Regulation of Blood Flow Flashcards
Cardiovascular reflexes adjust…
blood flow to meet immediate demand
- alters CO and/or TPR
Cardiovascular reflexes will monitor…
conditions in specific locations in cardiovascular system
Control mechanisms of cardiovascular reflexes are…
systemic
Cardiovascular reflex center is located in the…
medulla oblongata
CV reflex center gets input from…
- peripheral baroreceptor and chemoreceptors
- high centers
CV reflex center outputs via changes to…
PNS and SNS to heart and blood vessels
Hypothalamus provides _____ input to CV center
behavioral and thermal
Examples of behavioral input:
- fear
- anger
- pain
Behavioral input leads to…
- increase of SNS output
- decrease of PNS output
- increase in heart rate
- increase in SV
- increase in MAP
Behavioral input produces…
- venoconstriction to increase VR and CO
- vasoconstriction to increase TPR
Behavioral input is a stress response designed to…
provide body with increased available O2 and deliver to appropriately respond to stress
Thermal input comes from…
thermoreceptors in skin and blood perfusing hypothalamus
Thermal input leads to ____ output…
SNS output to peripheral blood vessels of skin
Thermal input will lead to the…
redistribution of blood flow
What happens with cold input?
- increased SNS output to skin
- constricts surface vessels
- reducing flow
- limiting heat loss
What happens with warm input?
- decreased SNS output to skin
- surface vessels dilate
- increases surface flow
- promoting heat loss
When body is stressed, it first pulls blood away from…
skin, GI, and reproductive system so it can flow to areas that need O2
Arterial baroreceptors are located in…
carotid sinuses and aortic arch
Arterial baroreceptors continuously…
monitor pressure in cardiovascular system
Arterial baroreceptors: increased MAP leads to an increase in…
- pressure on vessel wall
- vascular stretch and deformation
- firing
Sensitivity of arterial baroreceptors can be…
altered
- ex: high BP leads to adaptation (occurs due to stiffness of sinus and/or aorta)
Increased firing of baroreceptors will cause the CV center to respond by…
- decreasing SNS output to arterioles, which leads to decreased vasoconstriction and venoconstriction
- increasing PNS output, which leads to increased venous compliance and decreased VR, therefore decreased EDV
Decreased vasoconstriction leads to…
- decreased TPR
- increased outflow into venous system
- decreased MAP
Decreased venoconstriction leads to…
- increased venous compliance
- decreased VR
- decreased EDV
Reflex of arterial baroreceptors causes…
fast changes in blood pressure in response to abrupt changes in blood volume
- orthostatic hypotension: short term drop in VR due to gravity triggers decreased firing rate of baroreceptors
Cardiopulmonary baroreceptors are…
tonically active mechanoreceptors located in R atrium and pulmonary vessels
Increase in volume of blood in atria or pulmonary vessels lead to…
increase in stretch and firing of cardiopulmonary baroreceptors
Increased firing of cardiopulmonary baroreceptors lead to…
- decreased SNS output (especially to kidney)
- decreased ADH
- release of ANP from atrial myocytes
Cardiopulmonary baroreceptors: decreased SNS output to kidneys will…
- increases renal blood flow and urine flow
- helps to eliminate excess fluid
- decreases blood volume
Cardiopulmonary baroreceptors: decrease in ADH leads to…
- inhibition of release of anti-diuretic hormone from hypothalamus
- diuresis occurs: increase urine production removes excess fluid from cardio system
Decreased firing of cardiopulmonary baroreceptors lead to…
- increased SNS output to kidney
- increased release of angiotensin, aldosterone, and ADH vasopressin (reabsorption at kidney)
- helps retain salt and water by kidney
Peripheral chemoreceptors monitors…
level of O2/CO2 in blood leaving the heart
Peripheral chemoreceptors located in…
aortic and carotid bodies
Peripheral chemoreceptors are the primary input to..
respiratory center in medulla to provide respiratory adjustments
- direct input to CV center and indirect input through respiratory center
Increased peripheral chemoreceptors firing comes from…
- increased partial pressure of CO2 in arterial blood
- decrease in O2 pressure
- decrease in pH of blood
Increased firing of peripheral chemoreceptors lead to…
mild increase in SNS output from CV center
Central chemoreceptors monitor…
presence of wastes in the brain, which would inhibit activity of neurons
Central chemoreceptors are located in…
medulla
Central chemoreceptors are directly stimulated by…
- decrease of pH
- increase of CO2 pressure
T/F: O2 tension has a big direct effect on central chemoreceptors
F
Effect of hyperventilation on central chemoreceptors:
- decreased tonic action
- increase pH
- decrease CO2 pressure
Central ischemic response is…
insufficient blood flow to brain
- increased firing of central chemoreceptors, which lead to massive increase in SNS
Overall regulatory activity is a combo of…
extrinsic and intrinsic factors
In the brain and heart, does extrinsic or intrinsic factor systems dominate?
