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Advanced Human Physiology > Exam 3 - Cardiac Output, Blood Flow, and Blood Pressure Part #1 > Flashcards

Exam 3 - Cardiac Output, Blood Flow, and Blood Pressure Part #1 Flashcards

1
Q

cardiac output

A
  • volume of blood pumped per minute by left or right ventricle
  • ml/min
  • cardiac output = stroke volume (ml/beat) * cardiac rate (beats/min)
  • average 5.5 L/min
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2
Q

stroke volume

A
  • volume of blood pumped per beat by each ventricle
  • ml/beat
  • average is 70-80 ml/beat
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3
Q

mean arterial pressure of systemic circulation vs pulmonary circulation

A
  • systemic:
    • 70-105 mmHg
  • pulmonary:
    • 10-20 mmHg
  • cardiac output of right ventricle = cardiac output of left ventricle
    • this means pulmonary circulation must have low resistance, low pressure, and high blood flow
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4
Q

total blood volume

A
  • 5.5 L
  • each ventricle pumps the equivalent of the total blood volume each minute under resting conditions
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5
Q

norepinephrine from and epinephrine from bind to

receptors in the heart to stimulate the production of

A

norepinephrine from sympathetic axons and epinephrine from adrenal medulla bind to beta-1-adrenergic receptors in the heart to stimulate the production of cyclic AMP (that then acts on HCN channels and Ca channels of pacemaker cells)

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6
Q

chronotropic effect

A
  • mechanisms that affect the cardiac rate set by the SA node
    • those that increase cardiac rate have a positive chronotropic effect
    • those that decrease cardiac rate have a negative chronotropic effect
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7
Q

what affect do the sympathetic endings in the musculature of the atria and ventricles have?

A

increase the strength of contraction and causes a slight decrease in the time spent in systole when the cardiac rate is high

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8
Q

cardiac control center

A
  • coordinates activity of the autonomic innervation of the heart
  • found in the medulla oblongata
  • affected by higher brain areas and by sensory feedback from baroreceptors (pressure receptors) in the aorta and carotid arteries​
    • in this way, a fall in BP can produce a reflex increase in HR
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9
Q

three variables that regulate stroke volume

A
  • end diastolic volume (EDV)
    • amount of blood left in the ventricles at the end of diastole (immediately before contraction)
    • directly proportional
  • total peripheral resistance in arteries
    • inversely proportional
  • contractility of ventricular contraction
    • directly proportional
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10
Q

preload

A
  • the workload imposed on the ventricles prior to contraction (EDV)
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11
Q

afterload

A
  • impedance to ejection of blood from ventricle after contraction has begun
    • presented by high total peripheral resistance that decreases the stroke volume
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12
Q

ejection fraction

A
  • about 60%
  • remains relatively constant over a range of EDV, so that the amount ejected per beat (stroke volume) increases as the EDV increases
    • for this to be true, the strength of ventricular conraction must increase as EDV increases
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13
Q

Frank-Starling law of the heart

A
  • an increase in EDV results in increased contraction strength and in increased stroke volume
  • intrinsic property of the heart
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14
Q

stretching of myocardial cells during diastole increases the sensitivity of what channels?

A
  • Ca2+-release channels (ryanodine receptors, RyR2 type) in the sarcoplasmic reticulum
    • the greater release of Ca2+ contributes to a stronger contraction
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15
Q

Anrep effect

A
  • the frank-starling mechanism results in an initial rapid increase in contractility when the ventricles are stretched
    • this force then gradually increases over the next 10-15 minutes
  • this effect appears to be due to increased Ca2+ entering the cytoplasm through the reversal of Na/Ca exchanger
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16
Q

what mechanisms ensure that an increase in EDV intrinsically produces an increase in contraction strength and stroke volume?

A
  • frank-starling mechanism
  • increased sensitivity of RyR2 receptors
  • anrep effect
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17
Q

how does the frank-starling law explain how the heart can adjust to a rise in total peripheral resistance?

A
  1. a rise in peripheral resistance causes a decrease in the stroke volume, so that
  2. more blood remains in the ventricle and the EDV is greater for the next cycle; as a result,
  3. the ventricle is stretched to a greater degree in the next cycle and contracts more strongly to eject more blood
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18
Q

why must the rate of blood flow through the pulmonary and systemic circulations be equal?

A
  • to prevent fluid accumulation in the lungs
  • to deliver fully oxygenated blood to the body
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19
Q

what is the driving force for the return of blood to the heart?

A

venous pressure

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20
Q

how much of the total blood volume is located in the veins?

