Cardiovascular system (blood pressure, hypertension)
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This document provides an overview of the cardiovascular system, including the cardiac cycle, cardiac rhythm, blood pressure, and hypertension. It discusses topics such as: - The cardiac cycle occurs over 0.8 seconds and includes systole and diastole. - Sinus rhythm is normally set by the sinoatrial node at a rate of 70-80 beats per minute. - Blood pressure is the force of blood pushing against artery walls and is measured in millimeters of mercury (mmHg). - Hypertension is defined as a systolic pressure over 140 mmHg or diastolic over 90 mmHg. It can be primary (essential) or secondary due to other medical conditions.
Cardiovascular system (blood pressure, hypertension)
- 1. Md. Saiful Islam Dept. of Pharmaceutical Sciences North South University Facebook Group: Pharmacy Universe YouTube Channel: Pharmacy Universe CARDIOVASCULAR SYSTEM
- 2. CARDIOVASCULAR SYSTEM Blood pressure, Hypertension
- 3. Cardiac Cycle • Cardiac cycle (0.8 sec. in resting person) is one complete contraction and relaxation of all 4 chambers of the heart • Cardiac cycle refers to all events associated with blood flow through the heart – Systole – contraction of heart muscle – Diastole – relaxation of heart muscle • Quiescent period before next atrial systole (0.4 sec.)
- 4. Cardiac Rhythm & Cardiac Arrhythmias • Systole = contraction; diastole = relaxation • Sinus rhythm – The rhythm is set by SA node, adult at rest is 70 to 80 bpm
- 5. Cardiac Rhythm & Cardiac Arrhythmias • Ectopic foci – It is the region of spontaneous firing other than SA node. • Arrhythmia - abnormal cardiac rhythm – Tachycardia: Heart rate in excess of 100bpm – Bradycardia: Heart rate less than 60 bpm
- 6. Terminology • Blood Flow: Volume of blood flowing through a vessel/organ in a given period, ml per min (mL/min). The overall blood flow of an adult is about 5000ml/min. • Venous return- Amount of blood flowing into the right atrium each minute from the systemic circulation Approximately 5L/min • Stroke volume- Amount of blood ejected from a ventricle with each heart beat- usually 60-100ml
- 7. Cardiac Output, Resistance & Blood Pressure • Cardiac output (CO)- Amount of blood pumped into the aorta each minute by the heart. – Cardiac output of normal resting adult = 5 L/min • Peripheral resistance (PR)- Resistance to the flow of blood determined by vessel diameter and tone. • Blood pressure- It is the force or pressure of blood exerted on the walls of the arteries. Blood moves through vessels because of blood pressure. BP = CO X PR
- 8. Blood Pressure • Blood pressure (BP) is the pressure exerted by circulating blood upon the walls of blood vessels. In other words, Blood pressure is a measurement of the force against the walls of arteries as the heart pumps blood through the body. • Expressed as systolic/diastolic pressure. Normal – 120/80 mmHg High – 140/90 mmHg
- 9. Types of Blood Pressures • Systolic blood pressure: It is the maximum pressure during systole (ventricular contraction). It is about 100-140 mm Hg. Average 120 mm Hg. • Diastolic blood pressure: It is the maximum pressure during diastole (ventricular relaxation). It is about 60-90 mm Hg. Average 80 mm Hg. • Pulse Pressure (PP) – Difference between systolic and diastolic – PP = systolic - diastolic – It is about 30-40 mm Hg • Mean Arterial Pressure (MAP) – Average pressure in arteries. – It is the diastolic pressure plus one-third of pulse pressure. – MAP = diastolic + 1/3 (systolic – diastolic) = Diastole + 1/3 PP
- 10. Blood Pressure Measurement Auscultatory Method : Auscultation of the heart means to listen to and study the various sounds arising from the heart as it pumps blood. • BP is measured by listening for Korotkoff sounds produced by turbulent flow in arteries as pressure released from blood pressure cuff Instrument: 1. Sphygmomanometer 2. Stethoscope
