blood vessels and pressure (6c) Flashcards
what are the types of blood vessels and what do they do
arteries and arterioles: carry blood away from heart
capillary beds: play a role in exchanges between tissues and blood
veins and venules: return blood to heart
what is the anatomy of blood vessels
tunica intima: endothelium and loose connective tissue
tunica media: smooth muscle and elastic fibers (controlled by sympathetic nervous system)
tunica externa: collagen fibers
capillaries only have tunica intima
what are the anatomical differences between arteries and veins
arteries: extra layers called internal elastic lamina (tunica intima) and external elastic lamina (tunica media), the tunica media is thicker
veins: has valves and larger lumen, the tunica externa is thicker
which blood vessels have high/low pressure
arteries have high pressure and the pressure decreases as blood goes through capillaries to veins
relationship between cardiac output and venous return
they are equal
vein structures used for venous return
thinner tunica media and low pressure
larger lumen
valves prevent backflow
skeletal muscle contractions squeeze blood forward
characteristics of capillaries
only have tunica intima (one cell thick)
form networks called capillary beds
blood flow through capillary beds is called microcirculation
what are precapillary sphincters
direct blood flow by closing or opening
allow shunting
what are blood and osmotic pressures in terms of substances and what are the pressures in arteries/veins
BP: force that draws substances out of the capillaries
osmotic pressure: force that keeps substances in the capillaries
in arteries: BP is higher
in veins: osmotic pressure is higher
what is BP
the pressure that the blood exerts against the inner walls of the blood vessels (resistance to flow)
force that causes blood to continue to flow overcoming resistance
measures of blood pressure
systole/diastole
systolic pressure: pressure in arteries at the peak of ventricular contraction (110-140 mmHg)
diastolic pressure: pressure when ventricles relax (70-80 mmHg)
variables involved in BP
cardiac output (CO)
peripheral resistance (R)
blood volume (CO depends on volume)
delta P = CO x R
what are sources of peripheral resistance
blood viscosity
blood vessel length
blood vessel diameter (only one that changes frequently and significantly alters peripheral resistance)
- smaller diameter = more resistance = more pressure
what mechanisms regulate BP
short term by nervous system and hormones (changes R and CO)
long term by kidneys and hormones (changes blood volume)
how does the nervous system regulate BP rising
BP rises
baroreceptors in carotid sinuses and aortic arch are stimulated
impulses from baroreceptors stimulate the cardioinhibitory center and inhibit the vasomotor center
cardioinhibitory center decreases HR, contractility and CO
vasomotor center impulses decrease = vasodilation occurs and R decreases
how does the nervous system regulate BP falling
BP falls
baroreceptors in carotid sinuses and aortic arch are inhibited
impulses from baroreceptors stimulate the cardioacceleratory center and stimulate the vasomotor center
cardioinhibitory center increases HR, contractility and CO
vasomotor center impulses = vasoconstriction = R increases
what are hypo and hypertension
hypotension: low BP, systolic below 100, acute hypotension is a warning sign for circulatory shock
hypertension: high BP, sustained 140/90, warning for increases peripheral resistance
