The Nervous System29-*
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Learning Outcomes
29.1 Explain the difference between the central nervous system and the peripheral nervous system.
29.2 Describe the functions of the nervous system.
29.3 Describe the structure of a neuron.
29.4 Describe the function of a nerve impulse and how a nerve impulse is created.
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29.6 Describe the function of the blood-brain barrier.
29.7 Describe the structure and functions of meninges.
29.8 Describe the structure and functions of the spinal cord.
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29.9 Describe the location and function of cerebrospinal fluid.
29.10 Define reflex and list the parts of a reflex arc.
29.11 List the major divisions of the brain and give the general functions of each.
29.12 Explain the functions of the cranial and spinal nerves.
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Learning Outcomes (cont.)
29.13 Describe the differences between the somatic nervous system and autonomic nervous system.
29.14 Explain the two divisions of the autonomic nervous system.
29.15 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system.
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Introduction
Central nervous system (CNS)
Peripheral nervous system (PNS)
Controls all other organ systems and is important for maintaining balance within those systems
Disorders are numerous and often
difficult to diagnose and treat
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CNS
Brain
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Three types of neurons
Afferent or sensory nerves
Sensory information from environment or inside body to CNS for interpretation
Efferent or motor nerves
Impulses from CNS to PNS to allow for movement or action
Interneruons
Interpretive neurons between afferent and efferent nerves in the CNS
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___ Autonomic nervous system B. Governs skeletal or voluntary muscles
___ Afferent nerves C. Governs respiratory and GI systems
___ Efferent nerves D. Go-betweens or interpreters
___ Interneurons E. Sensory nerves
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Other neurons
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If destroyed, not replaced
Astrocytes – anchor blood vessels to nerves
Microglia – act as phagocytes
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Neuron Structure (cont.)
Neurons have cell body processes called nerve fibers that extend from the cell body.
Dendrites – short
Axons – long
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Schwann cells – neurological cells
Wrap around some axons
Cell membranes contain myelin
Myelin insulates axons and enables axons to send nerve impulses more quickly
Gray matter – axons without myelin sheath
Schwann cells
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___ Microglia act as phagocytes.
___ Oligodendrocytes are reproductive cells.
F
T
T
F
T
Neurons cannot reproduce.
GOOD JOB!
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Neuron cell membrane at rest is in a polarized state
Inside of cell membrane is negative
Outside of cell membrane is positive due to more Na+ and K+
As Na+ and K+ move into the cell, the membrane becomes depolarized
Inside becomes more positive
Action potential (nerve impulse) is created
Repolarization occurs when K+ and later Na+ move to the outside of the cell membrane
Return of the cell to polarized (resting) state
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Produce chemicals called neurotransmitters
Dendrites
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Cause glands to secrete products
Activate or inhibit neurons
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What is the function of neurotransmitters?
ANSWER: Neurotransmitters cause muscles to contract or relax, cause glands to secret products, activate neurons to send nerve impulses, or inhibit neurons from sending them.
Right!
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Blood-brain barrier
Formed by tight capillaries
Inflammation can make more permeable
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Dura mater
and spinal cord
surface of these structures
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Contains cerebrospinal fluid (CSF)
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Slender structure continuous with the brain
Descends into the vertebral canal and ends around the level of the first or second lumbar vertebra
31 spinal segments:
8 cervical segments
12 thoracic segments
5 lumbar segments
5 sacral segments
1 coccygeal segment  
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Contains neuron cell bodies and their dendrites
Divisions are called horns
Central canal runs down the entire length of the spinal cord through the center of the gray matter
CNS: Spinal Cord (cont.)
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Columns contain groups of axons called nerve tracts
Spinal Cord/Nerve
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One function of the spinal cord is to carry sensory information to and from the brain
Ascending tracts
Descending tracts
Carry motor information down from the brain to muscles and glands
CNS: Spinal Cord (cont.)
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Reflexes
Another function of the spinal cord is to participate in reflexes
Reflex – a predictable, automatic response to stimuli
Receptor
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Two cerebral hemispheres
Connected by a thick bundle of nerve fibers called the corpus callosum
Longitudinal fissure between hemispheres
Sulci – grooves on surface
Brain
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Lobes
Frontal
Parietal
Frontal
Parietal
Occipital
Temporal
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Cortex
Ventricles
Filled with CSF
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Thalamus
Relay station for sensory information going to the cerebral cortex for interpretation
Hypothalamus
CNS: Brain – Diencephalon
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Inferior portion of brain stem
Directly connected to spinal cord
Controls many vital activities, such as heart rate, blood pressure, and breathing
CNS: Brain – Brain Stem
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Location
Posterior to the pons and medulla oblongata
Coordinates
Complex skeletal muscle contractions that are needed for body movements
Fine movements
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Avoid diving into unknown waters
Always wear seat belts
Follow safety rules on playgrounds
Children should be in car seats appropriate for age and weight
Know how to get help quickly in emergencies
Follow traffic rules and signs while walking, biking, or driving
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___ Ascending tracts B. Stores memories and creates emotions
___ Descending tracts C. Grooves on the surface of the cerebrum
___ Cerebral cortex D. Carry sensory information to the brain
___ Hypothalamus E. Predictable, automatic response to stimuli
___ Sulci F. Maintains homeostasis
___ Reflexes H. Protects the brain and spinal cord
B
F
C
G
E
D
A
SUPER!