- 11. Measuring Blood Pressure • Blood pressure is measured with an instrument called a sphygmomanometer. • First, a cuff is placed around your arm and inflated with a pump until the circulation is cut off. • A small valve slowly deflates the cuff, and the doctor measuring blood pressure uses a stethoscope, placed over your arm, to listen for the sound of blood pulsing through the arteries. • That first sound of rushing blood refers to the systolic blood pressure; once the sound fades, the second number indicates the diastolic pressure, the blood pressure of your heart at rest. • Blood pressure is measured in millimeters of mercury (mm Hg) and recorded with the systolic number first, followed by the diastolic number. For example, a normal blood pressure would be recorded as something under 120/80 mm Hg. • Blood pressure readings can be affected by factors like: -Smoking -Coffee or other caffeinated drinks -A full bladder -Recent physical activity - Emotional status
- 12. Control of Arterial Blood Pressure • Rapidly acting mechanism (Nervous control) • Baroreceptor feedback mechanism – Baroreceptors (pressure-sensitive) • Chemoreceptor mechanism (acts like baroreceptor mechanism) • Intermediate acting mechanism • Renin-angiotensin vasoconstriction • Long-term mechanism • Renal blood volume control
- 13. Baroreceptor feedback mechanism Increased blood pressure stretches the carotid arteries and aorta causing the baroreceptors to increase action potential generation. Glossopharyngeal and vagus nerves conduct action potential to the cardioregulatory and vasomotor centers in the medulla oblongata. As a result of increased stimulation from the baroreceptors, the cardioregulatory center decreases sympathetic stimulation to the heart, which decreases the heart rate and stroke volume. The vasomotor centers decreases sympathetic stimulation to the blood vessels, causing vasodilation. The vasodilation, along with decreased heart rate and decreased stroke volume bring the elevated blood pressure back to normal. If the initial problem were a decrease in bp, the activities and effects of baroreceptors, cardiovascular center and vasomotor center would be opposite of what is illustrated.
- 14. Chemoreceptor mechanism Chemoreceptors in the carotid and aortic bodies monitor blood o2 ,Co2 and PH Glossopharyngeal and vagus nerves conduct action potential/impulse to the cardioregulatory and vasomotor centers in the medulla oblongata. Chemoreceptors in the medulla oblongata monitor blood o2 ,Co2 and PH Decreased blood o2 , IncreasedCo2 and decreased PH increase sympathetic stimulation of the heart which increases heart rate and stroke volume. Increased sympathetic stimulation of blood vessels increase vasoconstriction The vasoconstriction, along with increased heart rate and increased stroke volume ,increase blood pressure.
- 15. Kidney Action and Blood Pressure: Renin- Angiotensin Mechanism • Declining BP causes the release of renin, which triggers the release of angiotensin II • Angiotensin II is a potent vasoconstrictor that stimulates aldosterone secretion • Aldosterone enhances renal reabsorption and stimulates ADH release • As a result, BP is increased.
- 16. Renal body fluid mechanism When bp rises, output of water and salt by kidney increases This in turn decreases ECF volume and decreases blood volume. The decreased blood volume decreases pumping action of heart which return blood pressure back to normal
- 17. Hypertension Hypertension is a clinical condition characterised by continuos rise of blood pressure above normal range in respect to age and sex. • Hypertension occur when systolic blood pressure (SBP) is 140 mmHg or greater, diastolic blood pressure (DBP) of 90 mmHg or greater. Primary hypertension (90-95% of cases) • Essential hypertension refers to high blood pressure when no cause been identified. • Essential (or primary) hypertension accounts for approximately 90-95% of patients diagnosed with hypertension.
- 18. Hypertension Secondary hypertension (selected causes) • It is due to other causes.Such as- – Renal, Primary aldosteronism, Coarctation (congenital narrowing of a short section of the aorta.) of the aorta, Hyperthyroidism, Hypothyroidism, Chronic alcohol use, Drugs. • Major Risk Factors – Smoking, Dyslipidemia, Diabetes mellitus, Age older than 60 years, Sex (men and postmenopausal women), Family history of cardiovascular disease.
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