2. CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION

3. At the end of this lecture you should be able to
OBJECTIVES
At the end of this lecture you should be able to
Define blood pressure and Mean Arterial Pressure (MAP)
List the factors affecting MAP
Describe Short term and long term control of Blood Pressure

4. BLOOD PRESSURE REGULATING MECHANISMS
Short Term (Nervous System works within few seconds)
Baroreceptors
Chemoreceptors
CNS Ischemic Response
Long Term (Renal Control works within few days)
Intermediate (Within few hours)
Stress relaxation
Capillary fluid shift

5. VASOMOTOR CENTER (Area!)
1. Vasoconstrictor area
2. Vasodilator area
3. Sensory area

6. VASOMOTOR CENTER (Area!)
1. A vasoconstrictor area located bilaterally in upper medulla. excite vasoconstrictor neurons of the sympathetic nervous system.
2. A vasodilator area located bilaterally in the lower half of the medulla. inhibit the vasoconstrictor area, thus causing vasodilation.
3. A sensory area located bilaterally in medulla and pons (tractus solitarius). Receive sensory nerve signals from vagus and glossopharyngeal nerves and output control the vasoconstrictor and vasodilator areas An example is the baroreceptor reflex
Nervous Regulation of Circulation
The Autonomic Nervous System
Sympathetic Vasoconstrictor Tone (Vasomotor Tone)
Control of Vasomotor Center
Baroreceptor Control System

7. in most
tissues all the vessels except the capillaries, precapillary sphincters, and metarterioles
are innervated.
Continuous Partial Constriction of the Blood Vessels Is Normally Caused by Sympathetic Vasoconstrictor Tone.

8. CONTROL OF VMC Reticular Substance of Brain Stem Hypothalamus
Posterolateral portions Cause
Excitation. Anterior part can cause
Excitation or Inhibition
Cerebral Cortex
Motor Cortex Cause Excitation

9. Control of
blood pressure
Short-term
Control
Long-term
control
Baroreceptor
reflex
Renal
compensation

10. Baroreceptors

12. Baroreceptor Reflex Mediated Quick operation through (within few
autonomic nerves
Quick operation
(within few
seconds)
Influences
heart &
blood vessels
Adjusts CO &TPR
to restore BP
to normal

13. Renal Control It is perfect 100 % Mediated through
Kidneys Renin Angiotensin
aldosterone mechanism,
Slow operation
(within hours to Days)
Adjusts urinary output and TPR
to restore BP
to normal
Influences
Kidneys &
blood vessels

14. Components Of Baroreceptor Reflex Arc
Receptors
Baroreceptors in carotid sinuses & arch of aorta
Afferents
Carotid sinus nerves & nerve from arch of aorta
Center
Vasomotor Center in medulla oblongata
Efferents
Sympathetic & parasympathetic nerves
Effectors
Heart and blood vessels
Carotid sinus nerve runs along with glossopharyngeal nerve
Aortic nerve runs along with vagus nerve

15. BARORECEPTOR REFLEX ARC
COMPONENTS OF
BARORECEPTOR REFLEX ARC

16. Vasomotor Center in medulla oblongata Heart and blood vessels
Stimulus
Increase in BP
Receptors
Baroreceptors
Increase Firing of Glossopharyngeal and Vagus Nerves
Afferents
Vasomotor Center in medulla oblongata
Center
 Sympathetic &  parasympathetic firing
Efferents
Heart and blood vessels
Effectors
Heart rate and force of contraction
and Vasodilatation  BP
Effects

17. Stimulus Receptors Afferents Center Efferents Effectors Effects
Decrease in BP
Receptors
Baroreceptors
Minimal Firing of Glossopharyngeal and Vagus Nerves
Afferents
Vasomotor Center in medulla oblongata
Center
 Sympathetic &  parasympathetic firing
Efferents
Heart and blood vessels
Effectors
Heart rate and force of contraction
and Vasoconstriction  BP
Effects

18. Baroreceptor reflex Baroreceptor reflex  MAP  Firing of
baroreceptors
 Sympathetic tone
 Vagal tone
Vasodilatation
 HR
 SV
 TPR
 Cardiac output
 MAP

19. ? ? !! OR Can you guess ! Because the inhibitory
What shall be the effect of bilateral
clamping of the carotid arteries
proximal to the carotid sinuses? ? OR
Rise in blood pressure
and heart rate.
Because the inhibitory
control of sympathetic
is gone
Can you
guess !
What shall be the effect of
bilateral cutting of the
carotid sinus nerves? ? !!

20. Pressure on the carotid sinus, produced, for example by the
tight collar or carotid massage
can
cause
marked
bradycardia
vasodilatation
Fainting
or syncope

21. Transient loss of consciousness
Syncope
Transient loss of consciousness
Associated
with
Abrupt vasodilatation
Inadequate cerebral blood flow
Hypotension and bradycardia

23. Pressure “Buffer” Function of the Baroreceptor
Control System.

24. Pressure “Buffer” Function of the Baroreceptor
Control System.

25. COTROL OF ARTERIAL PRESSURE IS ALSO BY
Chemoreceptors
(Carotid and Aortic Bodies)
Atrial and Pulmonary Artery Reflexes
(Low Pressure Receptors)
CNS Ischemic Response

27. Pressure Natriuresis and
Pressure Diuresis

28. Two ways in which the arterial pressure can be increased: A, by
shifting the renal output curve in the right-hand direction toward
a higher pressure level or B, by increasing the intake level of salt
and water.

29. Increased Fluid Volume Can Elevate Arterial
Pressure by Increasing Cardiac Output or
Total Peripheral Resistance

30. Salt (NaCl) intake & Arterial Pressure Regulation

32. Renal control  MAP  Renin secretion Angiotensinogen Angiotensin I
ACE in Lungs
Angiotensin II
Vasoconstriction
Salt & water Retention
 TPR
 ECF Volume
 MAP

34. ACE synthesize Ang II (Vascoconstrictor) and Inactivates Bradykinin (Vasodilator)
Two related vasodilator peptides called kinins are found in the body. One is the nonapeptide bradykinin, and the other is the decapeptide lysylbradykinin, also known as kallidin (Figure 33–11). Lysylbradykinin can be converted to bradykinin by aminopeptidase. Both peptides are metabolized to inactive fragments by kininase I, a carboxypeptidase that removes the carboxyl terminal arginine (Arg). In addition, the dipeptidylcarboxypeptidase kininase II inactivates bradykinin and lysylbradykinin by removing phenylalanine-arginine (Phe-Arg) from the carboxyl terminal. Kininase II is the same enzyme as angiotensin-converting enzyme (see Chapter 39), which removes histidine-leucine (His-Leu) from the carboxyl terminal end of angiotensin I.

35. Renal control of blood presure
 MAP
 MAP
Renal control
of blood presure
 Urine formation
 Cardiac output
 Blood volume
 Stroke volume
 venous return
 EDV

39. THANKS