KNES 323 2nd HALF

what is blood pressure?

hydrostatic pressure measure, the force exerted by blood upon the walls of the blood vessels or the chambers of the heart

what are the components of arterial blood pressure in larger vessels?

in aorta and brachial, systolic, diastolic, pulse, and mean arterial pressure

what is systolic pressure?

peak arterial pressure resulting from a ventricular contraction

what is diastolic pressure?

arterial pressure of blood during ventricular relaxation

how are diastolic and systolic pressure reported?

as a ratio of two numbers with systolic pressure over diastolic 

what is pulse pressure?

difference between systolic and diastolic pressure, at least 25% of systolic pressure

what would be the pulse pressure of someone with systolic pressure of 120mmHg, and diastolic of 80mmHg?

40mmHg

what is meant by low/narrow pulse pressure?

pulse pressure <25% systolic pressure, may indicate low stroke volume as seen in congestive heart failure, stenosis of the aortic valve, or significant blood loss following trauma, poor circulation

what is meant by hide/wide pulse pressure?

common in healthy people during and following strenuous exercise, pulse pressure may increase temporarily to >100mmHg

what is meant by mean arterial pressure?

average pressure of blood in the arteries

how can we approximate MAP?

since cardiac cycle is about 1/3 in systole and 2/3 in diastole, adding 1/3 of pulse pressure to diastolic pressure, adding 1/3 systolic pressure to 2/3 of diastolic pressure

what are the 5 main variables affecting blood flow and blood pressure?

cardiac output, compliance, volume of blood, viscosity of blood, blood vessel length and diameter 

what is cardiac output?

measurement of blood flow from the heart through ventricles

What will increasing CO result in?

increasing CO via HR or SV increases BP (ex: sympathetic stimulation, epi, norepi, thyroid hormones, increased Ca)

What will decreasing CO result in?

decreasing CO via HR or SV will decrease HR (ex: parasympathetic stimulation, altered K+ levels, decreased Ca)

what is compliance?

ability of a vessel to expand to accommodate increased content 

what are the characteristics of a more compliant vessel?

able to expand with surges in blood flow without increased resistance or BP (veins are more compliant and can hold more blood)

when is compliance reduced and what is the effect of this?

arteries stiffen (hypertension) compliance is reduced and resistance to blood flow is increased, increases afterload and forces the heart to work harder when pumping blood

what happens if blood volume decreases by >20%?

pressure and flow decreases (dehydration, vomiting, severe burns, diarrhea or bleeding)

what happens if blood volume increases?

pressure and flow increase (retention of water and sodium) 

how does the viscosity of blood relate to flow?

directly proportional to resistance, any condition causing viscosity to increase will increase resistance and decrease flow rates

what are the two main determinants of blood viscosity?

formed elements, plasma proteins

how does vessel length relate to blood flow?

directly proportional to resistance, longer vessels have greater resistance and lower flow, shorter vessels have lower resistance and greater flow

how does blood vessel length change as we age?

increase in length as we grow and relatively unchanged in adults 

how does decreased vessel diameter impact flow?

a decreased lumen diameter increases amount of blood contacting vessel walls, increasing friction and resistance and BP

what is Poiseuille’s law? What is the main idea behind it?

resistance is inversely proportional to the radius of the blood vessel raised to the fourth power

what does Poiseuille’s law state?

if an artery or arteriole constricts to half its original radius resistance to flow will increase 16 times, it it dilates twice its initial radius then resistance will decrease to 1/16 of original value

what is blood pressure predominantly determined by?

factors affecting cardiac output, blood volume, and vascular resistance 

what factors help maintain pressure gradient between the veins and atria?

atria pressure (during diastole is low often approaching zero when atria are in diastole), physiological pumps (used to increase pressure and velocity of blood in the vein)

what is the function of the skeletal muscle pump?

increase the pressure in the veins through contraction of the surrounding skeletal muscles

what happens as leg muscles contract in the skeletal muscle pump?

exert pressure on nearby veins with their one way valves, causes blood to flow upward opening valves superior to the contracting muscles so blood flows through, valves inferior to contracting muscles close and prevents blood from flowing back towards the feet

what is the function of the respiratory pump?

aids blood flow through veins of thorax and abdomen

what is the role of the respiratory pump during inhalation?

volume of thorax increases and compresses the abdominal cavity, decreases air pressure and enables us to inhale, thoracic vein BP drops falling below pressure in abdominal veins, blood flows into thoracic region and promotes return of blood into the atria from thoracic veins

what is the role of the respiratory pump during exhalation?

air pressure increases in thoracic cavity, thoracic vein BP increases, increase velocity of blood flow to heart, valves in veins prevent blood from flowing backward from thoracic and abdominal veins

Why is mean arterial pressure not in the middle?

