ANTIHYPERTENSION

YUANDANI

FAKULTAS FARMASI

UNIVERSITAS SUMATERA UTARA

CONTENTS

Blood Pressure Regulation

Hypertension

ACE Inhibitor

ARB

Ca Channel Blocker

Beta Blocker

Others

Blood Pressure Regulation

Blood Pressure

Cardiovascular system must maintain an adequate blood pressure in order

for blood to be delivered to all of your organs and tissues.

If the pressure drops too low, the organs will not receive an adequate

perfusion of nourishing blood.

If the pressure rises too high, it could damage the delicate inner lining of

your blood vessels and eventually lead to heart disease or a stroke.

Blood pressure is defined as the pressure exerted by the blood against the walls of

the blood vessels, and it's at its lowest point during diastole and reaches a peak at

systole. or

blood pressure is the force exerted on the blood vessels by blood being pumped

by the heart, during contraction and relaxation.

Regulation of Blood Pressure: Short Term Regulation & Baroreceptor

http://study.com/academy/lesson/regulation-of-blood-pressure-short-term-regulation-baroreceptors.html

one cardiac cycle: Pressure fluctuates with each beat of your heart

a cardiac cycle has two phases:

Systole : the pressure at the height of the pressure pulse

Diastole : the lowest pressure

In healthy adults, the systolic pressure, ideally is less than 120 mm Hg and the

diastolic pressure, is less than 80 mm Hg

The arterial blood pressure reflects the rhythmic ejection of blood from the left

ventricle into the aorta. It rises during systole as the left ventricle contracts and

falls as the heart relaxes during diastole.

Blood Pressure

Systolic Pressure The systolic blood pressure reflects the amount of blood (stroke volume) that

is ejected from the heart with each beat, the rate and force with which it is ejected, and the elasticity or compliance of the aorta and large arteries.

Systolic: The blood pressure when the heart is contractingThe maximum arterial pressure during contraction of the left ventricle of the heart

Blood Pressure

Diastolic Pressure Diastolic: Referring to the time when the heart is in aperiod of

relaxation and dilatation Diastolic Pressure is specifically the minimum arterial pressure during

relaxation and dilatation of the ventricles of the heart when the ventricles fill with blood

Blood Pressure

Mean Arterial Pressure (MAP)

Mean arterial pressure is defined as

the average arterial blood pressure during a single cardiac cycle.

three important factors that affect mean arterial pressure:

cardiac output: the amount of blood pumped per minute by each ventricle. CO is related to two other factors: heart rate and stroke volume. When the heart rate is fast, CO is increases and when stroke volume is high, CO also increases. Therefore when CO increases, then the arterial pressure will also increase.

CO = stroke volume ×heart rate

total peripheral resistance, and

blood volume: the more volume of blood present means that the vessels and heart have to work hard to pump that blood through the Circulatory system.

blood pressure = cardiac output × peripheral vascular resistance

total peripheral resistance is

the total resistance to flow of blood in the systemic circulation.

as resistance increases, so does the pressure within the blood vessels.

For example, if an arteriole constricts, its lumen will decrease in size, but the blood will pass through the arterial with more force or pressure.

if you make it smaller, it's going to cause the water to shoot out under higher pressure.

Blood volume is also directly related to blood pressure.

the circulatory system is a closed system.

The more fluid a closed system holds, the greater the pressure.

The higher the cardiac output, the higher the mean arterial pressure, because there is more blood being pumped out of the heart and flowing into the arterial system.

The body maintains its blood pressure by adjusting the cardiac output to compensate for changes in peripheral vascular resistance and changes the peripheral vascular resistance to compensate for changes in cardiac output

Mean Arterial Pressure (MAP)

WHY IS REGULATION NEEDED?

As blood is pumped from the heart to the various blood vessels, enough

pressure is generated in order to send blood to all parts of the body.

Blood pressure keeps the blood flowing through all the branches so that

the cellsof the body can receive the oxygen and nutrients needed to

sustain life.

