Lecture 12: Muscle - Actions & Roles

Question 1

Muscular + _______ systems interact to produce muscle activity

Answer 1

• Nervous

Question 2

Why does the sarcoplasmic reticulum’s structure have to be slightly different?

Answer 2

• Because there are nuclei all up and down the muscle fibre

Question 3

What kind of messages do neurons carry?

Answer 3

• Electrical (action potential)

Question 4

Tissue between neuron and muscle fibre…

Answer 4

• Neuromuscular Junction

Question 5

Neuromuscular Junction features:

Answer 5

• Large SA
• Synaptic Cleft
• Chemicals in synaptic cleft

Question 6

Steps occurring in action potential event….

Answer 6

• Electrical –> Chemical –> Electrical

Question 7

What are t-tubules like?

Answer 7

• Tunnels that burrow through the muscle fibres

- Action potentials travel down t-tubules that trigger calcium release

Question 8

Why is Ca2+ so important for contraction?

Answer 8

• Myosin head exposed, come up and attach to actin filament, contract, and detach

Question 9

What is the sliding filament theory?

Answer 9

• Sarcomeres pulled toward each other

Question 10

A motor unit is…

Answer 10

• A motor neuron, all it’s little nerves, and all the muscle fibres it attaches to

Question 11

What’s controlling contraction?

Answer 11

• Electrical event

Question 12

Motor unit displays _____ or ______ activation of fibres

Answer 12

• All or none

Question 13

Force of contraction in a whole muscle depends on:

Answer 13

Characteristics of motor units:

• -> Size
• -> Number (increase = increase force of contraction)
• -> Rate of firing’

Muscle Attachments

• -> efforts needed for movement
• -> determines muscle role

Question 14

Think of bones as_____. Joint = ____. Muscle Contraction = ______. Load = _____.

Answer 14

• Lever
• Pivot
• Pull
• External / Internal

Question 15

Types of levers with muscle attachments:

Answer 15

• 1. Stabilise Joint Position (skull + muscles @ base)
• 2. Effective at overcoming loads (ankle)
• 3. Large range of movement and speed (biceps)

Question 16

Types of muscle action:

Answer 16

• Concentric
• Eccentric
• Isometric

Question 17

What happens during concentric contraction?

Answer 17

• Muscle is active
• Change in joint position
• Muscle is shortening at the same time
• (Flexion)

Question 18

What happens during isometric contraction?

Answer 18

• Muscle develops tension but length of muscle does not change
• eg. holding a book on hand

Question 19

What happens during eccentric contraction?

Answer 19

• Muscle is active and developing tension
• Change in joint position
• Muscle lengthening
• (Extension)

Question 20

Types of muscle role:

Answer 20

• Agonist
• Antagonist
• Stabiliser
• Neutraliser

Question 21

Agonist:

Answer 21

• Muscle creating desired movement (bicep flexing, developing tension, and shortening) // concentric

Question 22

Antagonist:

Answer 22

• Works against / with agonist, tricep + bicep

- Lengthening // eccentric

Question 23

Stabiliser:

Answer 23

• Any time you’re keeping still

- A muscle is active to hold a joint still

Question 24

Neutraliser:

Answer 24

• Muscle eliminates an unwanted movement (possibly caused by another muscle)
• Pronator muscles neutralise supinating effect of biceps brachii