Chapter 20: Circulatory System Flashcards
diffusion
substances leave or enter blood according to their concentration gradient (high to low concentration)
What diffuses from blood to interstitial fluid/in?
oxygen, hormones, and nutrients
what diffuses from tissue to blood/out?
carbon dioxide and wastes
the route diffusion takes depends on particle _______
size
vesicular transport
form fluid-filled vesicles at the plasma membrane and transport substances across the cell
endothelial cells use _____________ and ________________
pinocytosis and exocytosis
bulk flow
fluids flow down the pressure gradient
during bulk flow, large amounts of ________ and ____________ ________________ move
fluids and dissolved substances move
bulk flow’s movement direction depends on
net pressure of opposing forces
filtration
fluid moves out of the blood
what is blocked during filtration
large solutes
where does filtration occur
on arterial end of capillary
reabsorption
fluid moves back into the blood
where does reabsorption occur
on venous end of capillary
hydrostatic pressure (HP)
force exerted by a fluid
blood hydrostatic pressure (HPb)
- also called blood pressure
- force exerted per unit area by blood on vessel wall
- promotes filtration from capillary
interstitial fluid hydrostatic pressure (HPif)
- force of IF on outside of blood vessel
- close to zero in most tissues
colloid osmotic pressure (COP)
the “pull” on water due to the presence of proteins (colloid)
blood colloid osmotic pressure
- pulling pressure
- promotes reabsorption
- draws fluid into blood due to blood proteins (albumins)
interstitial fluid colloid osmotic pressure
- draws fluid into IF
- few proteins present in IF, meaning it is relatively low
net filtration pressure (NFP)
the difference between net hydrostatic pressure and net colloid osmotic pressure
NFP changes along
length of a capillary
NFP is ___________ at the arterial end than at the venous end
higher
equation to find NFP
NFP= (HPb - HPif) - (COPb - COPif)
lymphatic vessels look like
weak little veins
lymphatic system
- picks up excess fluid not reabsorbed at the venous capillary end
- filters fluid and returns it to venous circulation
process of “washing” blood vessels
blood plasma-> interstitial fluid -> lymph -> blood plasma again
local blood flow ___________ and not all capillaries are ____________ ____________
varies/ are filled simultaneously
blood flow must be
high enough to maintain adequate perfusion
local blood flow is dependent on
- degree of tissue vascularity
- myogenic response
- local regulatory factors altering blood flow
- total blood flow
degree of vascularization
the extent of vessels in a tissue
angiogenesis
formation of new vessels
- occurs over weeks to months to increase potential perfusion
regression
break down of unneeded blood vessels
- return to previous state of blood vessels
tumor angiogenesis
cancer cells require oxygen and nutrients and trigger growth of new vessels as tumor grows
myogenic response
smooth muscle in blood vessel wall keeps blood flow relatively constant
blood flow is regulated
locally
based on need:
- changes when metabolic activity changes
- tissue is damaged
vasoactive chemicals
alter blood flow
vasodilators
dilate arterioles and relax precapillary sphincters
vasodilators increase
flow into capillaries
vasoconstrictors
constrict arterioles and cause contraction of precapillary sphincters
autoregulation
the process by which a tissue regulates or controls its local blood flow as a response to its changing metabolic needs
when tissue activity increases, ________________ signals inadequate perfusion and act as ________________
varied stimuli/ vasodilators
when tissue activity increases ____________________ decline
oxygen and nutrient levels
when tissue activity increases __________, __________, _____, and ____, increase
carbon dioxide, lactic acid, H+, and K+
as perfusion __________, vessels __________ in response
increases/ constrict
reactive hyperemia and an example
increase in blood flow after it is temporarily disrupted
- e.g., enter a warm room after being cold
inflammation
damaged tissue, leukocytes, and platelets release vasoactive chemicals
inflammation mediators that cause arterioles to dilate
histamine and bradykinin
inflammation may also stimulate the release of ___________, another vasodilator
nitric oxide
tissue damage can also lead to release of _________________
vasoconstrictors
local hormones released in response to tissue damage
leukotrienes, thromboxanes, and prostaglandins
total blood flow
the amount of blood transported through vasculature per unit of time
total blood flow is equal to
cardiac output
total blood flow may
increase with exercise
mean arterial pressure (MAP)
