Cardiac Output, Blood Flow, And Blood Pressure

Front 1

Stroke volume (SV)

Back 1

blood pumped/beat by each ventricle

Front 2

Cardiac Output (CO)

Back 2

Is volume of blood pumped/min by each ventricle
=SV x HR
Total blood volume is about 5.5L

Front 3

chronotropic effect

Back 3

influence HR
Autonomic innervation of SA node
Symp and Parasymp nerve fibers modify rate of spontaneous depolarization

Front 4

NE and Epi -regulation of cardiac rate

Back 4

stimulate opening of pacemaker HCN channels
This depolarizes SA faster, increasing HR

Front 5

ACH - regulation of cardiac rate

Back 5

promotes opening of K+ channels
The resultant K+ outflow counters Na+ influx, slowing depolarization and decreasing HR

Front 6

Cardiac control center

Back 6

located in medulla
coordinates activity of autonomic innervation

Front 7

Total peripheral resistance (TPR)

Back 7

impedance to blood flow in arteries
(regulates mean arterial pressure)= afterload which impedes ejection from ventricle

Front 8

Contractility

Back 8

strength of ventricular contraction

Front 9

Ejection fraction

Back 9

is SV/ EDV
Normally is 60%; useful clinical diagnostic tool

Front 10

End diastolic volume (EDV)

Back 10

volume of blood in ventricles at end of diastole
workload (preload) on heart prior to contraction

Front 11

Frank-Starling Law of the Heart

Back 11

States that strength of ventricular contraction varies directly with EDV
Is an intrinsic property of myocardium
As EDV increases, myocardium is stretched more, causing greater contraction and SV

Front 12

sympathoadrenal

Back 12

involving the sympathetic nervous system and the adrenal glands, especially increased sympathetic activity that causes increased secretion of epinephrine and norepinephrine.

Front 13

Venous Return

Back 13

Is return of blood to heart via veins
Controls EDV and thus SV and CO
Dependent on:
Blood volume and venous pressure
Vasoconstriction caused by Symp
Skeletal muscle pumps
Pressure drop during inhalation

Front 14

capacitance vessels

Back 14

term due to veins hold most of blood in body (~70%)

Front 15

intracellular compartment

Back 15

contains 2/3 of body H2O is inside cells

Front 16

extracellular compartment

Back 16

contains 1/3 total body H2O
80% of this is interstitial fluid; 20% is blood plasma

Front 17

Net filtration pressure

Back 17

hydrostatic pressure in capillary (17-37 mm Hg) - hydrostatic pressure of ECF (1 mm Hg)

Front 18

colloid osmotic pressure

Back 18

osmotic pressure exerted by proteins in blood plasma that usually tends to pull water into the circulatory system.

Front 19

Starling forces

Back 19

net filtration pressure and forces opposing it
Pc + pi (fluid out) - Pi + pp (fluid in)

Pc = Hydrostatic pressure in capillary
pi = Colloid osmotic pressure of interstitial fluid
Pi = Hydrostatic pressure in interstitial fluid
pp = Colloid osmotic pressure of blood plasma

Front 20

Edema

Back 20

excessive accumulation of ECF resulting from:
High blood pressure
Venous obstruction
Leakage of plasma proteins into ECF
Low plasma protein levels resulting from liver disease
Obstruction of lymphatic drainage

Front 21

Myxedema

Back 21

(excess production of glycoproteins in extracellular matrix) from hypothyroidism
can cause edema

Front 22

glomerulus

Back 22

part of kidney that filters plasma in urine

Front 23

ADH (vasopressin)

Back 23

released by Post Pit when osmoreceptors detect high osmolality
From excess salt intake or dehydration
Causes thirst
Stimulates H2O reabsorption from urine
inhibited by low osmolality

Front 24

Aldosterone

Back 24

Is steroid hormone secreted by adrenal cortex
Helps maintain blood volume and pressure through reabsorption and retention of salt and water
Release stimulated by salt deprivation, low blood volume, and pressure

Front 25

angiotensin II

Back 25

produced when there is a salt deficit, low blood volume, or low pressure
causes a number of effects all aimed at increasing blood pressure:
Vasoconstriction, aldosterone secretion, thirst

Front 26

Atrial Natriuretic Peptide (ANP)

Back 26

Expanded blood volume is detected by stretch receptors in left atrium and causes release of ANP
ANP inhibits aldosterone, promoting salt and water excretion to lower blood volume
And promotes vasodilation
ANP, together with decreased ADH, acts in a negative feedback system to lower blood volume

Front 27

Physical Laws Describing Blood Flow

Back 27

Flow rate is directly proportional to difference (DP = P1 - P2)
Flow rate is inversely proportional to resistance
Flow = DP/R

Front 28

Poiseuille's Law

Back 28

Blood flow = DPr^4(pi)
nL(8)
Resistance is directly proportional to length of vessel (L) and viscosity of blood (n)
Inversely proportional to 4th power of radius

Front 29

the 2 major factors regulating blood flow

Back 29

Mean arterial pressure and vascular resistance

Front 30

total peripheral resistance

Back 30

Sum of all vascular resistances within the systemic circulation

Front 31

Extrinsic Regulation of Blood Flow
Sympathetic

Back 31

Sympathoadrenal activation causes increased CO and resistance in periphery and viscera
Blood flow to skeletal muscles is increased
Because their arterioles dilate in response to Epi and their Symp fibers release ACh which also dilates their arterioles
Thus blood is shunted away from visceral and skin to muscles

Front 32

Extrinsic Regulation of Blood Flow
Parasympathetic

Back 32

Parasympathetic effects are vasodilative
However, Parasymp only innervates digestive tract, genitalia, and salivary glands
Thus Parasymp is not as important as Symp
Angiotenin II and ADH (at high levels) cause general vasoconstriction of vascular smooth muscle
Which increases resistance and BP

