed into the dural venous sinuses via
the arachnoid villi.
© 2015 Pearson Education, Inc.
Figure 7.18a Ventricles and location of the cerebrospinal fluid.
Lateral ventricle
Anterior horn
Septum
pellucidum
Interventricular
foramen
Inferior
horn
Third ventricle
Cerebral aqueduct
Fourth ventricle
Lateral
aperture
Central canal
(a) Anterior view
© 2015 Pearson Education, Inc.
Figure 7.18b Ventricles and location of the cerebrospinal fluid.
Lateral ventricle
Anterior horn
Posterior
horn
Interventricular
foramen
Third ventricle
Inferior horn
Cerebral aqueduct
Fourth ventricle
Median
aperture
Central canal
Lateral
aperture
(b) Left lateral view
© 2015 Pearson Education, Inc.
Figure 7.18c Ventricles and location of the cerebrospinal fluid.
4
Superior
sagittal sinus
Arachnoid villus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
Choroid plexus
Corpus
callosum
1
Interventricular
foramen
Right lateral ventricle
(deep to cut)
Third ventricle
3
Choroid plexus
of fourth ventricle
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
(c) CSF circulation
1 CSF is produced by the
2
choroid plexus of each ventricle.
2 CSF flows through the
ventricles and into the
subarachnoid space via the
median and lateral apertures.
Some CSF flows through the
central canal of the spinal cord.
3 CSF flows through the
subarachnoid space.
4 CSF is absorbed into the
dural venous sinuses via
the arachnoid villi.
© 2015 Pearson Education, Inc.
Hydrocephalus in a Newborn
 Hydrocephalus
 CSF accumulates and exerts pressure on the brain if
not allowed to drain
 Possible in an infant because the skull bones have
not yet fused
 In adults, this situation results in brain damage
© 2015 Pearson Education, Inc.
Figure 7.19 Hydrocephalus in a newborn.
© 2015 Pearson Education, Inc.
Blood-Brain Barrier
 Includes the least permeable capillaries of the body
 Excludes many potentially harmful substances
 Useless as a barrier against some substances
 Fats and fat-soluble molecules
 Respiratory gases
 Alcohol
 Nicotine
 Anesthesia
© 2015 Pearson Education, Inc.
Blood-Brain Barrier
 Water-soluble items that can travel through barrier:
 Water
 Glucose
 Essential amino acids
 Items prevented from passing through:
 Metabolic wastes
 Most drugs
 Nonessential amino acids
 Potassium ions
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Traumatic Brain Injuries
 Concussion
 Slight brain injury
 No permanent brain damage
 Contusion
 Nervous tissue destruction occurs
 Nervous tissue does not regenerate
 Cerebral edema
 Swelling from the inflammatory response
 May compress and kill brain tissue
© 2015 Pearson Education, Inc.
Cerebrovascular Accident (CVA), or Stroke
 Results from a ruptured blood vessel supplying a
region of the brain
 Brain tissue supplied with oxygen from that blood
source dies
 Loss of some functions or death may result
 Hemiplegia—one-sided paralysis
 Aphasia—damage to speech center in left
hemisphere
 Transient ischemic attack (TIA)—temporary brain
ischemia (restriction of blood flow)
 Warning signs for more serious CVAs
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Alzheimer’s Disease
 Progressive degenerative brain disease
 Mostly seen in the elderly, but may begin in middle
age
 Structural changes in the brain include abnormal
protein deposits and twisted fibers within neurons
 Victims experience memory loss, irritability,
confusion, and ultimately, hallucinations and death
© 2015 Pearson Education, Inc.
Spinal Cord
 Extends from the foramen magnum of the skull to
the first or second lumbar vertebra
 Provides a two-way conduction pathway to and from
the brain
 31 pairs of spinal nerves arise from the spinal cord
 Ends around vertebra L1 or L2
 Cauda equina is a collection of spinal nerves at the
inferior end
© 2015 Pearson Education, Inc.
Figure 7.20 Anatomy of the spinal cord, posterior view.
Cervical
enlargement
Cervical
spinal nerves
C8
Dura and
arachnoid
mater
Lumbar
enlargement
Thoracic
spinal nerves
T12
End of spinal cord
Lumbar
spinal nerves
Cauda equina
End of
meningeal
coverings
© 2015 Pearson Education, Inc.
L5
S1
S5
Sacral
spinal nerves
Spinal Cord Anatomy
 Internal gray matter is mostly cell bodies
 Dorsal (posterior) horns house interneurons
 Receive information from sensory neurons in the
dorsal root
 Anterior (ventral) horns house motor neurons of the
somatic (voluntary) nervous system
 Send information out ventral root
 Gray matter surrounds the central canal, which is
filled with cerebrospinal fluid
© 2015 Pearson Education, Inc.
