Blood pressure is the force exerted by circulating blood on the walls of blood vessels.
It is crucial to maintain optimal blood pressure for the delivery of oxygen and nutrients to tissues and organs.
The regulation of blood pressure involves several mechanisms:
1) Baroreceptors:
Location: Aortic arch and carotid arteries.
Function: Detect changes in blood pressure.
Increased BP: Baroreceptors signal the medulla oblongata to activate the parasympathetic nervous system, reducing heart rate and dilating blood vessels, lowering BP.
Decreased BP: Signals the sympathetic nervous system, increasing heart rate and constricting blood vessels, raising BP.
2) Renin-angiotensin-aldosterone system (RAAS):
Activation: Triggered by low BP or blood volume.
Mechanism:
Renin (from kidneys) converts angiotensinogen into angiotensin I.
Angiotensin I is converted to angiotensin II by ACE.
Angiotensin II causes vasoconstriction and stimulates aldosterone release, promoting sodium and water retention, increasing BP and blood volume.
3) Kidneys:
Function: Regulate BP by managing fluid balance.
High BP: Kidneys excrete more sodium and water, lowering blood volume and BP.
Low BP: Kidneys retain sodium and water, increasing blood volume and BP.
4) Autonomic nervous system:
Sympathetic: Increases heart rate, contractility, and vasoconstriction to raise BP.
Parasympathetic: Slows heart rate and dilates blood vessels to lower BP.
5) Local factors:
Vasodilation: Local tissue hypoxia, pH changes, or chemicals like nitric oxide can cause blood vessels to dilate, reducing BP.
Vasoconstriction: Opposite effects can increase BP.