Control of Arterial Blood Pressure and Volume

Question 1

Describe acute changes in ABP

Answer 1

higher ABP: cough, sneeze, response to pain, response to stimuli, exercise

lower: cutaneous vasodilatation when hot, when standing, haemorrhage, dehydration

Question 2

Describe chronic changes in ABP

Answer 2

• healthy ageing - loss of elasticity
• essential hypertension due to increased TPR
• renal disease

Question 3

What are consequences of low ABP?

Answer 3

low flow, less oxygen delivery to tissues = faint

Question 4

What are consequences of high ABP?

Answer 4

increased workload for heart - heart needs to increase contraction - risk of stroke

Question 5

What affects blood volume?

Answer 5

• acute: fluid intake and fluid loss
• chronic: fluid loss from gut (diarrhoea, vomiting), poor renal function, HF
• distribution of body fluid: venous pooling, odeema

Question 6

What does reduced blood volume do to CO and ABP?

Answer 6

reduced CO and ABP

Question 7

What happens if you have inrease volume and heart failure?

Answer 7

adds to filling and distension of ventricles and creates problems

Question 8

Describe the baroreceptor reflex when ABP decreases.

Answer 8

less baroreceptor activity =

• increased sympathetic activity = release of NAd = arterioles constrict = increased TPR
• decreased parasympathetic activity = less Ach on muscuranic receptors = increased HR and contractility (so increased SV) = increased CO

Question 9

Why can high ABP be reached during stress and hypertension?

Answer 9

baroreceptor reflex sensitivity reduces during stress

reflex has higher set point in hypertension

Question 10

Where are the baroreceptors?

Answer 10

in the carotid sinus and aortic arch

Question 11

What is the volume reflex?

Answer 11

stretch receptors in right atrium affected by changes in CVP

regulate blood volume

Question 12

Describe the volume receptor reflex when blood volume is decreased.

Answer 12

decreased afferent activity to medulla = high sympatehtic activity to kidney = vasoconstriction = less renal perfusion, more renin release, more ADH released so more water and Na reabsorbed

less urine produced

Question 13

Describe the volume receptor reflex in those with heart and renal failure.

Answer 13

reflex has higher set point , and reflex sensitivty is reduced

Question 14

Compare the baroreceptor and volume receptors

Answer 14

baroreceptor reflex on ABP is much faster than volume reflex on CVP

sensitivity and set point can be changed eg exercise, emotional stress, hypertension, HF