When the heart contracts, pressure built up in the blood vessels increases

as the blood passes through, while the opposite is true when the heart

relaxes in between heart beats

http://www.interactive-biology.com/4008/blood-pressure-and-its-regulation/

The mechanisms used to regulate the arterial pressure depend on whether

short-term or

long-term

adaptation is needed

Blood Pressure Regulation

Short-Term Regulation

acting over minutes or hours,

to correct temporary imbalances in blood pressure, such as occur during

physical exercise and changes in body position.

responsible for maintenance of blood pressure at survival levels during life-

threatening situations such as during an acute hemorrhagic incident.

relies mainly on neural and humoral mechanisms

(the most rapid of which are the neural mechanisms)

Neural Mechanisms

The ANS control of blood pressure is mediated through:

intrinsic circulatory reflexes:

including the baroreceptor and chemoreceptor reflexes

located in the circulatory system

essential for rapid and short-term regulation of blood pressure.

extrinsic reflexes:

found outside the circulation.

they include blood pressure responses associated with factors such as pain and cold

Many of these responses are channeled through the hypothalamus

higher neural control centers: those caused by changes in mood and emotion.

Short-Term Regulation

Baroreceptors

Baroreceptors are special receptors that detect changes in your blood pressure.

pressure-sensitive receptors located in the walls of blood vessels and the heart.

The aorta and the carotid sinus contain important baroreceptorswhich constantly monitor blood pressure fluctuations.

These baroreceptors transmit their data to the CNS, and more specifically, to the cardio regulatory center of the medulla oblongata.

They respond to changes in the stretch of the vessel wall by sending impulses to cardiovascular centers in the brain stem to effect appropriate changes in heart rate and vascular smooth muscle tone.

Short-Term Regulation: Neuronal Mechanism

if the baroreceptors are detecting that blood pressure is too high:

the cardio regulatory center of the medulla will also decrease sympathetic input to the blood vessels

This causes vasodilation, which decreases total peripheral resistance and decreases blood

pressure.

Short-Term Regulation: Neuronal Mechanism

If the baroreceptors of the aorta or carotid sinus detect a drop in blood pressure:

Therefore, to raise blood pressure, the body will first cause an increase in sympathetic nerve activity to the SA node, causing it to fire more frequently, which increases the heart rate.

The heart muscle is also stimulated to pump with more force, and this increases the stroke volume.

When heart rate and stroke volume increase, we see an increase in cardiac output.

an increase in cardiac output causes an increased blood pressure, restoring blood pressure back to a normal level.

Second, this causes an increased sympathetic input to the blood vessels, which stimulate the smooth muscle to contract, causing vasoconstriction, which increases total peripheral resistance and increases blood pressure.

Short-Term Regulation: Neuronal Mechanism

The arterial chemoreceptors are chemosensitive cells that monitor

the oxygen, carbon dioxide, and hydrogen ion content of the

blood.

They are located in the carotid bodies

Although the main function of the chemoreceptors is to regulate

ventilation, they also communicate with cardiovascular centers in

the brain stem and can induce widespread vasoconstriction.

Whenever the arterial pressure drops below a critical level, the

chemoreceptors are stimulated because of diminished oxygen

supply and a buildup of carbon dioxide and hydrogen ions.

In persons with chronic lung disease, systemic and pulmonary

hypertension may develop because of hypoxemia.

Short-Term Regulation: Neuronal Mechanism

Arterial Chemoreceptors

Humoral Mechanisms

Reninangiotensin-aldosterone system

Vasopressin

Other humoral substances, such as epinephrine(have the effect of directly

stimulating an increase in heart rate, cardiac contractility, and vascular tone)

Short-Term Regulation: Humoral Mechanism

Renin angiotensin-aldosterone system

Renin is an enzyme that is synthesized, stored, and released by the juxtaglomerular cells of the

kidneys in response to:

an increase in sympathetic nervous system activity or

a decrease in blood pressure, extracellular fluid volume, or extracellular sodium concentration.

