1. Definitions and terminology used in arterial blood pressure. 2. Factors maintaining arterial blood pressure. 3. Regulation of arterial blood pressure.

1. Module

2. Arterial Blood Pressure
Edited By
Professor Atef Mansour

3. Contact Information
atefazim@mans.edu.eg
Mobile (Optional)
Academic Hours : ( Sunday : 10:00-11:00 am)
( Wednesday : 10:00-11:00 am)

4. 2
3
1
Learning Outcomes
Identify Definitions, normal standards and
physiological variations of arterial blood pressure
(ABP).
text
Determine factors maintaining the ABP.
Describe different regulatory mechanisms for ABP.

5. Definitions, normal standards and physiological variations
of arterial blood pressure (ABP).
Learning Outcome
1

6. • ABP is defined as the lateral
force exerted by the moving
column of blood on the
lateral wall of arteries.
• ABP is pulsatile. It is not
constant during the cardiac
cycle ranges between a
maximum called the systolic
blood pressure and a
minimum called the diastolic
blood pressure.
Arterial Blood pressure (ABP)

7. 1. Systolic pressure
• The systolic BP is caused by sudden
ejection of blood into the aorta during
heart systole.
• The systolic BP ranges from 90 to 140
mmHg.
2. Diastolic pressure
• During diastole, the stretched arterial
walls recoil passively (elastic recoil)
maintaining pressure in the arteries
• The diastolic BP ranges between 60
and 90 mmHg.

8. 3. Pulse pressure
is the difference between
the systolic and diastolic
pressures.
It equals about 40 mmHg.

9. 4. Mean arterial pressure
is the average arterial
pressure with respect to
time.
can be calculated
approximately as diastolic
pressure plus one-third of
pulse pressure.

10. Physiological variations that affect the
value of ABP
• age,
• gender,
• body built,
• posture,
• food intake,
• emotions,
• muscular exercise,
• and sleeping

11. How to measure the Arterial Blood
Pressure
See the practical session

12. 1- It maintains sufficient pressure to keep the blood
flowing.
2- It provides enough hydrostatic pressure inside the
capillaries essential for the formation of interstitial
fluid, urine, …. etc.
Physiological Importance of ABP

13. Factors Maintaining the ABP
Learning
Outcome
2

14. 1. Cardiac output
C O P = Stroke volume (SV) X Heart rate (HR)
-Changes in the stroke volume with the HR constant affect
the systolic more than the diastolic pressure.
-Changes in the HR with constant SV affect the diastolic
more than the systolic blood pressure

15. 2. Peripheral resistance
Factors that determine the PR:
PR = VL/r4
A-Viscosity of blood (V): It is the property by which a fluid resists a
change in shape. It represents the force with which the fluid
particles adhere to each other and resists their separation
B-Length of the blood vessels (L)
C-The diameters of arterioles (r)

16. Arterioles represent the main
peripheral resistance

17. Importance of elasticity of arterial wall

18. 3. Elasticity of the arterial wall
The elasticity of the aorta and its large branches buffer
excessive changes in the arterial blood pressure during
systole and diastole.
In atherosclerosis, there is marked increase in systolic and
decrease in diastolic blood pressure resulting in a higher pulse
pressure.

19. 4. The total blood volume in relation to capacity of
circulatory system:
A- Changes in blood volume:
1. Mild to moderate change
2. Severe change
B-Changes in the capacity of circulatory system:
1. An increase in the capacity
2. A decrease in the capacity

20. Different regulatory mechanisms of ABP.
Learning
Outcome
2

21. Different regulatory mechanisms of ABP
1. Fast, neurally mediated baroreceptors mechanism.
2. Slower, hormonally regulated renin-angiotensin-
aldosterone mechanism.
3. Other mechanisms.
Regulation of ABP

22. A. Fast neural mechanism for regulation of
ABP
• Includes the baroreceptor reflex.
• Is a negative feedback system that is responsible for the
minute-to-minute regulation of arterial blood pressure.
• Baroreceptors are stretch receptors located within the
walls of the carotid sinus near the bifurcation of the
common carotid arteries.

23. Baroreceptors in the carotid sinuses

24. Baroreceptor reflex

25. Baroreceptor reflex
Fall in pressure in carotid sinus and aortic arch leads to:
a. Reflex increase in heart rate (chronotropic effect).
b. Increase in force of ventricular contraction (positive inotropic effect).
c. Peripheral vasoconstriction of arterioles.
d. Vasoconstriction of veins.

