W6 Intro to Blood Pressure Regulation

Question 1

what is cardiac output? how is it calculated?

Answer 1

blood flow in volume / time - cardiac output = heart rate (beats per minute) x stroke volume (volume of blood per beat)

Question 2

what is systole?

Answer 2

ventricular contraction

Question 3

what is diastole?

Answer 3

ventricular filling (relaxation)

Question 4

what is end systolic volume (ESV)?

Answer 4

volume of the ventricle at the end of contraction

Question 5

what is end diastolic volume (EDV)?

Answer 5

volume of ventricle just before contraction/end of filling

Question 6

how do you calculate stroke volume?

Answer 6

SV = EDV - ESV

Question 7

what is mean blood pressure controlled by?

Answer 7

by changing peripheral resistance and/or cardiac output as pressure = CO x TPR

Question 8

cardiac output is controlled by S and PS nerves, what does this effect?

Answer 8

heart rate and force of contraction

Question 9

total peripheral resistance is controlled by nervous and chemical means which effects what?

Answer 9

constriction and dilation of arterioles and venules and elasticty

Question 10

what is arterial blood pressure measured in?

Answer 10

mm Hg (millimeters of mercury)

Question 11

what is systolic blood pressure?

Answer 11

the maximum arterial blood pressure during heart contraction

Question 12

what is diastolic blood pressure?

Answer 12

minimum arterial blood pressure during heart relaxation

Question 13

what is mean arterial pressure?

Answer 13

the mean pressure over the entire cardiac cycle (usually not equal to the mean of SBP and DBP as not the same duration)

Question 14

is heart rate higher in smaller or larger animals?

Answer 14

hr is higher in smaller animals due to small vessels and higher resistances

Question 15

what is the average systolic pressure of domestic animals, rats/mice, birds and giraffe?

Answer 15

125-145
100-120
175-250
280-350

Question 16

what is the average diastolic pressure of domestic animals, rats/mice, birds and giraffe?

Answer 16

80-95
70-80
150-170
200-300

Question 17

what is the average mean pressure (mmHG) of domestic animals, rats/mice, birds and giraffe?

Answer 17

100-110
85-100
160-200
300

Question 18

why is it important to maintain pressure within a range?

Answer 18

ensures adequate perfusion of vital organs

Question 19

what do baroreceptors do?

Answer 19

used for short term regulation of blood pressure - they are in the arterial wall and increase their firing rate in response to increased stretch (due to increased pressure)

Question 20

where are the most important baroreceptors found?

Answer 20

in the carotid artery (in carotid bodies) and the aortic arch (in aortic bodies)

Question 21

what is the net result of baroreceptors on blood pressure?

Answer 21

vasodilation, decreased heart rate, decreased contractility which restore arterial pressure to normal

Question 22

what do the carotid sinus baroreceptors detect?

Answer 22

changes in pressure to the brain

Question 23

what do the aortic arch baroreceptors detect?

Answer 23

changes in pressure to the body

Question 24

what are peripheral and central chemoreceptors stimulated by?

Answer 24

low arterial O2 and high arterial CO2 and low arterial pH

Question 25

what does activation of chemoreceptors produce?

Answer 25

peripheral vasoconstriction, increased lung ventilation (not when under water) and in some cases decreased heart rate

Question 26

what do coronary artery baroreceptors respond to?

Answer 26

arterial pressure but more sensitive than carotid and aortic ones

Question 27

what do veno-atrial mechanoreceptors respond to?

Answer 27

changes in central blood volume

Question 28

what do unmyelinated mechanoreceptors respond to?

Answer 28

distension of heart (ventricular ones during systole and atrial ones during inspiration)

Question 29

after how long does a decline in blood pressure need to last for the kidneys to get involved?

Answer 29

more than a few minutes

Question 30

rechanneling of blood to vital organs occurs in low bp, when this takes longer than expected bp drop is sensed by what? what does this activate?

Answer 30

sensed by specialised cells in the kidney (juxtaglomerular cells) that activate the renin angiotensin aldosterone system (RAAs)

Question 31

a decrease in perfusion is sensed by the JGA (juxtoglomerular apparatus) in what part of the kidney?

Answer 31

the macula densa

Question 32

what does renin do to angiotensionogen?

Answer 32

renin (released by juxtoglomerular cells) catalyzes the conversion of angiotensinogen into a decapeptide (10 amino acids) called angiontensin I

Question 33

what is angiotensin I converted to angiotensin II by?

Answer 33

angiotensin converting enzyme (ACE) in the lungs

Question 34

what effects does angiotensin II cause?

Answer 34

it is a major vasoactive product that causes vasconstriction, stimulates release of aldosterone from the adrenal gland and stimulates the release of ADH (antidiuretic hormone) from the pituitary gland