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Foundations of Medicine > Skeletal, smooth and cardiac muscle pt.1 > Flashcards

Skeletal, smooth and cardiac muscle pt.1 Flashcards

1
Q

What is the main function of muscle?

A

to generate force and movement
to express and regulate ourselves

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2
Q

What does skeletal muscle consist of?

A

large muscle masses attached on arms and legs
voluntary muscle, diaphragm

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3
Q

What does cardiac muscle consist of?

A

forms the main body of the heart

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4
Q

What types of muscle fall under striated category?

A

skeletal and cardiac muscles

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5
Q

What does striated mean?

A

means straight, regular appearance

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6
Q

What does smooth muscle mean?

A

can’t see any stripes
a lot thinner and can form thin linings

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7
Q

Function of smooth muscle?

A

there to open or contract the hollow tubes, and chambers, and spaces within the body.
Can generate a lot of tension and contraction

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8
Q

Give examples of smooth muscle?

A

blood vessels, vas deferens, airways, uterus, GI tract, bladder etc.

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9
Q

Describe physical appearance of skeletal muscle?

A

striated
multiple nuclei pushed out to the side, bumps on surface underneath membrane
very long but small diameter
bundles of muscle fibres with a very efficient blood supply explains why so red

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10
Q

Why are nuclei pushed out to side of cell?

A

absolutely packed with contractile proteins pushing multiple nuclei out to the side
fusion of multiple individual cells into one big long one

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11
Q

Describe physical appearance of cardiac muscle?

A

striated
exist as individual cells you’ll see individual nucleus in middle of them
ends of cardiac cells have projections to help them interconnect with neighbouring cells (intercalated disks) so ions and therefore electrical signals can flow between cells and get nice coordinated waves of contraction

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12
Q

Why do cardiac muscle cells need to be electrically conductive and linked together?

A

so a wave of contraction flows through the heart’s chambers in a nice, co ordinated and synchronous way

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13
Q

Describe physical appearance of smooth muscle cells?

A

not striated
a lot smaller and thinner
nucleus very visible

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14
Q

How do muscle cells squeeze and contract forcefully?

A

layers of muscle cells
can generate a lot of force in enclosed environment, contracting on a compressed area

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15
Q

What happens when you injure a piece of skeletal muscle?

A

as an adult or child we are not good repairing it
might not recover all movement and function
don’t have same supply of mono nucleate myoblasts
use satellite cells to differentiate to form new muscle fibres

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16
Q

What are connective tissue of skeletal muscle fibres for?

A

connect muscle masses to skeleton by tendons
tendons- connective tissue

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17
Q

What are satellite cells?

A

type of myoblast, precursor muscle cell
limited supply in skeletal muscle masses

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18
Q

Describe what happens at area of damage or scar tissue?

A

fibres around area of damage will try to hypertrophy and try to compensate

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19
Q

What is atrophy?

A

reduction in protein

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20
Q

How is skeletal muscle arranged in the bigger picture?

A

individual muscle fibre cells arranged in bundles and surrounded by sheaths. Bundles are bundles of fibre cells surrounded by more connective tissue and get big mass of muscle. Deep within muscles find lots of blood vessels to make sure deepest core gets oxygen and get rid of waste products.

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21
Q

What is Ischemia?

A

temporary interruption to blood supply from too much hypertrophy

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22
Q

What is a myofibril? and describe appearance

A

bundle of protein
stripes and lines

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23
Q

What is a sarcomere?

A

basic repeating unit within muscle that allows it to achieve its function-which is contraction.

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24
Q

Describe myosin filaments?

A

in the sarcomere, look like have little heads
thick proteins
formed of a protein called myosin

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25
Q

Describe actin filaments?

A

in the sarcomere
thinner proteins
interdigitating around myosin filaments

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26
Q

What governs how much contraction we get?

A

the way in which myosin and actin filaments interact
cross bridges at myosin filaments are binding sites where myosin and actin lock on to one another and help pull one another

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27
Q

What are Z and M lines?

