Lecture 12

Question 1

What does the motor neuron fibre (axon) do in order to make a muscle contract?

Answer 1

The motor neuron sends impulse that will signal the vesicles containing ACh (Acetylcholine) to interact with the receptors along the muscle fibre and release its contents.

Question 2

What effect does the ACh (Acetylcholine) have when it interacts with the ACh receptors along the muscle fibre?

Answer 2

The ACh interacts with the ACh receptors along the muscle fibre and causing a signalling cascade that causes calcium to be released into the muscle fibres, which is then used in some of the energy processes required to shorten the sarcomeres.

Question 3

Why is calcium important for muscle contractions?

Answer 3

Calcium flows into the muscle cell binding with troponin, allowing Actin and Myosin to bind. The Actin and Myosin cross bridges bind and contract using ATP.

Question 4

What is the sarcoplasmic reticulum?

Answer 4

The region inside the muscle cell that stores calcium, and releases calcium when muscle contraction occurs.

Question 5

The force of the contraction depends on which factors of the motor unit?

Answer 5

• Size.
• Number.
• Rate of firing.

Question 6

What does bones, muscles contraction, the joint and load mean in terms of anatomical lever.

Answer 6

Bones = levers
Muscle contraction = pull
Joint = pivot
Load = external or internal.

Question 7

What type of lever attachment is it when the resistance (weight) is on the end and the axis (pivot) is in the middle with the support force at the other end?

Answer 7

Stabilising joint position. (e.g. skull held in place by muscles in the neck).

Question 8

What type of lever attachment is it when the axis (pivot) is on one end, the resistance (weight) is in the middle and the support force is on the other end?

Answer 8

A joint that is effective at overcoming loads (e.g. calves when doing a standing calf raise).

Question 9

What type of lever attachment is it when when the axis is on one end, the resistance is on one end and the support force is in the middle?

Answer 9

A joint that allows for a large ROM and speed. (e.g. biceps/elbow joint).

Question 10

Define a concentric muscle contraction.

Answer 10

When the muscle shortens (muscle fibres remain the same length but overlap more) by the sacromeres moving closer together. This results in a change in joint position and develops tension.

Question 11

Define a isometric muscle contraction.

Answer 11

When a muscle remains the same length, but the muscle is active (develops tension) e.g. holding a book in place (no movement).

Question 12

Define a eccentric muscle contraction.

Answer 12

When the muscles lengthen (muscle fibres remain same length, however sarcomeres more further a part, fibres overlap less). e.g. lowering a weight using the biceps.

Question 13

Define the agonist muscle role.

Answer 13

The muscle that acts concentrically in a movement. (e.g. flexing biceps).

Question 14

Define the antagonist muscle role.

Answer 14

The muscle that acts eccentrically in a movement. (e.g. triceps when flexing biceps).

Question 15

Define the stabiliser muscle role.

Answer 15

When a muscle is active in order to hold a joint still. (e.g. biceps when holding a book, the biceps are isometric).

Question 16

Define the neutraliser muscle role.

Answer 16

A muscle that prevents unwanted movement caused by another muscle. e.g. drinking from a glass the pronator muscles neutralise the supinator muscles to hold the hand between the 2 positions).