Lecture 31 Flashcards
where are arterioles located
Located within individual organs (including muscle)
“They are the greatest contributors to Total peripheral resistance by increasing or decreasing the size of the lumen; important regulators of MAP”
arterioles
what “Determine blood flow to individual organs”
arterioles
what are the 2 major cell types that arterioles are comprised of:
Endothelial cells
Vascular smooth muscle
Why does pressure DROP so much at the arterioles?
dissipation of blood flow through all the different organs
high pressure to low pressure (pressure gradient)
This drop in pressure is necessary to ensure that the capillaries downstream, which have even smaller diameters, do not rupture under the pressure of the blood flow.
what are the Principal Determinants of Flow
1.Effect of pressure gradient:
The pressure gradient along the length of the tube
determines blood flow
2.Effect of radius (size of blood vessel):
Controls resistance
Resistance is also increased by tube length and
viscosity of blood
Lower resistance (greater radius) = greater flow
Blood flow to each organ is not the same. true or false
true
How does your body decide where to send the blood?
We have to be able to control the size of the blood vessels to alter resistance when we want to control which part of the body gets more or less blood
Functions of Endothelial Cells
Line heart and blood vessels; prevent blood cell and platelet adherence (thrombosis)
Control the exchange of fluid and nutrients in capillaries
Secrete vasodilator (nitric oxide) and vasoconstrictor (endothelin) substances
Mediate new capillary growth (angiogenesis)
Regular inflammatory responses
Functions of Smooth Muscle Cells
Maintain shape of blood vessel (structural support)
Regulate local blood flow via changing vessel diameter (vasoconstriction or vasodilation)
Signals that increase actin-myosin x-bridges cause…
vasoconstriction
Signals that decrease actin-myosin x-bridges cause…
vasodilation
Nitric Oxide (NO) is produced primarily by
endothelial cells
In each endothelial cell, there is an enzyme called
nitric oxide synthase
nitric oxide synthase enzyme turns l-arginine to…
nitric oxide
Nitric oxide is a small molecule that diffuses quickly into
smooth muscle
what does nitric oxide do in smooth muscle
In the smooth muscle, nitric oxide activates another enzyme called guanylate cyclase
once activated by nitric oxide what does Guanylate cyclase do in smooth muscle
Guanylate cyclase will create cGMP, causing relaxation of the smooth muscle cells
what does the relaxation of the smooth muscle cells via Guanylate cyclase do
This relaxation causes vasodilation; increases radius; decreases resistance; increases flow
Another enzyme, ______________________, creates ________________ from ____________________ It then cycles back to ______________
phosphodiesterase (PDE)
GMP (guanosine monophosphate)
cGMP
GTP
Why don’t we always want cGMP in our system
We don’t always want cGMP in our system because we don’t always want to be vasodilated
how do Dietary Nitrate Supplements work
When consumed in the diet, nitrate is converted in the body to nitric oxide (NO), a molecule that plays a key role in regulating blood flow and oxygen delivery to tissues.
Increased nitric oxide production: Dietary nitrate supplements increase the production of nitric oxide in the body, which can cause blood vessels to dilate, or widen, resulting in increased blood flow to muscles and other tissues.
Improved oxygen delivery: By improving blood flow, nitric oxide helps to deliver more oxygen to working muscles, which can improve exercise performance and delay the onset of fatigue.
Reduced oxygen consumption: Nitric oxide has been shown to reduce the amount of oxygen that muscles consume during exercise, which can improve endurance and delay the onset of fatigue.
Improved muscle efficiency: Nitric oxide can improve the efficiency of muscle contractions, allowing muscles to generate more force with less oxygen consumption.