A

thick deposits of protein which maintain structural integrity of how acting and myosin filaments are arranged

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28
Q

How is skeletal muscle so strong?

A

myosin filaments arranged in 3D space in triangular patterns and actin filaments surround each of myosin filaments in hexagonal pattern

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29
Q

What does titin filament do?

A

acts like spring
making sure myosin stays in centre -inbetween actin filaments and not too far from Z lines

30
Q

What is the sliding filament theory?

A

idea of how sarcomeres contracted and relaxed

31
Q

What do heads on myosin filament allow it to do?

A

can undertake a lot of attachment to actin filaments
myosin pulling on actin filaments and pulling Z lines closer

32
Q

What happens when we contract muscle in regards to actin and myosin?

A

slide actin filaments in between myosin filaments Heads on myosin filaments latch onto actin mol binding sites and heads on myosin flip and pull sarcomere into smaller contracted pattern

33
Q

Importance of ATP binding to myosin crossbridge heads?

A

Actin and the myosin only detach after a contraction when new ATP binds. Your muscle only relaxes when you bind new ATP. In order to make sure that you can relax but also to make sure you’re ready for next contraction. Binding of ATP also there to make sure you detach your muscle fibres at end of contraction and that means you can relax quite easily.

34
Q

What is rigor mortis?

A

when someone dies and muscles stiffen due to body’s inability to produce ATP

35
Q

What is the power stroke?

A

charging of crossbridge head with ATP and the flipping

36
Q

What is the crossbridge cycle?

A

series of cellular events which occur when muscle contracts and relaxes

37
Q

What does relaxation depend on?

A

Getting rid of calcium from intracellular environment

38
Q

What does more calcium mean?

A

more contraction

39
Q

Describe steps of cross bridge cycle?

A

thin actin filament bound to myosin cross bridge head. Crossbridge head already charged up because ATP has been hydrolyzed by the head into ADP and an inorganic phosphate.
(A+M+ADP+Pi) are acting as one physical entity.
Cross bridge head flips and ADP and Pi are released into the cellular environment will eventually be released by cell to be taken up by
blood supply.
Now only left with actin and myosin as physical entity
Muscle now in contracted state and in order to relax- must bind new ATP
ATP binds and detaches cross bridge head and hydrolysis of ATP
relaxation stage starts
Calcium conc lowering

40
Q

What is excitation-contraction coupling?

A

Process of converting a command from a nerve cell into a mechanical force- which is contraction within muscle is known as excitation- contraction coupling.

41
Q

Function of sarcoplasmic reticulum?

A

main storage facility for calcium ions within cells
within SR our storage proteins kind of latch onto calcium and make sure does not leak out inappropriately

42
Q

What are transverse tubules?

A

basically conduction systems - conduct the electrical command that comes from the motor neurone down and deep within core
passageways of membrane which reach deep within the muscle fibre core

43
Q

Why does mitochondria have a double membrane ?

A

because processes that go on within the mitochondria are quite chemically damaging and need to make sure rest of cell protected from it

44
Q

Why are their mitochondria within skeletal muscle cells?

A

to produce ATP

45
Q

Why would there be lots of blood vessels within mitochondria?

A

to make sure we always have access to fuel and oxygen to make ATP in mitochondria and also to take away waste products like CO2, ADP,Pi and lactate

46
Q

T tubules role in allowing action potential to travel all along muscle plasma membrane ?

A

Muscle action potential propagated: when you have motor neuron coming to piece of skeletal muscle it will be synapsing on the muscle plasma membrane. Will be a region which has receptors for neurotransmitter Acetylcholine coming from motor neuron. Ion channels built into acetylcholine receptors (ionotropic receptors).
Electrical depolarisation occurs at a very focussed, localised region on the bundle of skeletal muscle cells. Plasma membrane actually covered in voltage sensitive ion channels and allows that action potential to propagate and travel all along muscle plasma membrane.