Most of the renin that is released leaves the kidney and enters the bloodstream, where it acts

enzymatically to convert an inactive circulating plasma protein called angiotensinogen to

angiotensin I

Angiotensin I is then converted to angiotensin II, catalyzed by an enzyme called the

angiotensin-converting enzymethat is present in the endothelium o the lung vessels.

Short-Term Regulation: Humoral Mechanism

Angiotensin II functions:

in both the short- and long-term regulation of blood pressure.

It is a strong vasoconstrictor, particularly of arterioles and, to a lesser extent, of veins (short- term

regulation )

Angiotensin II also reduces sodium excretion by increasing sodium reabsorption by the proximal tubules

of the kidney.

stimulation of aldo sterone secretion from the adrenal gland increasing salt and water

retention by the kidney (contributes to the long-term regulation )

Short-Term Regulation: Humoral Mechanism

Vasopressin

also known as antidiuretic hormone (ADH): is released from the posterior pituitary gland in

response to:

decreases in blood volume and blood pressure,

an increase in the osmolality of body fluids,

has a direct vasoconstrictor effect

However, long-term increases in vasopressin cannot maintain an increase in blood pressure,

Short-Term Regulation: Humoral Mechanism

PORTH, C., Disorders of Blood Pressure

Regulation

Long-term mechanisms control the daily, weekly, and monthly regulation of blood pressure.

the long-term regulation of blood pressure is largely vested in the kidneys and their role in the regulation of the extracellular fluid volume

According to the late Arthur Guyton:the extracellular fluid volume and arterial blood pressure are regulated around an equilibrium point, which represents the normal pressure for a given individual

Long-Term Regulation

The function of the kidneys in the longterm regulation of blood pressure can be influenced by a number of factors: excess sympathetic nerve activity or the release of vasoconstrictor substances

changes in neural and humoral control of kidney function can shift the diuresis–natriuresis process to: a higher fluid or pressure level, thereby initiating an increase in arterial pressure

Long-Term Regulation

can alter the transmission of arterial pressure to the kidney

There are two general mechanisms by which an increase in fluid volume can elevate blood pressure: a direct effect on cardiac output Indirect, resulting from:

the autoregulation of blood flow its effect on peripheral vascular resistance.

Autoregulatory mechanisms function in distributing blood flow to the various tissues of the body according to their metabolic needs .When the blood flow to a specific tissue bed is excessive, local blood vessels constrict, and when the flow is deficient, the local vessels dilate. In situations of increased extracellular fluid volume and a resultant increase in cardiac output, all of the tissues of the body are exposed to the same increase in flow. This results in a generalized constriction of arterioles and an increase in the peripheral vascular resistance (and blood pressure).

Long-Term Regulation

PORTH, C., Disorders of Blood Pressure

Regulation

HYPERTENSION

Hypertension represents an elevation in systolic and/or diastolic blood pressure.

Essential hypertension :

characterized by a chronic elevation in blood pressure that occurs without

evidence of other disease, and

secondary hypertension

by an elevation of blood pressure that results from some other disorder, such

as kidney disease.

The seventh report of the Joint National Committee on Detection,

Evaluation, and Treatment of High Blood Pressure (JNC 7) of the

National Institutes of Health was published in 2003:

BP Classification

Normal: <120

Prehypertension: 120–139

Stage 1 Hypertension: 140–159

Stage 2 Hypertension: ≥160

HYPERTENSION

pathophysiologic factors:

increased sympathetic nervous system activity

overproduction of sodium-retaining hormones and vasoconstrictors

long-term high sodium intake

inadequate dietary intake of potassium and calcium

increased or inappropriate renin secretion: with resultant increased production of angiotensin II and

aldosterone;

deficiencies of vasodilators: prostacyclin, nitric oxide (NO), and the natriuretic peptides;

abnormalities of resistance vessels: including selective lesions in the renal microvasculature; diabetes

mellitus; insulin resistance; obesity;

increased activity of vascular growth factors; alterations in adrenergic receptors that influence heart

rate, inotropic properties of the heart, and vascular tone; and altered cellular ion transport

HYPERTENSION