Traffic - week 10 Flashcards
exchanges between blood and tissue cells takes place in the
the interstitial fluid
all organs receive fresh blood (need)
amount to each organ adjusted based on need
the blood is constantly “reconditioned” so (shower)
its constant
1. it increases cardiac output (digestive system, kidneys)
organization “vascular tree” (aacvv)
aacvv
- arteries
- arterioles
- capillaries
- venules
- veins
flow rate (volume of blood passing through a particular segment of vascular tree per unit time)
- directly proportional to pressure gradient
- inversely proportional (one value decreases another) to resistance (delay to flow from friction)
a. vessel radius - smaller vessels ➝ more resistance
b. viscosity of blood - thicker blood ➝ more resistance
c. length of vessel - longer vessel ➝ more resistance
Arteries are..
fast transport, large
act as a pressure reservoir (arteries)
- walls contain endothelial lining surrounded by smooth muscle and connective tissue fibers (collagen and elastin), which allow walls to stretch to contain pumped blood
- when the heart is relaxing the arteries recoil and keep the blood flowing
fluctuates
arterial pressure
blood pressure is the force exerted by blood on vessel walls
a. depends on blood volume and expansion of vessel
b. systolic pressure is the maximum pressure during systole (should be <120 mmHg)
c. diastolic pressure is the pressure during diastole (should be <80 mmHg)
mean arterial pressure is
the main driving force for blood flow to tissues. MAP = diastolic pressure + 1/3 pulse pressure
Arterioles
major resistance vessels (small radii) - radii adjusted by smooth muscle
- vasoconstriction and vasodilation (narrowing and enlarging)
- normally partially constricted (vascular tone) a. myogenic activity
b. sympathetic innervation
local control of arteriolar radius matches blood flow to…
tissue needs
metabolic factors causing vasodilation (in arterioles)
(1) decreased O2
(2) increased CO2
(3) increased acid (from CO2 and lactic acid)
(4) increased K+ (APs outpacing Na+-K+ pump in brain or skeletal muscle)
(5) increased osmolarity (more solutes formed during times of elevated metabolism)
(6) release of adenosine (in cardiac muscle)
(7) release of prostaglandins (not well understood)
local metabolic factors that cause vasodilation probably act by causing (epiq)
release of chemical mediators from endothelial cells (called vasoactive mediators), e.g. (1) endothelial-derived relaxing factor (EDRF), also known as nitric oxide (NO) inhibits Ca2+ influx in smooth muscle – vasodilator
(2) endothelin – vasoconstrictor
physical influences on vasodilation (runner - mye)
application of heat (vasodilation) or cold (vasoconstriction)
b. myogenic (muscle) responses to stretch (vasoactive substances probably contribute)
(1) tone increases in response to increased stretch (resists stretch) - important to keep flow to tissues constant as MAP changes (pressure auto regulation)
(2) tone decreases in response to decreased stretch - important in restoring flow to previously deprived tissue (reactive hyperemia)
extrinsic control of arteriolar radius helps..
regulate arterial BP
(extrinsic control of bp) sympathetic activity produces
generalized vasoconstriction, increasing resistance and BP (don’t vasoconstrict brain) MAP = CO x total peripheral resistance
a. NE at α receptors causes vasoconstriction
b. E at β2 receptors causes vasodilation (heart, skeletal muscles)
other hormones - extrinsic control of arteries (constrict angie)
a. vasopressin-important in fluid balance, vasoconstrictor
b. angiotensin II-important in fluid balance, vasoconstrictor
local control mechanisms can override
vasodilation
Capillaries are responsible for exchanges between
plasma and interstitial fluid (solute exchange mainly by diffusion)
capillaries have (window tree)
thin, high, slow, lipids, water soluble, transport, leakiness
thin-walled, narrow vessels
- highly branched
- blood flows slowly through individual vessels
- lipid soluble substances pass through cells (O2, CO2)
- water soluble substances pass through pores (ions, glucose, amino acids)
- some vesicular transport (hormones)
- degree of “leakiness” may change due to actin-myosin in capillary cells
precapillary sphincters
rings of smooth muscle can block flow through capillaries in less active tissues
a. sensitive to local metabolic changes
fluid shifts and bulk flow (only 2 fluids)
important in distribution of fluids between plasma and interstitial fluid
fluid(not proteins) pushed out through (art pressure cooker)
pores at arteriolar end (ultrafiltration)
(1) capillary blood pressure (pushes fluid out) exceeds plasma-colloid
osmotic pressure (oncotic pressure - force drawing water toward plasma proteins)
b. fluid reabsorbed at venule end
(1) capillary BP lower than plasma-colloid
osmotic pressure (pulling fluid in)
ultra filtration occurs in.. (open)
open capillaries, reabsorption in closed capillaries
fluid shifts occur as needed - capillaries (closet)
a. loss of blood, shifts to plasma
b. excess fluid in blood, shifts to interstitial fluid
c. keeps plasma volume relatively constant (temporary)
extra fluid picked up by lymph vessels (initial lymphatics) in capillary beds
large valve like openings allow in fluid and any leaked proteins (lymph)
- around larger lymph vessels, surrounding smooth muscle pushes fluid to larger and larger vessels, which contain one-way valves
