Human Anatomy and Physiology II
Exam 1, Version 7 - Feb. 13, 1998
Dr. Chabot
Multiple Choice (@3 points): Circle the letter of the one best answer. GOOD LUCK!
Answer only 20 out of 22! The first 20 answered will be graded.
1. Assume that an axon is artificially stimulated about halfway along its length. Which of the following will occur?
A. Negative organic (Pr-) ions move out of the cytoplasm to the outside of the axon.
B. The impulse may travel in both directions.
C. Sodium ions cross the membrane out of the cytoplasm; potassium ions move across the membrane into the cytoplasm of the axon.
D. The impulse will travel in only one direction because of absolute and relative refractory.
2. A nerve cell membrane may become repolarized from a depolarized state as a result of
A. the flow of K out of the cell
B. the flow of Na into the cell
C. the closing of K channels
D. the opening of Na channels
3. When an action potential passes over the surface of a pre-synaptic membrane, the contents of vesicles are released in response to the presence of
A. calcium ions
B. sodium ions
C. neurotransmitters
D. neuropeptides
4. Astrocytes function to
A. nourish neurons in the central nervous system
B. increase the conduction velocity of action potentials
C. insulate axons in the CNS
D. insulate axons in th peripheral nervous system
5. Neurotransmitters may be produced and packaged in the ________ of neurons.
A. axon
B. synapse
C. mitochondria
D. cell body
6. The units that can be best used to measure the amount of time it takes for an action potential to occur are
A. milliseconds
B. seconds
C. minutes
D. millivolts
7. When an inhibitory neurotransmitter combines with a receptor site on a postsynaptic membrane an:
A. influx (inward flow) of potassium ions occurs.
B. influx of sodium ions occurs.
C. efflux of sodium ions occurs.
D. efflux (outward flow) of potassium ions occurs.
8. A series of post synaptic potentials sum to produce a membrane potential of -40 mV at the axon hillock. Assume the threshold of this neuron is -45 mV. Which of the following will occur?
A. No action potential will be generated.
B. The action potential generated will be proportional to the strength of the PSPs.
C. The action potential generated will be inversely proportional to the strength of the PSPs.
D. An action potential will be generated.
9. Hyperpolarization of the neuronal membrane may be produced by any factor that:
A. increases the membrane's permeability to sodium ions.
B. decreases the membrane's permeability to sodium ions.
C. stimulates the sodium-potassium pump.
D. decreases the membrane's permeability to potassium ions.
10. Two neurons X and Y have excitatory input onto neuron Z. The terminal of neuron X is located 0.64 µm from the axon hillock of neuron Z, while the terminal of neuron Y is located 0.07 µm from the hillock. If, at different times, both X and Y stimulate neuron Z at the same rate and cause the same amount of post-synaptic depolarization at the terminals:
A. Neuron X will have a lesser chance of causing neuron Z to fire
B. Neuron Y will have a lesser chance of causing neuron Z to fire
C. They will both cause neuron Z to fire since action potentials are all-or-none
D. They both have an equal chance to cause neuron Z to fire.
11. If a constant depolarizing voltage is applied to a neuron and the neuron responds with a constant inward current, the neuron has probably been treated with:
