Chapter 15 Flashcards
which vessels have the thickest walls?
arteries
Which vessels have the thinnest walls?
veins
Which vessels have the largest lumens?
veins
Which vessels have the most smooth muscle?
arteries
Arteries act as ______ __________
pressure reservoir
What is the site of variable resistance?
arterioles
what are metarterioles?
branches of arterioles
What are the smallest vessels?
capillaries
what happens in the capillaries?
primary site of exchange between blood and interstitial fluid
_________ _________ open and close to direct blood flow to capillaries or venous circulation.
precapillary circulation
what do venules do?
- receive blood from capillaries
- convergent pattern of flow
Veins act as a ______ _________
volume reservoir
what are the functions of veins?
contain one way valves that prevent backward flow
what is angiogenesis?
development of new blood vessels
what is angiogenesis controlled by?
cytokines
Explain what creates blood pressure.
- measure of the strength of the pressure wave produced by ventricular contraction
- systolic pressure - diastolic pressure
Describe how blood pressure is estimated using sphygmomanometry.
- goal is to increase pressure to above systolic pressure
- cuff is inflated so that it stops arterial blood flow –> no sound can be heard through a stethoscope placed over the brachial artery below the cuff
- release pressure
- read gauge –> once the pressure in the cuff is equal to the systolic pressure –> blood is able to get thru
- hear flow of blood (estimate # on gauge –> systolic pressure)
- stop hearing blood flow when there is no more compression (estimate # on gauge –> diastolic pressure)
What is the equation used to find MAP?
MAP = diastolic pressure + ((1/3) x (pulse pressure)
If flow into arteries exceeds flow out, then arterial blood volume increases and MAP ______
increases
Cardiac output is flow out of ______ ______ (into aorta)
left ventricle
What is the relationship between blood volume and pressure?
direct relationship
Define myogenic autoregulation.
vascular smooth muscle regulates its own state of contraction
Explain myogenic autoregulation’s role in altering local blood flow.
- stretched vascular smooth muscle open mechanically gated Ca2+ channels
- Ca2+ flows into cell
- leads to contraction
List and describe the major paracrine molecules involved in local control of blood flow.
- stretch –> causes vasoconstriction
- paracrine –> released in response to metabolism + cause vasodilation
- endothelin –> in response to tissue damage (constricts vessel)
Sympathetic innervation releases ____ on most systemic arterioles.
NE
What does sympathetic innervation do?
- maintains arteriolar tone
- binds alpha receptors –> vasoconstriction
what does the adrenal medulla do?
- releases epinephrine into blood
- binds alpha receptors w/very low affinity –> vasoconstriction
- binds beta2 receptors on vascular smooth muscle of heart, liver, and skeletal muscle arterioles –> vasodilation
When blood pressure increases due to increased blood volume, what is the fast response?
compensation by cardiovascular system –> vasodilation + decreased cardiac output –> decreased blood pressure –> normal bp
When blood pressure increases due to increased blood volume, what is the slow response?
compensation by kidneys –> excretion of fluid in urine decreases blood volume –> decreased blood pressure –> normal bp
Describe the neural control of blood vessel diameter, including significant neurotransmitters + their receptor types.
Neural control:
- sympathetic –> alpha receptors –> constricts
- epinephrine
- alpha receptors –> vasoconstriction
- beta receptors –> vasodilation
- norepinephrine
- alpha receptors –> vasoconstriction
- beta receptors –> vasodilation
Explain how the body can use local + long distance signaling to direct blood flow to or away from specific organs or tissues.
- blood distribution varies according to metabolic needs –> local
- arterioles arranged in parallel (circuit) –> how body is able to do long distance –> (doesn’t need to flow thru the whole circuit to get back to the heart)
- can vasoconstrict a vessel to increase resistance + flow thru other vessels –> flow is taken to lower resistance vessels
Describe the control of blood flow to the brain + heart.
- cerebral blood flow stays nearly constant
- coronary blood flows parallel to the work of the heart
Describe in detail the steps of the baroreceptor reflex if the stimulus increases arterial pressure.
1) stimulus –> increased bp
2) sensor –> carotid + aortic baroreceptors
3) afferent pathway –> sensory neuron
4) integrating center –> medullary
cardiovascular control center (CVCC)
5) output signal –> parasympathetic
neurons –> more ACh on
muscarinic receptor
6) target –> SA node
7) tissue response –> decreased HR +
decreased cardiac output
8) systemic response –> decreased blood
pressure
9) negative feedback
What does the baroreceptor reflex control?
blood pressure
Where are the baroreceptors located?
baroreceptors located in carotid (to brain) arteries + aorta
What is the control center in the baroreceptor reflex?
CVCC –> cardiovascular control center (CVCC) in the medulla oblongata in brainstem
Describe in detail the steps of the baroreceptor reflex if the stimulus decreases arterial pressure.
Look on paper drawing
Describe the different types of capillaries and where they are found in the body.
1) continuous capillaries –> “normal” + found
in most of the body –> do not have holes
- have leaky junctions –> allow water +
small dissolved solutes to pass
- have endothelial cells beneath basement
membrane
- have transcytosis vesicles
2) fenestrated capillaries –> have holes + large
pores
- have epithelial cell junctions
- basement membrane is cut
- have transcytosis vesicles
- found in –> kidneys
3) sinusoids –> modified capillary vessel
- found in –> bone marrow, liver, and spleen
Explain why the velocity of blood flow is lowest in the capillaries.
- want slower velocity for exchange sites of oxygenated + deoxygenated blood
- smaller diameter + largest total cross sectional are
Explain the role of diffusion and transcytosis in capillary exchange.
transcytosis:
- only water + small dissolved solutes allowed to pass thru leaky/cell junctions
- everything else that doesn’t fit has to be transported via transcytosis
1) brings proteins + macromolecules across endothelium
2) some vesicles may fuse to create temporary channels (theorized)
diffusion:
- exchange between plasma + interstitial fluid occurs by:
- paracellular pathway –> going btw cells
- endothelial transport –> moving across
cell
- small dissolved solutes + gases
- depends on lipid solubility + concentration gradient
Explain the forces that influence capillary filtration and absorption.
filtration –> hydrostatic pressure encourages plasma to leave capillaries
absorption –> osmotic pressure (capillaries have plasma proteins that draw water inside to themselves)
What type of tissue are the capillary walls made up of?
single layer of flattened endothelial cells
What is capillary density related to?
metabolic activity of cells
Describe velocity of flow.
- the distance a fixed volume of blood travels in a given period of time
v = Q/A
Q = flow rate
A = cross-sectional area of the tube
Describe bulk flow.
a mass movement as a result of hydrostatic or osmotic pressure gradients
Describe filtration.
fluid movement out of capillaries
Describe absorption.
fluid movement into capillaries
Hydrostatic pressure ________ over the length of capillary due to friction + filtration.
decreases
Define hydrostatic pressure.
the pressure that fluid exerts on the walls of container –> plasma on capillary walls
Define osmotic pressure.
the pressure that causes osmosis due to solutes/proteins in fluid
_____ ______ determines direction of bulk flow.
net pressure
What is the equation for net pressure for systemic capillaries?
PNET = PH - π
If PH > π will it be absorption of filtration and at what location?
net filtration at arterial end
If PH < π will it be absorption of filtration and at what location?
net absorption at venous end
What are the functions of the lymphatic system?
1) returns fluid + proteins to circulatory system
2) absorbs fat from GI tract + transfers it to circulatory system
3) filters pathogens
4) allows for one way movement of interstitial fluid into the circulatory system
