Cardiovascular Physiology II Flashcards
What is necessary to have flow in a vascular system?
A pressure gradient is required; flow occurs from an area of higher pressure to an area of lower pressure.
What equation represents the relationship among pressure, flow, and resistance?
Flow = Pressure Gradient / Resistance
What happens to flow when resistance increases, assuming pressure remains constant?
Flow decreases as resistance increases.
What factors determine resistance in a tube (e.g., blood vessels)?
Resistance = (8 × viscosity × length) / (π × radius^4)
How does shortening a tube affect flow and resistance?
Shortening the tube decreases resistance, making it easier to maintain flow.
What effect does narrowing a tube have on flow?
Narrowing a tube increases resistance, making it harder to maintain the same level of flow.
How does viscosity affect the ease of flow through a tube?
Higher viscosity (like a milkshake) makes flow more difficult compared to lower viscosity (like soda).
Which factor has the greatest impact on regulating blood flow in the body?
The radius of the blood vessel; small changes in radius lead to significant changes in resistance.
How does vessel radius relate to resistance?
Resistance is inversely related to the fourth power of the radius, meaning small changes in radius can lead to large changes in resistance.
Can the length of blood vessels change acutely?
No, the length of blood vessels does not change acutely; they are structured to be as long as needed.
Under what circumstances can blood viscosity change significantly?
Blood viscosity can change in disease processes or in cases like blood doping, which can lead to cardiovascular events.
What primarily regulates blood flow distribution in the vascular system?
The diameter of the arterioles.
What are the two broad categories of mechanisms that change the diameter of arterioles?
Local mechanisms and distant mechanisms.
What are three examples of local mechanisms that affect arterioles?
- Tissue metabolites (leading to dilation)
- Myogenic response
- Endothelial factors
What is “active hyperemia”?
The increase in blood flow resulting from increased metabolic activity in a tissue.
What is “reactive hyperemia”?
The increase in blood flow following a temporary restriction of blood flow.
How do tissue metabolites affect arterioles during active hyperemia?
Increased metabolic activity releases metabolites that cause arterioles to dilate.
What role do endothelial cells play in regulating blood flow?
Endothelial cells release vasoactive substances in response to shear stress from blood flow, contributing to vasodilation.
What is “myogenic control” in relation to blood flow?
The ability of arterioles to respond to changes in blood pressure by dilating or constricting to maintain constant blood flow.
What is the baroreceptor reflex?
A rapid reflex that maintains blood pressure by adjusting heart rate and vascular resistance in response to changes in arterial blood pressure.
How does the sympathetic nervous system affect blood pressure during the baroreceptor reflex?
It increases cardiac output and total peripheral resistance to raise blood pressure when it decreases.
What is the renin-angiotensin-aldosterone system’s role in blood pressure regulation?
It increases blood pressure through mechanisms such as vasoconstriction, sodium reabsorption, and fluid retention.
How can pharmacological agents help manage high blood pressure?
By decreasing cardiac output (e.g., beta blockers), reducing total peripheral resistance (e.g., ACE inhibitors), or decreasing fluid volume (e.g., diuretics).
What are the components of mean arterial pressure?
Cardiac output and total peripheral resistance.
Why is the production of vasodilator metabolites important during exercise?
It facilitates the increase in blood flow to meet the heightened metabolic demands of active tissues.
What happens to cardiac output during exercise?
Cardiac output increases due to an increase in heart rate and stroke volume.
How is blood flow redistributed during exercise?
More blood flow is directed to active skeletal muscle, while less blood flow goes to other organs.
What is the effect of sympathetic nervous system activation on blood flow to the viscera?
The sympathetic nervous system causes vasoconstriction of the blood vessels feeding the viscera, leading to decreased blood flow.
How do active muscles receive increased blood flow despite sympathetic vasoconstriction?
Increased blood flow to active muscles is driven by local metabolic signals that induce vasodilation, counteracting the vasoconstrictor effect.
What is active hyperemia?
The increase in blood flow due to increased metabolic activity of the tissue.
What is reactive hyperemia?
The increase in blood flow following a temporary restriction of blood flow.
What contributes to the widening of the arterial-venous (a-v) oxygen difference during exercise?
The drop in venous oxygen content due to increased oxygen consumption by the muscles and blood shunting from less active tissues.
How does arterial oxygen content change during intense exercise?
Arterial oxygen content generally remains stable during peak exercise in most individuals.
What changes occur in blood pressure during exercise?
Mean arterial pressure increases modestly, diastolic blood pressure may remain constant or decrease, and systolic blood pressure increases linearly with workload.
What indicates a potential problem if systolic blood pressure falls during exercise?
A falling systolic blood pressure during increasing workload suggests possible ischemia or heart problems.
