P6

What stimulates the central chemoreceptors in the respiratory center of the brain?

Hypercapnia and acidosis.

What is hypercapnia?

An increase in the partial pressure of arterial carbon dioxide (PaCO2).

What is acidosis?

An increase in acidity in the body fluids.

How strong is the direct effect of carbon dioxide on the CNS compared with hypoxia on peripheral chemoreceptors?

About 10 times stronger.

Where are stretch receptors located?

In the vena cava and right atrium.

What are stretch receptors sensitive to?

Pressure or volume changes.

What happens to stretch receptor impulses during hypovolemia?

Fewer impulses are sent to the CNS.

What is hypovolemia?

A reduced blood volume.

How does the sympathetic nervous system respond to hypovolemia?

It increases heart rate and constricts peripheral blood vessels.

How do the kidneys respond when renal blood flow or pressure decreases?

They retain sodium and water.

Why does blood pressure rise when the kidneys retain sodium and water?

Because of fluid retention and activation of the renin-angiotensin-aldosterone mechanism.

What does the renin-angiotensin-aldosterone mechanism cause?

Vasoconstriction and sodium retention.

How does sodium retention affect fluid balance?

It causes fluid retention.

What hormone from the posterior pituitary regulates vascular volume?

Antidiuretic hormone (vasopressin).

How do emotional behaviors affect the cardiovascular system?

They stimulate the sympathetic nervous system to increase BP and HR.

What emotional behaviors can increase BP and HR?

Excitement, pain, and anger.

How does exercise affect BP and HR?

It increases both during activity.

How does body temperature affect cardiovascular activity?

By changing tissue metabolic needs.

What happens to BP in hypothermia?

Blood pressure falls.

Why does BP fall in hypothermia?

Tissues require fewer nutrients.

What happens to BP and HR in hyperthermia?

They rise.

Why do BP and HR rise in hyperthermia?

Tissues have greater metabolic requirements.

What is the primary function of the venous system?

To return blood from the capillaries to the right side of the heart.

What structures make up the venous system?

A series of veins located next to the arterial system.

What is the superficial venous circulation?

A venous network running parallel to the subcutaneous tissue of the extremities.

What connects the superficial veins to the deep veins?

Communicating veins.

In what direction is venous blood flow directed?

Toward the deep venous circulation.

What ability do veins have regarding blood volume?

They can accommodate large volume shifts with minimal pressure changes.

Why is venous flexibility important?

It allows accommodation of IV fluids, blood transfusions, blood loss, and dehydration.

What structures in veins help direct blood back to the heart?

Valves.

What is the function of venous valves?

To prevent backflow of blood.

Which veins generally contain valves?

Most superficial and deep veins except the smallest and largest veins.

How do skeletal muscles help venous circulation?

They push venous blood forward.

Which major veins are valveless?

The superior vena cava and inferior vena cava.

Why can blood return easily through the vena cavae?

Because they are large and valveless.