26. Rise in pressure in carotid sinus and aortic arch lead to:
a. Reflex decrease in heart rate.
b. Peripheral vasodilatation in both arterioles and veins.
c. Vasoconstriction of veins.
Baroreceptor reflex (continue)

27. Fast, neurally mediated baroreceptors mechanism

28. Example of the baroreceptor reflex: response to acute
blood loss

29. • This includes the renin-angiotensin-aldosterone system.
• This system is used in long-term blood pressure regulation by
adjustment of blood volume.
• Renin is an enzyme.
• Angiotensin I is inactive.
• Angiotensin II is physiologically active to elevate the ABP.
• Angiotensin II is degraded by angiotensinase. One of the peptide
fragments, angiotensin III, has some of the biologic activity of
angiotensin II.
B. Slow, hormonal mechanism for
regulation of ABP

30. Steps in the renin–angiotensin–aldosterone system
a. A decrease in renal perfusion
pressure causes the juxtaglomerular
cells of the afferent arteriole to
secrete renin.
b. Renin is an enzyme that catalyzes
the conversion of angiotensinogen to
angiotensin I in plasma.
c. Angiotensin-converting enzyme
(ACE) catalyzes the conversion of
angiotensin I to angiotensin II,
primarily in the lungs.

31. d. Angiotensin II has four effects:
– (1) It causes vasoconstriction of the arterioles, thereby
increasing TPR and arterial pressure.
– (2) It stimulates the synthesis and secretion of aldosterone
by the adrenal cortex.
– (3) It increases Na+–H+ exchange in the proximal convoluted
tubule.
– (4) It increases thirst.

32. – ACE inhibitors (e.g., captopril) block the conversion
of angiotensin I to angiotensin II and, therefore,
decrease blood pressure.
– Angiotensin receptor (AT1) antagonists (e.g.,
losartan) block the action of angiotensin II at its
receptor and decrease blood pressure.
Clinical applications

33. C. Other mechanisms of regulation of arterial
blood pressure
1. Chemoreceptors in the carotid and aortic bodies
are located near the bifurcation of the common carotid arteries
and along the aortic arch.
They have very high rates of O2 consumption and are very
sensitive to decreases in the partial pressure of oxygen (PO2).
Decreases in PO2 activate vasomotor centers that produce
vasoconstriction, an increase in TPR, and an increase in arterial
pressure.

34. Location and microscopic anatomy of carotid body

35. 2. Atrial natriuretic peptide (ANP)
Is released from the atria in response to an increase in blood
volume and atrial pressure.
a. This causes relaxation of vascular smooth muscle, dilation of
the arterioles, and decreased PR.
b. It also causes increased excretion of Na+ and water by the
kidney, which reduces blood volume and attempts to bring
arterial pressure down to normal. It also inhibits renin secretion.

36. 3. Vasopressin [antidiuretic hormone (ADH)]
Atrial receptors respond to a decrease in blood volume (or blood
pressure) and cause the release of vasopressin from the
posterior pituitary as in cases of hemorrhage.
Vasopressin has two effects that tend to increase blood pressure
toward normal:
a. It is a potent vasoconstrictor that increases TPR by
activating V1 receptors on the arterioles.
b. It increases water reabsorption by the renal distal tubule
and collecting ducts by activating V2 receptors.

37. 4. Cerebral ischemia
a. When the brain is ischemic, the partial pressure of carbon dioxide
(PCO2) in brain tissue increases.
b. Chemoreceptors in the vasomotor center respond by increasing
sympathetic outflow to the heart and blood vessels.
c. The Cushing reaction is an example of the response to cerebral
ischemia. Increases in intracranial pressure cause compression of the
cerebral blood vessels, leading to cerebral ischemia and increased
cerebral PCO2. The vasomotor center directs an increase in sympathetic
outflow to the heart and blood vessels, which causes a profound
increase in arterial pressure

38. Summary & Wrap up
1. ABP normally oscillates during the cardiac cycle reaching a
maximum during the cardiac cycle systole and a minimum at
the end of diastole.
2. Factors maintaining normal ABP are 4 important factors.
3. Factors regulating ABP are either: Fast, neurally mediated
baroreceptors mechanism. Or Slower, hormonally regulated
renin-angiotensin-aldosterone mechanism.

39. Questions
2
1
3
4
Question 1
Answer
………………………………………………………………...
Question 2
Answer
………………………………………………………………...
Question 3
Answer
………………………………………………………………...
Question 4
Answer
………………………………………………………………...

40. Angiotensin II:
A. Is formed by the action of an enzyme on angiotensin III.
B. Is a phospholipid.
C. Is released from the juxtaglomerular apparatus of the
kidneys.
D. Acts through stimulating vasomotor center.
E. Is formed due to presence of renin in the circulation.
MCQ 1

41. MCQ 2
The Cushing reflex comes into play when:
A. There is increased viscosity of blood
B. There is increased intra-cranial pressure
C. There is decreased CSF pressure
D. There is increased mean Arterial pressure

42. MCQ 3
Reduced firing of the atrial receptors will:
A. Inhibit renin secretion
B. Increase ANP secretion
C. Increase heart rate
D. Increase vasopressin (AVP) secretion
E. Cause a reflex reduction in blood volume

43. References
1. Guyton and Hall Textbook of Medical Physiology,
13th edition
2. BRS Physiology , Linda S. Costanzo, Sixth Edition