Which factors contribute to squid axon’s refractory period

Reference no: EM13289197

1. Which of the following is the cell type most directly relevant to battling the pathogens the bullet likely carried into the brain of Rep. Gabrielle Giffords?

A. Schwann cells

B. microglia

C. oligodendrocytes

D. astrocytes

E. arachnoid villi

2. Which of the following is a cell type important for re-myelinating axons in damaged portions of the recovering brain of Rep. Gabrielle Giffords?

A. Schwann cells

B. microglia

C. oligodendrocytes

D. astrocytes

E. arachnoid villi

3. Which of the following is the cell type interacting with endothelial cells via endfeet in the recovering brain of Rep. Gabrielle Giffords?

A. Schwann cells

B. microglia

C. oligodendrocytes

D. astrocytes

E. arachnoid villi

4. Rep. Gabrielle Giffords had to remain in the intensive care unit for longer than originally planned because of excessive intracranial pressure. Which of the following is most relevant to the uptake of the fluid responsible for causing this pressure?

A. carotid artery

B. choroid plexus

C. oligodendrocytes

D. astrocytes

E. arachnoid villi

5. Which of the following correctly describes how myelination alters the passive properties of the neuronal membrane?

A. causes faster decay of depolarization by reducing resistance

B. increases resistance, reduces capacitance

C. regenerates the action potential after skipping a large stretch of axon

D. decreases flux through Na+ channels, thereby speeds up action potential

E. none of the above are completely correct

MCDB 4777/5777 2/2/11 EXAM I Page 2

6. Which factors contribute to the squid axon’s refractory period?

A. inactivation domain of voltage gated potassium channel; flux through voltage gated sodium channel

B. inactivation domain of voltage gated sodium channel; flux through voltage gated potassium channel

C. inactivation domain of voltage gated sodium channel; flux through Na+/K+ ATPase

D. inactivation domain of calcium gated potassium channel; flux through inward rectifier potassium channel

E. none of the above are completely correct

7. In which of the following ways does the voltage-gated “delayed rectifier” potassium channel in the squid giant axon (i.e. the channel we discussed as important in the action potential) differ from the voltage-gated sodium channels?

A. depolarization causes the sodium channels to inactivate after their activation

B. the potassium channels lack selective permeability

C. flux through potassium channels does not affect the shape of the action potential

D. the potassium channels only allow ions to flow one way

E. potassium channels are formed from a single polypeptide chain having multiple similar domains, whereas sodium channels are tetramers

8. The proteins that use ATP to establish the ionic gradients responsible for action potentials are part of the larger category of:

A. ligand-gated ion channels

B. passive transporters

C. voltage-gated ion channels

D. inward rectifier or “leak” channels

E. active transporters

9. The example of NaV1.7, mutated in some congenital pain syndromes, provide evidence of all of the following excepta.

a mutation in an ion channel can lead to perception of stimuli that are not present

b. the sodium channel gene family likely evolved so that multiple different sodium channels can be expressed in a single neuron

c. targeting ion channels encoded by specific genes could lead to therapeutics with fewer side effects

d. different sodium channel genes are redundant, so loss of function of an individual gene has little effect

e. amino acid substitutions in many different parts of ion channels can lead to functional changes

10. The voltage clamp technique is most useful for…

a. measuring the resting potential (voltage) of the membrane

b. determining the normal shape of action potentials in an axon

c. determining the ion concentrations inside and outside the axon

d. measuring membrane permeability as a function of voltage

e. testing whether changing the concentration of an ion influences membrane voltage.

Reference no: EM13289197

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