Nervous System Test Review
1. What are the functions of the nervous system?
Sensory input – monitor changes inside and outside the body
Integration – processes sensory input and makes decisions about what to do
Motor output – effects a response
2. What is the basic unit of the nervous system? What is their function?
The neuron sends and receives electrochemical signals throughout the body.
3. What is the structure of a neuron and their functions?
Cell body – main center for metabolic functions
Dendrites – receive stimuli
Axon – action potential travels down to terminal and to effector or another neuron
Schwann cells – wrap around axon to form myelin sheath for protection (in the PNS)
Neurilemma – part of Schwann cell that is external to the myelin sheath
Nodes of Ranvier – gaps or indentations between Schwann cells at regular intervals
Axonal terminals – store and release neurotransmitters when a nerve impulse is transmitted
4. What are the types of neurons?
Afferent (sensory) – sending nerve impulses to the CNS
Efferent (motor) – sending nerve impulses away from the CNS
Association (interneurons) – connect motor and sensory neurons
5. What is the structure of a nerve?
Each neuron is surrounded by a delicate, connective tissue sheath called the endoneurium.
These fibers are bound together with coarser connective tissue called the perineurium to form fascicles.
The fascicles are bound together by a tough, fibrous sheath celled the epineurium to form a nerve.
6. What are a tract, nuclei, nerve, and ganglia?
Tract – bundles of nerve fibers (neuron processes) running through the CNS
Nuclei – clusters of cell bodies found in the CNS
Nerve – bundles of nerve fibers (neuron processes) running through the PNS
Ganglia – clusters of cell bodies found in the PNS
7. What are the supporting cells of the nervous system? What are their functions?
Collectively the supporting cells are called the neuroglia
Astrocytes – star-shaped, form a barrier between capillaries and neurons protecting it from harmful
substances in the blood, picks up excess ions, and recaptures released neurotransmitters
Microglia – spider-like phagocytes that dispose of debris, dead cells, and bacteria
Ependymal cell – line cavities of the brain and spinal cord, have cilia that beat to help circulate CSF
Oligodendrocytes – wrap flat extensions around nerve fibers in CNS to form myelin sheaths
8. What is the function of the cerebrum? What separates the two hemispheres?
Functions of the cerebral hemispheres are speech, memory, logical and emotional response,
consciousness, interpretation of sensation, and voluntary movement.
The longitudinal fissure separates the two hemispheres.
9. What is the function of the cerebellum?
Provides precise timing for skeletal muscle activity and controls balance and equilibrium.
10. What are the components and function of the brain stem?
The brain stem is a pathway for tracts and contains many small gray matter areas.
Midbrain – fiber tracts, vision and hearing
Pons – means bridge, thus mainly fiber tracts
Medulla oblongata – fiber tract area, centers controlling heart rate, blood pressure, breathing,
swallowing, and vomiting
11. What is the function of the hypothalamus?
Autonomic nervous system – regulation of body temperature, water balance, and metabolism
12. What is the function of the thalamus?
Relay station for sensory impulses passing upward to the sensory cortex, which includes crude
recognition of whether the sensation is pleasant/unpleasant.
13. What is the function of the reticular formation?
Also known as the reticular activating system (RAS) and is motor control of visceral organs,
consciousness (awake/sleep cycles).
14. What is the structure and function of the corpus callosum?
Large fiber tract connecting the two cerebral hemispheres for communication.
15. What is Broca's area, what is its function, and where is it located?
Found at base of precentral gyrus in the left frontal lobe of the cerebrum and functions in motor speech
or the ability to actually form words with your mouth.
16. What are a reflex arc, its parts, and their functions?
Reflex arcs are neural pathways that function in rapid, predictable, and involuntary responses to stimuli.
Reflex arcs are composed of a minimum of 5 elements – a sensory receptor (reacts to a stimulus),
afferent neuron (carries impulse to CNS), integration center (synapse between afferent and efferent
neurons) efferent neuron (carries motor output to PNS), and effector organ. Can have additional
association neurons between afferent and efferent neurons, but make reactions slower.
17. What is the spinal cord's structure and function?
Approximately 17 inches long, ends at approximately L2, white matter in 3 columns around
butterfly-shaped gray matter internally. Gray matter has projections called posterior/dorsal horns and
anterior/ventral horns which surround the central canal. Sensory neuron cell bodies are found in the
dorsal root ganglion and enter cord by dorsal root. Motor neuron cell bodies are found in the ventral
horns and their processes leave through the ventral root. These processes combine outside of the spinal
cord to form a missed nerve.
The spinal cord provides a two-way conduction pathway to and from the brain, and it is a major
reflex center.
