Regulation of blood pressure

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Presented To:

Ms. Komal Najam

Presented by:

Ali Mansoor

Abdullah Yaqoob

Harry Hamid


Arterial Blood-Pressure

a. Definition

b. Regulation

Mechanisms of B.P Regulation

Nervous mechanism for B.P regulation

a. Baro-receceptor Mechanism

b. Chemoreceptor mechanism

Renal mechanism for B.P regulation

Hormonal Mechaism

Local Mechanism

Reflexes and Responses

Marey Reflex

Atrium-brainbridge Reflex

Bezold-Jarisch Reflex


Definition:• Arterial blood pressure is defined as the lateral pressure exerted by the

column of blood on wall of arteries.• LOCAL FACTORS DETERMINIG THE ARTERIAL BLOOD

PRESSURE


There are four mechanisms for regulation of the blood pressure.

1. Nervous mechanism or shortterm regulatory mechanism

2. Renal mechanism or longterm regulatory mechanism

3. Hormonal mechanism

4. Local mechanism.


www.free-ppt -templates.com • Most rapid among all the mechanisms

• It operates through the vasomotor system.

Vasomotor SystemVasomotor system includes three components:

1. Vasomotor center (control heart rate)

2. Vasoconstrictor fibers (vasoconstriction)

3. Vasodilator fibers (vasodilation)

(Receives impulses from

Baroreceptors & Chemoreceptors.)



Rise in B.P activation of impulses to nucleus

baroreceptors of tractus solitarius

nucleus ofReduces vasomotor inhibition of tractus solitarius acts

. tone vasoconstrictor area on vasomotor center

excites vasodilator area

Redution in peripheral resistance Blood-

& Vasodilatation occur pressure

decreases(force of contraction &

Cardiac output decrease)

www.free-ppt -templates.com When blood pressure falls below

normalCarotid 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



Decreased blood pressure

Decreased flow of blood

Decrease in O2 & Increase in CO2

Excitation in the chemoreceptors

Send impulses to vasoconstrictors

Blood pressure rises and blood flow increases


www.free-ppt -templates.com • Long term regulation of Arterial B.P

• Renal Mechanism works even whennerous mechanism adapts to the newpressure.

• Two ways of regulation of B.P

1. By regulation of ECF volume

2. Through reninangiotensin mechanism.


Increase in excretion of water excretion of salts (sodium)

B.P (pressure diuresis) (Pressure Natriuresis)

Blood pressure decrease in blood decrease in ECF

restored volume volume

www.free-ppt -templates.com Decrease in reabsorption Increase in ECF

B.P from & Blood

renal-tubules volumes

Blood pressure Increase in cardiac

Restored output


www.free-ppt -templates.com Renin along with Angiotensin forms Renin-

Angiotensin system, which is a hormone systemthat plays an important role in the maintenance ofblood pressure

Renin - J.G Cells of

Kidney

Angiotensinogen - Liver Cells

ACE - Lungs





www.free-ppt -templates.com • Local mechanism regulates blood pressure by

Vasoconstriction & vasodilatation.

Local vasoconstrictors• Are also called EDCF (endothelium derived constricting

factors) as they are derived from vascular endothelium.

• Common EDCF are ET1, ET2 & ET3.

• Produced by stretching of blood vessels & causevasoconstriction.


Vasodilators of metabolic origin:

carbon monoxide, lactate, H+ & adenosine.

Vasodilators of Endothelial origin:

• Nitroxides

• NO3 (nitrate)

• NO+ (nitrosonium ion)

• NO- (nitroxyl anion)

www.free-ppt -templates.com • Vasomotor center regulates the cardiac activity by

receiving impulses from different sources in the body. After receiving the impulses from different sources, the vasodilator area alters the vagal tone and modulates the activities of the heart.

• Various sources from which the impulses reach the vasomotor center:

1. IMPULSES FROM BARORECEPTORS – MAREY REFLEX

2. IMPULSES FROM RIGHT ATRIUM – BAINBRIDGE REFLEX

3. BEZOLD-JARISCH REFLEX

www.free-ppt -templates.com • Baroreceptors regulate the heart rate through Marey reflex.

Stimulus for this reflex is increase in blood pressure.

• Marey reflex is a cardioinhibitory reflex that decreases heart rate when blood pressure increases.

• Whenever blood pressure increases, the aortic and carotid baroreceptor are stimulated.

• stimulatory impulses are sent to nucleus of tractus solitariusvia Hering nerve and aortic nerve.

• then nucleus of tractus solitarius stimulates vasodilator area and increase the vagal tone leading to decrease the heart rate

www.free-ppt -templates.com • Bainbridg reflex is a cardio accelerator reflex.

• Increases the heart rate when venous return is increased.

• This reflex rises from right atrium it right atrial reflex.

• Increase in venous return causes distention of right atrium and stimulation of stretch receptors, situated in the wall of right atrium.

• Stretch receptors, in turn, send nerve to vasodilator area of vasomotor center. Vasodilator area is inhibited, resulting in decrease in vagal tone and increase in heart rate.


• This is also called coronary chemoreceptors.

• Bezold- Jarisch reflex is a pathological reflex and it does not occur in physiological conditions.

• Conditions when Bezold-Jarisch Reflex Occurs.

1. Myocardial infarction

2 .Administration of thrombolytic agents

3. Hemorrhage

4. Aortic stenosis

5. Syncope.

www.free-ppt -templates.com • Hypertension

• Hypotension

• Hypertention; when sistolic pressure remain elevated above 150 mm Hg and distolic pressure

remains 90 mm Hg is called hypetrtention.

• Hypotention;when the sistolic pressure less then 90 mm Hg is called hypotention.



Education

Regulation of blood pressure