A

two-thirds

21
Q

capacitance vessels

A

veins (have a higher compliance)

22
Q

resistance vessels

A

arteries

23
Q

mean venous pressure vs mean arterial pressure

A
  • mean venous pressure is 2 mmHg
  • mean arterial pressure is 90-100 mmHg
24
Q

venous pressure in venules vs junction of venae cavae with the right atrium

A
  • venules is 10 mmHg
  • venae cavae is 2-6 mmHg
25
Q

things that promote venous return to the heart

A
  • pressure difference between venules and junction of venae cavae with right atrium
  • sympathetic nerve activity
    • stimulates smooth muscle contraction in venous walls and reduces compliance
  • skeletal muscle pump
  • respiratory pump
26
Q

blood pressure vs osmotic forces (effects on blood volume)

A
  • blood pressure promotes the formation of interstitial fluid from plasma
  • osmotic forces draw water from the tissues into the vascular system
27
Q

net filtration pressure

A
  • equal to the hydrostatic pressure of blood in capillaries minus the hydrostatic pressure of tissue fluid outside capillaries, which opposes filtration
28
Q

colloid osmotic pressure

A
  • the osmotic pressure exerted by proteins
    • the colloid osmotic pressure of plasma is much greater than the colloid osmotic pressure of interstitial fluid (due to restricted filtration of proteins through capillary pores)
29
Q

oncotic pressure

A
  • difference between colloid osmotic pressure of plasma and interstitial fluid
    • essentially equal to the colloid osmotic pressure of plasma, since the colloid pressure of interstitial fluid is low enough to be neglected
  • 25 mmHg
  • favors movement of water into the capillaries
30
Q

starling forces

A

opposing forces that affect the distribution of fluid across the capillary

31
Q

hydrostatic pressure at arteriolar end of systemic capillaries vs venular end

A
  • arteriolar end 37 mmHg
  • venular end 17 mmHg
32
Q

(edit)

A
  • positive value at the arteriolar end indicates that the starling forces that favor the filtration of fluid out of the capillary predominate
  • negative value at the venular end indicates that the net starling forces favor the return of fluid to the capillary
33
Q

% of filtrate returned directly to the blood capillaries?

how does the remaining filtrate return to the blood?

A
  • 85-90% of filtrate is returned directly to the blood capillaries
  • remaining 10-15% is returned to the blood by way of the lymphatic system
34
Q

what does edema result from?

A
  • high arterial blood pressure
    • this increases capillary pressure and causes excessive filtration
  • venous obstruction
  • leakage of plasma proteins into interstitial fluid
    • causes reduced osmotic flow of water into capillaries
    • occurs during inflammation and allergic reactions as a result of increased capillary permeability
  • myxedema
    • excessive production of a particular glycoprotein (mucin) in the extracellular matrix caused by hypothyroidism
  • decreased plasma protein concentration
    • as a result of liver disease or kidney disease
  • obstruction of the lymphatic drainage
    • in elephantiasis or surgery
35
Q

glomeruli

A

capillaries that filtrate plasma to form urine

36
Q

atrial natriuretic peptide

A

hormone secreted by the atria that increases the excretion of salt and water in the urine, thereby working to lower blood volume

37
Q

aldosterone

A
  • steroid hormone secreted by the adrenal cortex
  • stimulates the reabsorption of salt by the kidneys
    • “salt-retaining hormone”
  • increases blood volume, but does not produce a change in plasma osmolality
38
Q

renin-angiotensin-aldosterone system (edit)

A
39
Q

extrinsic regulation of blood flow

A

control by autonomic nervous system and endocrine system

40
Q

vasoconstriction in fight-or-flight

A
  • adrenergic sympathetic fibers (those that release norepinephrine) active alpha-adrenergic receptors to cause vasoconstriction in the digestive tract, kidneys, and skin
41
Q

vasodilation in fight-or-flight

A
  • arterioles in skeletal muscles receive cholinergic sympathetic fibers, which release acetylcholine
    • this causes vasodilation
    • vasodilation in skeletal muscles is also produced by epinephrine secreted by the adrenal medulla which stimulates beta-adrenergic receptors
42
Q

parasympathetic innervation of blood vessels is limited to…

A
  • digestive system
  • external genitalia
  • salivary glands
43
Q

paracrine regulators

A

molecules produced by one tissue that help to regulate another tissue of the same organ

44
Q

autoregulation

A

refers to the ability of some organs (i.e. brain and kidneys) to utilize intrinsic control mechanisms to maintain a relatively constant blood flow despite wide fluctations in blood pressure

45
Q

myogenic control mechanisms

A
  • type of intrinsic mechanism
  • direct responses by the vascular smooth muscle to changes in pressure
    • a decrease in arterial pressure causes cerebral vessels to dilate
    • high blood pressure causes cerebral vessels to constrict
46
Q

localized chemical conditions that promote vasodilation

A
  • decreased oxygen concentrations
  • increased carbon dioxide concentrations
  • decrease tissue pH
  • release of K and paracrine regulations
47
Q

reactive hyperemia

A
  • when constriction is removed and blood flow resumes, the metabolic products that have accumulated cause vasodilation
    • the tissue thus appears red
  • metabolic control mechanism
48
Q

active hyperemia

A
  • increase in blood flow to skeletal muscles and other organs as a result of increased metabolism
    • this increased blood flow can wash out the vasodilator metabolites, so that blood flow can fall to pre-exercise levels
  • metabolic control mechanism

Advanced Human Physiology (10 decks)

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