30 Questions
Which hormone regulates blood pressure by altering resistance and blood volume?
Angiotensin II
What is the role of the renin-angiotensin system in regulating blood pressure?
It initiates the synthesis of angiotensin II through the nervous system, which then causes the release of other hormones.
What is the role of aldosterone in regulating blood pressure?
Aldosterone increases fluid retention and sodium reabsorption to increase blood volume and pressure.
How does antidiuretic hormone (ADH) regulate blood pressure?
ADH increases fluid retention and water reabsorption to increase blood volume and pressure.
What is the effect of atrial natriuretic peptide (ANP) on blood pressure?
ANP increases urine output to decrease blood volume and pressure.
Where does the liver-produced angiotensinogen (an inactive hormone) come from?
The liver continuously releases angiotensinogen into the blood.
What is the role of baroreceptors in response to an increase in blood pressure?
Increase the frequency of nerve signals to the cardiac and vasomotor centers
What effect does the activation of the cardioacceleratory center have on the heart rate?
Decreases heart rate
How does the cardioinhibitory center affect the SA and AV nodes?
Decreases nerve signals along parasympathetic pathways
What is the result of decreasing nerve signals along sympathetic pathways to blood vessels?
Vasodilation and decrease in resistance
How does the decrease in cardiac output affect blood pressure?
Lowers blood pressure
What does shifting blood to venous reservoirs result in?
Decrease in venous return
What is the purpose of the tight junctions between endothelial cells?
To secure the endothelial cells to one another
What is the main function of the intercellular clefts between endothelial cells?
To facilitate the movement of fluid containing small substances
What is the purpose of the fenestrations in fenestrated capillaries?
To provide small, thin regions in the endothelial cells
Which of the following is NOT a characteristic of continuous capillaries?
They have fenestrations in the endothelial cells
What is the main difference between continuous and fenestrated capillaries?
Continuous capillaries have a complete, continuous lining of endothelial cells, while fenestrated capillaries have fenestrations
Where are continuous capillaries found in the body?
In muscle, skin, thymus, lungs, brain, and spinal cord
What is the term used to describe the cyclical process of the precapillary sphincters contracting and relaxing?
Vasomotion
What percentage of the total capillary beds are open at any given time?
25%
What is the typical range for the rate of contracting and relaxing of the precapillary sphincters?
5-10 cycles per minute
What is the typical unit used to express perfusion, the specific amount of blood entering capillaries per unit time per gram of tissue?
mL/min/g
What is the purpose of veins in the cardiovascular system?
To serve as a blood reservoir
What are the smallest veins, measuring 8 to 100 micrometers in diameter?
Venules
What is the relationship between blood pressure gradient and total blood flow?
As the blood pressure gradient increases, total blood flow is greater.
What is the relationship between cardiac output and blood pressure gradient?
An increase in cardiac output will increase the pressure gradient.
What is the relationship between blood flow and resistance?
Blood flow is inversely related to resistance.
What factors can increase blood resistance?
Increase in blood viscosity and vessel length, and decrease in vessel lumen diameter.
How does an increase in resistance affect systemic blood pressure?
Increased resistance leads to elevated arterial blood pressure.
What is the effect of a decrease in vessel lumen diameter on blood flow?
Decreased vessel lumen diameter decreases blood flow.
Study Notes
Hormonal Regulation of Blood Pressure
- Angiotensin II, aldosterone, antidiuretic hormone, and atrial natriuretic peptide are hormones that regulate blood pressure by altering resistance, blood volume, or both.
Renin-Angiotensin System
- The renin-angiotensin system is involved in both short-term neural regulation and long-term hormonal regulation of blood pressure.
- The liver produces angiotensinogen, an inactive hormone, which is converted to angiotensin II, a hormone that increases blood pressure.
- Angiotensin II causes the release of other hormones, such as aldosterone, which increases blood volume by promoting sodium retention in the kidneys.
Baroreceptors and Blood Pressure Regulation
- Baroreceptors in the aortic arch, carotid sinuses, or both detect increased stretch in the blood vessel wall, reflecting an increase in blood pressure.
- Signals are relayed to the cardioacceleratory center, which decreases heart rate and stroke volume, resulting in a decrease in cardiac output.
- The vasomotor center simultaneously decreases nerve signals to blood vessels, resulting in net vasodilation and a decrease in resistance.
Capillaries and Blood Flow
- Continuous capillaries have a complete, continuous lining of endothelial cells and a complete basement membrane.
- Fenestrated capillaries have thin areas called fenestrations that allow the movement of small substances, such as water, glucose, and ions.
- Precapillary sphincters cycle through contraction and relaxation, controlling blood flow into capillaries.
Veins and Blood Flow
- Veins merge and drain into larger vessels with increasing diameter, serving as a blood reservoir for the cardiovascular system.
- Venules are the smallest veins, measuring from 8 to 100 micrometers in diameter, and drain blood from capillaries.
Blood Flow and Blood Pressure
- Blood flow is directly proportional to the pressure gradient and inversely proportional to resistance.
- Increasing cardiac output increases the pressure gradient, while increasing resistance decreases blood flow.
Test your knowledge on how baroreceptors detect increased stretch in blood vessels and the subsequent response in the medulla oblongata. Understand the role of sensory neurons, vagus nerve, glossopharyngeal nerve, and the cardioacceleratory center.
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