REGULATION OF REGULATION OF ARTERIAL ARTERIAL

BLOOD PRESSUREBLOOD PRESSURE

TERMSTERMS

•SBP

•DBP

•PP

•MAP

PHYSIOLOGICAL PHYSIOLOGICAL VARIATIONSVARIATIONS

•AGE•SEX•BODY BUILT•RACE•DIURNAL

VARIATIONS•POSTURE

•AFTER MEALS

•DURING SLEEP

•AFTER EXERCISE

•EMOTIONAL CONDITIONS

DETERMINANTS OF DETERMINANTS OF ARTERIAL BLOOD ARTERIAL BLOOD

PRESSUREPRESSURE

•AP = CO x TPR

•CO = SV x HR

•SV = EDV ( – ) ESV

DETERMINANTS OF ARTERIAL BLOOD PRESSURE

REGULATION OF ARTERIAL REGULATION OF ARTERIAL BLOOD PRESSUREBLOOD PRESSURE

Regulation of Blood Pressure

NervousMechanism

Renal Mechanism

HormonalMechanism

LocalMechanism

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 REGULATION OF ARTERIAL BLOOD PRESSUREBLOOD PRESSURE

•SHORT-TERM CONTROL(IN SEC – MIN)

• INTERMEDIATE-TERM CONTROL

(30 MIN – HOURS)

•LONG – TERM CONTROL

SHORT-TERM CONTROL OF SHORT-TERM CONTROL OF APAP

•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 REGULATION OF BLOOD PRESSURE BY PRESSURE BY

BARORECEPTOR MECHANISMBARORECEPTOR MECHANISMIncrease in Blood Pressure

Baroreceptors

Stimulation

Impulses via IX and X Cranial Nerves

Normal Blood Pressure

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

Rate of firing in afferent nervesCardiovascular center

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

and

total peripheral resistance

Blood pressure decreased toward normal

BARORECEPTOR REFLEXES TO RESTORE BLOOD PRESSURE TO NORMAL

When blood pressure falls below normal

Carotid sinus and aortic arch receptor potential

Rate of firing in afferent nervesCardiovascular center

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

and

total peripheral resistance

Blood pressure increased toward normal

BARORECEPTOR REFLEX

CHEMORECEPTOR REFLEX

INTERMEDIATE CONTROL INTERMEDIATE CONTROL OF APOF AP

•RENIN - ANGIOTENSIN – VASOCONSTRICTOR MECH.

•STRESS RELAXATION OF VASCULATURE

•FLUID – SHIFT THROUGH THE CAPILLARY WALL

REGULATION OF BLOOD REGULATION OF BLOOD PRESSURE BY RENIN-PRESSURE BY RENIN-

ANGIOTENSIN MECHANISMANGIOTENSIN MECHANISM

Decrease in Blood Pressure

Stimulation

Juxtaglomerular apparatus

Renin

Angiotensinogen Angiotensin I

Converting enzyme

Angiotensin II

Normal Blood Pressure

Vasoconstriction

SITES OF PRODUCTION

Renin - J.G Cells of

Kidney

Angiotensinogen - Liver Cells

ACE - Lungs

LONG – TERM CONTROL OF LONG – TERM CONTROL OF APAP

•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 LOCAL MECH. FOR CONTROL OF APOF AP

A. Vasodilatos1. EDRF

2. Bradykinin3. Histamine4. ANP5. VIP6. Substance P

7. Prostacyclin8. Adenosine

9. K+

10. Acidosis [ CO2]

11. Hypercapnia12. Hypoxia13. Temperature

B. Vasoconstrictors

1. Endothelin-12. Angiotensin II3. Norepinephrine4. ADH5. Serotonin6. Thromboxane A27. Neuropeptide-Y8. Cold

HORMONAL MECH. FOR HORMONAL MECH. FOR CONTROL OF APCONTROL OF AP

•HORMONES RAISING AP–ADRENALINE–NORADRENALINE–THYROXINE–ALDOSTERONE–VASOPRESSIN–ANGIOTENSIN–SEROTONIN

HORMONAL MECH. FOR HORMONAL MECH. FOR CONTROL OF APCONTROL OF AP

•HORMONES DECREASING AP–VIP–BRADY KININ–PROSTAGLANDIN–HISTAMINE–ACETYLCHOLINE–ANP

PATHOLOGICAL PATHOLOGICAL VARIATIONSVARIATIONS

•HYPERTENSION

•HYPOTENSION