average arterial blood pressure across entire cardiac cycle
regulation of total flow depends on both the ________ and __________
heart and vessels
how to find pulse pressure
subtract the systolic pressure from the diastolic pressure
MAP equation
MAP= diastolic pressure + 1/3 pulse pressure
MAP provides
index of perfusion
venous blood pressure
low and does not pulsate
venous return of blood to the heart depends on
pressure gradient, skeletal muscle pump, and respiratory pump
venous BP is ___ mm Hg in venules and almost ___ in vena cava
20/ 0
skeletal muscle pump
assists venous return from limbs
respiratory pump
assists venous return in the thorax
resistance
friction blood encounters; opposes blood flow (F)
resistance is due to
contact between blood and vessel wall
peripheral resistance
resistance of blood in blood vessels (as opposed to heart)
peripheral resistance is affected by 3 variables that oppose blood flow
viscosity, vessel length, and lumen size
blood viscosity
resistance of fluid to its flow
resistance and vessel length
longer vessels create more resistance
____________ occurs along length of vessel
friction
resistance and vessel radius
smaller radius creates more resistance
blood has ____________ flow
laminar
laminar flow
different flow rate within vessel
total blood flow equation
F 🐟 △P/R
blood flow porportional to pressure gradient/resistance
systematic blood pressure gradient =
△P (change in BP from high to low)
in systematic blood pressure gradient, if the gradient ____________, total blood flow __________
increases/ increases
blood flow is ____________________ to pressure gradient but ________________________ to resistance
directly proportional/ inversely proportional
resistance=
R
as resistance ______________, total blood flow ______________
increases/decreases
resistance can be increased by what 3 variables
1- INCREASING blood viscosity
2- INCREASING vessel length
or
3- DECREASING vessel lumen diameter
receptors collect
data
baroreceptors
check on BP in carotid arteries and the aorta
chemoreceptors
detect oxygen and carbon dioxide
The cardiovascular center of the medulla contains what 2 autonomic nuclei
1- cardiac center
2- vasomotor center
cardiac center
influences BP by influencing cardiac output
vasomotor center
influences BP by influencing vessel diameter
vessel constriction influences
resistance
chemoreceptor reflexes influence
BP
stimulation of chemoreceptors brings about _________________________ to return blood chemistry to _________
negative feedback reflexes/ normal
chemoreceptors responses in _________________ and _______________ systems
respiratory and cardiovascular systems
hypothalamus can increase __________________ and ________________-
cardiac output and resistance
limbic system can alter ________________ in response to emotions or memories
blood pressure
renin-angiotensin system
- liver is continuously releasing inactive angiotensinogen in the blood
- kidneys release renin in response to BP or sympathetic nervous system
- renin converts angiotensinogen to angiotensin I
- ACE (angiotensin-converting enzyme), which is located in the capillaries of the lungs, converts angiotensin I to angiotensin II
- angiotensin II raises BP in 3 ways
baroreceptors are located
in the kidneys
3 ways angiotensin II can regulate BP
1- acts as a powerful vasoconstrictor
2- stimulates thirst center
3- acts on kidneys to decrease urine formation
-ogen
inactive
ACE inhibitor helps
lower BP
angiotensin II stimulates the release of _________________ and ____________________ causing vasoconstriction
aldosterone and antidiuretic hormone
aldosterone
- released from adrenal cortex
- release triggered by several stimuli, including angiotensin II
- increases absorption of sodium ions and water in the kidney (decreases urine output)
antidiuretic hormone (ADH)
- released from posterior pituitary gland
- release triggered by nerve signals from the hypothalamus
ADH effects
- increases water reabsorption in kidney
- stimulates thirst center to increase fluid intake
- in large amounts, it causes vasoconstriction
ADH is termed a
vasopressin
atrial natriuretic peptide (ANP)
- decreases BP
- released from atria of heart when walls are stretched by high volume
- stimulates vasodilation
- increases urine output
- mechanisms for BP homeostasis involve CO, R, & BV
variables directly relate to pressure:
increasing any of them will raise BP
BP measured indirectly using
sphygomanometer
systolic pressure is the
top number
diastolic pressure is the
bottom number
hypertension
chronically elevated blood pressure
atherosclerosis
progressive disease of the elastic and muscular arteries
arteriosclerosis
hardening of the arteries
hypotension
chronically low blood pressure
