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KP222 > Quiz #5 > Flashcards

Quiz #5 Flashcards

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1
Q

List the 3 main muscle types in order from lowest to highest duration of muscle twitch.

A

skeletal
cardiac
smooth

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2
Q

What similar electrical properties does cardiac muscle have to skeletal muscle?

A

T-tubules
Ca2+ in SR
troponin-tropomyosin regulation

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3
Q

What similar electrical properties does cardiac muscle have to smooth muscle?

A

gap junctions

extracellular Ca2+

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4
Q

What are the steps for electrical activity in the heart?

A

current spreads through gap junctions to contractile cells

action potentials travel along plasma membrane and T-tubules

Ca2+ channels open in SR and plasma membrane

Ca2+ induces Ca2+ release from SR

Ca2+ binds to troponin, exposing myosin-binding sites

cross bridge cycle

Ca2+ actively transported back to SR/ECF

tropomyosin reblocks myosin-binding sites, muscle fiber relaxes

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5
Q

What are the 2 main periods of the cardiac cycle?

A

systole - ventricular contraction

diastole - ventricular relaxation

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6
Q

When do the AV valves open?

A

when atrial pressure is greater than ventricular pressure

blood can flow high to low pressure areas

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7
Q

When do the semilunar valves open?

A

when ventricular pressure is greater than arterial pressure

blood can flow high to low pressure areas

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8
Q

How long is the cardiac cycle?

A

about 0.8 seconds

  • 0.3 seconds systole
  • 0.5 seconds diastole

when HR increases all phases shorten

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9
Q

What are the 4 phases of the cardiac cycle?

A

phase 1 - ventricular filling (diastole)

phase 2 - isovolumetric contraction (systole)

phase 3 - ventricular ejection (systole)

phase 4 - isovolumetric relaxation (diastole)

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10
Q

How does aortic pressure vary during the cardiac cycle?

A

lowest during diastole
- aortic valve closes as blood is still leaving the aorta, so pressure falls

highest during systole
- aortic valve opens and pressure rises rapidly with ejection

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11
Q

How does the aorta ensure continuous blood flow during the cardiac cycle?

A

can stretch out alot to store energy during systole so during diastole, can recoil and release energy to continue pumping blood

there is never no blood flowing through the aorta

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12
Q

What is EDV?

A

end diastolic volume

volume of blood in the ventricle at the end of diastole (before contraction)

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13
Q

What is ESV?

A

end systolic volume

volume of blood in the ventricle at the end of systole (after contraction)

some amount will always remain

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14
Q

What is SV?

A

stroke volume

amount of blood ejected from the ventricle each cycle

SV = EDV - ESV

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15
Q

What is ejection fraction?

A

fraction of EDV ejected during a heartbeat

EV = SV/EDV

for a healthy individual, 54% of EDV is ejected into aorta

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16
Q

What is cardiac output?

A

volume of blood pumped by each ventricle per minute

CO = SV x HR

average = 5 L/min at rest
- average HR is 70 bpm, average SV is 70 mL

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17
Q

How long does it take the entirety of the blood volume to circulate through the body at rest?

A

once per minute

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18
Q

What components of cardiac output are regulated by the CNS?

A

HR and SV

ANS nerves effect entire heart
SNS and PNS take opposite effects

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19
Q

Where on the heart do parasympathetic nerves innervate?

A

SA node and AV node

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20
Q

Where on the heart do sympathetic nerves innervate?

A

SA node and AV node and ventricular myocardium

sympathetic system can change contractile force in ventricles, parasympathetic cannot

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21
Q

What determines the heart rate?

A

firing frequency of SA node

without extrinsic control, SA node would fire at 100 bpm

under control of ANS and hormones, parasympathetic system dominates and keeps HR at 75 bpm at rest

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22
Q

How does the PNS act to decrease heart rate?

A

PNS neurons release ACh, binds to muscarinic cholinergic receptors on SA nodal cells

open K+ channels and close funny and T-type channels

slows depolarization on decreases conduction speed of impulses

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23
Q

What is the role of epinephrine on HR?

A

increases HR and conduction velocity

released from adrenal medulla to enforce SNS activity

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24
Q

What division of the nervous system controls stroke volume?