A. oubain
B. TTX
C. TEA
D. pronase
12. A factor that contributes to the ability of neurons to quickly repolarize after an action potential occurs is:
A. the action potentials die out with distance travelled
B. there is a positive feedback loop that serves to keep APs going along the axon
C. the Na inactivation gate closes
D. K enters the cell
13. Sodium and potassium ion channel selectivity appears to be based on:
A. different charges on the ions
B. channel recognition factor
C. the fact that one is a salt
D. size and shape differences between channels
14. Relative refractory refers to
A. an all or none action potential
B. the time after an action potential during which a neuron is less sensitive to stimulus
C. an amount of time during which the neuron is not sensitive to further stimulus
D. the fact that neurons are rapidly repolarized
15. During an action potential in a large axon
A. a small percentage of the total number of Na ions diffuse into the cell
B. a small percentage of the total number of K ions diffuse out of the cell
C. a large percentage of the total number of Na ions diffuse into the cell
D. a large percentage of the total number of K ions diffuse out of the cell
E. A and B only
16. Which of the following is not true about an action potential in a nerve cell?
A. It is normally caused by a sudden increase in sodium-potassium pump activity.
B. It is associated with a sudden increase in sodium permeability (gates open) and a somewhat slower increase in potassium permeability (gates open).
C. It can occur in a neuron because of the unequal distribution of ions across the membrane.
D. It does not vary in amplitude with the strength of the stimulus used to trigger it.
17. After an action potential, the nerve cell membrane re-develops a resting potential and
A. potassium channels in the membrane open and potassium ions diffuse outward
B. ion channels close and the membrane becomes more permeable to sodium and potassium
C. sodium channels in the membrane open and sodium ions diffuse inward
D. many ion channels close and the membrane becomes less permeable to sodium and potassium
18. Neurons have different nutritional requirements than other cells in that they
A. require glucose as a source for producing ATP
B. require O2 for the breakdown of glucose
C. must aerobically respire
D. all of the above
E. none of the above
19. Ion pumps are important for which of the following?
A. long term maintenance of the resting potential
B. short term maintenance of the resting potential
C. long term maintenance of the action potential
D. short term maintenance of the action potential
20. At the neuromuscular junction which of the following is true?
A. Norepinephrine is released and is removed from the synapse by diffusion.
B. Norepinephrine is released and is removed from the synapse via reuptake.
C. Acetylcholine is released and is removed from the synapse via enzymatic breakdown.
D. Acetylcholine is released and is removed from the synapse via reuptake.
21. The effects that a neurotransmitter will have on the postsynaptic membrane is determined primarily by:
A. the chemical structure of the transmitter
B. the type of pre-synaptic cell
C. the types of enzymes located in the synapse
D. the structure of the post-synaptic receptor
22. Inhibitory post-synaptic potentials are produced when:
A. a neurotransmitter causes Na channels to open.
B. a neurotransmitter to be broken down
C. a neurotransmitter causes Na channels to close
D. a neurotransmitter causes K channels to open
FILL-INS (@2 points):
Complete the following sentences with the most appropriate (one or two) words.
Choose 10 out of 12 only.
1. The difference in electrical charge between the inside and outside of a polarized nerve cell membrane is
called the _______________________ _________________________.
2. A(an) __________________ is the junction between the parts of two neurons.
3. The minimum membrane potential required to open voltage mediated Na channels is called _________.
4. The “poison” that can turn of the Na/K membrane pumps is called _________________.
5. The period of time during which a neuron an AP cannot be elicited in a neuron no matter how strong the stimulus is called _____________________.
6. The type of feedback loop that allows the AP to be regenerative is called a __________ feedback loop.
7. Proteins which allow ions to pass through membranes only after they are stimulated by chemical messengers are called ________________.
8. The cells that help to insulate axons in the central nervous system are ________________________.
9. Achetylcholine is removed from the synapse via _________________________________.
10. The name of the poison that binds irreversibly to Ach receptors is called _______________________.
11/12. The maximum speed at which axons can carry APs is determined by the __________ of the axon
and whether or not it is _________________.
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Essay/Short Answer (@ 10 pts). Answer only 2 of the following 3. The first 2 answered will be graded.
1) Compare/contrast the differences between axonal type of membrane versus the post-synaptic membrane found at the synapse.
2) Draw and label a graph that illustrates both the membrane potential and the underlying currents over time before, during and after an action potential.
3) Draw and label a axonal membrane approximately 3 mSec after it has been stimulated past threshold. Be sure to include enough detail to show me that you understand what is happening to the membrane and important ions at that time.