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Mammalian Physiology > Muscle > Flashcards

Flashcards in Muscle Deck (119)
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1
Q

3 types of muscle

A

skeletal, cardiac, smooth

2
Q

skeletal is the only one that is?

A

voluntary one

3
Q

cell membrane is the

A

sarcolemma

4
Q

skeletal muscle

A

attached to bones by tendons

5
Q

flexor

A

brings bones togeher- biceps

6
Q

extensor

A

moves bones away- triceps

7
Q

when do skeletal muscles contract

A

only when response from a motor neuron

8
Q

epi, peri, ende -mysium

A

epi- around the whole thing
peri- binding fascicles (bundles) together
endo-covers individual muscle fibres

9
Q

t-tubules

A

are formed from inward extensions of the sarcolemma

- allow electrical signals to go deeper into the cell

10
Q

triad

A

formed from a triplet ( one T-tubual and 2 terminal cristae) of tubules made of the sarcoplasmic reticulum which surrounds the T-tubule

11
Q

I band

A

only thin filaments

12
Q

H zone

A

only thick filaments

13
Q

A band

A

both thick and thin

14
Q

myosin

A

thick filament

15
Q

actin

A

thin filament

- globular protein that forms wo strands that twist together

16
Q

troponin

A

holds tropomyosin molecules in place

17
Q

tropomyosin

A

protein that blocks the active sites on the actin molecule

18
Q

titin

A

provides elasticity and stabilizes myosin

19
Q

nebulin

A

helps to align the actin

20
Q

muscle fibres contain lots of?

A

mitochondria and several nuclei

21
Q

what are myofilaments?

A

the microfilaments- thick and thin in myofibrils

22
Q

segment of myofibril between 2 successive Z lines?

A

sacromere

23
Q

conratile unit of muscle fibres?

A

sacromere

24
Q

each myofibril consist of many contractile units called

A

sacromeres

25
Q

Z line

A

anchor for myofibriles

- thiner striation than the A band

26
Q

A band

A

wide dark stripe

27
Q

what band gives muscles their striation look?

A

A band

28
Q

4 things muscle fibres contain?

A

sarcolemma
t-tubules
sarcoplasm ( which has myofibrils, mito, SR)
multiple nuclei

29
Q

6 types off myofibriles

A

actin, troponin, tropomyosin (thin)

myosin (thick)
titin and nebulin

30
Q

sarcolemma

A

muscle cell plasm

31
Q

SR stores?

A

Ca2+

32
Q

4 types of protein that make up the myofilament?

A

myosin, actin, tropomyosin and troponin

33
Q

______ filaments DO NOT attach to z lines

A

thick (myosin)

- just in the centre A band area

34
Q

Actin

A

globular protein that forms two fibrous strands that twist around each other to form bulk of the thin filaments

35
Q

tropomyosin

A

protein that blocks the active sites (for myosin to bind to actin) on the actin molecules

36
Q

troponin

A

protein that holds tropomyosin molecules in place

37
Q

titin and nebulan are____ proteins

A

regulatory

38
Q

nebulin helps to ?

A

align actin

39
Q

titan provides?

A

elasticity and stabilizes myosin

40
Q

motor neurons connect to sarcolemma at _____

A

motor endplate

this is a neuromuscular junction

41
Q

neuromuscular junction

A

is a synapse where neurotransmitter molecules transmit signals

42
Q

motor neuron releases at the motor endplate

A

acetylcholine (ACH) which binds with receptors on the muscle fibre and depolarizes the cytoplasmic membrane of the muscle fibre

43
Q

what happens when the fibre is stimulated by ACH

A

net entry of Na2+ into the muscle through ACH channel receptors ( they open to let Na inside) which creates an
electrical impulse which travels from the sarcolemma and down t-tubules where the voltage change triggers the opening of voltage gated Ca2+ channels—-> which allows Ca2+ to diffuse out of the SR and this is what causes contraction –. Ca2+ interacts with troponin, allowing actin-myosin binding

44
Q

RyR

A

ryanodine receptor channel- it is in the ER membrane, when the action potenical travels down the t-tubuleit alters the conformation of DHP receptor which then opens RyR channel and Ca2+ can flow out of SR

45
Q

DHP-

A

calcium channel that is in t-tubules and when triggered by an action poetical will open up RyR to allow Ca2+ to flow out of the SR

46
Q

ca2+ binds to __________, which allows _________ to shift and expose the actin site

A

ca binds to troponin

allowing tropomyosin to shift and expose the active site for mason heads to bind to actin

47
Q

the binding of myosin heads triggers?

A

the hydrolysis of ATP into ADP and P

48
Q

when calcium is absent the active _____ binding sites on actin are??

A

myosin binding sites

covered by tropomyosin

49
Q

describe relaxation?