A

SNS

sparse PNS fibers in ventricular myocardium

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25
What is ventricular contractility?
more forceful contractions expel more blood sympathetic control: norepinephrine binds to beta1 adrenergic receptors, augmenting open Ca2+ channels to increase Ca2+ release from SR
26
What 3 factors affect stroke volume?
ventricular contractility end-diastolic volume afterload
27
How does EDV affect SV?
more blood in the heart at the end of diastole increases SV Starlings Law - increased EDV stretches muscle fibers closer to optimal length - results in greater strength of contraction and therefore increased SV
28
What are the limits to Starlings Law?
ventricular expansion is limited by connective tissue and the pericardial sac
29
What is afterload?
pressure in the arterial system after contraction begins - how resistant is the periphery to accepting blood flow combined load of EDV and arterial resistance during ventricular contraction increase in arterial pressure will decrease SV
30
What is flow?
flow = delta P/resistance delta P = force pushing blood against various factors resisting the flow of liquid in a pipe delta P = MAP - CVP flow occurs from high to low pressure
31
What is MAP?
mean arterial pressure pressure in aorta 2/3 DBP + 1/3 SBP
32
What is CVP?
central venous pressure pressure in vena cava
33
What is the relationship between flow and pressure gradient?
directly proportional
34
Which circuit of circulation has less resistance?
pulmonary pressure gradient is much less than in systemic circuit
35
What are some factors that affect the resistance of flow?
radius of vessel length of vessel viscosity of fluid
36
According to Poiseuille's Law, what variable influences pressure the most?
change in radius
37
What is the relationship between resistance and flow?
inversely proportional
38
What are the 2 types of radius changes in arterioles?
vasoconstriction - decreased radius = increased resistance - typically associated with decreased metabolic activity vasodilation - increased radius = decreased resistance - typically associated with increased metabolic activity
39
What is TPR?
total peripheral resistance combined resistance of all blood vessels within the systemic circuit
40
What is the equation for cardiac output in relation to TPR and MAP?
CO = MAP/TPR
41
What structures make up microcirculation?
arterioles, capillaries, venules
42
What are the 3 layers of blood vessels?
tunica externa - collagen fibers tunica media - smooth muscle and elastic fibers - thicker in arteries tunica intima - endothelium
43
What is the vasa vasorum?
capillary network designed so large blood vessels can supply itself with blood
44
What is blood pressure?
force that blood exerts on the arterial wall
45
What are systolic and diastolic blood pressures?
systolic = peak BP during contraction diastolic = lowest BP during relaxation - not zero due to elastic recoil
46
What is pulse pressure?
SBP-DBP strength of pressure wave
47
What is compliance?
a measure of how the pressure of a vessel will change with a change in volume ex. a small increase in volume will cause a large increase in blood pressure in a small compliance vessel
48
What is healthy blood pressure around?
120/80 (systolic/diastolic)
49
How is blood pressure measured?
usually in elastic arteries, often brachial want to inflate cuff to higher than systolic pressure to pinch off blood flow slowly release pressure, once equal blood will start to flow through, listen for Korotkoff sounds indicative of systolic pressure (due to turbulent blood flow) when sounds are gone, indicative of diastolic pressure
50
What is the role of arterioles?
where the greatest resistance occurs due to rings of smooth muscle to regulate radius control blood flow to individual capillary beds and regulate TPR connect arteries to capillaries
51
What is arteriolar tone?
contraction level (radius) independent of extrinsic influences
52
What determined the regulation of blood flow to organs?
based on needs of each organ regulated by varying resistance of vessels that supplies that organ (if a tissue doesn't have high metabolic needs at that time resistance will be increased so decreased flow goes to that organ) organ blood flow = MAP/organ resistance
53
What is active hypermia?
increased blood flow in response to increased metabolic activity when metabolism is increased O2 is consumed faster than delivered and CO2 is produced faster than it is removed, vasodilation occurs to increase blood flow, delivering more O2 and removing more CO2
54
What is reactive hypermia?
increased blood flow in response to a previous reduction in blood flow (ex. an occlusion) metabolites increase and oxygen decreases to blocked off tissues, vasodilation occurs when blockage is released, increased blood flow due to low resistance, metabolites are removed and oxygen is delivered
55
What are the 2 major physiological regulators of blood flow?
blood pressure | peripheral resistance
