p2: muscles

Question 1

smooth muscles

Answer 1

• contract without conscious control
• walls of internal organs eg: stomach, intestine

Question 2

cardiac muscles

Answer 2

• contract without conscious control (myogenic)
• only found in heart

Question 3

skeletal muscles

Answer 3

• striated
• attached to bone by tendons
• used in locomotion (movement)
  eg: biceps and triceps

Question 4

agonist and antagonist

Answer 4

agonist: muscle contracting
antagonist: muscle relaxing

Question 5

describe the banding pattern in striated muscle

Answer 5

• lightest band is i band, actin only
• darkest band is overlapping region, actin and myosin
• medium shading is H zone, myosin only

Question 6

describe the sliding filament theory

Answer 6

• crossbridges between actin and myosin heads
• power stroke, movement of myosin heads
• detachments of myosin heads
• energy from ATP returns myosin heads to original position

Question 7

describe the function of calcium ions in muscle contraction

Answer 7

• calcium ions bind to troponin to form tropomyosin
• exposes actin binding sites
• myosin head attaches
• activates ATP hydrolase

Question 8

nerve impulses arriving at the presynaptic membrane at the neuromuscular junction results in the shorterning of the sarcomere. describe how.

Answer 8

• entry of calcium ions
• vesicles fuse with preSN membrane and release acetylcholine
• neurotransmitter diffuses
• binds to receptors on postSN
• depolarisation of post SN
• release of Ca ions
• bind to troponin
• expose binding sites on actin
• actinomyosin cross bridges form
• myosin head moves
• ATP hydrolase activated
• rachet mechanism

Question 9

sliding filament theory

Answer 9

Ca ions rleeased from sarcoplasmic reticuluum into sarcoplasm
- ca ions diffuse and bind to troponin, cause a change in 3 sturtcure
- cause tropomyosin to move exposing the myosin head binding sites on actin filament
- myosin heads bind to actin binding sites forming actinomyosin bridges
- myosin head moves pulling actin filament
- atp binds to myosin head, activates ATP hydrolase, energy released by hydrolysis recocks yosin head

Question 10

explain the importance of ATP hydrolase dyring muscle contraction

Answer 10

• hydrolysis of ATP releases energy
• breaks actinomyosin crossbridges

Question 11

muscle contraction requires ATP. what are the advantages of using aerobic rathet than anaerobic RP to provide ATP in long distance race?

Answer 11

• aerobic RP releases MORE energy/produces more ATP
• no lactate produced
• avoids cramps
• CO2 removed by breathing

Question 12

why is ATP required?

Answer 12

• provides energy for sliding of filaments during contraction
• active transport of ca ions into sarcoplasmic reticuluum

Question 13

ATP and phosphocreatine

Answer 13

• donates Pi to ADP to produce ATP
• ADP + phosphocreatine > ATP + creatine
• energy released from hydrolysis of phosphocreatine used to phosphorykate ATP, whihc is used in muscle contraction

Question 14

slow twitch fibres

Answer 14

• slow contractions over long periods of time
• slower rate of contraction
• slow to fatigue
• in legs and maintain posture

Question 15

fast twitch fibres

Answer 15

• produce strong, rapid contractions
• faster speed of contraction
• short time periods
• fast to fatigue due to build up of lactate

Question 16

contrast fast and slow twitch muscle fibres

Answer 16

slow vs fast
- large store of myoglobin
- large supply of capillaries vs fewer
- fewer glycogen vs more
- less extensive SR
- more mitochondria
- aerobic energy system vs anaerobic
- smaller in diameter
- no phosphocreatine

Question 17

a muscle fibre contracts when it is stimulated by a motor neuron. describe how transmission occurs across the synapse between a motor neurone and a muscle fibre.

Answer 17

• Ca channel proteins open
• Ca ions enter
• vesicles fuse with preSN membrane
• release acetylcholine
• diffusion across synapse
• binds to receptor in postSN

Question 18

after death, cross bridges remain firmly bound resulting in rigor mortis. explain what causes crossbridges to remain firmly bound.

Answer 18

• RP stops
• no ATP produced
• ATP required to break actinomyosin bridges

Question 19

describe the role of calcium ions in the contraction sarcomere

Answer 19

• interacts with tropomyosin
• reveals myosin binding heads on actin filament
• actinomyosin crossbrdiges form
• activates ATP hydrolase

Question 20

describe how slow twitch muscle fibres work

Answer 20

• lots of mitochondria
• more myoglobin

Question 21

describe how fast twitch muscle fibres

Answer 21

• used for rapid contractions
• phosphocreatine makes more ATP
• anaerobic respiration involved
• ATP used to reform phosphocreatine
• no myoglobin in fast twitch
• lots of phosphocreatines in fast twitch

Question 22

describe thge role of phosphocreatine

Answer 22

• provides energy and phosphorylates
• to make ATP from ADP and Pi

Question 23

people who have mcardles disease produce less ATP than healthy people. as a result, cant maintain strong muscle contractions during exercise.

use knowledge of sliding filament theory to suggest why,

Answer 23

• axtinomyosin bridges form
• power stroke
• detachment of myosin heads
• myosin heads move back to original position

Question 24

describe the role played by tropomyosin and myosin in myofibril contractions

Answer 24

tropomyosin:
- moves out of the way when ca ions bind
- actinomyosin bridges form

myosin:
- head of myosin binds to actin and pulled it over it
- detaches and resets
- uses ATP

Question 25

the mitochondria in muscles contain many cristae. explain the advantage of this.

Answer 25

- larger SA for ETC - provides ATP

Question 26

explain why increased cardiac output is an advantage during exercise

Answer 26

- in exercise, more respirTION - higher cardiac output increases oxygen supply to respiring muscles - increases glucose supply to muscles - increases CO2 removal from muscles - increases heat removal from muscles