A

immediately after Ca ions are released, SR begins to actively pump them back into sacs

50
Q

resting muscles store _____ in the high energy bonds or ______

A

ATP,
phosophocreatine
(ATP + creatine–> ADP + phosphocreatine)

51
Q

working muscles break down _______ into _____ + _____

A

phosphocreatine + ADP–> creatine + ATP

52
Q

muscles store very limited _______, but can store _______ used to make ___ on creatine

A

very little ATP reserves, but can store phosphate used to make ATP on creatine as PHOSPHOCREATINE

53
Q

three types of muscle fibres?

A

slow twitch oxidative (SO), fast twitch oxidative (FOG),, fast twitch glycolytic (FG)

54
Q

slow oxidative

A

use aerobic metabolism and oxidative phosphorylation to produce low power contractions over a long period of time and do not fatigue as fast
- red in colour and lots of mito

55
Q

Fast oxidative

A

oxidative phosphorylation to produce higher tensoion contractions

56
Q

fast glycolytic

A

rely on anaerobic glycolysis to produce ATP and powerful contractions but fatigue very quickly

57
Q

describe the look of the cardiac muscle

A

branched, and forms junctions called intercalated disks with adjacent cardiac fibres

  • not as highly organized as skeletal muscles
  • contain SR and T-tubules
58
Q

cardiac muscle fibers form a ____________ around the heart chambers that conducts a single impulse across a virtually continuous sarcolemma

A

contractile band

59
Q

compare the T-tubules of cardia vs skeletal

A

cardiac- T-Tubules are larger and form dads ( not triads) with a rather sparse SR

60
Q

other important aspects about cardiac muscle

A

self-stimulating
does not run low on ATP
no fatigue
sustains each impulse for longer than skeletal muscles

61
Q

Smooth muscles

A

small tapered cells with a single nuclei
- no T-tubules and only a loosely organized SR
no striations, bc thick and thin oil are arranged differently
- myofilaments are NOT organized into sarcomeres!

62
Q

do Smoot muscles have sarcomeres?

A

no

63
Q

if the SR in smooth muscles is loosely organixized where does the Ca2+ come from? does it still store Ca2+?

A

no the calcium comes from outside of the cell and binds to calmodulin instead of troponin to trigger a contraction
SR can still hold some but not a lot

64
Q

Ca in smooth muscle binds to ______ instead of ______ to trigger a contraction?

A

Calmodulin instead of troponin

65
Q

Contraction in smooth muscles can be described as?

A

“balling up”

66
Q

2 types of smooth muscle include

A
single unit (visceral)
Multiunit
67
Q

single-unit smooth muscle tissue

A
  • many cells contract as a unit
  • impulses are passed to adjacent muscle cells through gap junctions

gap junctions join smooth muscles fibres into large, continuous sheets
this is the most common type, forms a muscular layer in the walls of hollow structures such as digestive, urinary and reproductive tracts
-exhibits autorythmicity- for peristalsis

68
Q

multiunit smooth muscle tissues

A

each cell stimulated independently
does not act as a single unit bu tis composed of many independent cell units
each fibre responds only to nervous input

69
Q

Smooth muscle contraction steps/proccess

A

-Ca concentration increase as Ca moves in from SR and outside the cell
-ca binds to calmodium
ca-calmodium activates myosin light chain kinase (MLCK)
- MLCK phosphorylates light chaos in myosin heads and increases myosin ATPase activity
- active myosin crossbrisges slide along actin

70
Q

smooth muscle relaxation

A
  • ca actively pumped back out of cell or into SR
71
Q

smooth muscle contracts ______ and is _______

A

slowly and is prolonged

72
Q

smooth muscle characteristics

A

much smaller than skeletal,
has longer actin and myosin filaments, myosin light chain plays regulatory role, no sarcomeres, less SR, controlled by hormones and paracrine, variable electrical responses

73
Q

smooth muscle cells contain ___________ calcium channels, that open when ________

A

stretch-activated

  • ops when press or other force distorts cell membrane
  • known as myogenic contraction
74
Q

myogenic contraction is?

A

when stretch -activated calcium channels open due to pressure to force distorting cel membrane

75
Q

atria

A

are the two upper chambers that receive blood from systemic veins (right) and the pulmonary veins (left atrium)

76
Q

ventrilces

A

two lower chamber that pump blood out of heart

77
Q

the inter ventricular septum separates the low-oxygen blood on the ____ side of the heart from the high-oxygen blood on the ___ side of the heart

A

low= right

high=left

78
Q

the right atrium receives blood from the ?

A

systemic viens (low O2)

79
Q

the left atrium receives blood from the?

A

pulmonary veins (which are the only veins that are high o2 bc just coming from the lungs)

80
Q

the heart wall consists of three layers

A

endocardium
myocardium
epicardium

81
Q

endocardium

A

inner thin layer of the heart

82
Q

myocardium

A

middle layer of the heart

thick and intestine looking

83
Q

epicardium

A

external membrane of the heart

84
Q

heart is composed of mostly?