18. How does a nerve send impulses?
A resting nerve is considered polarized because there are more positive ions outside than inside
the plasma membrane of the neuron. A stimulus is received by the dendrites, causing the plasma
membrane to become permeable to Na+, which changes the polarity of the neuron’s membrane in an
event called depolarization. If the stimulus is strong enough then the depolarization activates the neuron
to initiate and transmit an action potential over the entire axon. After depolarization and the action
potential the Na+ close and K+ diffuses out of the cell in an event called repolarization. The polarity of
the membrane is now correct, but the ions are on the wrong side of the membrane, so the Na-K pump
goes to work to bring K+ back into the cell and send Na+ out.
As the action potential travels down the myelinated fibers it actually jumps from node to node in
a type of impulse propagation called salutatory conduction. This is much faster than an impulse traveling
down the entire length of an unmyelinated fiber. As the impulse reaches the axonal terminal the
neurotransmitter is released into the synaptic cleft to bind with the receptors on the next neuron or
effector cell.
For another nerve impulse to be conducted the neuron must be completely back to normal and
polarized.
19. What are the two types of neurons? How does a nerve impulse travel along these neurons?
Same as #4
20. Where is cerebrospinal fluid made and how does it travel through the brain?
Formed in the ventricles from clusters of capillaries called choroid plexuses. CSF leaves the lateral
ventricles, travels down to the 3rd and 4th ventricles where most of it leaves to circulate around the brain
in the subarachnoid space and return to the blood through the dural sinuses. Some of the CSF from the
4th ventricle travels into the central canal of the spinal cord.
21. What are the two divisions of the autonomic nervous system? What are their structures and functions?
The two divisions of the autonomic nervous system are the sympathetic and parasympathetic.
The sympathetic nerves are in thoracic and lumbar regions where their short preganglionic axons
leave the cord and synapse with a long postganglionic neuron that transmits impulse to effector. The
sympathetic responds to unusual stimuli and takes over to increase activities in anticipation of “fight-orflight” and is concerned with the “E’s” – exercise, excitement, emergency, and embarrassment. The
neurotransmitters are norepinephrine and epinephrine.
The parasympathetic nerves are located in the brain and sacral regions and send out axons to
synapse with a second motor neuron in a terminal ganglion, and from there the postganglionic axon
travels a short distance to the organ it serves. The parasympathetic is most active when the body is at
rest and not threatened and is chiefly concerned with the “D’s” – digestion, defecation, and diuresis. The
neurotransmitter is acetylcholine.
22. Compare the somatic motor division and autonomic nervous system.
Somatic cell bodies are in the CNS, axons extend to the skeletal muscle they are serving, and use
acetylcholine as the neurotransmitter.
The autonomic nervous system is a chain of two motor neurons (first in CNS – preganglionic
axon) and synapses in PNS with another motor neuron (postganglionic axon) and act on smooth muscle,
cardiac muscle and glands using the neurotransmitters norepinephrine, epinephrine, and acetylcholine.
23. What composes the CNS and the PNS? Mixed nerve?
The CNS is composed of the brain and spinal cord.
The PNS is everything outside the CNS including cranial and spinal nerves.
A mixed nerve is a nerve containing the processes of motor and sensory neurons and their impulses
travel to and from the CNS.
24. What are some common neural diseases and how do they affect the nervous system?
Multiple sclerosis – myelin sheaths are gradually destroyed and converted to hardened sheaths
which short-circuit the neuron causing inability to control muscles.
Cerebrovascular accidents (CVAs) – third leading cause of death in the US, when blood
circulation to a brain area is blocked by a clot or ruptured blood vessel and the brain tissue dies which
often results in aphasia (inability to speak or understand words).
25. What are the meninges of the CNS?
Connective tissue layers that cover and protect the CNS
Dura mater – tough outer layers surrounding the brain, fused except for dural sinuses
Arachnoid mater – looks like a cobweb in space between arachnoid and pia mater (subarachnoid space)
where CSF circulates
Arachnoid villi – specialized projections that protrude through dura mater into dural sinuses for CSF to
be absorbed into the venous blood
Pia mater – delicate layer clinging tightly to the surface of the brain and spinal cord following every fold
26. What is the blood-brain barrier permeable and impermeable to?
Least permeable capillaries in the whole body; water, glucose, and essential amino acids pass easily but
metabolic waste, ureas, toxins, proteins, and most drugs are prevented from entering. It is useless against
fats, respiratory gases, and other fat-soluble molecules (alcohol, nicotine, and anesthetics).
27. What happens to the brain as we age?
No more neurons are formed after we are born, but grow and mature for several years which can be seen
in a developing child. The brain reaches maximum weight as a young adult. The supporting cells of the
nervous system do continue to divide and thus learning can continue.