Spinal Cord Anatomy
 Exterior white mater—conduction tracts
 Dorsal, lateral, ventral columns
 Sensory (afferent) tracts conduct impulses toward
brain
 Motor (efferent) tracts carry impulses from brain to
skeletal muscles
© 2015 Pearson Education, Inc.
Figure 7.21 Spinal cord with meninges (three-dimensional view).
Dorsal root
ganglion
White matter
Central canal
Dorsal (posterior)
horn of gray matter
Lateral horn of
gray matter
Spinal nerve
Dorsal root of
spinal nerve
Ventral root
of spinal nerve
Ventral (anterior)
horn of gray matter
Pia mater
Arachnoid mater
Dura mater
© 2015 Pearson Education, Inc.
Figure 7.22 Schematic of ascending (sensory) and descending (motor) pathways between the brain and the spinal cord.
Interneuron carrying
sensory information
to cerebral cortex
Cerebral cortex
(gray matter)
White matter
Integration (processing
and interpretation of
sensory input) occurs
Interneuron carrying
response to motor
neurons
Cerebrum
Thalamus
Interneuron
carrying response
to motor neuron
Cell body of sensory
neuron in sensory
ganglion
Nerve
Skin
Sensory
receptors
Brain stem
Interneuron carrying
sensory information to
cerebral cortex
Cervical spinal cord
Muscle
White matter
Gray matter
Motor output
Interneuron
Motor neuron cell body
© 2015 Pearson Education, Inc.
Spinal Cord Anatomy
 Meninges cover the spinal cord
 Spinal nerves leave at the level of each vertebra
 Dorsal root
 Associated with the dorsal root ganglia—collections of
cell bodies outside the central nervous system
 Ventral root
 Contains axons
© 2015 Pearson Education, Inc.
Peripheral Nervous System (PNS)
 PNS consists of nerves and ganglia outside the
central nervous system
 Nerve  bundle of neuron fibers
 Neuron fibers are bundled by connective tissue
© 2015 Pearson Education, Inc.
PNS: Structure of a Nerve
 Endoneurium surrounds each fiber
 Groups of fibers are bound into fascicles by
perineurium
 Fascicles are bound together by epineurium
© 2015 Pearson Education, Inc.
Figure 7.23 Structure of a nerve.
Axon
Myelin sheath
Endoneurium
Perineurium
Epineurium
Fascicle
Blood
vessels
© 2015 Pearson Education, Inc.
PNS: Classification of Nerves
 Mixed nerves
 Both sensory and motor fibers
 Sensory (afferent) nerves
 Carry impulses toward the CNS
 Motor (efferent) nerves
 Carry impulses away from the CNS
© 2015 Pearson Education, Inc.
PNS: Cranial Nerves
 12 pairs of nerves that mostly serve the head and
neck
 Only the pair of vagus nerves extends to thoracic
and abdominal cavities
 Most are mixed nerves, but three are sensory only:
1. Optic
2. Olfactory
3. Vestibulocochlear
© 2015 Pearson Education, Inc.
PNS: Cranial Nerves Mnemonic Device
 Oh – Olfactory
 Oh – Optic
 Oh – Oculomotor
 To – Trochlear
 Touch – Trigeminal
 And – Abducens
 Feel – Facial
 Very – Vestibulocochlear
 Green – Glossopharyngeal
 Vegetables – Vagus
 A – Accessory
 H – Hypoglossal
© 2015 Pearson Education, Inc.
Table 7.2 The Cranial Nerves (1 of 6)
© 2015 Pearson Education, Inc.
Table 7.2 The Cranial Nerves (2 of 6)
© 2015 Pearson Education, Inc.
Table 7.2 The Cranial Nerves (3 of 6)
© 2015 Pearson Education, Inc.
Table 7.2 The Cranial Nerves (4 of 6)
© 2015 Pearson Education, Inc.
Table 7.2 The Cranial Nerves (5 of 6)
© 2015 Pearson Education, Inc.
Table 7.2 The Cranial Nerves (6 of 6)
Cervical
nerves
© 2015 Pearson Education, Inc.
Figure 7.24 Distribution of cranial nerves.
III Oculomotor
IV Trochlear
VI Abducens
I Olfactory
V Trigeminal
V Trigeminal
II Optic
VII Facial
Vestibular
branch
Cochlear
branch
VIII Vestibulocochlear
X Vagus
IX Glossopharyngeal
XII Hypoglossal
© 2015 Pearson Education, Inc.
