Chapter 8 -

Question 1

How do muscles contract?

Answer 1

A nerve must stimulate skeletal muscle or it will not contract. CNS - Motor nueron - Muscle

Question 2

What does a neuron do?

Answer 2

It transmits electrical signals from the CNS to the muscle

Question 3

What is a motor unit?

Answer 3

The motor neuron and all of the muscle fibers it innervates

Question 4

How does the size of a motor unit change for fine movements versus gross movements?

Answer 4

Neuromuscular junction - the site where the motor neuron and muscle cell meet.
Synaptic Cleft - Space between the end of the motor neuron and muscle fiber.
Motor end plate - “the pocket” formed on the sarcolemma at the neuromuscular junction.

Question 5

How do nerves initiate the signal to begin muscular contractions?

Answer 5

Stimulation from motor neutrons initiates contraction process

Question 6

What is the charge of cells?

Answer 6

Cells are positively charged on the outside and negatively charged on the inside

Question 7

Why does sodium stay outside of the cell?

Answer 7

Proteins within the membrane close the gates.

Question 8

What is the resting membrane potential?

Answer 8

-70 mV

Question 9

What is the resting membrane potential ?

Answer 9

At rest all cells are negatively

Question 10

How do nerves initiate the signal to begin muscular contractions?

Answer 10

Stimulation from motor neurons initiates contraction process.

Question 11

At rest, cells are positively charged on the outside and negatively charged on the inside. Why does sodium stay outside of the cell?

Answer 11

Proteins within the membrane close the gates

Question 12

What is the resting membrane potential?

Answer 12

At rest cells are negatively charged, the cell is polarized and the charge difference is called the resting membrane potential.

Question 13

When a stimulus of sufficient strength reaches the neuron, sodium gates open and sodium enters the cell.

Answer 13

This makes the cell more positive

Question 14

When is threshold reached and what happens when threshold is reached?

Answer 14

Sodium gates open and action potential (nerve impulse) is formed and transmitted.

Question 15

Explain “all or none” principle

Answer 15

A muscle cell contracts normally or not at all

Question 16

What happens when the nerve and muscle meet?

Answer 16

The muscle and nerve come together at the neuromuscular junction but the nerve does not actually touch the nerve: there is a gap between them

Question 17

What is the name given to the space between the nerve and muscle?

Answer 17

Synaptic Cleft

Question 18

What is the motor end plate?

Answer 18

The end of a motor neuron that transmits neural impulses to a muscle.

Question 19

What are the small sacks called at the end of the motor nerve?

Answer 19

Synaptic Vesicles

Question 20

What is in the synaptic vesicles?

Answer 20

Acetylcholine

Question 21

What are the 7 steps that happen when an action potential arrives at the neuromuscular junction?

Answer 21

1. When an action potential arrives at the neuromuscular junction, it causes the release of calcium
2. The calcium triggers the synaptic vesicles to release acetylcholine into the synaptic cleft
3. The acetylcholine binds to receptors on the sarcolemma.
4. This results in the opening of sodium channels
5. Na+ enter the cell, it depolarizes, and an action potential occurs.
6. The wave of depolarization spreads across the sarcolemma in all directions and deep into the muscle in the transverse tubules.
7. This causes calcium to be released from the sarcoplasmic reticulum.