BIOLOGY 12: UNIT M/N - CHAPTER 17 - REVIEW WORKSHEET KEY
NERVOUS SYSTEM
A. CHAPTER REVIEW
1. The 2 main divisions of the nervous system:
-Central nervous system (CNS): includes the brain and spinal cord
-Peripheral nervous system (PNS): includes nerves
2. -Cell bodies, dendrites and axons
-Dendrite = conducts nerve impulses towards the cell body
-Axon = conducts nerve impulse away from cell body
3. -Sensory neuron = takes message from receptor in sense organ to CNS, has long
dendrite and short axon
-Motor neuron = takes message away from CNS to an effector (muscle/gland), has short
dendrite, long axon
-Interneuron = conveys messages between parts of system, has short dendrites and either
long or short axons
4. Schwann cells lay down several layers of cellular membrane containing myelin which
plays an important role in nerve regeneration in the PNS.
5. Resting membrane potential = voltage recorded from inside neuron when it isn’t
conducting nerve impulses. Value = -65mV
6. [Sodium ions] = greater outside axon than inside, [Potassium ions] = greater inside axon
than outside. Unequal distribution maintained by sodium-potassium pump; sodium ions
pumped out, potassium ions pumped in
7. Because membrane is more permeable to potassium ions and ions diffuse to lower [ ];
there are more positive ions outside the axoplasm and there are large negative proteins in
plasma that contributes to negative charges
8. Sodium ions flow into axon, charge inside axon changes from negative to positive depolarization
9. Potassium ions flow outside repolarization
10. Na+/K+ pump important because nerve impulses can be conducted (only small
number of ions exchanged with each impulse)
11. The time period in which the neuron is unable to conduct a nerve impulse is termed the
refractory period.
12. Faster because AP jumps from 1 node of Ranvier to another node of Ranvier, called
saltatory conduction
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13.
a) In synapse, membrane of neuron opposite postsynaptic membrane
b) The small region b/w an AB & either the dendrite or the cell body of another neuron
c) Small gap between the presynaptic and postsynaptic membranes
d) In the synapse, it is the neural membrane opposite of the presynaptic membrane
14. a) Axomembrane becomes permeable to calcium ions, allow calcium ions to enter AB
b) The substances that are released are termed neurotransmitters (NTs)
15. Excitatory NTs cause a depolarizing effect on the postsynaptic neuron by producing a
signal that promotes an AP
Inhibitory NTs cause a hyperpolarizing effect on the postsynaptic neuron by producing a
signal that decreases the chance of achieving an AP
16. Acetylcholine (ACh) and norepinephrine (NE), enzyme acetylcholinesterase (AChE)
and enzyme monoamine oxidase breaks down norepinephrine
17. What determines whether a nerve will fire?
This is called integration: the summation of excitatory & inhibitory signals
18. CNS sums up information it receives from all over to make decisions.
19. PNS is made up of nerves, cell bodies are found in ganglia.
20. Sensory nerve fibres: carry info to the CNS
Motor nerve fibres: carry info away from the CNS
Mixed nerves: contain both types of nerves
21. Humans have 31 pairs of spinal nerves and 12 pairs of cranial nerves. All spinal nerves
have mixed nerves.
22. Dendrites of sensory neurons are found in dorsal roots. Axons of motor neurons are
found in ventral roots. Somatic nervous system serves musculoskeletal system and
receptors (skin).
23. Reflex = automatic, involuntary responses to changes occurring inside or outside of
body
Simple reflex arc = receptor (in skin) sensory neuron (dendrite) cell body and CNS
(dorsal root ganglion) sensory neuron (axon) cord (via dorsal root of spinal nerve) interneuron motor neuron (short dendrites and cell body) axon (motor neuron) cord
(via ventral root of spinal nerve) muscle fibres
24. Automatic nervous system = regulates homeostasis by controlling cardiac & smooth
muscle, & glands; controls internal organs automatically and subconsciously.
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25. Sympathetic division arises from thoraco-lumbar (middle) portion of spinal cord.
Preganglionic fibre = short
Postganglionic fibre = long
System important for emergency situations
Postganglionic fibre releases norepinephrine
26. Parasympathetic division arises from the sacral (bottom) portion of the spinal cord;
preganglionic fibres = long, postganglionic fibres = short. Important for normal situations;
releases NT: acetylcholine
27. 2 parts of CNS = brain and SC; meninges = 3 protective membranes that wrap the
brain + spinal cord. Cerebrospinal fluid = fluid that cushions and protects CNS.
28. Spinal cord = centre for reflex actions; provides means of communication between
brain and spinal nerves. Grey matter in spinal cord found in spinal nerves.
29. Medulla oblongata
30.
a) Hypothalamus
b) Pons
c) Thalamus
d) i) Thalamus ii) Reticular Activating System (RAS)
e) Cerebellum
31. LARGEST part of the human brain that is responsible for consciousness.
Outer grey layer Cerebral cortex
Four lobes of the brain: Frontal, parietal, temporal and occipital
Cerebrum
32. Association areas (parietal lobe) receive info from lobes and integrates it.
Corpus callosum = white matter composed of nerve fibres connecting right and left
hemispheres
33. Malfunctioning of the basal nuclei = cause of Parkinson and Huntington disease.
34. a) B/c alcohol crosses placenta freely and causes fetal alcohol syndrome in newborns.
b) Fat accumulation fibrous scar tissue appears cirrhosis of liver (liver cells die, harden
and turn orange.
