Some natural and synthetic compounds block potassium channels, in some cases eli

Question

Some natural and synthetic compounds block potassium channels, in some cases eliminating permeability to K+. What would happen to membrane potential (Vm) with these compounds? HINT: GHK Equation

Question 5 options:

a)

Membrane potential would go all the way to the sodium equilibrium potential +60 mV.

b)

Membrane potential would become less negative (e.g, -40 mV)

c)

No change in membrane potential

d)

Membrane potential would become more negative (e.g., -90 mV)

Which of the following statements about the central nervous system are true?

Question 7 options:

a)

The descending tracts carry efferent (motor) signals from the brain.

b)

The ascending tracts carry sensory information to the brain.

c)

The dorsal root of each spinal nerve carries incoming sensory information

d)

The ventral root of each spinal nerve carries information from the CNS to muscles and glands.

e)

All of these statements are true.

a)

Membrane potential would go all the way to the sodium equilibrium potential +60 mV.

b)

Membrane potential would become less negative (e.g, -40 mV)

c)

No change in membrane potential

d)

Membrane potential would become more negative (e.g., -90 mV)

Explanation / Answer

5)

The resting membrane potential is -60mV when there is equilibrium between the sodium (Na+) and potassium (K+) channels. The mebrane becomes positive to K+ equilibrium and the membrane potential reaches to -90mV when the potassium cahnnels are open. When the potassium channels are closed or less permeable, then the membrane potential becomes less negative or -40mV. According to GHK equation, the Na+ channels are normally closed but could be opened by a depolarization. Therefore, voltage dependent Na+ channels change the membrane potential to +40mV. The opposite occurs with K+ channels and membrane potential becomes less negative. Therefore, option b is correct.

7)

The ascending tracts carry the sensory information to brain. The descending tracts carry motor or efferent signals information from brain to muscles and glands. The dorsal root of spinal nerve gathers the incoming sensory information. The ventral or anterior roots of spinal nerves carry information from central nervous sytem to various effectors or muscles and organs. Therefore, option e is correct.

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