structure and contraction of skeletal muscle

Question 1

properties of muscle

Answer 1

• excitability: ability of respond to stimuli e.g. action potential
• contractility: ability to muscle tissue to contract
• extensibility: ability of muscle tissue to stretch when relaxed
• elasticity: ability of muscle tissue to regain its shape when extended or contracted

Question 2

types of muscle tissue

Answer 2

skeletal muscle (also striated/ striped):
- attaches to and moves skeleton
- under conscious control

cardiac muscle (in heart):
- striated appearance
- under involuntary control
- does not require an external stimulus to initiate muscle contraction

smooth muscle:
- doesn’t have striated appearance
- found where the body controls contractions and relaxations automatically e.g lining the alimentary canal, uterus and bladder

Question 3

differences between involuntary and voluntary control

Answer 3

IN: no conscious control over the muscle
VO: deliberately control and relax the muscle

Question 4

nerve and blood supply of muscle

Answer 4

well vascularised:
- uncle contraction requires a large amount of energy and must be supplied with nutrients and oxygen
- produces a large amount of waste products hat must be removed

well innervated:
- muscle contracts in response to a nerve impulse

Question 5

structure of skeletal muscle

Answer 5

• each muscle is made up of numerous fascicles
• each fascicle is made up of bundles of muscle cells (fibres)
• CT sheath protects and strengthens the muscle
• CT sheath extended at either extreme of the muscle to form the tendon
• tendon attaches muscle to bone
• within CT sheath are muscle fibres

Question 6

structure of skeletal muscle cells

Answer 6

• long cylindrical multi-nucleated cells
• sarcolemma (plasma membrane)
• T-tubules (invagination of sarcolemma)
• sarcoplasm (cytoplasm)
• sarcoplasmic reticulum (specialised smooth ER, stores Ca2+)
• each muscle cell is made up of long contractile filaments called myofibrils (located within the sarcoplasm
• myofibril contains filaments: myosin and actin (myofilaments)

Question 7

structure of muscle filaments

Answer 7

2 types: thick myosin and thin actin
- do not extend the length of the myofibril
- myofibril is made up of sarcomeres (functioning units)
- A and I band on top and Z and H zone
- Z= separate each functioning unit
- H= thick only
- A = tick filaments and overlap with thin filaments
- I = thin only

Question 8

order of muscle

Answer 8

muscle
fascicle
fibres (cells)
myofibrils
myofilaments

Question 9

muscle growth

Answer 9

• mostly due to muscle fibre hyper trophy e.g increased fibre size
• muscle fibre hyperplasia may also occur

Question 10

connective tissue

Answer 10

• epimysium - outer covering (specialised fascia) of entire muscle
• perimysium- extension of epimysium that divides muscle into bundle of fibres called fasciculi
• endomysium- surrounds muscle fibres (extension of perimysium)

dense CT description