Skeletal Muscle Phys (Muscle Switch, Latent Period)

Question 1

What does the motor unit consist of?

Answer 1

• motor neurons

- all muscle fibers it innervates

Question 2

Where do the motor neurons and muscle fibers intersect?

Answer 2

-neuromuscular junction

Question 3

Where is the location of the neuromuscular junction?

Answer 3

• where the axon terminal of the neuron meets a specialized region of the muscle fibers plasma membrane, called the motor end plate

Question 4

All of the events in the neuromuscular junction lead to what kind of potential?

Answer 4

-end-plate potential

Question 5

Step by step process of excitation- contraction coupling

Answer 5

1. Action potential in a motor neuron triggers the release of ACh from its terminal
2. ACh diffuses onto the muscles fibers plasma membrane (Sarcolemma) and binds to receipts in the motor end plate, initiating a change in ion permeability that results in grade depolarization of the muscle plasma membrane (end plate potential)
3. End-plate potential triggers a series of events that results in the concentration of a muscle cell.

Question 6

What is a muscle twitch?

Answer 6

-mechanical response to a single action potential

Question 7

What are the 3 phases of a muscle twitch?

Answer 7

1. Latent period: period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle contraction
   
   • no force generated
   • chemical changes occur intracellularly in preparation for contraction
2. Contraction phase: starts at the end of latent period and ends when muscle tension peaks
3. Relaxation phase: period of time from peak tension until the end of the muscle contraction

Question 8

Skeletal muscles are connected to bones by

Answer 8

Tendons

Question 9

Skeletal muscles are composed of hundred to thousands of individual cells called

Answer 9

Fibers

Question 10

What is the period of time that elapses between the generation of an action potential and the start of muscle tension development in a muscle fiber?

Answer 10

-latent period

Question 11

What occurs during the latent period of these isometric contractions?

Answer 11

-all steps of excitation-contraction coupling occur

Question 12

An action potential in a motor neuron triggers the release of which neurotransmitter?

Answer 12

• Acetylcholine

Question 13

The term skeletal muscle fiber refers to

Answer 13

-an individual skeletal muscle cell

Question 14

The graded depolarization in the skeletal muscle fiber that is elicited in response to one action potential from the motor neuron is called

Answer 14

-EPP (end-plate potential)