intrinsic
- limited tolerance for decrease in CO2 pressure
In the skin and splancnic (blood flow to GI), does extrinsic or intrinsic factor systems dominate?
extrinsic
- regulate themselves locally during rest
- allows body to divert flow of blood away during stress
In skeletal muscles, does extrinsic or intrinsic factor systems domintate?
intrinsic
Mean arterial pressure is sensed and corrected by…
- baroreceptor reflex
- chemoreceptor reflex
- hormones
Which hormones regulate mean arterial pressure?
- renin-angiotensin-aldosterone (RAA) system
- epi and norepi
- anti-diuretic hormone (ADH)
- atril natriuretic peptide (ANP)
Long term regulation of blood pressure is based on…
vascular health and adequate circulating volume
Decrease in vascular health leads to…
atherosclerosis: age and disease related changes in vascular wall
Atherosclerosis gives a fixed…
volume of blood vessels and reduces ability to compensate by altering diameter
Effects of atherosclerosis:
- stiffens wall and narrows lumen
- decrease in arterial compliance
- contributes to elevated pulse pressure
- reduces overall sensitivity of baroreceptors
Circulating volume is primarily under control of…
kidneys and GI systems
Kidney controls…
excretion and reabsorption of salt and water
GI system mediates…
absorption of salt and water
Inadequate circulation of blood volume can be corrected by…
- activating thirst mechanisms
- shifting blood volume from peripheral vascular beds to heart
- increasing venomotor tone
- orthostatic changes
- reabsorption of interstitial fluid at capillaries due to changes in starling forces
Hemorrhage, hypotension, and exercise all cause…
primary changes in either CO or TPR
- has to be matched by compensatory changes elsewhere
Hemorrhage is…
blood loss
- abnormal change, so body has to compensate for changes not caused by altered metabolic activity
What does a hemorrhage look like?
- cutaneous veins collapsed
- pale, moist skin
- fast breathing
Vital signs during hemorrhage:
- decrease in arterial systolic and diastolic pressures
- decrease in VR -> decrease in EDV and SV
- decrease in CO = decrease in MAP
- arterial pulse is rapid and feeble
Response to a hemorrhage:
mobilize blood stored in veins and spleen to restore bp by restoring blood volume
To fix the decrease in MAP caused by a hemorrhage, what is required?
- increase in CO
- increase in TPR
If MAP decreases but is above 60 mmHg during a hemorrhage, what can restore bp?
baroreceptor reflexes
What happens when baroreceptor reflexes kick in during a hemorrhage?
- decreases stretch on aortic arch and carotid sinus
- decreases firing of baroreceptors
- decrease in PNS
- increase in SNS
- increase in CO via increase in HR and SV
- venoconstriction
Venoconstriction leads to…
- increased VR, which will increase EDV, which in turn increases SV, which finally increases CO
If MAP decreases below 60 mmHg during a hemorrhage, what happens?
chemoreceptor reflexes, which leads to increase in firing
What happens when chemoreceptor reflexes kick in during a hemorrhage?
- increased SNS
- respiration stimulated leads to ancillary pump increasing VR
If MAP decreases below 40 mmHg during a hemorrhage, what happens?
cerebral ischemia responses lead to massive increase in SNS
Increase in MAP leads to neural changes via increase in…
- HR
- cardiac contractility
- TPR
- venoconstriction
Prolonged response to hemorrhage occurs over…
12-24 hours to increase blood volume
Ways to increase blood volume during a hemorrhage:
- decreasing capillary hydrostatic pressure
- thirst mechanism
- release of endogenous constrictor substances
Decreasing capillary hydrostatic pressure increases blood volume during a hemorrhage by…
increasing reabsorption of fluid from ISF
The thirst mechanism increases blood volume during a hemorrhage by…
increasing fluid ingestion and absorption
Examples of endogenous constrictor substances:
- epi from adrenal medulla (SNS)
- vasopressin (ADH): decreases urine production
- renin-angiotensin system (RAS) ANG II
Function of renin-angiotensin system (RAS) ANG II:
- potent vasoconstrictor
- stimulates release of aldosterone
- renal conservation of salt and water
- decreases urine production
A severely prolonged response to a hemorrhage occurs over…
24 H
What happens during a severely prolonged response to a hemorrhage?
