Control of Blood Pressure

Question 1

why is blood pressure so tightly controlled

Answer 1

BP - driving force of tissue perfusion
too low bp - tissue will not perfuse properly
too high bp - pathological damage occurs in tissues

Question 2

poor renal perfusions lead to

Answer 2

drop in filtration and acute kidney injury

Question 3

poor brain defusion leads to

Answer 3

unconsciousness and death

Question 4

too high blood pressure in the eye

Answer 4

retinopathy (damage to the capillaries in the eye)

Question 5

too high blood pressure in the nephrons

Answer 5

– nephropathy (damage to the nephrons in the kidney)

Question 6

too high blood pressure in the CVS

Answer 6

remodelling of the cardiovascular system (both heart and vasculature)

Question 7

pressure gradient /_\

Answer 7

flow (Q) x Resistance (R)

Question 8

flow is equal to

Answer 8

pressure gradient / resistance

Question 9

how does flow vary in relation to pressure gradient

Answer 9

• Flow varies proportionally with the pressure gradient and inversely with resistance

Question 10

mean arterial pressure

Answer 10

product of the volume of blood in the
circulation and the resistance to flow
– mean arterial pressure = cardiac output x total peripheral resistance

Question 10

mean arterial pressure

Answer 10

product of the volume of blood in the
circulation and the resistance to flow
– mean arterial pressure = cardiac output x total peripheral resistance

Question 11

systemic arterial pressure

Answer 11

120/80 mmHg

Question 12

pulmonary arterial pressure

Answer 12

25/10 mmHg

Question 13

Systemic Pulse Pressure

Answer 13

40 mmHg

Question 14

Pulmonary Pulse Pressure

Answer 14

15mmHg

Question 15

Systemic Mean Arterial Pressure

Answer 15

93 mmHg

Question 16

Pulmonary Mean arterial pressure

Answer 16

15

Question 17

Systemic capillary pressure

Answer 17

17

Question 18

pulmonary capillary pressure

Answer 18

6-10

Question 19

systemic venous pressure

Answer 19

0-4

Question 20

pulmonary venous pressure

Answer 20

2-6

Question 21

how is blood pressure monitored and mediated

Answer 21

baroreceptor reflex 
Sensory afferents (baroreceptors) -> Central relays -> CVS centres of brain stem (medulla oblongata) -> effector efferents (innervating heart and blood vessels)

Question 22

what do baroreceptors sense

Answer 22

rate of rise in pressure and the magnitude of pressure
– rate = dynamic sensitivity
– magnitude = static sensitivity

Question 23

as the arterial pressure increases what happens to the baroreceptors

Answer 23

baroreceptor firing rate increases too

Question 24

A fibres of baroreceptors

Answer 24

fewer - fast conducting (small diameter unmyelinated) high threshold 70-140mmHg no. activated increases as pressure rises

Question 25

where is the primary site for regulating SNS and PNS outflow

Answer 25

medulla oblongata

Question 26

what part of the medulla oblongata receives input from baroreceptors and chemoreceptors

Answer 26

nucleus tractus solitarius

Question 27

what modifies the activity of the medullary centres

Answer 27

hypothalamus and higher centres

Question 28

how does the venous return change when in the supine position

Answer 28

When supine, venous return is increased | – effect of gravity is reduced and so preload is ample (Starling’s Law)

Question 29

how does venous return change when standing and why

Answer 29

On standing, gravity causes venous pooling and venous return falls – with falling preload, so cardiac output drops (Starling’s Law again) – as so does cardiac output (since VR = CO

Question 30

how does a fall in cardiac output change the blood pressure

Answer 30

A falling cardiac output leads to a decrease in blood pressure – MAP = CO x TRP, so if CO falls so does MAP

Question 31

baroreceptor reflex

Answer 31

drop in blood pressure firing of baroreceptors central control - medulla and hypoth drop in PNS - increase heart rate Increase in SNS - increase force of contraction, venoconstriction and vasoconstriction Thus increasing peripheral resistance and cardiac output

Question 32

cardiac effects of baroreceptor reflec

Answer 32

– increased heart rate (due to increased SNS/decreased PNS) – increased contractility (due to increased SNS) – increased preload (due to SNS venoconstriction) – overall increase in cardiac output

Question 33

vascula r effect of baroreceptor reflex

Answer 33

``` increased vasoconstriction (due to increased SNS) – overall increased in total peripheral resistance ```

Question 34

how can chemoreceptor in carotid body induce change in blood pressure

Answer 34

pH/PaO2 | sensors in carotid bodies, primarily involved in ventilation control

Question 35

cardiopulmonary reflexes

Answer 35

contribute to overall circulatory regulation | – diverse group of receptors located mainly on low pressure side of circulation

Question 36

how long will baroreceptor reflex last

Answer 36

1-2 days

Question 37

long term regulation example

Answer 37

fluid regulation

Question 38

examples of fluid regulation

Answer 38

renin-angiotensin system (RAS) – anti-diuretic hormone (vasopressin) – natriuretic peptides

Question 39

Renin-Angiotensin System

Answer 39

``` Angiotensinogen (453 aa) - from liver SNS drops = increase in blood pressure Angiotension I - inactive precursor Angiotensin II - > vasocontriction Aldosterone - promotes water expansion by increasing Na+ retention Salt and water retention ```

Question 40

Renin-Angiotensin System is regulated

Answer 40

by production of renin

Question 41

when is renin relesaed

Answer 41

in response to SNS activity particularly due | to low blood pressure and/or volume

Question 42

how is renin released

Answer 42

SNS activation via the baroreceptor reflex (β1 -AR) – intrarenal stretch receptor (juxtaglomerular cells)

Question 43

hypertension

Answer 43

``` Consistent readings with a systolic over 140 mmHg or a diastolic over 90 mmHg (Grade I) ```

Question 44

grade II hypertension

Answer 44

150/100mm

Question 45

grade II hypertension

Answer 45

150/100mm hG

Question 46

HOW DOES SYSTOLIC Pressure change with age

Answer 46

~120 mmHg at 20 to an average of 160 mmHg by 70 years of age – mainly due to arterial stiffening