The time spent in systole vs diastole is not the same

Which key property does diastolic pressure determine?

After load

What does pulse pressure show you?

How efficient, smaller the number the more trouble the heart is having

If we have a low or narrow pulse pressure what does this indicate?

The system isn’t able to deliver nutrients to working body

What can extremely high blood pressures cause?

Cardiovascular failure, after load increases so heart has to work really hard and vessels are more stiff leading to more wear and tear, fatigue, thinning of walls, rupture

What do extremely low blood pressures lead to?

Brain impairments due to insufficient nutrient supply

how does the pressure in the brain and legs compare to the mean arterial Pressure ?

Higher in legs, lower in brain

How does high viscosity of blood impact the structure of the hearts vessels?

More wear and tear

Is vessel length or diameter more important in determining BP?

Diameter

What does Poiseuille’s law show you?

How changing vessel diameter impacts flow

If we have increased pressure due to constriction in one vessel how does this change blood flow?

Causes redistribution of blood to other vessels

What is mean arterial pressure determined by?

Factors affecting CO (effectiveness of heart as pump), blood volume (determined by fluid intake and loss, passive or regulated by kidney) and vascular resistance (determined by arterials diameter), distribution of blood between arterial and venous BV (determined by diameter of veins?

What key factor in relation to BP is shown in diagram one?

Vessel diameter

What key factor in relation to BP is shown in diagram TWO?

Average blood pressure

What key factor in relation to BP is shown in diagram THREE?

Cross sectional area

What key factor in relation to BP is shown in diagram four?

velocity of blood

how does cardiac suction impact venous return?

increase causes decrease in pressure in the heart and increase in pressure gradient 

how does pressure imparted to blood by cardiac contraction impact venous return?

increase venous pressure and gradient

how does sympathetic vasoconstrictor activity impact venous return?

increase venous pressure and pressure gradient, decrease venous capacity

what is a key factor in ensuring adequate blood to tissues?

blood flow must be continually redirected to the tissues as they becoe more active

what are baroreceptors?

specialized stretch receptors located within thin areas of blood vessels and send impulses to cardiovascular center in the medulla oblongata to regulate BP 

where are vascular baroreceptors typically found?

aorta and carotid sinuses

what is the role of stretch receptors if blood pressure falls?

receptors decrease their firing rates initiating sympathetic reflexes to accelerate HR, increase force of contraction and promote vasoconstriction

what is the role of stretch receptors if blood pressure rises?

receptors increase their firing rates initiating parasympathetic reflexes to decelerate HR, decrease force of contraction, and promote vasodilation

what is the relationship between HR and BP?

resting Bp and HR work like a teeter totter to maintain cardiac output as evenly as possible 

what do chemoreceptors monitor?

levels of O2, CO2, and H+ (pH) to contribute to vascular homeostais

where are chemoreceptors found?

close to baroreceptors in aortic and carotid sinuses and transmit their signals to cardiovascular center and respiratory centers in medulla oblongata

what do chemoreceptors respond to?

increasing CO2 and H+ levels (falling pH) by increasing CO and constricting peripheral vessels increasing return to lungs, decreasing CO2 and H+ levels (rising pH) by decreasing CO and dilating peripheral vessels decreasing return to lungs

what does neurological regulation of BP depend on?

cardiovascular centers in medulla oblongata

how do cardiovascular centers in medulla oblongata decrease cardiac function?

decrease HR and SV via parasympathetic stimulation

how do cardiovascular centers in medulla oblongata augment cardiac function?

regulating HR and SV via sympathetic stimulation

how do cardiovascular centers in medulla oblongata control vessel tone?

control vessel tone or contraction of smooth muscle in tunica media via vasomotor centres

how does the endocrine system play a role in managing the cardiovascular system?

through catecholamines (epi and norepi), and several hormones that interact with kidneys to regulate blood volume 

what is the function of catecholamines?

enhance and extend the body’s sympathetic response, increase HR and contractile force, increase blood flow to liver, muscles, and heart, decrease blood flow to organs not essential for flight or fight responses (digestion, urinary)

what is ADH secreted by?

cells in the hypothalamus and released by posterior pituitary

what is the role of ADH in BP control?

signals kidneys to reabsorb more water, decreasing fluid lost in urine, increase overall fluid levels and help restore blood volume/pressure, small role in peripheral vessel constriction

what is the major effect of renin-angiotensin aldosterone mechanism on the cardiovascular system?

