Lecture 13- Blood Pressure Regulation

Question 1

blood pressure

Answer 1

the force exerted upon vessel walls as blood flows through

Question 2

what is required to exchange substances/ fluids across capillary networks

Answer 2

a minimum pressure (capillary hydrostatic pressure)

Question 3

formula for blood pressure

Answer 3

cardiac output x total peripheral resistance

Question 4

what total peripheral resistance dependant on

Answer 4

dependant upon arteriolar radius

Question 5

autoregulation of local flow is also known as

Answer 5

intrinsic control of blood flow

Question 6

what system is responsible for short term regulation

Answer 6

neural/ nervous system

Question 7

what system is responsible for long term regulation

Answer 7

endocrine system

Question 8

outline intrinsic control when local blood flow in a tissue is too low

Answer 8

1. homeostasis disturbed from physical stress (trauma, high temp etc), chemical changes (lower oxygen, lower pH, increased carbon dioxide or increased vasodilatory metabolites) or increased tissue activity (lactate)
2. inadequate local blood pressure and blood flow
3. autoregulation: precapillary sphincters relax and vasodilatory metabolites (nitrogen, potassium ions, hydrogen ions, carbon dioxide and lactate) enter arterioles allowing capillary regulation
   4.local decrease in resistance and increase in blood flow
4. homeostasis returns

Question 9

what occurs if blood pressure is still too low to meet demands even after autoregulation

Answer 9

central mechanisms are activated to increase systemic blood pressure

Question 10

which branch of the autonomic nervous system is activated to restore blood pressure if intrinsic control can’t bring the body back to homeostasis

Answer 10

sympathetic nervous system

Question 11

how does the SNS help regulate blood pressure

Answer 11

increases heart rate and stroke volume
enhances vasoconstriction

Question 12

what centres in the CNS are activated by baroceptors

Answer 12

cardiovascular centres

Question 13

baroreceptors

Answer 13

sensitive to changes in pressure and found in aorta and carotid sinus (blood flow to brain/ cerebral blood flow)

Question 14

what effect does a fall in blood pressure have on baroreceptors

Answer 14

inhibition (less activation/ firing of the baroreceptors)

Question 15

when baroreceptors are inhibited what centres are activated

Answer 15

cardio acceleratory centre activation and vasomotor centre activation (region in medulla)

Question 16

what centre is inhibited when baroreceptors are inhibited

Answer 16

cardioinhibitory centre

Question 17

what effect does a rise in blood pressure have on baroreceptors

Answer 17

baroreceptor stimulation

Question 18

when baroreceptors are stimulated, what centres are inhibited

Answer 18

cardio acceleratory centre and vasomotor centre

Question 19

when baroreceptors are stimulated, what centres are activated

Answer 19

cardioinhibitory centre

Question 20

what occurs when blood pressure is too high

Answer 20

less sympathetic activity and more parasympathetic activity
reduced peripheral resistance

Question 21

where are peripheral chemoreceptors found

Answer 21

body/ blood

Question 22

why is there a fall in pH with increased CO2

Answer 22

co2 dissolves in the blood and forms hydrogen ions lowering the pH

Question 23

what is activated by an increased respiratory rate

Answer 23

respiratory centre activation

Question 24

what does respiratory centre activation lead to

Answer 24

a rise in CO2

Question 25

effect of a rise in co2 on cerebral vessels

Answer 25

vasodilation of cerebral vessels leading to increased blood flow to the brain (must be a preserved blood flow to the brain at all times)

Question 26

what receptors are found in the medulla which are sensitive to co2

Answer 26

central chemoreceptors

Question 27

central chemoreceptors

Answer 27

activate the respiratory centre

Question 28

why is the respiratory centre activated when there is a rise in co2

Answer 28

there is not enough o2 and too much co2 so there is no point increasing more blood as it won't be able to pick up enough oxygen as not breathing fast enough so respiratory centre is activated meaning more oxygen in the lungs so the increased blood can pick up more oxygen

Question 29

what centres are activated and inhibited when chemoreceptors are activated

Answer 29

cardio acceleratory centre activation cardioinhibitory centre inhibition vasomotor centre activation

Question 30

what does activation of the vasomotor centre lead to

Answer 30

peripheral vasoconstriction

Question 31

what are the three endocrine responses to a low blood pressure even after autoregulation

Answer 31

ADH/ vasopressin Erythropoietin Renin-Angiotensin-Aldosterone System (RAAS)

Question 32

how does ADH regulate a low blood pressure

Answer 32

pituitary gland secretes ADH ADH is a vasoconstrictor and increases fluid retention (increases thirst) increase permeability of the csm of the collecting duct

Question 33

how does erythropoietin help regulate a low blood pressure

Answer 33

fall in blood oxygen stimulates erythropoietin (main hormone in the formation of rbcs) is a vasoconstrictor more rbcs increases the blood volume more minor compared to the others

Question 34

how does Renin-Angiotensin Aldosterone System (RAAS) help regulate a low blood pressure

Answer 34

kidney cells have their own baroreceptors which stimulate the enzyme renin which converts angiotensinogen to angiotensin 1 angiotensin 1 is inactive but the angiotensin converting enzyme converts t into angiotensin 2 which is an active and potent vasoconstrictor (causes a greater increase in vasoconstriction and peripheral resistance) angiotensin 2 stimulates aldosterone (increases the activity of sodium potassium ATPase pump so more sodium ions are absorbed in the distal convoluted tubule and collecting duct therefore more water is reabsorbed which increases the volume of the blood within the vascular system )

Question 35

role of sensors in muscle cells of atria and ventricles

Answer 35

able to detect when they are being stretched too much

Question 36

what is secreted when there is increased stretching of atria and ventricles when blood pressure is too high

Answer 36

secretion of natriuretic peptides from muscle cells

Question 37

what natriuretic peptides do the atria and ventricles secrete

Answer 37

atria: atrial natriuretic peptides ventricles: brain natriuretic peptides

Question 38

renal effect of natriuretic peptides

Answer 38

act on the kidney increased sodium loss in the urine ( inhibits sodium potassium pump therefore less sodium is reabsorbed in the kidney and more water lost in the urine) reduced thirst (inhibit secretion of ADH) reduce blood volume

Question 39

vascular effects of natriuretic peptides

Answer 39

inhibition of ADH, aldosterone, NA and adrenaline release peripheral vasodilation reduce blood pressure

Question 40

what are the 5 consequences of blood loss (severe haemorrhage)

Answer 40

decreased atrial pressure altered blood gases RAS activation catecholamine release vasopressin release

Question 41

role of chemo and baroreceptor reflex in severe blood loss

Answer 41

cardiac stimulation systemic vasoconstriction fluid and volume redistribution

Question 42

role of RAAS and ADH secretion in sever blood loss

Answer 42

restore blood volume, inhibit secretion of water at kidneys, recall fluid from the tissues, less ADP sceretion as want more retention of water