REGULATION OF ARTERIAL
BLOOD PRESSURE
TERMS
• SBP
• DBP
• PP
• MAP
PHYSIOLOGICAL VARIATIONS
•
•
•
•
•
AGE
SEX
BODY BUILT
RACE
DIURNAL
VARIATIONS
• POSTURE
• AFTER MEALS
• DURING
SLEEP
• AFTER
EXERCISE
• EMOTIONAL
CONDITIONS
DETERMINANTS OF ARTERIAL
BLOOD PRESSURE
• AP
=
CO x
TPR
• CO
=
SV x
HR
• SV
=
EDV ( – ) ESV
DETERMINANTS OF ARTERIAL BLOOD PRESSURE
REGULATION OF ARTERIAL
BLOOD PRESSURE
Regulation of Blood Pressure
Nervous
Mechanism
Renal
Mechanism
Hormonal
Mechanism
Local
Mechanism
By
Vasomotor
Center and
Impulses
from
Periphery
By
Regulation
of ECF
Volume and
renin –
angiotensin
mechanism
By
Vasocons-trictor and
Vasodilator
Hormones
By Local
Vasocons-trictors and
Vasodilators
REGULATION OF ARTERIAL
BLOOD PRESSURE
• SHORT-TERM CONTROL
(IN SEC – MIN)
• INTERMEDIATE-TERM CONTROL
(30 MIN – HOURS)
• LONG – TERM CONTROL
SHORT-TERM CONTROL OF AP
• CNS ISCHAEMIC RESPONSE
• BARORECEPTOR REFLEX
• CHEMORECEPTOR REFLEX
CUSHING REFLEX
Gross hypotension or increased ICP
Decreased cerebral blood flow or
decreased blood flow to VMC
Hypoxia and hypercapnia at VMC
Strong stimulation of VMC
Intense vasoconstriction
Increased pressure in carotid sinus
Activation of baroreceptor reflex
Reflex bradycardia
REGULATION OF BLOOD PRESSURE
BY BARORECEPTOR MECHANISM
Increase in Blood Pressure
Normal Blood Pressure
Stimulation
Baroreceptors
Impulses via IX and
X Cranial Nerves
Dilatation of
blood vessels
Bradycardia and reduction
in cardiac output
Decrease in
vasomotor tone
Increase in
vagal tone
Inhibition of
vasoconstrictor area
Stimulation of
vasodilator area
Nucleus of tractus solitarius
BARORECEPTOR REFLEXES TO RESTORE BLOOD
PRESSURE TO NORMAL
When blood pressure becomes
elevated above normal
Carotid sinus and aortic arch
receptor potential
Cardiovascular center
Rate of firing in afferent nerves
Sympathetic cardiac nerve activity
and
Sympathetic vasoconstrictor nerve activity
and
Parasympathetic nerve activity
Heart rate
and
stroke volume
and
arteriolar and venous
vasodilation
Cardiac output
Blood pressure decreased
toward normal
and
total peripheral resistance
BARORECEPTOR REFLEXES TO RESTORE BLOOD
PRESSURE TO NORMAL
When blood pressure falls
below normal
Carotid sinus and aortic arch
receptor potential
Cardiovascular center
Rate of firing in afferent nerves
Sympathetic cardiac nerve activity
and
sympathetic vasoconstrictor nerve activity
and
parasympathetic nerve activity
Heart rate
and
stroke volume
and
arteriolar and venous
vasoconstriction
Cardiac output
Blood pressure increased
toward normal
and
total peripheral resistance
BARORECEPTOR REFLEX
CHEMORECEPTOR REFLEX
INTERMEDIATE CONTROL OF AP
• RENIN - ANGIOTENSIN –
VASOCONSTRICTOR MECH.
• STRESS RELAXATION OF
VASCULATURE
• FLUID – SHIFT THROUGH THE
CAPILLARY WALL
REGULATION OF BLOOD PRESSURE
BY RENIN-ANGIOTENSIN MECHANISM
Decrease in Blood Pressure
Normal Blood Pressure
Stimulation
Juxtaglomerular apparatus
Renin
Angiotensinogen
Angiotensin I
Converting enzyme
Angiotensin II
Vasoconstriction
SITES OF PRODUCTION
Renin
-
J.G Cells of
Kidney
Angiotensinogen -
Liver Cells
ACE
Lungs
-
LONG – TERM CONTROL OF AP
• RENAL FLUID SHIFT (THROUGH
ADH / VOLUME RECEPTORS)
• RENIN – ANGIOTENSIN –
ALDOSTERONE MECH.
RESTORATION OF FLUID VOLUME OF THE BODY BY ADH IN VOLUME
DEPLETION STATE. [NTS: NUCLEUS TRACTUS SOLITARIOUS]
Sequential events by which increased salt
intake increases the arterial pressure.
Increased salt intake
Increased extracellular volume
Increased arterial pressure
Decreased renin and angiotensin
Decreased renal retention of salt and water
Return of extracellular volume almost to normal
Return of arterial pressure almost to normal
LOCAL MECH. FOR CONTROL OF AP
A. Vasodilatos
7. Prostacyclin
1. EDRF
8. Adenosine
2. Bradykinin
+
9. K
3. Histamine
10. Acidosis [ CO2]
4. ANP
11. Hypercapnia
5. VIP
12. Hypoxia
6. Substance P 13. Temperature
B. Vasoconstrictors
1.
2.
3.
4.
5.
6.
7.
8.
Endothelin-1
Angiotensin II
Norepinephrine
ADH
Serotonin
Thromboxane A2
Neuropeptide-Y
Cold
HORMONAL MECH. FOR
CONTROL OF AP
• HORMONES RAISING AP
– ADRENALINE
– NORADRENALINE
– THYROXINE
– ALDOSTERONE
– VASOPRESSIN
– ANGIOTENSIN
– SEROTONIN
HORMONAL MECH. FOR
CONTROL OF AP
• HORMONES DECREASING AP
– VIP
– BRADY KININ
– PROSTAGLANDIN
– HISTAMINE
– ACETYLCHOLINE
– ANP
PATHOLOGICAL VARIATIONS
• HYPERTENSION
• HYPOTENSION