Question

1. The membrane is more permeable to K+ than to Na+:

a. At resting membrane potential

b. During the depolarization phase of an action potential

c. After a neurotransmitter in an excitatory synapse binds to the postsynaptic cell

d. More than one of the above is correct

2. During an action potential, the depolarization of the neuron membrane is the result of:

a. Sodium moving into the cell

b. Potassium moving into the cell

c. Sodium moving out of the cell

d. Potassium moving out of the cell

3. Phoneutriatoxin, produced by the banana spider, slows the closing of the voltage-gated sodium channels. which of the following is the best prediction of how action potentials would be impacted if an individual is poisoned with this toxin?

a) no action potentials would occur at all

b) the action potential would be shorter in time and smaller in magnitude

c) the ability to fire action potentials in rapid succession would be decreased

4. Assume that normal potassium concentration in the ICF is 140 mM, and that normal potassium concentration in the ECF is 4 mM. If the potassium concentration in the extracellular fluid of the brain decreases to 2 mM, neural activity in the brain would:

a. Increase b. Decrease c. Not change

Answer 1

Ans 1: (a) At resting membrane potential

Explanation: Resting Membrane Potential is the voltage difference across the cell membrane in the moment when the cell is at the condition of rest. It is the sum total of charges.

Ans 2: (a) Sodium moving into the cell

Explanation: The depolarization of membrane is associated during action potential as a result of sudden and transient influx of sodium ions via opened voltage gated sodium channels. During rest, these channels are closed.

Ans 3: (a) no action potentials would occur at all

In case if the Na+ channel is blocked, the cell will be unable to depolarize. The action potential will not be generated. By adding 120 mM K+ to the extracellular fluid, the cell will get depolarized without an action potential

Ans 4: (b) decrease

A lack of potassium in brain is associated with hallucination, palpitation, confusion, psychosis and depression. Muscle weakness, muscle cramps and arrythmia may also develop.