Unit 3.4: Mechanics of Muscle Contraction and Body Movement

Question 1

What is a motor unit?

Answer 1

Basic unit of contraction in an intact skeletal muscle

Question 2

What is a motor unit composed of?

Answer 2

• a group of muscle fibers

- the somatic motor neuron that controls them

Question 3

What are the 2 types of skeletal muscle fibre type?

Answer 3

• Fast-twitch motor unit

- Slow-twitch motor unit

Question 4

True or False:

Each motor unit contracts in an all-or-none fashion

Answer 4

True.

Question 5

How can the contraction of a muscle be varied?

Answer 5

1. Changing the type of motor unit that is activated

2. Changing the number of motor units that are active

Question 6

How is the force of a contraction of a muscle increased?

Answer 6

By using more motor units

Question 7

Which one has a higher threshold for stimulation:
- Slow oxidative fibres
or
- Fast glycolytic fibres?

Answer 7

Fast glycolytic fibres

Question 8

Which will have more muscle fibres per motor unit, those involved in fine movements or those used for course movements?

Answer 8

Course

Question 9

What are the 2 main types of muscle contraction?

Answer 9

• isotonic

- isometric

Question 10

What is an isotonic body movement?

Answer 10

• creates force and moves a load

- load is constant and the muscle length changes

Question 11

What is an isometric body movement?

Answer 11

• create force WITHOUT movement
• muscle length is constant
• load is greater than the force that can be applied

Question 12

How can an isometric contraction create force if there is no change in muscle length?

Answer 12

Even though sarcomeres shorten, muscle length stays constant because these elastic elements stretch to take up force until fully stretched