specialized cells in the kidneys secrete renin in response to decreased blood flow, renin activates angiotensinogen into angiotensin I, which is converted to angiotensin II in the lungs 

where is angiotensinogen produced?

liver

what is the function of angiotensin II?

stimulates thirst in hypothalamus, powerful vasoconstrictor that increases BP, stimulates release of ADH and aldosterone increasing reabsorption of Na (and water) into blood by kidneys

what are the overall effects of the renin-angiotensin-aldosterone mechanism?

limit losses in blood volume, and vasoconstriction to raise BP

what is the thirst response?

as blood becomes more concentrated, blood osmolality increases above ideal value the hypothalamus transmits signals that result in conscious awareness of thirst 

what are osmoreceptors?

sensory receptors in thirst center in hypothalamus that monitor the concentration of solutes (osmolality) of the blood

how does a person typically respond to thirst response?

respond by drinking water

what is atrial natriuretic hormone?

secreted by cells in atria when blood volume is high enough to cause extreme stretching of the cardiac cells

how does ANH release relate to angiotensin II and BP control?

antagonists to angiotensin II, promotes loss of Na and water from kidneys, suppress renin, aldosterone, and ADH production and release

what is the overall effect of ANH?

promote loss of fluid from body so blood volume and BP decrease

what are the characteristics of autoregulation mechanisms?

don’t need specialized nervous stimulation or endocrine control, local, self-regulatory mechanisms that allow each region of tissue to adjust its own blood flow and perfusion

what do autoregulation mechanisms control in relation to BP?

control local blood flow through chemical and physical alterations

what is the role of chemical signals in BP control?

work at level of precapillary sphincters to trigger either constriction or relaxation

what are the effects of chemical signals in BP control?

dilating precapillary sphincter allows blood to flow in as a result of NO released from endothelial cells (decreased O2, increased CO2, histamine release), constricting precapillary sphincter temporarily shuts off blood flow as result of endothelins (vasoconstrictors) released from endothelial cells (increased O2 and decreased CO2, antihistamine release)

what is the role of physical signals in BP control?

work at myogenic level due to reaction to stretching of arteriole smooth muscles due to changes in blood flow occur through the vessels, largely protective function against dramatic fluctuations in BP and blood flow to maintain homeostasis

what is the response to increased transmural pressure in BP control?

evokes myogenic response (bayliss effect) causing activation of Na and Ca channels in the smooth muscle layer of the blood vessel

what is a part of the short term control of BP?

baroreceptors, cardiovascular system 

what is a part of the long term control of BP?

renal/blood volumes, endocrine function

what is the valsalva maneuver?

forced expiration against closed glottis, mimics many normal activities such as straining during defecation, blowing p a balloon, or playing the saxophone

what does performing a valsalva maneuver result in?

increase in intrathoracic pressure leading to reduction in preload to heart especially by restriction of IVC

what is phase I of the valsalva maneuver?

onset of strain, transient rise in BP because of emptying of some blood from the large veins and pulmonary circulation 

what is phase II of the valsalva maneuver?

follows positive intrathoracic pressure leading to reduced venous return to heart, preload, SV, and BP falls activating baroreceptors, vagal withdrawal followed by increased sympathetic discharge ensues and marked tachycardia, increased CO and vasoconstriction leading to recovery of BP to normal

what is phase III of the valsalva maneuver?

transient phase involving release of strain leading to sudden dip in BP, release of positive pressure leads to expansion of pulmonary vascular bed and reduces left ventricular cross-sectional area resulting in a transient fall in BP

what is phase IV of the valsalva maneuver?

overshoot of BP above baseline, because of resumption of normal venous return to heart stimulated by sympathetic NS during phase II, overshoot leads to stimulation of baroreflex leading to bradycardia and return of BP to baseline

how many phases are their in the valsalva maneuver?

4 

why do we have baroreceptors in the internal carotid?

we can monitor stuff going on in the brain, close to aorta 

when blood pressure rises how do the stretch receptors cause vasodilation?

promote it by decreasing innervation of PNS, not direct reduction

what do the parasympathetic and sympathetic neurons impact in BP control?

parasympathetic impact heart, sympathetic impact veins, arterioles, ventricles, and heart

what does the input to cardiovascular centers include in BP control?

nerve impulses, from higher brain centers (cerebral cortex, limbic system, hypothalamus), proprioceptors (monitor joint movements), baroreceptors, chemoreceptors

what are the outputs to effectors from the cardiovascular center in the brain?

increased frequency of nerve impulses, decrease rate or increase rate and contractility in heart, vasoconstriction of BV