13.9 Voluntary And Involuntary Muscles

Question 1

3 types of muscle in the body

Answer 1

Skeletal
Cardiac
Involuntary

Question 2

Structure and function of skeletal muscles

Answer 2

Responsible for movement
Striated fibre appearance
Regularly arranged so muscle contracts in one direction
Rapid contraction speed
Short contraction length
Fibres are tubular and multi nucleated

Question 3

Structure and function of cardiac muscle

Answer 3

Specialised striated fibres
Involuntary control
Cells branch and interconnect causing simultaneous contraction
Intermediate contraction speed
Intermediate contraction length
Show faint striations
Branched and uni nucleated fibres

Question 4

Structure and function of involuntary muscles

Answer 4

Non striated fibre appearance
Involuntary control
No regular arrangement - different cells contract in different directions
Slow control
Can remain contracted for a reasonably long time
Non striated/un striped
Spindle shaped and uni nucleated fibres

Question 5

Sarcolemma

Answer 5

Plasma membrane surrounding muscle fibres

Question 6

Sarcoplasm

Answer 6

Shared cytoplasm within a muscle fibre

Question 7

Why do parts of the sarcolemma fold inwards?

Answer 7

Help spread electrical impulses throughout the sarcoplasm

Question 8

Myofibrils

Answer 8

Cylindrical organelles made of actin and myosin that are specialised for contraction

Question 9

Actin

Answer 9

Thinner filament
Consists of two strands twisted around each other

Question 10

Myosin

Answer 10

Thicker filament
Long rod shaped fibres with bulbous heads on one side

Question 11

Light band

Answer 11

Region where actin and myosin don’t overlap
AKA I band

Question 12

Dark band

Answer 12

Presence of thick myosin filaments
Edges are dark where myosin overlaps with actin
AKA A band

Question 13

Z line

Answer 13

Line at the centre of each light band

Question 14

Sarcomere

Answer 14

Distance between adjacent Z lines
Functional unit of the sarcomere
Shortens during muscle contraction

Question 15

H zone

Answer 15

Lighter coloured region in the centre of the dark band
Only myosin filaments
When muscle contracts, H zone decreases

Question 16

2 types of muscle fibres

Answer 16

Slow twitch
Fast twitch

Question 17

Slow twitch fibres

Answer 17

Fibres contract slowly
Less powerful contractions over a longer period of time
Used for endurance activities
Gain energy from aerobic respiration
Rich in myoglobin
Rich supply of blood vessels and mitochondria

Question 18

Fast twitch fibres

Answer 18

Fibres contract very quickly
Produce powerful contractions but only for short periods
Used for short bursts of speed and power
Gain energy from anaerobic respiration
Low myoglobin and blood vessels
Store creatinine phosphate - can rapidly generate ATP from ADP in anaerobic conditions