Muscle Flashcards

1
Q

tropomyosin

A

blocks binding sites on actin filaments which prevents myosin cross-bridge binding and prevents contraction in muscle as a result

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2
Q

troponin

A

blocks tropomyosin in place in the actin binding site
has a high affinity for Ca2+so when calcium levels rise they bind to troponin and move it and therefore move tropomyosin too unblocking the binding site

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3
Q

which topic do you remember the sarcolemma from?

A

autonomic physiology and Neuromuscular junction!!!

it’s the membrane on post synaptic terminal at NMJ

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4
Q

the sarcolemma has ___ that that penetrate into interior of muscle

A

it has transverse tubules that penetrate into the centre of skeletal and cardiac muscle

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5
Q

what do you have in cardiac and skeletal muscle

A

blood supply
mitochondria
sarcoplasmic reticulum

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6
Q

what is the function of the sarcoplasmic reticulum

A

calcium storage (easy access for the muscle)

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7
Q

characteristics of the transverse tubules

A

they protect depolarisation

are specific

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8
Q

release of Ca2+ from sarcoplasmic reticulum

A

depolarisation (caused by neurotransmitter binding on post-synaptic terminal receptors) flows down the transverse tubules

receptors on the S.R detect this depolarisation and it causes voltage gated Ca2+ channels (these aren’t on tubule side) to open allowing Ca2+ to pass through into the interior of muscle

as calcium levels rise it binds to troponin which pulls tropomysin away from actin binding site unblocking it. Myosin is now able to bind and MUSCLE CONTRACTION CAN NOW OCCUR

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9
Q

how and why is calcium taken back up

A

it’s taken back up into S.R by active transport- active calcium pumps keeps pumping it back into storage
re-blocking actin binding site. Ends contraction and muscle fibre relaxes

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10
Q

what happens when Ca2+ levels are high for too long?

A

muscle fatigue

and tension crashes once it’s at maximum

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11
Q

what do contraction and relaxation rely on

A

ATP

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12
Q

isotonic twitch

A

2 types contracting- shortening length, extending- lengthening
a constant tension but shortening or lengthening of muscle at same time
ie bicep curls

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13
Q

isometric twitch

A

holding a pose or fixed position
has same tension/ contraction is held
e.g like holding a glass of water in a position and someone filling it- you’re increasing the load but force exerted by muscle is the same

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14
Q

what is tetanus

A

when multiple twitches/small contractions that are from separate motor units but happen close together summate and feel like one big contraction

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15
Q

during vigorous muscle contraction what happens when maximum tension is reached

A

all the actin binding sites are exposed so myosin goes through cycle until it can’t increase muscle force anymore (no matter increasing calcium or A.Ps)

because there is a finite ATP supply you can’t maintain vigorous excersise- the cycle can’t be completed
Need ATP and O2 for muscle contraction and relaxation

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16
Q

what is the only thing you can measure to create a grade of force? and what is measured by this

A

frequency
Action potentials are one intensity (non-decremental, all or none)
they can be measured

17
Q

what are the two different types of fibres and what do they do differently?

A

oxidative
glycolytic
they produce ATP in different ways

18
Q

oxidative fibres

A

they carry out oxidative phsophorylation (ATP SYNTHASE- ETC)
have many mitochondria in their fibres
have fast and slow types
slow are the most resistant to fatigue

19
Q

glycolytic

A

split glucose for energy

fast glycolytic- fatigue quickly- have few mitochondria

20
Q

what is recruitment

A

activating more motor units (muscle and motor neuron) to accommodate an increase in load on a muscle

21
Q

which fibres would be activated first

A

slow oxidative as most resistant to fatigue

22
Q

difference of SMOOTH muscle to cardiac and skeletal

A

innervated by autonomic nervous system not somatic
actin and myosin are arranged diagonally across cells not straight
different cross bridge cycle but still relies on Ca2+

23
Q

Smooth muscle cross-bridge cycle

A

increase in calcium levels
calcium released from sarcoplasmic reticulum
it then binds to calmodulin protein activating it

calmodulin binds to myosin light chain kinase which goes on to phosphorylate myosin cross-bridges with ATP
the phosphorylated cross-bridge binds to actin filaments and CONTRACTION occurs

24
Q

how does smooth muscle relax

A

dephosphorylation of cross bridges by myosin light chain phosphatase

25
Q

persistant stimulation and increase of Ca2+ in SMOOTH muscle

A

you can dephosphorylate cross bridges are whilst still bound to actin
then there is a decrease in ATP and this slows the cross bridge cycle which means you can maintain tension for a long time with low ATP consumption
USEFUL in blood vessel walls that need to stay open fr long periods

26
Q

sources of cytosolic Ca2+ for smooth muscle contraction

A

there is less sarcoplasmic reticulum in smooth muscle than skeletal
extracellular Ca2+ comes through voltage gates channels too
Ca2+ is removed from cytosol by pumping it back into S.R and out of the cell by Ca2+ ATPases SLOWER PROCESS- more going on

27
Q

smooth muscle single unit

A

GIT, uterus, small blood vessel
signals travel between cells linked by gap junctions
contract synchronously
stretch evokes contraction

28
Q

smooth muscle multi unit

A

airways, large arteries, hairs
few or no gap junctions
richly innervated by autonomic nervous system- need more as multiunit is less responsive
don’t respond to stretch

29
Q

what factors affect contractile activity in smooth muscle

A

hormones - oxytocin- lactation in breast muscle
stretch
spontaneous electrical activity in muscle membranes- pacemaker

30
Q

autorhythmicity

A

creating own rhythm- cardiac muscle cells

31
Q

intercalated discs

A

join cardiac muscle cells together
gap junction
allow for cell-cell communication

32
Q

what is the cardiac action potential

A

it is a brief change in voltage (membrane potential) across the cell membrane of heart cells

33
Q

what is the pacemaker potential

A

the slow, positive increase in voltage across the cell’s membrane that occurs between the end of one action potential and the beginning of the next action potential so recovers it