Muscle Microstructure

Question 1

What is muscle?

Answer 1

-large complex bundle of fibres surrounded by fascia and a layer of epimysium

Question 2

What is fasciculus

Answer 2

Smaller compartments containing thousands of muscle fibres

Question 3

What are muscle fibres?

Answer 3

The Individual muscle cell
-fuses with the tendon

Question 4

What are myofibrils

Answer 4

Several thousand myfibrils contained in each muscle cell

Question 5

What are filaments?

Answer 5

Contained in each myofibril are filaments actin and myosin (seen as light and dark striations of the muscle fibre)

Question 6

What is the sliding filament theory?

Answer 6

-Myosin heads create cross bridges attaching to actin
-if nerve impulse is strong enough the myosin pulls the two actin filaments together, which shortens the length of the muscle fibre

-the muscle fibres become thicker due to overlapping of filaments

Question 7

What’s the transmitter from a nerve impulse called?

Answer 7

Acetylcholine
- causes calcium ions to be released from the cell membrane

Question 8

4points of muscle contracting completely or not at all

Answer 8

• all fibres in a motor unit get same stimulation
• all fibres react maximally when threshold is met
• Gross motor unit : many units stimulated
• fine motor unit : few units stimulated