[15.7] structure of a skeletal muscle Flashcards
1
Q
what are the 3 types of muscles in the body?
A
- cardiac
- smooth
- skeletal
2
Q
describe cardiac muscle
A
- found only in the heart
- myogenic, can maintain its own contractions
- does not fatigue but have to keep supplying glucose and oxygen for aerobic respiration
3
Q
describe smooth muscle
A
- found in walls of blood vessels and in digestive system
- contracts slowly and fatigues slowly
- does not contract with a lot of force
- can be temporarily switched off when adrenaline favours blood to skeletal muscles
4
Q
describe skeletal muscle
A
- muscle attached to bone
- maintains posture
- initiates movement
- contracts fast + forcefully
- fires rapidly
- requires voluntary, conscious effort
5
Q
describe the structure of a whole muscle
A
- whole muscle -> bundles of muscle fibres
- bundles of muscle fibres -> nerves, blood capillaries, single muscle fibres
- single muscle fibres -> myofibrils
6
Q
describe the structure of a single muscle fibre
A
- sarcolemma
- striations
- nucleus
- myofibrils in sarcoplasm
7
Q
what is the sarcolemma?
A
cell membrane surrounding a skeletal muscle fibre
8
Q
what is the sarcoplasm?
A
cytoplasm surrounding muscle tissue
9
Q
what types of protein filaments are in myofibrils?
A
- actin
- myosin
10
Q
describe the difference in structure between actin and myosin
A
- actin - thinner, has two strands twisted around one another
- myosin - thicker, has long rod-shaped tails with bulbous heads
11
Q
describe the features of the microscopic structure of a myofibril
A
- I band (light band)
- A band (dark band)
- Z-line
- M-line
- H-zone
12
Q
what is the I band?
A
area with only horizontal actin strands, no overlap with myosin
13
Q
what is the A band?
A
- entire width of the myosin block
- doesn’t only have myosin; some overlap with actin towards ends
14
Q
what is the Z-line?
A
vertical strand connecting actin block (I band)
15
Q
what is 1 sarcomere defined by?
A
distance between two Z-lines