- synthesis of plasma proteins by liver
- stimulation of erythropoeisis in bone marrow to increase hematocrit
What happens when hemorrhage stops but MAP drops below 50 mmHg?
- can cause death due to circulatory shock
- severe tissue damage, irreversible circulatory collapse and death
- positive feedback downward spiral
What are the downstream effects of hypotension due to hemorrhage?
- cardiac failure
- CNS depression
- kidney failure
- aberrations of blood clotting
CNS depression due to hemorrhage leads to..
- decreased cerebral blood flow
- acidosis
Shock is the failure of the cardiovascular system to…
deliver enough O2 and nutrients to meet cellular metabolic needs
What are the four types of shock?
- hypovolemic
- cardiogenic
- vascular
- obstructive
Shock homeostatic compensation:
- activation of renin-angiontensin-aldosterone system
- secretion of ADH
- release of local vasodilators
Orthostatic hypotension:
low blood pressure resulting from failure to return blood volume from veins to heart
T/F: orthostatic hypotension is true blood loss
F, it’s just a change in distribution
Orthostatic hypotension has a ____ effect
gravitational
- occurs when shifting from prone (lying down) to upright or standing for long time
What happens via orthostatic hypotension during standing?
- superficial veins in neck collapse
- can induce fainting
- lack of muscular pump -> decrease in VR
Orthostatic hypotension can be completely compensated for via…
mechanisms initiated by baroreceptors
Thermal effect:
- pooling of blood in dependent vessels
- interferes with compensatory vasomotor reaction and absence of muscle activity
Thermal effect is caused by…
- warm ambient temp: induces vasodilation, so more blood moves into venous system
- heavy clothing: prevents heat loss
Exercise is a normal change in…
metabolic activity
Cardiovascular adjustments due to exercise is a combo of…
neural and local (chemical) factors
Neural factors for cardiovascular adjustments:
- central command: cerebrocortical activity of SNS
- mental anticipation increases SNS and decreases PNS output
- not controlled by baroreceptor reflex
What increases due to neural factors in cardiovascular adjustments?
- HR
- myocardial contractibility
- TPR
- MAP prior to muscle activity
Reflexes for cardiovascular adjustments originate in…
skeletal muscle
- alters SNS output via mechanoreceptors by stretch and tension
Local/humoral factors causes cardiovascular adjustments in three ways:
- K+ released by contracting muscle
- adenosine and decrease in tissue pH
- circulating epi
In local/humoral factors in cardiovascular adjustments, K+ acts as…
vasodilator
- partly responsible for initial decrease in vascular resistance
In local/humoral factors in cardiovascular adjustments, adenosine sustains…
vasodilation in blood vessels of skeletal muscle as exercise is sustained
In local/humoral factors in cardiovascular adjustments, circulating epi contributes to vasodilation by…
binding to beta receptors on blood vessels w/in skeletal muscle bed
When there is an anticipation of mild to moderate exercise, ____ is increased and ____ is decreased
SNS, PNS
When SNS is increased for mild to moderate exercise, what happens?
- decreased blood flow to viscera
- increase in CO
- increase in blood flow to active muscle
- increase in myocardial flow
What is blood flow like in the skin during mild to moderate exercise?
- decreases to skin at first
- increases as body temp increases
During mild to moderate exercise, there is marked…
capillary recruitment
- only small % of capillaries perfused at rest
- more perfused during exercise
During mild to moderate exercise, there is an increase in…
- hydrostatic pressure in capillaries: water and solutes move into ISF
- tissue hydrostatic pressure: fluid carries away by lymphatics
Blood volume loss is limited during mild to moderate exercise by…
- increase in tissue hydrostatic P
- increase in plasma osmolarity
- decrease in urine formation
During severe exercise, what beings to fail?
compensation mechanisms
During severe exercise, there is an increase in _____ and a decrease in _____
- SNS, which leads to vasoconstriction so body temp increases
- tissue and blood pH due to increase in lactic acid and CO2 production
Limits of exercise performance:
- pump limitation
- O2 supply to muscle
- regular exercise improves cardiovascular performance
Max effective HR is…
180 beats/min