A

myocardium

85
Q

pericardium

A

fluid filled sac that encases the heart

86
Q

blood returning from the systemic circulation enters the _____ through the _____

A

right atrium

vena cava

87
Q

blood leaving the right ventricle through _______ goes to the ______ and is oxygen ______

A

pulmonary arteries
lungs
poor

88
Q

venae cava

A

blood from systemic system to right atrium

89
Q

pulmonary circulation is ____ pressure while systemic is _____ pressure

A

low pressure, Hugh pressure

90
Q

what can increase blood viscosity?

A
high hematocrit ( % RBC)
high plasma protein concentration
91
Q

which side of the heart does more work?

A

left side ( has to pump into a longer high resistance system )

92
Q

chordae tendinae

A

heart strings that play a role in holding the AV (atrioventricular) valves in place- prevent them from being inverted

93
Q

which AV valve is bicuspid? which is tricuspid?

A

bi- left

tai-right

94
Q

semilunar valves separate?

A

major arterial trucks from ventricles

aorta and pulmonary parties

95
Q

semilunar valves open when?

A

the pressure in the ventricles are higher than the pressure in the aorta

96
Q

how does the heart contract?

A

as a result of an AP that it produces itself

97
Q

what are the 2 specialized types of cardiac muscle cells?

A

contractile and autorhythmic

98
Q

contractile cells in the heart functin

A

99% of the cells- do the pumping- they do not initiate!

99
Q

autorhythmic cells of the heart

A

initiate and conduct action potencial- they do not contract!

100
Q

what is the hearts pacemaker?

A

the sinoatrial node

101
Q

where is the sinoatrial node located? why?

A

the arteria wall

- because the ratio need to contract first

102
Q

how is the rythm maintained?

A

specialized cells inside the node possess an intrinsic rythm

103
Q

what happens if the SA node gets “derailed”

A

it gets passed to the next node ( AV node) and the AV node will now set pace

  • will be abnormal rate
  • how does it get derailed?
104
Q

what is ectopic focus?

A

occasionally a different area of the heart gets overly excited and depolarizes faster than the SA node

  • as a result of anxiety, lack of sleep, caffeine, nicotine or heart disease
  • results in the whole heart being driven faster)
105
Q

describe the route of contraction

A

SA node- in artia initiates AP

  • -> traves to AV node–> conduction slows to allow complete contraction of the artia before the contraction reaches the ventricles
  • after the AV node, contraction velocity increases,
  • impulse travels to right and left branches of the bundle fibres and Purkinje fibres- this tells ventricles to contract! (simultaneously)
106
Q

cardiac autorythmic cells do not have a?

A

resting potencial

- instead they have pacemaker activity

107
Q

describe pacemaker activity

A

the membrane potential’s slow drift to threshold is caused by cyclical decrease in passive outward flux of K+ and constant inward leak of NA+ and inward Ca2+

108
Q

within the intercalated disc what 2 types of junctions are there?

A

gap and desmosomes

109
Q

gap junctions in intercalated discs function

A

areas of low electrical resistance and allow or electrical impulses to spread from cardiac cell to the next

110
Q

how is the threshold reached in cardiac contractile cells?

A

activation of voltage gated Na+ channels (same as other cells)
- unlike other cells the plate phase is prolonged

111
Q

cardiac troponins

A

are indicators of heart damage

  • they are released when the heart muscle has been damages
  • determined in blood test
  • high levels say that a heart attack has occured
112
Q

do cardiac muscle cells have a RP?

A

yes and a refractory period

- the resting potenicail of cardiac muscle cells is -90 (not -60 as in ARC) and the threshold is -70

113
Q

parasympathetic control of heart rate

A

various autonomic nervous system input can change the rate of the heartbeat

  • the parasympathetic nerve is the vagus nerve which primarily affects the atrium and the SA node
  • decrease it by releasing acetylcholine which increases the permeability of the K+ channels ( more K+ out of cell) which has a hyper polarization effect
114
Q

parasympathetic nerve is the

A

vagus nerve

115
Q

parasympathetic mechanism to

A

releases acetylcholine which increase K+ out of cell- hyper polarization effect on cell

116
Q

sympathetic control of heart rate

A

stimulates SA node by releasing norepinephrine by accelerating inactivation of K+ channel–> K+ stays in the cell

cell becomes less negative
swifter drift to AP

117
Q

what are baroreceptors

A

receptors sensitive to changes in pressure
- they send nerve fibres to the cardia control centre in the medullar oblongata
-stretch receptors
-

118
Q

what are the two baroreceptors in the heart

A

carotid and aortic

119
Q

what do baroreceptors do

A

coordinate with the integators in the cardiac control centre in negative feedback loops to oppose changes in blood pressure by adjusting the heart rate