p2: muscles Flashcards
smooth muscles
- contract without conscious control
- walls of internal organs eg: stomach, intestine
cardiac muscles
- contract without conscious control (myogenic)
- only found in heart
skeletal muscles
- striated
- attached to bone by tendons
- used in locomotion (movement)
eg: biceps and triceps
agonist and antagonist
agonist: muscle contracting
antagonist: muscle relaxing
describe the banding pattern in striated muscle
- lightest band is i band, actin only
- darkest band is overlapping region, actin and myosin
- medium shading is H zone, myosin only
describe the sliding filament theory
- 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
describe the function of calcium ions in muscle contraction
- calcium ions bind to troponin to form tropomyosin
- exposes actin binding sites
- myosin head attaches
- activates ATP hydrolase
nerve impulses arriving at the presynaptic membrane at the neuromuscular junction results in the shorterning of the sarcomere. describe how.
- 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
sliding filament theory
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
explain the importance of ATP hydrolase dyring muscle contraction
- hydrolysis of ATP releases energy
- breaks actinomyosin crossbridges
muscle contraction requires ATP. what are the advantages of using aerobic rathet than anaerobic RP to provide ATP in long distance race?
- aerobic RP releases MORE energy/produces more ATP
- no lactate produced
- avoids cramps
- CO2 removed by breathing
why is ATP required?
- provides energy for sliding of filaments during contraction
- active transport of ca ions into sarcoplasmic reticuluum
ATP and phosphocreatine
- 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
slow twitch fibres
- slow contractions over long periods of time
- slower rate of contraction
- slow to fatigue
- in legs and maintain posture
fast twitch fibres
- produce strong, rapid contractions
- faster speed of contraction
- short time periods
- fast to fatigue due to build up of lactate
contrast fast and slow twitch muscle fibres
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
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.
- Ca channel proteins open
- Ca ions enter
- vesicles fuse with preSN membrane
- release acetylcholine
- diffusion across synapse
- binds to receptor in postSN
after death, cross bridges remain firmly bound resulting in rigor mortis. explain what causes crossbridges to remain firmly bound.
- RP stops
- no ATP produced
- ATP required to break actinomyosin bridges
describe the role of calcium ions in the contraction sarcomere
- interacts with tropomyosin
- reveals myosin binding heads on actin filament
- actinomyosin crossbrdiges form
- activates ATP hydrolase
describe how slow twitch muscle fibres work
- lots of mitochondria
- more myoglobin
describe how fast twitch muscle fibres
- 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
describe thge role of phosphocreatine
- provides energy and phosphorylates
- to make ATP from ADP and Pi
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,
- axtinomyosin bridges form
- power stroke
- detachment of myosin heads
- myosin heads move back to original position
describe the role played by tropomyosin and myosin in myofibril contractions
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
the mitochondria in muscles contain many cristae. explain the advantage of this.
- larger SA for ETC
- provides ATP
explain why increased cardiac output is an advantage during exercise
- 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
