Question

1. What channels or carriers are NOT found at the axon to the axon terminal?

Select one:

a. Na⁺ leaky channels

b. Cl^- gated channels

c. Na⁺ gated channels

d. Na⁺-K⁺ ATPase

e. None of the above

2. What is TRUE about action potential in the neuron? There may be more than one answer.

Select one or more:

a. At resting membrane potential (-70mV), the inactivation gate of the Na⁺ channel is closed while the activation gate is opened.

b. During depolarization from -55mV to +30mV, the K⁺ gated channel is closed while both inactivation gate and activation gate of Na⁺ channel are opened causing Na⁺ influxes.

c.During repolarization from +30mV to -55mV, the K⁺ gated channel is open and its gate will remain open during hyperpolarization, which begins from -70mV to -90mV.

d. From -70mV to -90mV of the after hyperpolarization, the K⁺ gated channel will remain open and influxes of K⁺ will occur. From -90mV to -70mV, Na⁺ leaky channel, K⁺ leaky channel, and Na⁺-K⁺ ATPase will bring the membrane potential back to resting membrane potential.

e. Myelinated axon and smaller diameter of the axon will cause a faster conduction velocity of action potential.

3. Which of the following describes the characteristics of a muscle fiber? There may be more than one answer.

Select one or more:

a. Slow oxidative fibers have the highest endurance, larger motor unit size, and involved during asynchronous and synchronous motor unit recruitment.

b. All muscle fibers are polynucleated, cylindrical, and striated.

c. Fast oxidative fibers have high levels of mitochondria, capillary, and myoglobin but have less endurance than slow oxidative fibers but greater endurance than fast glycolytic fibers.

d. Fast glycolytic fibers have the greatest force generating capacity but only recruited during maximal contraction.

e. When a muscle fiber is at its optimal muscle length (I_o) (optimal overlap of the thick and thin filaments) at the onset of contraction, the percent of maximal tension develop will be 100%.

4. The whole muscle tissue is protected by a layer of __________, while the muscle fascicle is protected by ________, and individual muscle fiber is surrounded by _______, respectively.

Select one:

a. epimysium, endomysium, perimysium

b. endomysium, perimysium, epimysium

c. epimysium, perimysium, endomysium

d. endomysium, epimysium, perimysium

e. perimysium, epimysium, endomysium

5. What is FALSE about the neuromuscular junction?

Select one:

a. When an action potential reaches the axon terminal, Ca²⁺ gated channel will open and Ca²⁺ influx will occur.

b. Exocytosis of acetylcholine can bind to nicotinic receptor or it can bind to acetylcholine esterase at the motor-end plate.

c. When one acetylcholine binds to nicotinic receptor, the gate at the receptor will open and allow greater Na⁺ influxes more than K⁺ effluxes, causing an excitatory end-plate potential.

d. Acetylcholine esterase at the motor-end plate splits acetylcholine into acetyl and choline, causing an inhibitory end-pate potential.

e. Curare blocks the nicotinic receptor at the neuromuscular junction while botulinum toxin blocks the release of acetylcholine from the axon terminal. Both leads to respiratory failure or paralysis.