Muscles Flashcards
Describe the banding pattern in a striated muscle
Lightest band is l band is actin only
Darkest band is overlapping region of actin and myosin
Medium shading is H zone band is myosin only
Describe the sliding filament theory
Cross bridges between actin and myosin heads
Pulls actin filament
Myosin head then detaches
Myosin head then moves back to original position
Describe the function of calcium ions in the muscle contraction
Ca2+ binds changing the tertiary structure
Exposes actin binding sites
Myosin head attaches to actin forming cross bridge
Activating atp hydrolase
Nerve impulses arriving at the presynaptic membrane at the neurotransmitter junction result in the shortening of sarcomeres. Describe how .
Ca2+ move into presynaptic membrane
Vesicles fuse with membrane releasing acetylcholine
Neurotransmitter diffuses
Binds to receptor on post synaptic membrane
Depolarisation occurs
Releasing calcium ions
Removing tropomyosin
Exposing binding sites on the actin
Actinomyosin cross bridges form
Myosin head moves pulling the actin along
Atp hydrolyse then activated
Explain the importance of atp hydrolyses during muscle contraction
Hydrolysis of atp releasing energy
Used to form and break actinomyosin cross bridges
Muscle contraction requires atp. What are the advantages of using aerobic rather than anaerobic respiration to provide atp in a long distance run
Aerobic respiration releases more energy
No lactate accumulates
Avoids muscles fatigue
CO2 easily removed from the body
A muscle fibre contracts when stimulated by a motor neuron.
Describe how transmission works between a motor neurone and a muscle fibre
Ca2+ channel open
Ca2+ enter
Vesicles fuse with pre synaptic membrane
Exocytosis of neurotransmitter into synaptic cleft
Diffusion across synaptic cleft
Binds to receptor on post synaptic membrane
Na+ channels open
Describe the role of ca2+ in the contraction of sacromere
Interacts with tropomyosin
To reveal binding sites on actin
Allowing myosin heads to bind
Activating atp hydrolase
Describe slow twitch fibres
Have lots of mitochondria
More myoglobin
Describe fast twitch muscle fibres
Used for rapid strong contractions
Phosphocreatine used up readily during the contraction
Anaerobic respiration involved
ATP used to reform phosphocreatine
Lots of phosphocreatine in fast touch fibres
No myoglobin
Describe the role of phosphocreatine
Provides phosphate
To make atp from adp and pi
People with McArdles disease produce less atp as a result they are unable to produce strong muscle contraction during exercise
Use your knowledge of the filament sliding theory to suggest why
ATP is required to form cross bridge between actin and myosin
For the myosin to pull actin
Detachment of myosin heads
Myosin heads move back to original position
Describe the part played by tropomyosin and myosin in myofibril contraction
Tropomyosin-
Moves out the way when ca2+ binds
Allows myosin to bind to actin to form cross bridge formation
Myosin-
Head binds to actin and pulls actin past
Myosin detaches from actin and resets
Requiring atp
The mitochondria in muscles contain many cristae
Explain an advantage of this
Larger surface area for oxidative phosphorylation
Provides ato
Explain why increased cardiac output is an advantage during exercise
In exercise more energy release
Higher cardiac output increasing o2 supply to muscles
Increase glucose supply to muscles
Increase co2 removal
Increase heat removal for cooling
