15.7 Structure of skeletal muscle

Question 1

cardiac muscle

Answer 1

found in heart

Question 2

smooth muscle

Answer 2

found in walls of blood vessels and gut

Question 3

skeletal muscle

Answer 3

bulk of body muscle in vertebrates
attached to bone
acts under voluntary conscious control

Question 4

myofibrils

Answer 4

millions of tiny muscle fibres that make up individual muscles

Question 5

advantage of myofibrils

Answer 5

lined up parallel to give maximum force

Question 6

sarcoplasm

Answer 6

shared cytoplasm between muscle fibres
found round circumference of fibre
has large conc mitochondria and endoplasmic reticulum

Question 7

structure of muscle cells

Answer 7

fused together, sharing nuclei and sarcoplasm
no junction as would be weakness pint that would reduce strength of muscle

Question 8

actin

Answer 8

thinner protein filament
2 strands twisted around one another

Question 9

myosin

Answer 9

thicker protein filament
consists of long rod-shaped tails with bulbous heads that project to the side

Question 10

I bands

Answer 10

isotropic bands that appear lighter because thick and thin filaments don’t overlap

Question 11

A bands

Answer 11

anisotropic bands appear darker because thick and thin filaments overlap in this region

Question 12

H zone

Answer 12

centre of each band

Question 13

Z line

Answer 13

centre of I band

Question 14

sacromere

Answer 14

distance between adjacent z lines

Question 15

tropomyosin

Answer 15

fibrous strand around actin filament

Question 16

slow twitch fibres

Answer 16

contract slower
less powerful
over longer period

Question 17

slow twitch features

Answer 17

• large store myoglobin
  -rich supply blood vessels to deliver oxygen and glucose for aerobic respiration
• many mitochondria to produce ATP

Question 18

slow twitch adaptation

Answer 18

endurance- contract constantly to maintain body in upright position

adapted for aerobic respiration
-avoid build up of lactic acid

Question 19

fast twitch fibres

Answer 19

contract rapidly
produce powerful contraptions
only short period

Question 20

fast twitch adaptation

Answer 20

adapted for intense excercise

Question 21

fast twitch features

Answer 21

-thicker and more numerous myosin filaments
-high conc glycogen
-high conc enzymes involved in anaerobic respiration to provide ATP
-store of phosphocreatine

Question 22

phosphocreatine

Answer 22

molecule can rapidly generate ATP from ADP in anaerobic conditions and provide energy for muscle contractions

Question 23

neuromuscular junction

Answer 23

motor neurone meets skeletal muscle fibre

Question 24

muscle contraction

Answer 24

many junctions along muscle

fibres contract rapidly and powerfully when stimulated by action potentials

Question 25

motor unit

Answer 25

muscle fibres supplied by single motor neurone act together as single functional unit

gives control over force muscle exerts

Question 26

similarity between neuromuscular junction and synaps

Answer 26

• have neurotransmitters transported by diffusion
  -have receptors that when binded with neurotransmitter, cause influx of Na ions
  -used Na-K pump to polarise axon
  -use enzymes to break down neurotransmitter

Question 27

nerve impulse at neuromuscular junction

Answer 27

• when impulse arrives, synaptic vesicles fuse with presynaptic membrane and realeases acetylcholine

-acetylcholine diffuses to postsynaptic membrane

-permeability ro Na+ ions changes and they enter, depolarising membrane

-acetylcholine broken down by acetylcholinesterase to ensure muscle isn’t overstimulated

-choline and acetyl diffuse back to neurone