Functional Anatomy - Year 12

Question 1

Structure of a skeletal muscle

Answer 1

Epimysium - surrounds the whole muscle belly
Perimysium - surrounds the fasicle
Endomysium - surrounds each muscle fibre
Fascicle - bundle of muscle fibres -> inside the fasicle is the …
Muscle fibres - which contain the myofibrils
Myofibrils - contain the sarcomers for muscle contraction

Question 2

Describe the sliding filament theory

Answer 2

1. Neuromuscular junction is activated by acetylcholine, so that calcium is released from the muscle.
2. Calcium initiates cross bridges to find ATP
3. Cross bridges from myosin pull on actin molecule
4. Sarcomere shortens and muscle contracts

Question 3

Force velocity

Answer 3

When a force is low = a muscle contracts with high velocity

When a force is high = a muscle contracts with low velocity

Question 4

Force length

Answer 4

• the length of a muscle effects how well it creates tension
• the force length relationship shows how muscle force varies at different lengths.
• peak force occurs at normal resting length (120°) because there is maximal cross bridge attachments for the the actin and myosin.

Question 5

Types of muscle contraction types

Answer 5

Concentric - muscle shortens
Eccentric - muscle lengthens
Isometric - muscle length stays the same

Question 6

All or nothing principal

Answer 6

States that once a threshold is met, all muscle fibres in a motor unit will either contract with 100% or not at all.
When we want a muscle to contract …
- we have to activate the motor units and an electrical impulse is sent down from the CNS
- the electrical impulse must reach a threshold
- all of the fibres of that Motor unit will contract at the same time to their maximal effort

Question 7

Motor unit

Answer 7

A motor neuron and the fibres it stimulates

Question 8

Structure of a motor neuron…

Answer 8

1. Cell body - directs the neurons activities, connects to the dendrites and axon, contains the nucleus
2. Dendrites - receives impulses from other neurons and feeds it to the cell body.
3. Axon - transmits the message away from the cell body towards the muscle.

Question 9

Spinal cord

Answer 9

Sends sensations to the brain from the body and return motor commands to the various parts of the body

Question 10

Types of neurons

Answer 10

Motor neurons - conduct impulses from the brain to the muscles.
Sensory neurons - conduct impulses from the sensory organs eg eyes to the brain.

Question 11

Characteristics of slow twitch fibres

Answer 11

Slow twitch ;

• Have a slow contraction time
• high resistance to fatigue
• used for aerobic activity
• low force production
• high capillary density
• fuel source; triglycerides and glycogen

Question 12

Characteristics of fast twitch (type IIa)

Answer 12

Type IIa)

• fast contraction time
• medium resistance to fatigue
• used for long term anaerobic activities
• high force production
• intermediate capillary density
• fuel source; creatine phosphate and glycogen

Question 13

Fast twitch (type IIb)

Answer 13

• very fast contraction time
• low resistance to fatigue
• used for short term anaerobic activity
• very high force production
• low capillary density
• fuel source; creatine phosphate and glycogen