MCAT fluids and the circulatory system study guide

What is fluid density?

Density (C1) is mass per unit volume. Formula: C1 = \frac{m}{V} Units: kg/m³ or g/cm³.

State Pascal's principle.

In a confined fluid at rest, any change in pressure applied at any point is transmitted undiminished throughout the fluid.

True or False: Fluids can resist shear stress.

False. Fluids flow and cannot resist shear stress, unlike solids.

What is hydrostatic pressure?

Hydrostatic pressure (C0) increases with depth. Formula: C0 = C1gh Where: C1 = density, g = acceleration due to gravity, h = depth.

Fill in the blank: The equation of continuity states that ___.

mass flow rate remains constant in a closed system. Formula: C1_1A_1v_1 = C1_2A_2v_2.

Comparison: Flow rate vs. velocity.

Flow rate (Q) is volume per time: Q = Av. Velocity (v) is distance per time.

What does Bernoulli's equation relate to?

Bernoulli's equation relates pressure, velocity, and height in flowing fluids. Formula: P + \frac{1}{2}C1v^2 + C1gh = constant.

Cause → Effect: Increased fluid velocity leads to ___.

Decreased pressure, according to Bernoulli's principle.

Define viscosity.

Viscosity is a measure of a fluid's resistance to flow. Units: Pa·s (Pascal-seconds) or N·s/m².

True or False: Ideal fluids are compressible.

False. Ideal fluids are incompressible and non-viscous.

What is laminar flow?

Laminar flow is smooth and orderly, with parallel layers. Velocity is consistent across the fluid.

Fill in the blank: In turbulent flow, fluid particles move ___.

in chaotic paths, resulting in mixing and eddies.

Describe the role of surface tension in fluids.

Surface tension causes the surface of a fluid to behave like an elastic sheet. It affects droplet formation and capillary action.

What is the principle of Archimedes?

An object submerged in a fluid experiences a buoyant force equal to the weight of the fluid displaced.

Cause → Effect: Increased temperature in a fluid results in ___.

Decreased viscosity, allowing easier flow.

What is the significance of Reynolds number?

Reynolds number predicts flow regime: - < 2000: Laminar flow - > 4000: Turbulent flow - 2000-4000: Transitional flow.

What is the primary function of the circulatory system?

Transport nutrients, gases, hormones, and waste throughout the body.

Define cardiac output.

The volume of blood the heart pumps per minute, calculated as $\displaystyle CO = HR imes SV$.

True or False: Blood viscosity decreases with higher hematocrit.

True. Higher hematocrit increases blood viscosity, making flow more resistant.

What is the role of the valves in the heart?

Prevent backflow of blood, ensuring unidirectional flow through the heart.

Fill in the blank: Blood pressure is highest in the _____.

Aorta.

List the three main components of the circulatory system.

- Heart - Blood vessels - Blood

How does resistance affect blood flow?

Increased resistance decreases blood flow according to the equation: $\displaystyle Q = \\frac{P}{R}$.

What factors influence blood flow?

- Blood vessel diameter - Blood viscosity - Blood pressure gradient

True or False: Blood flow is constant in all blood vessels.

False. Blood flow varies based on vessel diameter and location.

What is the significance of the Frank-Starling law?

It states that the stroke volume increases with the end-diastolic volume.

Compare arteries and veins.

Arteries carry blood away from the heart; veins return blood to the heart.

What happens during systole?

The heart contracts, ejecting blood into the arteries.

List factors that increase stroke volume.

- Increased venous return - Increased contractility - Decreased afterload

What is the effect of vasodilation on blood pressure?

Vasodilation decreases peripheral resistance, leading to lower blood pressure.

How does the body regulate blood pressure?

Through baroreceptors, hormonal responses, and renal function adjustments.

What is systemic circulation?

The circulation pathway that delivers oxygenated blood to tissues and returns deoxygenated blood to the heart.

Define mean arterial pressure (MAP).

MAP is the average pressure in a person's arteries during one cardiac cycle, calculated as $\displaystyle MAP = DBP + \\frac{1}{3}(SBP - DBP)$.

What role does the autonomic nervous system play in circulation?

Regulates heart rate and blood vessel tone, influencing blood pressure.

Describe the flow of blood through the heart.

Blood flows: Right atrium → Right ventricle → Lungs → Left atrium → Left ventricle.

True or False: Capillaries have thicker walls than arteries.

False. Capillaries have thin walls to facilitate gas exchange.

What is the relationship between blood flow and pressure?

Blood flow is directly proportional to pressure. As pressure increases, flow increases if resistance is constant.

True or False: Increased resistance decreases blood flow.

True. According to Poiseuille's law, flow decreases as resistance increases.

Fill in the blank: Blood flow is inversely proportional to ______.

Resistance.

What is Poiseuille's law?

It states that $\displaystyle Q = \\frac{\Delta P \pi r^4}{8 \eta L}$, where $\displaystyle Q$ is flow rate.

Describe how blood pressure is regulated.

- Baroreceptors monitor pressure - Autonomic nervous system adjusts heart rate - Hormones like adrenaline affect vascular tone.

What factors influence vascular resistance?

- Vessel diameter - Vessel length - Blood viscosity.

Which has higher resistance, arterioles or veins?

Arterioles have higher resistance due to their smaller diameter.

True or False: Blood flow is constant throughout all vessels.

False. Blood flow varies depending on the vessel type and its resistance.

Cause → Effect: Increased vessel diameter leads to ______.

Decreased resistance and increased blood flow.

What happens to blood flow during exercise?

Blood flow increases to muscles due to decreased resistance and increased cardiac output.

Define cardiac output (CO).

CO = stroke volume (SV) x heart rate (HR). It represents the volume of blood the heart pumps per minute.

What is the equation for blood pressure?

Blood pressure = cardiac output x systemic vascular resistance.

Which vessel type has the lowest blood pressure?

Veins have the lowest blood pressure compared to arteries and capillaries.

True or False: Blood flow is the same in systemic and pulmonary circulation.

True. Despite different pressures, flow rates remain equal.

What role do capillaries play in blood flow?

Capillaries allow for nutrient and gas exchange due to their large surface area and thin walls.

What happens to blood pressure in atherosclerosis?

Blood pressure increases due to increased vascular resistance from plaque buildup.

How does vasodilation affect blood pressure?

Vasodilation decreases vascular resistance, leading to a decrease in blood pressure.

What is the equation for resistance in blood vessels?

Resistance $\displaystyle R = \\frac{8 \eta L}{\pi r^4}$, where \displaystyle  is viscosity, $\displaystyle L$ is length, and $\displaystyle r$ is radius.

How does blood viscosity affect flow?

Higher viscosity results in greater resistance and reduced flow.

Describe the role of the autonomic nervous system in blood flow.

- Sympathetic nerves increase heart rate and contractility - Parasympathetic nerves decrease heart rate.