Chapter 9 Part 4

Question 1

Though exceedingly close, axonal ends and muscle fibers are always separated by a space called the _______.

Answer 1

synaptic cleft

Question 2

When a nerve impulse reaches the end of an axon at the neuromuscular junction, voltage-regulated ______ channels open and allow ______ to enter the axon.

Answer 2

When a nerve impulse reaches the end of an axon at the neuromuscular junction, voltage-regulated calcium channels open and allow Ca²⁺ to enter the axon.

Question 3

Ca²⁺ inside the axon terminal causes axonal vesicles to fuse with the axonal membrane. This fusion releases ______ into the synaptic cleft via ______.

Answer 3

Ca²⁺ inside the axon terminal causes axonal vesicles to fuse with the axonal membrane. This fusion releases ACh into the synaptic cleft via exocytosis.

Question 4

Binding of ACh to its receptors initiates an _______ in the muscle.

Answer 4

action potential

Question 5

Acetylcholine bound to ACh receptors is quickly destroyed by the enzyme _______.

Answer 5

Acetylcholinesterase

Question 6

What is the name for a transient depolarization event that includes polarity reversal of a sarcolemma (or nerve cell membrane) and the propagation of an action potential along the membrane?

Answer 6

Action Potential

Question 7

What is an action potential?

Answer 7

A transient depolarization event that includes polarity reversal of a sarcolemma (or nerve cell membrane)

And the propagation of an action potential along the membrane.

Question 8

____ and ____ diffuse in and the interior of the sarcolemma becomes less negative.

This event is called _______.

Answer 8

Na^{<strong>+</strong>}and K⁺ diffuse in and the interior of the sarcolemma becomes less negative.

This event is called depolarization.

Question 9

In a polarized sarcolemma, the outside (extracellular) face is ______, while the inside face is ______.

The difference in this charge is called ______.

Answer 9

In a polarized sarcolemma, the outside (extracellular) face is positive, while the inside face is negative.

The difference in this charge is the resting membrane potential.

Question 10

In a polarized sarcolemma, the predominant extracellular ion is ____.

While the predominant *intracellular *ion is ____.

Answer 10

In a polarized sarcolemma, the predominant* extracellular* ion is Na⁺.

While the predominant intracellular ion is K⁺.

Question 11

When Na⁺ enters the cell, the resting potential is ______ and ______ occurs.

If the stimulis is strong enough, an ______ is initiated.

Answer 11

When Na⁺ enters the cell, and the resting potential is decreased** and **depolarization occurs.

If the stimulis is strong enough, an action potential is initiated.

Question 12

Repolarization occurs in the same direction as depolarization, and must occur before the muscle can be stimulated again. This is called the _______.

Answer 12

Repolarization occurs in the same direction as depolarization, and must occur before the muscle can be stimulated again. This is called the refractory period.

Question 13

What restores the ionic concentration of the resting state?

Answer 13

The ionic concentration of the resting state is restored by the Na⁺ - K⁺ pump

Question 14

What powers excitation-contraction coupling?

Answer 14

the hydrolysis of ATP powers excitation-contraction coupling.

Question 15

What occurs when the muscle is in a state of physiological inability to retract?

Answer 15

Muscle fatigue occurs when the muscle is in a state of physiological inability to retract.