L23 Muscle Physiology Flashcards
How do muscles contract?
interactions between actin and myosin filaments
what 2 tissues can generate action potentials? (muscle, nerve, connective and epithelial)
nerve and muscle
what system controls/ regulates skeletal muscles?
efferent neurons ->motor system
what system controls/ regulates smooth muscle like lungs and cardiac muscle like heart?
efferent neurons-> autonomic nervous system
how are skeletal muscles paired?
antagonistically - they work opposingly to eachother
what occurs in the skeletal muscle when moving lower forearm upwards?
bicep contracts, tricep relaxes (flexion)
what occurs in skeletal muscle when lowering forearm?
biceps relax and triceps contract (extension)
skeletal muscle are made of bundles of long fibres, what are they made of?
smaller myofibrils ‘striped’
what is the functional unit of a muscle cell?
sacromere which is bordered by z lines
what is m-line?
the middle of myosin and actin filaments stacked within sacromere unit
what happens during muscle contraction?
sacromere contracts and shortens, z lines come closer together, this happens along whole myofibril - all myofibrils in skeletal muscle contract together
how does muscle contraction occur at molecular level?
1) globular head of myosin combines with actin forming a crossbridge
2) power stroke - crossbridge allows myosin to pull actin towards centre/ m-line of sacromere (shortening)
3) cross-bridge cycling - repeated cycles of binding and release (causes muscle contraction)
what is the energy source for cross-bridge cycling?
ATP
What type of reaction is muscle contraction/ cross-bridge cycling?
thermogenic = heat generating
what are shivers?
involuntary contraction of muscles to generate heat
why does muscle fatigue?
lack of ATP
what happens during exercise/ oxygen depletion?
we use lactic acid fermentation to produce ATP
What neurotransmitter is muscle contraction dependent on?
calcium
how does calcium control muscle contraction?
free calcium binds to tropomyosin and troponin proteins allowing myosin and actin to bind - crossbridge occuring
what happens when Ca2+ concentrations are low?
muscle contraction cannot occur
what initiates the repsonse of muscle contraction?
acetylcholine neurotransmitters from motor neurons
how does muscle contraction initiation occur at action potential level?
1) pre-synaptic terminal releases ACh
2) ACh neurotransmitter binds to nicotinic receptor on muscle
3) depolarisation of muscle
4) action potential in muscle
5) electroexcitation of muscle causes sarcoplasmic reticulum to release calcium
5) calcium binds to troponin - freeing myosin binding sites to bind with actin
6) sarcomere shortens continuously - muscle contraction
what is required for muscle contraction?
motor nerve, ATP, calcium, Ach at neuro-muscular junction
how does the nervous system grade the response of muscle contraction (strong/weak)
1) varying number of fibres that contract
2) vary rate at which fibres are stimulated