47
Q

T tubules role?

A

muscle action potential is propagated
and travels deep within core of muscle fibre using voltage sensitive ion channels to conduct signals

48
Q

Steps after electrical depolarisation to generate power stroke?

A

DHP receptors- dihydropypiridine (special type of calcium channel)
In response to the electrical depolarisation coming from main muscle membrane coming down transverse tubule, cause some calcium to enter cell. Nearby there are other calcium sensitive receptors known as ryanodine receptors and when they are triggered by some calcium coming through DHP. Ryanodine receptors will amplify that signal and cause mass activation of lots of ryanodine receptors and other calcium releasing channel across entire surface of sarcoplasmic reticulum. Release of calcium ions from lateral sacks of sarcoplasmic reticulum.
Because released calcium throughout cell- allows us to bind calcium to troponin which twists and removes blocking action of tropomyosin. Enables cross bridge to interact with actin binding sites and get power stroke.

49
Q

How do we get rid of calcium from intracellular environment?

A

calcium pumped out of cellular environment by atp powered pumps (calcium ATPases) on surface of sarcoplasmic reticulum.

50
Q

What is issue with having a single neuron innovating multiple muscle cells in biceps ?

A

very vulnerable as damage to single neuron means damage to entire bicep

51
Q

Why do we have multiple nerve cells innervating multiple muscle cells?

A

if one motor neuron fails we dont lose contraction in one entire area- lose a bit across whole bicep but compensated by another motor unit.

52
Q

What is a motor unit?

A

arrangement of a motor neuron synapsing with multiple muscle fibres

53
Q

What is term for force exerted by muscle?

A

tension

54
Q

What is an isometric contraction ?

A

contraction with constant length

54
Q

What is term for force exerted on muscle?

A

load

55
Q

What is an isotonic contraction?

A

contraction with shortening length

56
Q

What is a lengthening contraction?

A

contraction with increasing length

57
Q

Why is there a latent period after a single action potential stimulates muscle?

A

time before excitation contraction starts
represents the time for all molecular machinery to occur.
-start triggering rise in calcium

58
Q

What type of contractions do weightlifters aim for and why?

A

can do quicker than isotonic
isometric contraction and this is a big, long and controlled contraction

59
Q

What type of contractions are seen in runners and why?

A

not worried about generating as much force
trying to shorten muscle however shortening takes more time than just generating force
short muscle contractions

60
Q

What happens when you increase the load on a muscle?

A

contraction, velocity and ability to shorten muscle gets less the more load you place on it

61
Q

How long is an action potential?

A

1-2 ms long

62
Q

How long can a twitch last for?

A

last up to 100ms

63
Q

Describe summation?

A

multiple action potentials fired even when the muscle is still contracting from first AP
contraction starts to build up

64
Q

What is tetanus?

A

normal part of physiology
produce longer and sustained reactions for as long as want to and relax when muscle gets tired

65
Q

What is tetanic tension?

A

greater, more prolonged event than an initial twitch tension

66
Q

Why can we generate more contraction for tetanic tension?

A

calcium concentration never gets low enough to cause proper relaxation or for troponin tropomyosin to reblock myosin binding sites

67
Q

What happens if you overstretch muscle?

A

acting and myosin don’t overlap anymore and crossbridge heads cant bind to actin
therefore less tension

68
Q

What happens when you overcompress muscle?

A

actin and myosin too close together and therefore start to clash.
Therefore don’t have optimum contraction

69
Q

What is the optimal length?

A

window of overlap where we can generate greatest amount of tension

70
Q

What are antagonist muscles?

A

one does opposite to other
- for e.g. one will contract other will relax
-for e.g. one will flex , other will extend

71
Q

What are the benefits of muscles being in groups?

A

more ability to generate force
more ability to shorten and contract muscles with more velocity and more accuracy
more ability to generate manoeuverability

Foundations of Medicine (61 decks)

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