Blood pressure and its regulation

Arterial blood pressure can be defined as the lateral pressure exerted by the moving column of blood on the walls of the arteries.

1. BLOOD PRESSURE- NEURAL AND CHEMICAL REGULATION BY, S.HARSRITHA (17BIOB07)

2. BLOOD PRESSURE Arterial blood pressure can be defined as the lateral pressure exerted by the moving column of blood on the walls of the arteries . measured as mmHg. Changes in pressure are the driving force that moves blood through the circulatory system.

3. SIGNIFICANCE To ensure the blood flow to various organs . Plays an important role in exchange of nutrients and gases across the capillaries. Required to form urine . Required for the formation of the lymph.

4. NORMAL VALUES Normal Adult range Can fluctuate within a wide range and still be normal Systolic/diastolic 100/60 - 140/80

5. Normal Adult range  Can fluctuate within a wide range and still be normal  Systolic/diastolic  100/60 - 140/80 The maximum pressure during ventricular contraction is called the systolic pressure. Normal range (90-140 mm Hg). The lowest pressure that remains in the arteries before the next ventricular contraction is called the diastolic pressure. Normal range (60 -90 mm Hg). Arterial blood pressure rises and falls according to cardiac cycle phases.

6. Pulse pressure is a measure of the strength of the pressure wave. Denotes the difference between systolic and diastolic pressure.

7. Mean arterial pressure is estimated as diastolic pressure plus one-third of pulse pressure. Mean arterial pressure is closer to diastolic pressure than to systolic pressure because diastole lasts twice as long as systole.

8. Mean arterial pressure (MAP) is a function of cardiac output and resistance in the arterioles (peripheral resistance ). The cardiac output is defined as the volume discharged from the ventricle per minute. Peripheral resistance defined as the resistance to flow offered by the arterioles BP = Cardiac output X PR

9. FACTORS MAINTAINING BLOOD PRESSURE Cardiac output (CO= SV X PR ) Circulating blood volume ( This mainly affects systolic B.P ) Elasticity of the vessel wall Peripheral resistance.

10. RECORDING OF BLOOD PRESSURE Palpatory method Auscultatory method PALPATORY METHOD which records the pressure at which the subject feels the first pulse in the artery. The detected pressure is systolic pressure.

11. MEASUREMENT DEVICE Automated bp device Aneroid sphygmomanometer Simple mercury sphygmomanometer

12. AUSCULTATORY METHOD in which the researcher detects the pulse by listening via a stethoscope placed in the antecubital fossa over the brachial artery. When the cuff pressure is higher than the systolic pressure, no sound is to be heard. The pressure at which the first sound is heard is the systolic pressure, at which the blood flow resumes and is turbulent. As the cuff pressure continues to drop, the sound becomes muffler and finally disappears. The pressure at which the sound disappears was the considered the diastolic pressure

13. PRINCIPLE INVOLVED IN RECORDING BLOOD PRESSURE

14. HYPERTENSION: High blood pressure, clinically diagnosed when above 140/90 mmHg. HYPOTENSION: Low blood pressure, clinically diagnosed when below 100/60 mmHg.

15. NEURAL REGULATION REGULATION OF BLOOD PRESSURE Achieved through the role of cardiovascular centers located in the medulla oblongata and baroreceptor stimulation This cluster of neurons responds to changes in blood pressure as well as blood concentrations of oxygen, carbon dioxide, and other factors such as pH . Baroreceptor: A nerve ending that is sensitive to changes in blood pressure.

16. CARDIAC CENTER Autonomic control of heart

17. VASOMOTOR CENTER Autonomic control of blood vessels Stimulation of vasomotor center: VASOCONSTICTION Inhibition of vasomotor center: VASODILATION

18. BARORECEPTOR FUNCTION Receptors located within thin areas of blood vessels and heart chambers that respond to the degree of stretch caused by the presence of blood. Send impulses to the cardiovascular center to regulate blood pressure. Vascular baroreceptors are found primarily in sinuses (small cavities) within the aorta and carotid arteries. The aortic sinuses are found in the walls of the ascending aorta just superior to the aortic valve, whereas the carotid sinuses are located in the base of the internal carotid arteries.

19. BARORECEPTOR REFLEXES

20. CHEMICAL REGULATION Dilation or constriction of the blood vessels by vasodilators and vasocontrictors .

21. CHEMICAL VASOCONSTRICTION Increased concentration of calcium (Ca2+ ions) and phosphorylated myosin within vascular smooth muscle cells. A signal transduction cascade leads to increased intracellular calcium from the sarcoplasmic reticulum through IP3 mediated calcium release. Enhances calcium entry across the sarcolemma through calcium channels . The rise in intracellular calcium interacts with calmodulin, which in turn activates myosin light chain kinase.

22. This enzyme is responsible for phosphorylating the light chain of myosin to stimulate cross-bridge cycling. Once elevated, the intracellular calcium concentration is returned to its basal level through a variety of protein pumps and calcium exchanges located on the plasma membrane and sarcoplasmic reticulum. This reduction in calcium removes the stimulus necessary for contraction allowing for a return to baseline . Endogenous vasoconstrictors include ATP, epinephrine, and angiotensin II.

23. Vasodilation is modulated by calcium ion concentration and myosin phosphorylation within vascular smooth muscle cells. Dephosphorylation by myosin light-chain phosphatase and induction of calcium symporters and antiporters that pump calcium ions out of the intracellular compartment both contribute to smooth muscle cell relaxation and therefore vasodilation. This is accomplished through reuptake of ions into the sarcoplasmic reticulum via exchangers and expulsion across the plasma membrane . Endogenous vasodilators include arginine and lactic acid. CHEMICAL VASODILATION

24. HORMONAL REGULATION EPINEPHRINE NOR EPINEPHRINE

25. ANTIDIURETIC HORMONE: VASOPRESSIN Increased release by posterior pituitary gland in response to decreased blood pressure and decreased blood volume. Promotes water reabsorption by kidneys Vasoconstriction of vessels

26. RENAL REGULATION When blood volume is low, renin, excreted by the kidneys , stimulates production of angiotensin I, which is converted into angiotensin II. This substance has many effects , including increase in blood pressure due to its vasoconstrictive properties . The cells that excrete renin are called juxtaglomerular cells . When blood volume is low, juxtaglomerular cells in the kidneys secrete renin directly into circulation. Plasma renin then carries out the conversion of angiotensinogen released by the liver to angiotensin I. Aldosterone secretion from the adrenal cortex is induced by angiotensin II and causes the tubules of the kidneys to increase the reabsorption of sodium and water into the blood, thereby increasing blood volume and blood pressure.

27. RENIN ANGIOTENSIN ALDOSTERONE SYSTEM

28. REFERENCES: Rodney Rhoades, David R. Bell Medical Physiology: Principles for Clinical Medicine. http://www.interactive-biology.com/4301/blood-pressure-short-term-and-long-term-control-measures / Boundless Anatomy and Physiology