56
What are the 3 major physiological regulators of blood pressure?
heart rate stroke volume peripheral resistance
57
What are some endocrine mechanisms of regulating blood flow?
NE and E, antidieuretic hormone, and angiotensin II increase cardiac output and cause vasoconstriction atrial natriuretic peptide causes vasodilation
58
What are some neural mechanisms of regulating blood flow?
adjusts cardiac output and peripheral resistance to maintain blood flow to tissues SNS - increases cardiac output and peripheral resistance (vasoconstriction) PNS - decreases cardiac output - no innervation of blood vessels
59
How do baroreceptors function to regulate high blood pressure (hypertension)?
BP rises above normal range baroreceptors stimulated, increase # of impulses, causes activation/inhibition of certain centres decreases sympathetic impulses to heart to decrease HR, contractility, resistance, and cardiac output returns BP to normal range
60
How do baroreceptors function to regulate low blood pressure (hypotension)?
BP falls below normal range baroreceptors inhibited, decrease # of impulses, causes activation/inhibition of certain centres increases sympathetic impulses to heart to increase HR, contractility, resistance, and cardiac output bring BP back to normal range
61
What is the baroreflex?
stretch sensitive mechanoreceptors monitor pressure of blood flow carotid - to brain aortic - to body sends info to CV control centre
62
What are the 2 types of capillaries?
continuous - small gaps between endothelial cells to allow small water-soluble molecules to move through - in muscle, lungs, adipose, brain - most common fenestrated - large gaps between endothelial cells forming pores (fenestrations) - allow proteins and in some cases blood cells to move through - kidneys, endocrine, intestine
63
What are the different ways in which exchange can occur over capillary walls?
diffusion - most common - simply travelling over membrane, through membrane if lipophilic or through channels if lipophobic transcytosis - exchangeable proteins - endocytosis on one side, exocytosis on the other mediated transport - ex. GLUT4 transporter in brain
64
What is filtration?
movement out of capillary into interstitial space
65
What is absorption?
movement into capillary from interstitial space
66
What are the Starling force that act across capillary walls?
hydrostatic pressure gradient - force due to fluid presence - capillary favours filtrations osmotic pressure - force exerted on water by non-permeating solutes - pulls water to where there is more solute
67
What are the 2 types of hydrostatic pressure?
capillary hydrostatic pressure - exerted by presence of fluid inside the capillary - direction of force: filtration interstitial fluid hydrostatic pressure - exerted by pressure of fluid inside the interstitial fluid - direction of force: absorption
68
What are the 2 types of osmotic pressure?
capillary osmotic pressure - force due to presence of proteins in capillary plasma - direction of force: absorption interstitial fluid osmotic pressure - force due to presence of proteins in interstitial fluid - direction of force: filtration
69
What is NFP?
net filtration pressure difference between forces for filtration and absorption if positive - in direction of filtration if negative - in direction of absorption
70
What are all the different equations to find cardiac output/flow?
SV x HR MAP/TPR delta P/F Q = CO = F
71
What are the 2 ways in which redistribution of venous reserve is accomplished in times of need?
systemic venous constriction - venoconstriction of medium veins shifts blood from venous system to arterial system venomotor tone - smooth muscle tension in veins - increase in the tone increases CVP, decreasing venous compliance, increasing venous return
72
What happens to Q distribution during exercise?
most tissues decrease at the expense of skeletal muscle heart and brain receive more but the same/lower relative amounts
73
Describe the ventricular filling phase of the cardiac cycle.
- blood returning to heart enters relaxed atria - passes AV valves into ventricles - at the end, atria contract driving more blood into ventricles
74
Describe the isovolumetric contraction phase of the cardiac cycle.
- once ventricular pressure exceeds atrial pressure, AV valves close (LUB), pressure continues increasing - ventricles begin to contract - once pressure is high enough, semilunar valves open
75
Describe the ventricular ejection phase of the cardiac cycle.
- ventricular volume decreases, blood ejected until semilunar valves close (DUB) to prevent back flow as ventricle now has lower pressure than aorta
76
Describe the isovolumetric relaxation phase of the cardiac cycle.
- heart is resting - some blood still remains present - pressure still present as tension takes time to decrease - back to phase 1 when ventricular pressure allows AV valves to open and blood to enter

KP222 (7 decks)

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