XI Accessory
PNS: Spinal Nerves
 There is a pair of spinal nerves at the level of each
vertebra, for a total of 31 pairs
 Formed by the combination of the ventral and dorsal
roots of the spinal cord
 Named for the region from which they arise
© 2015 Pearson Education, Inc.
Figure 7.25a Spinal nerves.
C1
Cervical
nerves
2
3
4
5
6
7
8
T1
2
Ventral rami form
cervical plexus
(C1 – C5)
Ventral rami form
brachial plexus
(C5 – C8; T1)
3
4
Thoracic
nerves
5
6
7
8
9
10
Lumbar
nerves
Sacral
nerves
11
No plexus
formed
(intercostal
nerves)
(T1 – T12)
12
L1
2
3
4
Ventral rami form
lumbar plexus
(L1 – L4)
5
S1
2
(a)
© 2015 Pearson Education, Inc.
3
4
Ventral rami form
sacral plexus
(L4 – L5; S1 – S4)
PNS: Anatomy of Spinal Nerves
 Spinal nerves divide soon after leaving the spinal
cord
 Ramus—branch of a spinal nerve; contains both
motor and sensory fibers
 Dorsal rami—serve the skin and muscles of the
posterior trunk
 Ventral rami—form a complex of networks (plexus)
for the anterior
© 2015 Pearson Education, Inc.
Figure 7.25b Spinal nerves.
Dorsal
root
Dorsal
root
ganglion
Spinal
cord
Ventral
root
Spinal nerve
(b)
© 2015 Pearson Education, Inc.
Dorsal
ramus
Ventral
ramus
PNS: Spinal Nerve Plexuses
 Plexus–networks of nerves serving motor and
sensory needs of the limbs
 Form from ventral rami of spinal nerves in the
cervical, lumbar, and sacral regions
 Four plexuses:
1.
2.
3.
4.
Cervical
Brachial
Lumbar
Sacral
© 2015 Pearson Education, Inc.
Table 7.3 Spinal Nerves Plexuses (1 of 3)
© 2015 Pearson Education, Inc.
Figure 7.26a Distribution of the major peripheral nerves of the upper and lower limbs.
Axillary nerve
Humerus
Radial
nerve
Musculocutaneous
nerve
Ulna
Radius
Ulnar nerve
Radial nerve
(superficial
branch)
Median
nerve
(a) The major nerves
of the upper limb
© 2015 Pearson Education, Inc.
Table 7.3 Spinal Nerves Plexuses (2 of 3)
© 2015 Pearson Education, Inc.
Figure 7.26b Distribution of the major peripheral nerves of the upper and lower limbs.
Femoral
Lateral
femoral
cutaneous
Obturator
Anterior
femoral
cutaneous
Saphenous
(b) Lumbar plexus, anterior view
© 2015 Pearson Education, Inc.
Table 7.3 Spinal Nerves Plexuses (3 of 3)
© 2015 Pearson Education, Inc.
Figure 7.26c Distribution of the major peripheral nerves of the upper and lower limbs.
Superior
gluteal
Inferior
gluteal
Sciatic
Posterior
femoral
cutaneous
Common
fibular
Tibial
Sural (cut)
Deep
fibular
Superficial
fibular
Plantar
branches
(c) Sacral plexus, posterior view
© 2015 Pearson Education, Inc.
PNS: Autonomic Nervous System
 Motor subdivision of the PNS
 Consists only of motor nerves
 Also known as the involuntary nervous system
 Regulates activities of cardiac and smooth muscles
and glands
 Two subdivisions:
1. Sympathetic division
2. Parasympathetic division
© 2015 Pearson Education, Inc.
PNS: Differences Between Somatic
and Autonomic Nervous Systems
Somatic Nervous
System
Autonomic Nervous
System
Nerves
One-neuron system; it
originates in the CNS,
and axons extend to
the skeletal muscles
served
Two-neuron system
consisting of
preganglionic and
postganglionic
neurons
Effector organ
Skeletal muscle
Smooth muscle,
cardiac muscle,
glands
Subdivisions
None
Sympathetic and
parasympathetic
Neurotransmitter
Acetylcholine
Acetylcholine,
epinephrine,
norepinephrine
© 2015 Pearson Education, Inc.
Figure 7.27 Comparison of the somatic and autonomic nervous systems.
Central
nervous
system
Peripheral nervous system
Effector organs
Acetylcholine
Somatic nervous
system
Skeletal
muscle
Acetylcholine
Autonomic
nervous
system
Sympathetic
division
Smooth muscle
(e.g., in stomach)
Norepinephrine
Ganglion
Epinephrine and
Acetylcholine
norepinephrine
Blood
vessel
Parasympathetic
division
KEY:
Preganglionic
axons
(sympathetic)
© 2015 Pearson Education, Inc.
