What are arterioles?

Control valves to regulate local blood flow.

What do veins do?

serve as resevoir for blood.

Are arteries distensible? 

No.  Therefore, increase in AP causes onlly small increase in arterial diameter.

Are veins distensible?

Yes, highly distensible.  Therefore, small increases in venous pressure cause large increases in venous diameter.

How much blood is in the adult circulatory system and how much stays in the stemic veins?

5L of blood

64% is in systemic veins

3 mechanisms help ensure venous return to the heart.  What are they?

1.  Negative pressure in right atrium sucks blood toward heart.

2.  Constricted veins increases venous pressure and drives blood toward heart

3.  Constriction of skeletal muscles pumps blood toward heart.

Which system increases HR?

Which system decreases HR?

Sympathetic

Parasympathetic

What determines SV?

Myocardial contractility

Cardiac Preload

Cardia Afterload

Define preload.

What determine preload in the heart?

-the amount of tension/stretch applied to a muscle prior to contraction

-by the force of venous return.

Define Afterload.

What determines afterload in the heart?

-load against which a muscle exerts force

-avterial pressure (AP) that the left ventricle must overcome to eject blood.  (peripheral resistance)

What does Starling's Law state?

-the force of ventricular contraction is proportional to myocardial fiber length; because of this relatyionship, when more blood enters the heart, more is pumped out.

In a healthy heart, it's able to precisely match output with venous return.

What regulates AP?

1.  RAAS

2. ANS

3. Kidneys

4.  Natriuetic peptides

Through what 2 mechanisms does the ANS regulate AP?

1.  Baroreceptor reflex

2.  Tonic control of the heart rate and PR

The Baroreceptor Reflex only controls AP in the short term.

Why is that?

When pressure remains elevated or lowered, the system RESETS to the new pressure within 1-2 days, and

ceases to respond.

What can cause reflex tachycardia?

What happens to BP lowering drugs?

When the baroreceptor reflex is triggered by BP lowering drugs, reflex tachycardia happens.

consequently, baroreceptor reflex can negate BP lowering drugs temporarily.

How does the RAAS support AP?

1.  Causes constriction of arterioles and veins

2.  Retention of H20 by kidneys

In the RAAS, what mediates vasoconstriction?

Angiotensin II

In the RAAS, what mediates water retention?

Release of aldosterone

How do the natriuretic peptides defend the cardiovascular system?

By reducing blood volume and promoting vasodilation.