muscle notes

Question 1

what are the 3 types of muscles

Answer 1

• voluntary (skeletal)
• cardiac
• involuntary (smooth)

Question 2

what are the key things to note about voluntary (skeletal muscles)

Answer 2

• cell membrane = sarcolemma
• cytoplasm = sarcoplasm
• many mitochondria
• multinucleate
• extensive SER
• number of myofibrils make up contractile units called sarcomeres arranged end to end.

Question 3

what are the key things to note about cardiac muscle

Answer 3

• cells form branched fibres, with cross bridges
• cells separated by intercalated discs joining cells at ends
• good supply of capillaries
• abundant mitochondria

Question 4

what are the key things to note about involuntary (smooth) muscles

Answer 4

• spindle shaped cells
• tapered at both ends
• contains bundle of actin and myosin
• single nucleus
• forms sheets
• numerous mitochondria

Question 5

what are the 7 key components of a muscle fibre/cell

Answer 5

• 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

Question 6

what makes up microfibrils

Answer 6

sarcolemma’s

Question 7

what are the two muscle filaments

Answer 7

• actin
• myosin

Question 8

which is the thin muslce filament

Answer 8

actin

Question 9

what is the thick filament

Answer 9

myosin

Question 10

what is the I band

Answer 10

only actin filaments, i.e. no overlap of proteins

Question 11

what is the H zone

Answer 11

inner region of sarcomere with myosin only

Question 12

what is the M line

Answer 12

anchors the myosin

Question 13

what is the A band

Answer 13

where the actin and myosin filaments overlap

Question 14

what happens to the sarcomere when the muscle contracts

Answer 14

it shortens

Question 15

what happens to the I band and H - zone and when the muscle contracts

Answer 15

the I band decreases and the H zone gets smaller

Question 16

what happens to the A band when the muscle contracts

Answer 16

The A band remains the same length

Question 17

what is embedded in the myosin head?

Answer 17

ATPase

Question 18

Contraction of the muscle

Answer 18

• 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.

Question 19

what is a neuromuscular junction

Answer 19

A specialized form of synapse (synaptic cleft) that forms between the branches of a motor neurone and muscle fibre.

Question 20

be able to describe the movement of an action potential across a synapse into a muscle fibre.

Question 21

what is the function of acetylcholinesterase

Answer 21

• hydrolyses ACH into an acetyl group + choline -> recycled/taken back up into the pre - synaptic knob.
• breaks acetylcholine, into acetic acid and choline.