Neural control of BP - 2 • The vasomotor center integrates all these information • The vasomotor sends decision to the ANS center: - Both parasympathetic and sympathetic innervate the S/A node can accelerate or slow down the heart rate - The sympathetic NS innervates the myocardium and the smooth muscle of the arteries and veins promotes vasoconstriction
Hormonal control of BP • Hormones can control blood • Control of blood vessel radius vessel radius and blood volume, - Epinephrine stroke volume and heart rate - Angiotensin II - Vasopressin (?) • On a normal basis, blood vessel radius and blood volume are the • Control of blood volume main factors - Anti-diuretic hormone (vasopressin) • If there is a critical loss of - Aldosterone pressure, then the effects on HR and SV will be noticeable (due to • Control of heart rate and stroke epinephrine kicking in) volume - Epinephrine
Control of blood vessel radius • Epinephrine: secreted by the • Angiotensin II secretion: - Decreased flow of filtrate in kidney adrenal medulla and ANS reflex increase HR, stroke volume and tubule is sensed by the promotes vasoconstriction of most Juxtaglomerular apparatus (a small blood vessel smooth muscles. organ located in the tubule) secretion of renin • Angiotensin II promotes - Renin activates angiotensinogen, a protein synthesized by the liver and vasoconstriction circulating in the blood angiotensin I - Angiotensin I is activated by a lung enzyme, Angiotensin-Activating Enzyme (ACE), angiotensin II - Angiotensin II is a powerful vasoconstricted of blood vessel smooth muscles
Control of blood volume • Anti-diuretic hormone = ADH - Secreted by the posterior pituitary in response to ↑blood osmolarity (often due to dehydration) - Promote water reabsorption by the kidney tubules H2O moves back into the blood less urine formed
Control of blood volume • Aldosterone: - Secretion by the adrenal cortex triggered by angiotensin II - Promotes sodium reabsorption by the kidney tubules (Na+ moves back into the blood) - H2O follows by osmosis - Whereas ADH promotes H2O reabsorption only (in response to dehydration), aldosterone promotes reabsorption of both H2O and salt (in response to ↓ BP)
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