H
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Peripheral nerves
Two types:
Cranial nerves
Spinal nerves
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II.  Optic nerves
III. Oculomotor nerves
Found within the muscles that move the eyeball, eyelid, and iris
IV. Trochlear nerves
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V.  Trigeminal nerves
Carry sensory information from the surface of the eye, the scalp, facial skin, the lining of the gums, and the palate to the brain for interpretation
Also found within the muscles needed for chewing
VI. Abducens nerves
PNS: Cranial Nerves (cont.)
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VII. Facial nerves
Found in the muscles of facial expression as well as in the salivary and tear glands
Also carry sensory information from the tongue
VIII. Vestibulocochlear nerves
Carry hearing and equilibrium information from the inner ear to the brain for interpretation
PNS: Cranial Nerves (cont.)
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IX. Glossopharyngeal nerves
Carry sensory information from the throat and tongue to the brain for interpretation
Also act in the muscles of the throat
X. Vagus nerves
Carry sensory information from the thoracic and abdominal organs to the brain for interpretation
Also found within the muscles in the throat, stomach, intestines, and heart
PNS: Cranial Nerves (cont.)
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XI. Accessory nerves
Found within the muscles of the throat, neck, back, and voice box
XII. Hypoglossal nerves
PNS: Cranial Nerves (cont.)
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31 pairs of spinal nerves
8 pairs of cervical nerves (C1 through C8)
12 pairs of thoracic nerves (T1 through T12)
5 pairs of lumbar nerves (L1 through L5)
5 pairs of sacral nerves (S1 through S5)
1 pair of coccygeal nerves (C0)
PNS: Spinal Nerves
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Main portions of spinal nerves fuse to form nerve plexuses
Cervical – supply skin and muscles of neck
Phrenic nerve originates from this plexus
Controls diaphragm
Lumbosacral – lower abdomen, external genitalia, buttocks, thighs, legs, and feet
Sciatic nerve originates from this plexus
Controls muscles of legs
PNS: Spinal Nerves (cont.)
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Nerves that connect the CNS to skin and skeletal muscle
“Voluntary” nervous system
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Nerves that connect the CNS to organs and other structures
“Involuntary” nervous system
Neuron cell bodies outside the CNS
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“Fight or flight” – Prepares body for stressful or emergency situations
Neurons release neurotransmitter norepinephrine
Slows down muscles of the stomach and intestines
Dilates pupils
PNS: Autonomic Nervous System (cont.)
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Controls most of the body’s organs
Releases acetylcholine
Constricts pupils
No communication with blood vessels
Sympathetic and parasympathetic divisions are antagonistic
PNS: Autonomic Nervous System (cont.)
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What is the difference between the sympathetic and parasympathetic nervous systems?
ANSWER: The sympathetic nervous system prepares the body for stress. It releases norepinephrine, causing an increase in heart and respiratory rate, slows down the GI system, and dilates pupils. The sympathetic system also controls constriction of blood vessels.
The parasympathetic system prepares the body for resting and digesting. It releases acetylcholine, which slows heart and respiratory rate, constricts pupils and stimulates the GI system. It has no effect on most blood vessels.
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Cerebral angiography
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Cranial nerves III, IV, and VI
Have patient track movement of finger
Cranial nerve V
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Cranial nerve XII
Have patient extend his tongue and move it from side to side
Neurologic Testing – Cranial Nerve Tests (cont.)
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Knee reflex
Abdominal reflexes
Neurologic Testing: Reflex Testing
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___ State of consciousness A. Determines the health of peripheral nerves
___ Reflex activity B. Loss of balance, abnormal posture
___ Speech patterns C. Stupor, delirium, vegetative
___ Motor patterns D. Loss of ability to form words
A
D
B
C
ANSWER:
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Amyotrophic lateral sclerosis (ALS)
Lou Gehrig’s disease Degeneration of neurons in the spinal cord and brain
Bell’s palsy
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Disease/Disorder
Description
Brain tumors and cancers
Abnormal growths Can be primary or secondary tumors Most common – gliomas
Epilepsy and seizures
Occurs as a result of bursts of electrical signals that disrupt normal brain functioning
Guillain-Barré Syndrome
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Disease/Disorder
Description
Headaches Tension Migraines Cluster
Episodic or chronic With aura/without aura Form of migraines; occurs in groups
Meningitis
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Disease/Disorder
Description
Neuralgias
Sciatica
Stroke
Brain cells die because of an inadequate blood flow; “brain attack”
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the brain.
___ Epilepsy is due to degenerative neurons in the spinal cord
and brain.
___ Stroke occurs when brain cells die because of inadequate
blood flow.
F
F
T
Due to a burst of electrical signals that disrupt brain function.
They are group of disorders referred to as nerve pain.
Bravo!
T
ANSWER:
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Responding to and carrying out motor functions
Neurons are responsible for functions
Divisions
CNS – brain and spinal cord
PNS – cranial and spinal nerves
Knowledge of this system is essential when assisting the physician during a neurologic exam
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End of Chapter
Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.”
~ Dr. Ralph Gerard