Muscle Fibers & Activity

Question 1

List the 3 types of contractile units and describe them. (3)

Answer 1

1. Myosin → contractile protein found in muscle
2. Actin → contractile protein
3. Sacromere → smallest contractile unit of the muscle

Question 2

What are the 5 roles or functions of muscles? (5)

Answer 2

1. Produce movements
2. Maintain posture and body position
3. Stabilize joints
4. Generate heat
5. Protection

Question 3

How does the sarcolemma present under a microscope? (1)

Answer 3

1. Many oval nuclei just beneath the plasma membrane

Question 4

What’s another way to refer to the sarcolemma?

Answer 4

Muscle husks

Question 5

List 4 functional properties of skeletal muscles. (4)

Answer 5

1. Irritability (responsiveness) is the ability to receive and respond to a stimulus
2. Contractility is the ability to forcibly shorten when stimulated
3. Extensibility is the ability of muscle fibers to stretch
4. Elasticity is their ability to recoil and resume their resting length after being stretch

Question 6

Define: depolarization

Answer 6

Loss of a state of polarity; loss of a negative charge inside the plasma membrane

Question 7

What does the muscle require in order to contract?

Answer 7

Stimulation

Question 8

How many muscle fibers can one motor neuron stimulate?

Answer 8

A few muscle fibers to hundreds of them, depending on the particular muscle and the work it does

Question 9

Define: action potential

Answer 9

An electrical event occurring when a stimulus of sufficient intensity is applied to a neuron or muscle cell, allowing sodium ions to move into the cell and reverse the polarity

Question 10

What is the purpose/operation of the sodium-potassium pump?

Answer 10

Actively transport sodium and potassium ions back to their initial positions

Question 11

How must ATP be regenerated if contractions are to continue?

Answer 11

ATP must be regenerated continuously

Question 12

What are the 3 pathways used to regenerate ATP? (3)

Answer 12

1. Direct Phosphorylation of ADP by creatine phosphate
2. Aerobic respiration
3. Anaerobic glycolysis and lactic acid formation

Question 13

What breaks down to form pyruvic acid?

Answer 13

Glucose

Question 14

Briefly describe the 2 types of muscle contractions

Answer 14

1. Isotonic → the myofilaments are successful in their sliding movement; the muscle shortens and movement occurs
2. Isometric → contraction where the muscles do not shorten

Question 15

In isometric contractions, what increases despite the lack of movement?

Answer 15

The tension in the muscle keeps increasing

Question 16

Define: muscle tone

Answer 16

The result of different motor units scattered through the muscle

Question 17

How is muscle ton stimulated?

Answer 17

In a systemic way

Question 18

Define: flaccid

Answer 18

Soft and flabby

Question 19

Define: atrophy

Answer 19

to waste away

Question 20

During contraction, what part of the skeletal muscle moves and towards what does it move to?

Answer 20

A skeletal muscle INSERTION moves towards the ORIGIN