Pressure, Flow and Resistance Flashcards

Question

What happens during vasodilation?

Answer 1

During vasodilation: The arteriole radius increases, resulting in reduced resistance.

Answer 2

Adrenaline Atrial natriuretic peptide Histamine Flow

Answer 3

At rest, arterioles are partially constricted.

Answer 4

The thicker the fluid, the higher the viscosity, and the higher the resistance. Red cell mass and plasma proteins make blood very viscous, which reduces flow.

Answer 5

Blood is 3-4 times thicker than water, which would alone reduce the flow

Answer 6

Since blood is a non-Newtonian fluid, it behaves differently from simple fluids, and the usual relationship between viscosity and flow does not apply in the same way.

Answer 7

Laminar flow occurs when viscous drag at the sides of the tube slows the fluid, so the fastest movement (flow) happens in the center of the tube. This effect becomes more apparent as the radius of the tube becomes smaller.

Answer 8

In laminar flow, cells tend to align in the fastest-moving fluid, a phenomenon known as **axial streaming.**

Answer 9

In small vessels, laminar flow effectively reduces viscosity, which is known as the **Fåhraeus-Lindqvist effect.**

Answer 10

Red blood cells = 7 μm. Capillaries = 6 μm.

Answer 11

Red blood cells are very deformable and can slip easily through the capillaries, allowing them to pass through despite their size difference.

Answer 12

The viscosity of blood in capillaries is similar to plasma because red blood cells are able to pass through easily.

Answer 13

High viscosity (e.g., from a high red blood cell count) can lead to: Increased total peripheral resistance (TPR) Increased mean arterial pressure (MAP), which may contribute to hypertension.

Answer 14

Turbulent flow can occur when: There is high velocity, Sharp edges or branch points are present, especially in large tubes. These factors can disrupt laminar flow, leading to turbulence.

Answer 15

Turbulence significantly increases resistance in the blood vessels.

Answer 16

Narrowed heart valves causing high velocity blood flow leads to murmurs. Narrowed airways causing high velocity airflow leads to wheezing.

Answer 17

Turbulence can also cause: Damage to the vessel wall, Activation of clotting mechanisms.

Answer 18

Flow increases more gradually with pressure, as shown by the green line representing flow autoregulation (e.g., cerebral circulation). Passive distention occurs with pressure, causing a rapid increase in flow, as shown by the red line (e.g., pulmonary circulation). In rigid tubes (blue line), flow increases linearly with pressure.

Answer 19

As the fluid flows through an artery (modeled as a resistor), the pressure drops from a region of high pressure (P₁) on the left to a region of lower pressure (P₂) on the right. This causes the pressure to decrease as the fluid flows from left to right.

Answer 20

The total pressure drop is the sum of the individual pressure drops across the resistances in series and parallel: pressure drop across RA = PX pressure drop across RB = PY

Answer 21

the nephron is represented with 2 regions: region A - total resistance RA = R1+ R2, where R1 is the afferent arteriole and R2 is the efferent arteriole region b - total resistance RB = 1/ [1/r3 + 1/r4), where R3 and R4 represent the peritubular capillaries.

Answer 22

The cardiovascular system is a single circulation with two pumps in series: The right ventricle pumps deoxygenated blood to the lungs. The left ventricle pumps oxygenated blood to the systemic tissues.

Answer 23

The pulmonary vasculature has: Low resistance, Low pressure (~16 mmHg), and It is in series with the systemic vasculature.

Answer 24

The systemic vasculature has: High resistance, High pressure (~92 mmHg), and It is mostly in parallel with the vascular structures of the brain, GI tract, and muscles.

Answer 25

The flow out of the RV must match the flow out of the LV. Cardiac output (CO) is the same for both ventricles (~5 L/min

Answer 26

The venous return (~5 L/min) must match the flow into the RV, ensuring the same volume as the flow out of the LV.

Answer 27

Filling pressure is determined by Central Venous Pressure (CVP) and is also known as PRELOAD.

Answer 28

Resistance to flow is known as Total Peripheral (Systemic) Resistance (TPR), which determines the pressure load on the left heart and is referred to as AFTERLOAD.

Answer 29

Cardiac output (CO) is the product of Stroke Volume (SV) and Heart Rate (HR):

Answer 30

The two levels of control are: Changing perfusion pressure will change blood flow. Blood flow through each organ/tissue can be regulated independently because they are in parallel with each other.

Answer 31

Blood flow can be regulated independently by selective regulation of vascular resistance in the target organ.

Answer 32

Perfusion pressure refers to the pressure of the blood within the individual tissues, NOT the mean arterial pressure (MAP).

Answer 33

CO = Cardiac output TPR = Total peripheral resistance

Answer 34

Flow control (the pump): Regulated by heart rate (HR) and stroke volume (SV). Resistance control: Regulated by arteriolar radius.

Answer 35

This can be achieved by increasing the vascular resistance (e.g., RA) in the tissue of interest. This will reduce the flow to that tissue while maintaining MAP and blood flow to the other tissues.

Answer 36

When vascular resistance increases (e.g., in tissue 1, shown as RA increases), the total flow to that tissue decreases. To maintain MAP, cardiac output (CO) will decrease, which reduces flow through all tissues, but the relative flow to other tissues remains the same.

Answer 37

By adjusting cardiac output (CO) downward in response to increased resistance in one tissue, MAP is maintained, even as flow to the affected tissue is reduced.

Answer 38

To greatly increase blood flow through one tissue without significantly changing MAP, total peripheral resistance (TPR) can be selectively reduced in that tissue while cardiac output (CO) is increased to maintain blood pressure.

Answer 39

During exercise: Cardiac output (CO) is increased to supply more oxygen to the tissues. Total peripheral resistance (TPR) is decreased in certain tissues, such as muscles, to allow more blood to flow through.

Answer 40

At rest (with a total cardiac output of 5L/min): Brain (RA): 700 ml/min (14% of total blood flow) Kidneys (RB): 1000 ml/min (20% of total blood flow) Muscles (RC): 1000 ml/min (20% of total blood flow) Other organs: Share the remaining 2300 ml/min (46% of total blood flow)

Answer 41

During moderate exercise (with a cardiac output of 10L/min, doubled from rest): Brain: Partial constriction, still receives 700 ml/min (7% of total blood flow). Kidneys: Strong constriction, reduced to 300 ml/min (3% of total blood flow). Muscles: Strong dilation, receives 6000 ml/min (60% of total blood flow). Other organs: The remaining 3000 ml/min is shared by other organs (30% of total blood flow).

Answer 42

As arteries branch into arterioles, their radius decreases, which increases resistance. Small changes in radius result in significant changes in resistance and pressure (P₁ - P₂).