muscle notes Flashcards
what are the 3 types of muscles
- voluntary (skeletal)
- cardiac
- involuntary (smooth)
what are the key things to note about voluntary (skeletal muscles)
- cell membrane = sarcolemma
- cytoplasm = sarcoplasm
- many mitochondria
- multinucleate
- extensive SER
- number of myofibrils make up contractile units called sarcomeres arranged end to end.
what are the key things to note about cardiac muscle
- cells form branched fibres, with cross bridges
- cells separated by intercalated discs joining cells at ends
- good supply of capillaries
- abundant mitochondria
what are the key things to note about involuntary (smooth) muscles
- spindle shaped cells
- tapered at both ends
- contains bundle of actin and myosin
- single nucleus
- forms sheets
- numerous mitochondria
what are the 7 key components of a muscle fibre/cell
- nuclei
- parts of the sarcolemma fold inwards, to help spread electrical impulses
- the sarcoplasmic reticulum, contains calcium ions, which are released in order to generate muscle contraction
- myofibrils are long cylindrical organelles, made of proteins called actin and myosin
- many mitochondria, between the myofibrils, which provide ATP for muscle contraction
what makes up microfibrils
sarcolemma’s
what are the two muscle filaments
- actin
- myosin
which is the thin muslce filament
actin
what is the thick filament
myosin
what is the I band
only actin filaments, i.e. no overlap of proteins
what is the H zone
inner region of sarcomere with myosin only
what is the M line
anchors the myosin
what is the A band
where the actin and myosin filaments overlap
what happens to the sarcomere when the muscle contracts
it shortens
what happens to the I band and H - zone and when the muscle contracts
the I band decreases and the H zone gets smaller
what happens to the A band when the muscle contracts
The A band remains the same length
what is embedded in the myosin head?
ATPase
Contraction of the muscle
- calcium, bins to tropomyosin causing it to change shape
- this dislodges tropinmyosin and the binding sites on the actin are exposed
- myosin has a long tail with two heads, (two binding sites) one can now bind to actin, and one binds to ATP which will cause the head to detach after binding.
what is a neuromuscular junction
A specialized form of synapse (synaptic cleft) that forms between the branches of a motor neurone and muscle fibre.
be able to describe the movement of an action potential across a synapse into a muscle fibre.
what is the function of acetylcholinesterase
- hydrolyses ACH into an acetyl group + choline -> recycled/taken back up into the pre - synaptic knob.
- breaks acetylcholine, into acetic acid and choline.