- skeletal muscles help squeeze lymph through 4. eventually empty into thoracic veins
edema
accumulation of excess interstitial fluid, reduces exchange between blood and cells
edema causes
low plasma proteins
a. more fluid filtered out, less reabsorbed
b. kidney or liver disease, diet deficient in protein, burns
2. increased permeability of capillaries a. loss of proteins
b. injuries, allergic responses
Veins transport to…
back to heart - blood reservoir
factors influencing venous return - sympathetic activity
a. vasoconstriction drives more blood toward heart
b. still low resistance vessels (large radius)
Blood Pressure (tv car)
MAP is main driving force
- high enough to get blood to tissues
- not too high or extra work for heart, increased risk of vascular damage
short term regulation (seconds) - blood pressure (door - bev)
baroreceptor reflex
a. pressure sensors in carotid sinus and aortic arch sense changes in MAP and pulse pressure (1) rate of firing increases with increasing pressure, decreases with decreasing pressure
long term regulation (minutes to days) - blood pressure
adjustments in total blood volume via salt/water balance - urinary system and thirst (volume receptors in left atrium, osmo receptors in hypothalamus)
other contributing factors - blood pressure - chemoreceptors
in carotid and aortic arteries a. sense low O2 and high acid
(1) increase respiratory activity but also increase BP (signals CV center)
neurotransmitter effects in brain (poorly understood)
cerebral cortex - blood pressure (hypo path)
hypothalamic pathway influence emotional/behavioral responses
exercise - blood pressure
may be unidentified “exercise centers”
hypothalamic temperature regulation overrides..
baroreceptor reflex for skin vessels
vasoactive (affects diameter) substances come from…(blood pressure) (till the end)
endothelial cells
Hypertension - diseases (AEN) and BP
BP above 140/90 (high-normal is 135/85)
cause identified in about 10% of cases (secondary hypertension)
a. include atherosclerosis,endocrine disorders, nervous system defects
cause of hypertension (cont) (heart- fridge)
stresses heart and blood vessels, congestive heart failure, stroke, heart attack, too many lipids, atherosclerosis, kidney failure, loss of vision
baroreceptors reset at higher level
- stresses heart and blood vessels
a. congestive heart failure from increased after load
b. rupture of vessels - stroke, heart attack
c. damage to vessels may cause accumulation of lipids and lead to atherosclerosis
d. kidney failure due to damaged vessels e. loss of vision from damaged vessels
hypotension (low) (transient)
BP below 100/60
- transient
a. standing up-gravity decreases venous return b. in some people emotional stress decreases sympathetic activity (may be adaptive)
arteries carry
blood from heart toward tissues
arterioles adjust… (art couch)
blood flow to tissues
capillaries (xmas)
exchanges made
venules
small veins. carries blood to veins
veins carry blood from…
tissues toward heart
additional edema causes (edna - door)
increased venous pressure
a. also increased capillary pressure b. congestive heart failure, pregnancy
blocked lymph vessels
a. lymph node removal, parasite
systolic-diastolic =
pulse pressure (the pressure felt in arteries near the body surface)
factors influencing venous returns - skeletal muscle activity (gym)
acts as pump
factors influencing venous returns - valves (one way)
one-way valves every few centimeters allow flow toward heart only
factors influencing venous returns (sympathetic) - respiratory activity (bike pump)
acts as pump due to decreased pressure in thoracic cavity
factors influencing venous returns (sympathetic) - cardiac suction
blood “sucked in” as ventricles relax
primary causes of hypertension (kitchen - kidney)
a. kidney salt regulation
b. excessive salt intake
c. diet low in fruit, vegetables, dairy (low in K+and Ca2+) d. defects in Na+-K+ pumps
e. abnormal local vasoactive substances
f. excess vasopressin
short term regulation in blood pressure - integrating center is…(purple heart)
cardiovascular control center in medulla of brain stem
adjusts sympathetic/parasympathetic activity
hypotension - when blood flow to tissues is inadequate, it’s called…(chair)
circulatory shock
a. many causes
(1) loss of blood volume (hemorrhage, diarrhea) \
(2) weakened heart
(3) vasodilation (septic or anaphylactic)
(4) loss of sympathetic tone (extreme pain as in crushing injury)
b. may become irreversible
veins are..(stretching)
- stretchable with little recoil
- storage decreases effective circulating volume
a. can be altered based on need
peripheral resistance increases
blood pressure
sympathetic activity increases
blood pressure
systemic arteries have higher
oxygen levels (going towards tissue)
pulmonary arteries have lower
oxygen levels (going towards lungs)
map decreases as it flows..
from arteries down to venules and veins.
only sympathetic innervation
blood vessels
map =
CO x total peripheral resistance OR heart rate x stroke volume x total peripheral resistance. if any decrease, then MAP decreases.
vasoconstriction in arterioles…
holds the blood back (because they are small)
vasoconstriction in veins..
pushes blood forward (the valves keep it from moving backwards)
normal respiration is not controlled by
partial pressure