Postganglionic
axons
(sympathetic)
Glands
Acetylcholine
Cardiac
muscle
Ganglion
Myelination
Preganglionic
axons
(parasympathetic)
Postganglionic
axons
(parasympathetic)
PNS: Anatomy of the Parasympathetic
Division
 Preganglionic neurons originate from the
craniosacral regions:
 The cranial nerves III, VII, IX, and X
 S2 through S4 regions of the spinal cord
 Because it is the site of preganglionic neuron
origination, the parasympathetic division is also
known as the craniosacral division
 Terminal ganglia are at the effector organs
 Neurotransmitter: acetylcholine
© 2015 Pearson Education, Inc.
Figure 7.28 Anatomy of the autonomic nervous system.
Parasympathetic
Sympathetic
Eye
Brain stem
Salivary
glands
Heart
Eye
Skin
Cranial
Cervical
Sympathetic
ganglia
Salivary
glands
Lungs
Lungs
T1
Heart
Stomach
Stomach
Thoracic
Pancreas
Liver
and gallbladder
Pancreas
L1
Liver and
gallbladder
Adrenal
gland
Lumbar
Bladder
Genitals
© 2015 Pearson Education, Inc.
Bladder
Sacral
nerves
(S2–S4)
Genitals
PNS: Anatomy of the Sympathetic Division
 Preganglionic neurons originate from T1 through L2
 Ganglia are at the sympathetic trunk (near the
spinal cord)
 Short preganglionic neuron and long postganglionic
neuron transmit impulse from CNS to the effector
 Neurotransmitters: norepinephrine and epinephrine
(effector organs)
© 2015 Pearson Education, Inc.
Figure 7.28 Anatomy of the autonomic nervous system.
Parasympathetic
Sympathetic
Eye
Brain stem
Salivary
glands
Heart
Eye
Skin
Cranial
Cervical
Sympathetic
ganglia
Salivary
glands
Lungs
Lungs
T1
Heart
Stomach
Stomach
Thoracic
Pancreas
Liver
and gallbladder
Pancreas
L1
Liver and
gallbladder
Adrenal
gland
Lumbar
Bladder
Genitals
© 2015 Pearson Education, Inc.
Bladder
Sacral
nerves
(S2–S4)
Genitals
Figure 7.29 Sympathetic pathways.
Lateral horn of
gray matter
Dorsal ramus
of spinal nerve
Dorsal root
Sympathetic
trunk
Spinal
nerve
(a)
(b)
(c)
Ventral root
Sympathetic
trunk
ganglion
Splanchnic
nerve
Ventral ramus
of spinal nerve
To effector:
blood vessels,
arrector pili
muscles, and
sweat glands
of the skin
Gray ramus
communicans
White ramus
communicans
Collateral ganglion
(such as the celiac)
Visceral effector organ
(such as small intestine)
© 2015 Pearson Education, Inc.
PNS: Autonomic Functioning
 Sympathetic—“fight or flight” division
 Response to unusual stimulus
 Takes over to increase activities
 Remember as the “E” division:
 Exercise
 Excitement
 Emergency
 Embarrassment
© 2015 Pearson Education, Inc.
PNS: Autonomic Functioning
 Parasympathetic—“housekeeping” activites
 Conserves energy
 Maintains daily necessary body functions
 Remember as the “D” division
 Digestion
 Defecation
 Diuresis
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Table 7.4 Effects of the Sympathetic Divisions of the Autonomic Nervous System (1 of 2)
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Table 7.4 Effects of the Sympathetic Divisions of the Autonomic Nervous System (2 of 2)
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Developmental Aspects of the Nervous
System
 The nervous system is formed during the first month
of embryonic development
 Any maternal infection can have extremely harmful
effects
 Oxygen deprivation destroys brain cells
 The hypothalamus is one of the last areas of the
brain to develop
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Developmental Aspects of the Nervous
System
 Severe congenital brain diseases include:
 Cerebral palsy
 Anencephaly
 Hydrocephalus
 Spina bifida
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Developmental Aspects of the Nervous
System
 Premature babies have trouble regulating body
temperature because the hypothalamus is one of
the last brain areas to mature prenatally.
 Development of motor control indicates the
progressive myelination and maturation of a child’s
nervous system.
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Developmental Aspects of the Nervous
System
 Brain growth ends in young adulthood. Neurons die
throughout life and are not replaced; thus, brain
mass declines with age.
 Healthy aged people maintain nearly optimal
intellectual function.
 Disease—particularly cardiovascular disease—is
the major cause of declining mental function with
age.
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