BP control Flashcards
what is the equation relating MAP, CO and TPR
MAP = CO x TPR (total peripheral resistance)
CO= HR x SV
what affect do the following have on stroke volume
- SNS activity, Frank Starling mechanisms, and right atrial pressure
All increase SV
what are the three short term, rapid (sec-min) regulation mechanisms of blood pressure
- baroreceptors
- low-pressure receptors
- brainbridge reflex
what are the two intermediate, (minutes to hours) regulation mechanisms to control BP
- capillary fluid shift
- stress relaxation
what are the two long, slow (hours+) regulation mechanisms to control BP
- renin angiotensin system
- antidiuretic hormone
baroreceptors are strategically located to monitor MAP. What do they respond to?
vascular stretch induced by changes in blood pressure
carotid sinus baroreceptor is innervated by what nerve
glossopharyngeal nerve
aortic branch baroreceptor is innervated by what nerves
right and left vagus nerve
what causes an increase firing rate in baroreceptors
increases in arterial Pressure
What are the BP thresholds for evoking impulses (min and max)
- impulses occur at 50-60 mmHg
- maximum rates at 200mmHg
an increasing rate of pressure change (dP/dT) has what effect on baroreceptor firing rate
increases firing rate
*frequency during the rising systolic pressure is greater than that in diastole
maximal sensitivity is normally at what MAP?
100 mmHg
with chronic HTN, what happens to the set point , point of maximal sensitivity?
set point is reset at a higher pressure, the curve shifts to the right
with chronic HTN, what happens to the sensitivity of the reflex to operate
there is a loss of sensitivity of the reflex to operate
*the slope is decreased
in the baroreceptor reflex arc, what structure recieves sensory neurons from the baroreceptors in carotid sinus and arch of aorta?
medulla oblongata
what happens to arterial blood pressure as a person moves from lying down to standing upright?
normally, BP drops briefly then increases back to its orginial value
function of atrial natiuretic peptide (ANP) released from the distended atria
- peripheral vasodilation
- increased sodium and water excretion
**decreased blood volume
function of antidiuretic hormone (vasopressin)
- increase water reabsorption
- enhance permeability to water in kidney via insertion of water channels
- increase vascular resistance
**released is enhanced in hypotension
role of renal vasodilation to decrease blood volume
increases water and sodium excretion
what is the bainbridge reflex
- right atrial distension activates the vagus nerve which activates the NTS in the medulla oblongata
- this produces an increase in heart rate
in the bainbridge reflex, why does HR increase
- decrease pressure in vena cavae by moving blood out of right atrium, decreasing RAP
- this decrease in RAP brings in more blood from cavae resulting in a decrease in the venous pressure of the great veins (continues until RAP returns to normal levels)
- increase in HR increases CO which increases renal perfusion pressure, enhancing water and sodium loss
why is the Bainbridge reflex important
- helps prevent damming of blood in the atria, large veins and pulmonary vessels
- assist in matching of CO on both sides of heart
- increase in HR is important when venous return is increased, such as with exercise
what is capillary fluid shift
the interstitial fluid forms a reserve pool that is available to the vascular system
- decrease MAP
- decrease capillary pressure
- increase reabsorption from ISF
- increase in arterial fluid volume
- return of MAP to normal
stress-relaxation is a property of which vessels
large blood vessels
what is the relationship between tension, pressure and radius
pressure is proportional to tension/radius
what is the stress-relaxation property of large blood vessels
- increase volume
- increase MAP (stress)
- increase stress on vessel wall
- vessel wall begins to relax
- decrease in vessel wall tension
- with constant volume, pressure begins to drop (relaxation)
- decrease in MAP
what cells release renin
juxtaglomerular cells in the kidney
what are the functions of angiotensin II
- increase vasopressin
- increase thirst
- increase arteriolar vasoconstriction
- act on adrenal cortex to release aldosterone
function of renin
converts angiotensinogen to angiotensin I
how is ADH (antidiuretic hormone) released?
- decrease in BP decreases the stretch of baroreceptors and decreases thier rates of firing
- this reduction stimulation removes the inhibition on ADH release, leading to an increase in ADH from hypothalamic magnocellular neurons
