Ch. 12 (Vascular) pt. 4

what is the endothelium?

single-cell layer that forms inner lining of vessels in contact with blood

Do arteries & veins have high or low resistance?

low resistance (basically none)

Systemic circulation of the vascular?

arteries→arterioles→capillaries→venules→veins

What are the 2 types of arteries? characteristics of them?

1) elastic

-has walls of smooth muscle + elastin

-expands as BP increases

-recoils as ventricles relax

2) muscular

-less elastic & thicker smooth muscle layer

Main function of arteries? What is it known as?

arteries modulate blood pressure

“pressure reservoir”

How do arteries regulate blood pressure?

1) during systole→arteries expand as blood goes thru them

2) during diastole→arteries recoil (or ig relax) as blood goes thru them & prevents BP from dropping too low(prevents arteries from being in that expanded state)

What is Mean Arterial Pressure(MAP) & the equation for it?

-average pressure driving blood into the tissues averaged over an entire cardiac cycle

MAP=DP+1/3(SP-DP)

What is Pulse Pressure?

difference between systolic pressure & diastolic pressure (SP-DP)

Does the heart spend more time in Systole or Diastole?

Diastole

What happens to the MAP as we age and why? consequences of this?

MAP increases bc we lose elasticity, which means harder for arteries to expand

-SP increases & vessels are more likely to get damaged

What are arterioles known as? They have a high percentage of _____.

blood flow modulators

-high % of smooth muscle

Main purpose of arterioles?

they can vasoconstrict/vasodilate to control blood resistance. This allows them to control how much blood goes to each organ.

vasoconstriction=more resistance

vasodilation=less resistance

As blood flows from arteries to arterioles, what happens?

1) increase in resistance bc arterioles are smaller

2) greatest pressure drop bc more resistance

what is intrinsic tone?

arterioles are always maintaining some degree of contraction allowing them to adjust blood flow when necessary

What happens when epinephrine binds to Beta-Adrenergic receptors vs. Alpha adrenergic receptors?

beta-adrenergic receptors=vasodilation (mainly to increase heart rate)

alpha-adrenergic receptors=vasoconstriction

What does Nitric Oxide do & what is it known as?

-vasodilator known as Endothelium-Derived Relaxing Factor

How is Nitric Oxide made & how does it do what it does?

made in the Endothelium by eNOS which converts L-Arginine→NO

NO diffuses into the smooth muscle where it activates sGC(soluble guanyly cyclase)→vasodilation & cGMP

How can vasodilation be maintained?

PDE5 inhibitors prevent Phosphodiesterase 5 from breaking down cGMP=vasodilation maintained

How can angina(chest pain) be treated?

introducing Nitroglycerin→becomes NO in body to vasodilate