CIRCULATORY

Question 1

What is the key difference between flow and velocity in blood vessels?

Answer 1

Flow is volume per time (L/min); velocity is distance per time (cm/s).

Question 2

What relationship defines blood flow through a vessel?

Answer 2

Flow = Pressure gradient / Resistance.

Question 3

According to Poiseuille’s Law, which factor has the greatest impact on resistance?

Answer 3

Vessel radius (resistance ∝ 1/radius⁴).

Question 4

What role does cortisol play in vascular tone?

Answer 4

Regulates α₁ receptor expression on arteriolar smooth muscle.

Question 5

Which receptors mediate sympathetic vasoconstriction in most arterioles?

Answer 5

α₁ adrenergic receptors.

Question 6

Which receptors mediate vasodilation in skeletal and cardiac muscle arterioles?

Answer 6

β₂ adrenergic receptors.

Question 7

What parasympathetic receptor type is found in reproductive organ vasculature?

Answer 7

Muscarinic M₂ receptors.

Question 8

What are the primary determinants of vascular resistance?

Answer 8

Viscosity, vessel length, and especially radius.

Question 9

What is the main function of large arteries?

Answer 9

To serve as pressure reservoirs that maintain flow during diastole.

Question 10

What happens to pulse pressure when arterial compliance decreases?

Answer 10

Pulse pressure increases.

Question 11

Which pressure starts around 93 mm Hg and falls to 37 mm Hg across the arterioles?

Answer 11

Mean arterial pressure (MAP).

Question 12

What causes arteriolar vasoconstriction?

Answer 12

Increased O₂, decreased CO₂ or H⁺, cold, sympathetic stimulation, angiotensin II.

Question 13

What causes arteriolar vasodilation?

Answer 13

Increased CO₂, H⁺, K⁺, adenosine, prostaglandins, or heat; decreased O₂ or sympathetic tone.

Question 14

What is the primary local vasodilator released by endothelial cells?

Answer 14

Nitric oxide (NO).

Question 15

What endothelial factor causes vasoconstriction?

Answer 15

Endothelin.

Question 16

Define myogenic tone.

Answer 16

The intrinsic contraction of vascular smooth muscle in response to stretch.

Question 17

What happens to arteriolar tone when transmural pressure decreases?

Answer 17

Tone decreases, causing vasodilation.

Question 18

What is the equation linking MAP to cardiac output and resistance?

Answer 18

MAP = CO × TPR.

Question 19

Which brain region serves as the cardiovascular control center?

Answer 19

The medulla oblongata.

Question 20

What receptors detect acute changes in arterial pressure?

Answer 20

Baroreceptors in the carotid sinus and aortic arch.

Question 21

How do baroreceptors respond to increased blood pressure?

Answer 21

Increase firing, leading to parasympathetic activation and decreased sympathetic output.

Question 22

During hypotension, what changes occur in autonomic tone?

Answer 22

Increased sympathetic and decreased parasympathetic activity.

Question 23

What is the typical capillary hydrostatic pressure at the arterial end?

Answer 23

Approximately 37 mm Hg.

Question 24

What is the typical capillary hydrostatic pressure at the venous end?

Answer 24

Approximately 17 mm Hg.

Question 25

What force favors fluid reabsorption into capillaries?

Answer 25

Plasma colloid osmotic pressure (~25 mm Hg).

Question 26

What is the net exchange pressure formula for bulk flow?

Answer 26

(Pc + πif) − (πp + Pif).

Question 27

What happens when net exchange pressure is positive?

Answer 27

Ultrafiltration occurs (fluid moves out of capillary).

Question 28

What is the consequence of decreased plasma proteins on capillary exchange?

Answer 28

Reduced reabsorption, leading to edema.

Question 29

How does histamine increase capillary permeability?

Answer 29

It causes endothelial gaps to widen, allowing proteins to escape.

Question 30

What is the primary function of the lymphatic system?

Answer 30

To return excess interstitial fluid and proteins to the circulation.

Question 31

How much lymph is typically returned to circulation each day?

Answer 31

About 3 liters.

Question 32

What structural feature of lymph capillaries allows fluid entry but prevents backflow?

Answer 32

Overlapping endothelial cells acting as one-way valves.

Question 33

What are four common causes of edema?

Answer 33

Reduced plasma proteins, increased capillary permeability, elevated venous pressure, lymphatic obstruction.

Question 34

What percent of total blood volume is contained in the venous system?

Answer 34

Approximately 64%.

Question 35

What effect does sympathetic stimulation have on venous capacity?

Answer 35

Decreases capacity, increasing venous return.

Question 36

What two mechanical factors promote venous return?

Answer 36

Skeletal muscle pump and respiratory pump.

Question 37

What defines venous capacity?

Answer 37

The volume of blood the veins can hold at a given pressure.

Question 38

What is the role of baroreceptors in short-term blood pressure control?

Answer 38

Rapid reflex adjustments of heart rate, contractility, and vessel tone.

Question 39

What mechanisms control blood pressure long-term?

Answer 39

Osmoreceptors and volume receptors via renal and hormonal regulation of fluid balance.

Question 40

In hypertension, what blood pressure threshold defines the condition?

Answer 40

≥140/90 mm Hg.

Question 41

What distinguishes secondary hypertension from primary hypertension?

Answer 41

Secondary has a known cause (renal, endocrine, or neurogenic).

Question 42

Which vasoactive molecule is often reduced in primary hypertension?

Answer 42

Nitric oxide.

Question 43

What physiological condition can lead to orthostatic hypotension?

Answer 43

Impaired baroreceptor response or autonomic dysfunction.

Question 44

In hypovolemic shock, what is the primary initial cause of hypotension?

Answer 44

Decreased venous return due to fluid loss.

Question 45

What type of shock results from vasodilation due to severe infection?

Answer 45

Septic shock.

Question 46

What is the “shock index,” and how is it calculated?

Answer 46

HR/SBP; used to estimate severity of circulatory compromise.

Question 47

Clinical scenario: A patient loses 30% of blood volume. What happens to cardiac output and MAP?

Answer 47

Both decrease; compensatory sympathetic and renal responses activate.

Question 48

Clinical scenario: Why does edema occur in severe protein malnutrition?

Answer 48

Low plasma oncotic pressure reduces capillary reabsorption.

Question 49

Clinical scenario: A patient with heart failure develops peripheral edema. Explain the mechanism.

Answer 49

Elevated venous pressure increases capillary hydrostatic pressure, promoting filtration.

Question 50

Clinical scenario: In septic shock, why does metabolic acidosis develop?

Answer 50

Inadequate tissue perfusion leads to anaerobic metabolism and lactic acid accumulation.