Chapter 20 - Section 20.2 - Study Guide - Assess Your Learning Outcomes - Page 798: 18

**Mechanisms of Action by Various Hormones on Blood Pressure:** **1. **Angiotensin II:** - Angiotensin II is a potent vasoconstrictor hormone. It acts on blood vessels, particularly arterioles, causing them to constrict. This increases peripheral resistance, leading to an elevation in blood pressure. Angiotensin II also stimulates the release of aldosterone, which promotes sodium and water retention, further increasing blood volume and pressure. **2. **Aldosterone:** - Aldosterone is a hormone produced by the adrenal glands that regulates electrolyte and fluid balance. It acts on the kidneys, promoting the reabsorption of sodium and water and the excretion of potassium. This mechanism increases blood volume by retaining sodium and water, which subsequently raises blood pressure. **3. **Natriuretic Peptides:** - Natriuretic peptides, such as atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are released by the heart in response to increased blood volume and pressure. These peptides have vasodilatory and diuretic effects. They relax blood vessels, reduce peripheral resistance, and increase urinary excretion of sodium and water, leading to decreased blood volume and pressure. **4. **Antidiuretic Hormone (ADH) - Vasopressin:** - ADH, also known as vasopressin, is released by the posterior pituitary gland in response to increased osmolarity or decreased blood volume. ADH acts on the kidneys to enhance water reabsorption, concentrating urine and conserving water. This helps maintain blood volume and elevate blood pressure. **5. **Epinephrine and Norepinephrine:** - Epinephrine and norepinephrine are released by the adrenal glands and sympathetic nerve endings during the body's "fight or flight" response. These hormones have similar effects on blood pressure: - They bind to adrenergic receptors on blood vessel walls, causing vasoconstriction, especially in arterioles. This increases peripheral resistance and raises blood pressure. - They stimulate the heart, increasing heart rate and contractility, leading to an increase in cardiac output and subsequent blood pressure elevation. - They can also promote the release of renin, initiating the renin-angiotensin-aldosterone system, which contributes to blood pressure regulation. In summary, these hormones play critical roles in regulating blood pressure through their effects on vascular tone, blood volume, and cardiac function. They collectively contribute to maintaining blood pressure within a narrow range, ensuring adequate tissue perfusion while responding to changes in physiological demands and stressors.

**Mechanisms of Action by Various Hormones on Blood Pressure:** **1. **Angiotensin II:** - Angiotensin II is a potent vasoconstrictor hormone. It acts on blood vessels, particularly arterioles, causing them to constrict. This increases peripheral resistance, leading to an elevation in blood pressure. Angiotensin II also stimulates the release of aldosterone, which promotes sodium and water retention, further increasing blood volume and pressure. **2. **Aldosterone:** - Aldosterone is a hormone produced by the adrenal glands that regulates electrolyte and fluid balance. It acts on the kidneys, promoting the reabsorption of sodium and water and the excretion of potassium. This mechanism increases blood volume by retaining sodium and water, which subsequently raises blood pressure. **3. **Natriuretic Peptides:** - Natriuretic peptides, such as atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are released by the heart in response to increased blood volume and pressure. These peptides have vasodilatory and diuretic effects. They relax blood vessels, reduce peripheral resistance, and increase urinary excretion of sodium and water, leading to decreased blood volume and pressure. **4. **Antidiuretic Hormone (ADH) - Vasopressin:** - ADH, also known as vasopressin, is released by the posterior pituitary gland in response to increased osmolarity or decreased blood volume. ADH acts on the kidneys to enhance water reabsorption, concentrating urine and conserving water. This helps maintain blood volume and elevate blood pressure. **5. **Epinephrine and Norepinephrine:** - Epinephrine and norepinephrine are released by the adrenal glands and sympathetic nerve endings during the body's "fight or flight" response. These hormones have similar effects on blood pressure: - They bind to adrenergic receptors on blood vessel walls, causing vasoconstriction, especially in arterioles. This increases peripheral resistance and raises blood pressure. - They stimulate the heart, increasing heart rate and contractility, leading to an increase in cardiac output and subsequent blood pressure elevation. - They can also promote the release of renin, initiating the renin-angiotensin-aldosterone system, which contributes to blood pressure regulation. In summary, these hormones play critical roles in regulating blood pressure through their effects on vascular tone, blood volume, and cardiac function. They collectively contribute to maintaining blood pressure within a narrow range, ensuring adequate tissue perfusion while responding to changes in physiological demands and stressors.