week 14: Cardiovascular System Lecture 2

Comprehensive practice flashcards covering the structure and function of blood vessels, capillary exchange, hemodynamics, and the cardiovascular response to exercise.

What are the three primary layers of a blood vessel wall?

The three layers are the tunica intima (inner), tunica media (middle), and tunica externa (outer).

What specific substances does the endothelium release to regulate vascular tone and blood flow?

It releases vasodilators such as Nitric Oxide and vasoconstrictors such as Endothelin.

How does the tunica media differ between a typical artery and a typical vein?

In an artery, the tunica media is thick and dominated by smooth muscle cells and elastic fibers; in a vein, it is thin and dominated by smooth muscle cells and collagen fibers.

What are the 'vasa vasorum'?

They are 'vessels of vessels'—small arteries and veins located in the walls of large arteries and veins that serve the cells of the tunica media and tunica externa.

What are the three types of capillaries mentioned in the lecture?

Continuous capillaries, fenestrated capillaries, and sinusoids.

Where are fenestrated capillaries primarily found in the body?

They are found in the choroid plexus, endocrine organs, kidneys, and the intestinal tract.

How do sinusoid capillaries facilitate exchange, and where are they located?

They have gaps between endothelial cells to permit free exchange of water and large plasma proteins; they are located in the liver, spleen, bone marrow, and endocrine organs.

According to the distribution of blood volume, what percentage is held in the systemic venous system?

$$64\%$$

What is the function of the precapillary sphincter?

It guards the entrance to each capillary and opens or closes to cause blood to flow in pulses.

What is the formulaic relationship between flow ($F$), pressure gradient ($\Delta P$), and resistance ($R$)?

$$F \propto \frac{\Delta P}{R}$$

What three factors affect total peripheral resistance in the cardiovascular system?

1. Vascular resistance (friction), 2. Blood viscosity, and 3. Turbulence.

What are the blood pressure thresholds for hypertension?

Greater than $140/90$.

How does blood flow to active muscles change from rest to exercise?

It increases from $7\,ml$ per $100\,g$ of muscle at rest to $75\,ml$ per $100\,g$ of muscle during exercise.

How does the parasympathetic nervous system regulate heart rate?

It acts via the vagus nerve to slow heart rate by inhibiting the SA and AV nodes.

What causes the initial increase in heart rate at the onset of exercise up to approximately $100\,bpm$?

The withdrawal of parasympathetic tone.

What is the Frank-Starling Mechanism?

The principle stating that the force of contraction is proportional to fiber length.

At what intensity does stroke volume typically plateau in untrained individuals?

At approximately $40\%VO_{2}max$.

What is the maximum cardiac output ($Q$) achievable by highly trained endurance athletes compared to untrained individuals?

Highly trained athletes can reach $35\,l/min$, whereas untrained individuals typically reach $20 - 25\,l/min$.

How is maximum heart rate calculated according to the lecture notes?

$$\text{Max HR} = 220 - \text{age}$$