35. It prevents the uptake of the NT dopamine at the presynaptic membrane, causing the
feeling of a head rush
Binge period: lack of hunger or tiredness, increased sex drive
Crash period: fatigue, depression, irritability, memory/concentration problems, decreased
sex drive
Causes physical dependence, & requires HIGHER dosage to satisfy cravings
Cardiac seizures & respiratory arrest, brain damage
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36. Derived from morphine, an alkaloid of opium
Alleviates pain by binding to receptors meant for the NT endorphins (natural painkillers)
Endorphin production decreases, resulting in increased dependency
B. COMPLETION AND SHORT ANSWER QUESTIONS
1. Somatic and automatic divisions.
2. Long axon and short dendrites.
3. Sodium ions.
4. Synapse.
5. Reflexes.
6. Opposite effects.
7. Cerebrum.
8. Decrease.
9. Meninges.
10. Conduct nerve impulses toward the cell body.
11. Contain the nucleus.
12. Conduct nerve impulses away from the cell body.
13. Contain neurotransmitters and release them into the synapse.
14. The nerve cell of the nervous system is called the neuron of which there are three types:
sensory neurons, motor neurons and interneurons. Each type is made up of an axon, cell
body, and a dendrite.
Nerves are composed of a number of nerve fibres. Cell bodies are found in the CNS and in
the ganglia of the PNS. The sensory neuron cell body is found in the dorsal-root ganglion.
The postganglionic cell body of the Sympathetic division is found in ganglia that lie
alongside the spinal cord, and the postganglionic cell body of the Parasympathetic
division is found in ganglia located near the brain and lower spinal cord.
15. Schwann cells may encircle an axon and lay down several layers of cellular membrane
that contains myelin, which gives nerve fibres their white, glistening appearance. The gaps
between Schwann cells on myelinated nerve fibres are called the nodes of Ranvier, which
cause the speed of nerve impulse conduction to be much faster.
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16. The outer part of the cerebrum is called the cerebral cortex, and the two halves of the
cerebrum are called the right cerebral hemisphere and the left cerebral hemisphere.
17. In the spinal reflex arc, a stimulus is received by a sense organ, which initiates a nerve
impulse in the sensory neuron. The sensory neuron takes the message to the spinal cord
and transmits it to the interneuron. This neuron passes the impulse to the motor neuron,
which takes the message from the spinal cord and innervates a muscle.
18.
BRAIN PART
a. Cerebrum
FUNCTION
Responsible for consciousness and higher mental processes
b. Thalamus
Receives sensory impulses from other parts of the CNS and channels
only certain of these to the cerebrum
c. Hypothalamus
Concerned with homeostasis and controls the pituitary gland
d. Cerebellum
Controls balance and complex muscular movements
e. Medulla oblongata Controls centres for heartbeat, breathing, and blood pressure
19.
a) frontal
b) parietal
c) temporal
d) occipital
20. a) cranial sensory nerves: long dendrites of sensory neurons only
b) cranial motor nerves: long axons of motor neurons only
c) spinal mixed nerves: both long dendrites of sensory neurons and long axons of motor
neurons
21. It is dependent on the release of NTs which diffuse across the synaptic cleft, a small
space separating neuron from neuron.
22. 1) Function automatically and usually subconsciously in an involuntary manner
2) Innervate all internal organs
3) Utilize 2 motor neurons and 1 ganglion for each impulse.
23.
Type of situation used
NT released
Ganglia near SC or near
organ?
Spinal nerves only OR spinal
nerves + vagus (X) cranial
SYMPATHETIC
Emergency (fight or flight)
Norepinephrine
Near cord
PARASYMPATHETIC
Normal relaxed state
Acetylcholine
Near organ (or within)
Spinal nerves
Spinal nerves plus vagus cranial
nerve
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nerve?
24.
25. During the time of rest, the sodium-potassium pump restores the original distribution of
ions across the membrane of a nerve fibre.
26. The nerve impulse is the same in all neurons. It consists of an increase in membrane
permeability so that sodium moves to the inside of the axon and potassium moves to the
outside. The significance of this is that an electrochemical change has occurred, which is
propagated along the nerve until it reaches the axon bulb. Here a neurotransmitter is
released, and this enters the synaptic cleft. The nerve impulse is one-way because the
synaptic vesicles are only at the bulbous ends of axons. After passage across the synapse,
acetylcholine (ACh) is destroyed by the enzyme acetylcholinesterase (AChE).
27. Drugs. Complete the following table.
NAME
MODE OF ACTION
a. Alcohol
Potentiates GABA
PSYCHOLOGICAL EFFECTS
Poor judgement and motor incoordination
b. Marijuana
Alterations in vision and judgement, no
Acts on seratonin
concentration, incoherent speech
c. Cocaine
Affects dopamine in brain
“Rush”-irritable, restless and depressed
“Crash”-fatigue, depression, no memory
d. Heroin
Binds to receptors meant for
Perspiration, restlessness, defecation, increases
body’s own endorphins
systolic pressure and respiratory rate
28. Stimulated
Depression.
29. Ganglia contain cell bodies. Nerves contain axons, which are LONG in motor neurons,
and axons which are SHORT in sensory neurons.
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30. a. 2 b. 4 c. 1 d. 1 e. 3 f. 4 g. 2 h. 4
31. a. Synaptic vesicles b. Ganglia c. Motor Neurons d. Nodes of Ranvier
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