Blood Pressure Physiology

Question 1

Blood Pressure

Answer 1

Outwards pressure exerted by the blood on the blood vessel walls.
Involves contraction and relaxation of the heart during the cardiac cycle

Question 2

Systolic arterial BP

Answer 2

The pressure exerted on the walls of the aorta and systemic arteries when the heart contracts.
Should not normally exceed 140mmHg (resting condition)

Question 3

Diastolic arterial BP

Answer 3

The pressure exerted on the walls of the aorta and systemic arteries when the heart relaxes.
Should not normally exceed 90mmHg (resting conditions)

Question 4

Laminar blood flow (noise)

Answer 4

Not audible through the stethoscope

Question 5

Turbulent blood flow

Answer 5

Audible through the stethoscope.

Occurs between systole and diastole

Question 6

Kortokoff sounds (5)

Answer 6

1. First appearance of sound - peak systolic pressure
   2-3. Intermittent sounds of turbulent flow
2. Last sound heard is muffled
3. Sound disappears - diastolic pressure

Question 7

MABP equations

Answer 7

MABP = CO X TPR
MABP = [(2d)+s]/3
MABP = (d) + 1/3[s-d]

Question 8

MABP normal ranges

Answer 8

70-105mmHg
MABP of at least 60mmHg is needed to perfuse vital organs
MABP must be regulated within narrow ranges

Question 9

Cardiac Output (CO)

Answer 9

Volume of blood pumped per ventricle per minute

Question 10

TPR

Answer 10

Sum of resistance of all peripheral vasculature in the systemic circulation
Regulated by vascular smooth muscles

Question 11

Arterioles

Answer 11

Major resistance vessels

Question 12

Baroreceptor reflex

Answer 12

Short term regulation of MABP
Prevents postural changes
Carotid baroreceptors - leave carotid sinus via CN IX
Aortic baroreceptors - leave aortic arch via CN X
Increased BP - rate of firing increases
Decreased BP - rate of firing decreases

Question 13

Response to decrease in BP

Answer 13

Decreased baroreceptor discharge 
Decreased vagal activity
Increased sympathetic activity 
Increased HR, Increased SV = Increased CO
Increased contraction
Vasoconstriction
Increased TPR 
Increased CO and Increased TPR = Increased MABP

Question 14

Response to increase in BP

Answer 14

Increased baroreceptor discharge
Increased vagal activity 
Decreased sympathetic activity 
Decreased HR, Decreased SV = Decreased CO 
Increased relaxation
Vasodilation 
Decreased TPR 
Decreased CO and Decreased TPR = Decreased MABP

Question 15

Postural Hypotension

Answer 15

When someone suddenly stands up from a lying position
Due to a failure of baroreceptors to respond to movements from horizontal to vertical position
Venous return to heart decreases (due to gravity)
MABP transiently decreases (Response to decreased BP)
Rapid correction of decreased MABP

Question 16

Long term regulation of MABP

Answer 16

Hormones which regulate blood plasma volume :-
RAAS
ANP
ADH

Question 17

RAAS

Answer 17

Long term regulation of MABP as it has an important role in regulating plasma volume and TPR

Renin - released from kidney in response to a decreased BP. Converts angiotensiogen -> angiotensin I. Rate limiting step.

ACE - Converts angiotensin I -> angiotensin II (vasovonstrictor)

Angiotensin II - Stimulates the release of aldosterone from the adrenal cortex, causes vasoconstriction

Aldosterone - acts on kidneys to increase Na+ and H2O retention

Ultimately a pathway in response to decrease in BP to increase the BP

Question 18

ANP

Answer 18

Released in response to hypovolaemic states.
Causes excretion of salt and water in the kidneys so it reduces blood volume and decreases BP
Vasodilator

Question 19

ADH

Answer 19

Synthesised in hypothalamus, stored in posterior pituitary
Increases extracellular and plasma volume
Vasoconstriction
Increases BP