1. Blood Flow

2. Due to the pressure difference of two vessel ends

3. The rate of blood flow to an organ is related to the resistance to flow in the small arteries and arterioles that serve the organ Vasodilatation decreases resistance and increases the flow, where as vasoconstriction increases the resistance and decreases the flow

4. Length of the blood vessel – When the length is more resistance also increase Viscosity of blood – when the viscosity increases resistance also increases Radius of the blood vessel – when the radius is more resistance is less

5. The sum of all the vascular resistances within the systemic circulation is called the Total Peripheral Resistance

6. Vasodilators Nitric oxide Bradykinin Prostacyclin Vasoconstrictors Endothelin 1

7. When the vascular blood pressure is high the vessels constrict and reduce the blood flow to the tissues When the vascular blood pressure is low the vessels dilate and increase the blood flow to the tissues

8. When the Oxygen concentration decreases due to increased metabolic rate and when the Carbon Dioxide concentration increases local vasodilatation occurs and increase the blood flow to the tissues

9. By Anti Diuretic Hormone ( ADH ) By Aldosterone By Atrial Natriuretic Factor ( ANF ) By Renin – Angiotensin system

10. When blood plasma osmolality ( osmotic pressure / thickness ) increases; it detects by osmoreceptors in hypothalamus and stimulate the posterior pituitary to secrete ADH ADH stimulate water reabsorption from the filtrate during the urine formation and thereby increase the fluid volume in the plasma as well as the pressure

11. Aldosterone secreted by Adrenal Cortex stimulates the reabsorption of salt Retention of salt indirectly promotes retention of water Which will lead to increase the pressure and volume of blood

12. ANF is produced by the atria of the heart and promoting salt and water excretion in the urine By that it reduces the blood volume as well as the pressure

13. When blood flow and pressure reduce in renal artery a group of cells in kidney secretes an enzyme called Renin in to blood This renin leads to activation of Angiotensin which can increase vasoconstriction of arteries and thereby increase the pressure

14. It also leads to secretion of aldosterone which leads to salt and water retention by kidneys and increase the volume of blood