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pharmacology > Skeletal muscles > Flashcards

Skeletal muscles Flashcards

1
Q

what allows movement to occur ?

A

the skeletal muscles that are controlled by motor nerves

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2
Q

voluntary or involuntary and what are they controlled by ?

A

voluntary and somatic nervous system

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3
Q

why does a muscle action potential occur ?

A

due to a rise in Ca2+ ions and a contraction occurs

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4
Q

what is the length of each cell ?`

A

runs the length of the muscle so can be over 30cm long

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5
Q

do the cells have one nuclei or more ?

A

multiple

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6
Q

the muscle fibres are striated , what does this mean ?

A

they are striped due to the arrangement of contractile filaments myosin ( thick) and actin ( thin).

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7
Q

is smooth muscle striated ?

A

nope

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8
Q

the muscle fibres contain troppomysoin and troponin , what do these do ?

A

play important roles in regulating contraction.

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9
Q

what does the term contraction mean ?

A

to the turning on of the force-generating sites— the cross bridges—in a muscle fibre.

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10
Q

what neurotransmitter does the synaptic vesicle contain ?

A

acetylcholine

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11
Q

how is it released ?

A

by diffusion

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12
Q

where are the acetylcholine receptors ?

A

the sarcolemma

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13
Q

are there inhibitary nerves at the neuromuscular junction ?

A

no , only excitatory ones.

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14
Q

the acetylcholine released by nerves binds to what

A

nicotinic ACh-receptors

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15
Q

what does this lead to ?

A

a Na+ influx and end-plate potential. The action potential propagates across plasma membrane and the action potential propagates into T-tubules

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16
Q

then what?

A

The voltage-sensor activates Ryanodine Receptor on Sarcoplasmic Retiulum and Ca2+ released into cytosol

17
Q

then what ?

A

When calcium is released this binds to the troponin and this removes the blocking action of tropomyosin on the actin filament where myosin want to bind to.

18
Q

what does tropomysoin do ?

A

blocking action

19
Q

what does the ATP hydrolysis do ?

A
  1. energises myosin and the cycle of ATP binding, hydrolysis, ADP/Pi release drives ratchets myosin towards Z-line.
  2. Restoration of plasma-membrane ion gradients (Na+/K+-ATPase)
  3. Removal of Ca2+ from cytosol back into sarcoplasmic reticulum (Ca2+-ATPase) ATP is required.
20
Q

whats the actin and mysoin cycle ?

A

The binding of calcium to troponin causes the tropomyosin to be removed and this exposes the myosin binding site on the actin. The mysoin then requires a molecule of ATP which is broken down to ADP and phosphate. This moves the myosin into an extended stretched position . The Phosphate is then lost and this allows the myosin to bind and slide past the actin , after this the ADP is lost.

21
Q

how much can ATP consumption be increased during muscle contraction ?

A

x100

22
Q

how can ATP be resupplied ?

A
  1. phosphorylation of ADP by creatine phosphate
  2. mitochondrial oxidative phosphorylation , requires oxygen (aerobic)
  3. glycolysis: anaerobic metabolism of glucose supplied by
  4. blood
  5. catabolism of muscle glycogen
23
Q

why are some muscle fibres red ?

A

contain lots of mitochondria , and have lots of oxygen binding myoglobin proteins. There are many small blood vessels and they are red due to the oxidative fibres.

24
Q

why are some muscle fibres white ?

A

have few mitochondria and lots of glycolytic enzymes to increase ATP and stores of glycogen. They are white with glycolytic fibres ( chicken breast

25
Q

fast twitch muscle fibres ?

A

fibres contain very fast acting myosin ATPase and these are called fast twitch fibres

26
Q

slow twitch muscle fibres ?

A

contain slower acting myosin ATPase and are called slow twitch fibres.

27
Q

describe type I slow oxidative fibres ?

A

oxidative as their primary ATP source and they have many mitochondria for ATP. They receive their blood supply from high levels of myoglobin and capillaries. They have low levels of glycogen and glycolytic enzymes. They have slower myosin ATPase and contraction of speed. They muscle rate of fatigue is slow.

28
Q

type II fast glycolotyic fibres ?

A

have glycolytic as their primary source of ATP and they have few levels of mitochondira. They receive blood supply from low levels of myoglobin and few capillaries. They have high levels of glycogen and glycolytic enzymes. They have faster myosin ATPase and a fast contraction speed. The muscle rate of fatigue is fast.

29
Q

type IIa fast oxidative glycolotyic fibres ?

A

) fibres have oxidative as their primary source of ATP and they have many mitochondria. They also have high levels of myoglobin and many capillaries. They have intermediate levels of glycogen and glycolytic enzymes. The myosin ATPase faster and the contraction speed is intermediate. The rate of fatigue is intermediate

30
Q

is a whole skeletal muscle made up of many motor units or just one ?

A

many , never just one

31
Q

what is whole muscle tension a sum of ?

A

the recruitement of motor units

32
Q

recruitment speed of motor units in type I (slow)

A

fast

33
Q

recruitment speed of motor unit Type II ( fast)

A

slow

34
Q

motor neuron size in type I ?

A

small

35
Q

motor neuron size in type II ?

A

large

36
Q

what does the calcium rise allow ?

A

myosin-actin cross-bridge cycling to contract muscle

pharmacology (21 decks)

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