Front 33

Nitric oxide (NO), bradykinin, prostacyclin

Back 33

endothelium produces several paracrine regulators that promote relaxation:

Front 34

NO

Back 34

involved in setting resting “tone” of vessels
Levels are increased by Parasymp activity
Vasodilator drugs such as nitroglycerin or Viagra act

Front 35

Endothelin 1

Back 35

vasoconstrictor produced by endothelium

Front 36

Myogenic control mechanisms

Back 36

occur in some tissues because vascular smooth muscle contracts when stretched and relaxes when not stretched
matches blood flow to local tissue needs

Front 37

Intrinsic Regulation of Blood Flow (Autoregulation)

Back 37

Maintains fairly constant blood flow despite BP variation

Front 38

active hyperemia

Back 38

Low O2 or pH; or high CO2, adenosine, or K+ from high metabolism cause vasodilation which increases blood flow

Front 39

Heart (and brain) must receive adequate blood supply at all times
Heart is most aerobic tissue--each myocardial cell is within 10 mm of capillary
Contains lots of mitochondria and aerobic enzymes
During systole the coronary vessels are occluded
Heart gets around this by having lots of myoglobin
]

Back 39

Aerobic Requirements of the Heart

Front 40

Regulation of Coronary Blood Flow

Back 40

Blood flow to heart is affected by Symp activity
NE causes vasoconstriction (a effect); Epi causes vasodilation (b effect).
However, dilation accompanying exercise is due mostly to intrinsic regulation

Front 41

Regulation of Blood Flow Through Skeletal Muscles

Back 41

At rest, flow through skeletal muscles is low because of tonic sympathetic activity (via NE)
Flow through muscles is decreased during contraction because vessels are constricted

Front 42

Circulatory Changes During Exercise

Back 42

Symp activity causes vasodilation via Epi and local ACh release
Blood flow is shunted from periphery and visceral to active skeletal muscles
intrinsic regulation is major vasodilator
Symp effects cause SV and CO to increase
HR and ejection fraction also increases (vascular resistance goes down reducing afterload)

Front 43

Cerebral Circulation

Back 43

Gets about 15% of total resting CO
Held constant (750ml/min) over varying conditions
Is not normally influenced by sympathetic activity

Front 44

myogenic regulation

Back 44

When BP increases, cerebral arterioles constrict; when BP decreases, arterioles dilate

Front 45

Cerebral Circulation 2

Back 45

Regulated almost exclusively by intrinsic mechanisms
Arterioles dilate and constrict in response to changes in CO2 levels (leads to a drop in pH)

Front 46

metabolic regulation

Back 46

increases in local neural activity Arterioles are very sensitive to
Areas of brain with high metabolic activity receive most blood

Front 47

thermoregulation

Back 47

Skin blood flow is adjusted to keep body core temp at 37oC
By arterial dilation or constriction and activity of arteriovenous anastomoses which control blood flow through surface capillaries
Symp activity closes surface beds during cold and fight-or-flight, and opens them in heat and exercise

Front 48

Blood Pressure (BP)

Back 48

Arterioles play major role in control and distribution
contolled mainly by by HR, SV, and peripheral resistance
increase in these increases this
Sympathoadrenal activity raises BP via arteriole vasoconstriction and by increased CO
Kidney plays role in BP by regulating blood volume and thus stroke volume

Front 49

baroreceptors

Back 49

(stretch receptors) located in aortic arch and carotid sinuses
Increase in BP causes walls of these regions to stretch, increasing frequency of APs
send APs to vasomotor and cardiac control centers in medulla
Is most sensitive to decrease and sudden changes in BP

Front 50

Atrial Stretch Receptors

Back 50

Are activated by increased venous return and act to reduce BP
Stimulate reflex tachycardia (fast HR)
Inhibit ADH release (decreases blood volume) and promote secretion of ANP (decreases blood volume, antagonizes the vasoconstriction actions of angiotensin II)

Front 51

auscultation

Back 51

to examine by listening)

Front 52

laminar flow

Back 52

normal, quiet, smooth blood flow)
No sound is heard

Front 53

Korotkoff sounds

Back 53

sound is heard at pressure that blood is 1st able to pass thru cuff (= systolic pressure); last occurs when one can no long hear sound because cuff pressure = diastolic pressure

Front 54

Pulse pressure

Back 54

(systolic pressure) – (diastolic pressure)

Front 55

Mean arterial pressure (MAP)

Back 55

represents average arterial pressure during cardiac cycle
diastolic pressure + 1/3 pulse pressure

Front 56

Hypertension

Back 56

Blood pressure in excess of normal range for age and gender (> 140/90 mmHg)
Afflicts about 20% of adults

Front 57

primary or essential hypertension

Back 57

Increase in peripheral resistance is universal
CO and HR are elevated in many
Secretion of renin, Angio II, and aldosterone is variable
Sustained high stress (which increases Symp activity) and high salt intake act synergistically in development of hypertension
Prolonged high BP causes thickening of arterial walls, resulting in atherosclerosis
Kidneys appear to be unable to properly excrete Na+ and H2O

Front 58

Secondary hypertension

Back 58

caused by known disease processes

Front 59

Treatment of Hypertension

Back 59

Often includes lifestyle changes such as cessation of smoking, moderation in alcohol intake, weight reduction, exercise, reduced Na+ intake, increased K+ intake
Drug treatments include diuretics to reduce fluid volume, beta-blockers to decrease HR, calcium blockers, ACE inhibitors to inhibit formation of Angio II, and Angio II-receptor blockers

Front 60

myoglobin

Back 60

an O2 storage molecule that releases O2 to heart during systole