Regulation of arterial pressure in animals
Two mechanisms regulate the arterial pressure. Rapidly acting short term regulatory mechanism operates through nerves or hormones and Long term control of arterial pressure.
When the BP undergoes change, after few hours to few days the nerves loose their power to control pressure because receptors adapt. Long-term mechanisms come into play, which involve renal fluid volume-pressure control mechanisms.
Short term regulation
- Nervous regulation
- Baroreceptor reflex
- Atrial volume receptor reflex
- Bain bridge reflex
- Psychogenic responses
- Defense alarm reaction
- Vaso-vagal syncope
- Chemoreceptor reflex
- Hormonal regulation
- Renin- angiotensin system
- Vasopressin
Long term Regulation
Long term control is brought about by renal regulation of blood volume. Blood volume has a direct effect on cardiac output and therefore affects blood pressure.
Direct renal mechanism
An increase in BP or blood volume causes increased filtration rate in the kidney. As filtration rate exceeds the reabsorption rate in the kidney tubules, more urine is produced resulting in increased fliud loss and decreased blood volume.
Indirect renal mechanism
If arterial BP declines, Renin angiotensin system comes into play. Angiotensin II also stimulates ADH release from the posterior pituitary gland. ADH increases water reabsorption from the kidney tubules. Increased sodium and water reabsorption from the kidneys leads to increased blood volume and BP.