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74 Cards in this Set
- Front
- Back
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Functions of vascular endothelium? (4)
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1. Angiogenesis
2. Barrier function 3. Hemostasis 4. Release of local factors |
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What is angiogenesis?
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Initiation of capillary sprouting involving basement membrane degredation & synthesis
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What stimulates endothelial cell growth? (3)
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1. Fibroblast growth factor
2. Angiogenin 3. Endothelial cell growth factor |
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What happens to endothelium in response to alkalosis or cell damage?
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Endothelial cells release:
endothelial cell growth factor --> stimulates growth of nearby smooth muscle cells |
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How does endothelium form a physical barrier?
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Adjacent cells form tight junctions
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Function of tight junctions in endothelial cells?
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Keeps small ion permeability low & electrical resistance high
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What is fenestrated endothelium?
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Has large openings that permit free passage of large molecules --> only limited physical barrier
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How does endothelium constitute a biochemical barrier?
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Contains enzymes for transmitter uptake & digestion
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Endothelium continuously releases factors such as ____ & ____ which inhibit platelet aggregation?
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1. Prostacyclin
2. Nitric oxide |
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Aggregating platelets release what 3 things to stimulate endothelial cells to release _____ factors ?
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Platelets release:
1. Thrombin 2. ADP 3. Serotonin Endothelial cells release: vasodilator factors --> increase blood flow & flush away platelets |
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What factor stimulates platelet binding to subendothelial structures?
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Willibrand factor (VIII)
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In absence of intact endothelium, what is released from aggregating platlets to promote vasoconstriction?
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Serotonin
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Major relaxant factor?
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NO
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NO is synthesized from what & by what?
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L arginine --> NO by nitric oxide synthase
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Prostacyclin is derived from?
What enzyme catalyzes this? |
arachodonic acid --> Prostacyclin by cyclooxygenase
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Which enzyme does NO stimulate?
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NO --> GC on adjacent smooth muscle cells --> cGMP --> vasodilation
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Prostacyclin does what?
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Prostacylcin --> membrane receptors on adjacent smooth muscle cells --> cAMP --> vasodilation
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Most potent vasoconstrictors discovered?
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Endothelins
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Primary goal of CV homeostasis?
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Coupling flow & metabolism
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What does metabolic theory of blood flow state?
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End products of metabolism directly vasodilate resistance arteries to increase blood flow in a negative feedback manner
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What is active hyperemia?
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Increase in blood flow to tissue in response to increased work of tissue
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What is reactive hyperemia?
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Increase in blood flow to a tissue obvserved following occlusion of arteries supplying that tissue
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What is oxygen debt?
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Increased blood flow that persists even after work has ceased
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Oxygen debt is attributed to?
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Attributed to washout of vasodilator metabolites & resynthesis of key tissue molecules consumed during work
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Key products of metabolism? (6)
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1. Acidosis (H)
2. Temperature (heat= vasodilator) 3. CO2 4. K 5. Osmolarity 6. Adenosine |
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What is wall tension?
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Force required to close longitudinal slit in the side of an artery & may be key variable in myogenic rxns
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Law of LaPlace states?
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Wall tension is product of pressure & artery radius
Tension = Pressure x Radius |
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What is transmural pressure?
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Pressure difference across the wall of an artery --> determined by arterial pressure & tissue pressure
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Tissue pressure is normally high or low?
How does local edema effect tissue pressure? |
Normally low
Significant increase --> edema |
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Which organs are susceptible to increases in tissue pressure?
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Brain & kidney-- w/ in rigid containers
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Myogenic theory of blood flow control states?
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Arterial diameter is regulated via transmural pressure-induced contractions & relaxations that tend to maintain constant artery diameter
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Which type of Ca channels have been proposed to explain myogenic reactivity?
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Stretch activated channels
Stetch (due to bp) --> Ca channels open --> Ca enters & stimulates contraction of smooth muscle |
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What is co-release?
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Vasoactive peptides released w/ traditional transmitters in response to single action potential from single nerve --> leads to complex changes
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What is reuptake?
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Active transport of released transmitter back into nerve terminal by proteins in synpatic membrane
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What is pre-synaptic feedback?
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Release transmitters & other agonists bind to specific receptors on synaptic neuronal membrane to inhbit further transmitter release
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What is overflow?
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When reuptake & pre-synaptic feedback both become saturated--> synaptic transmitter concentrations rise & diffuse out of synapse
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3 types of perivascular innervation?
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1. Sympathetic
2. Parasympathetic 3. Peptidergic |
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What is main transmitter of adrenergic sympathetic nerves?
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Norepinephrine
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Function of norephinephrine on alpha & beta receptors?
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alpha receptors --> vasoconstriction
beta receptors --> vasodilation |
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What is divergence?
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One preganglionic fiber activates many postganglionic fibers
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Where is divergence found?
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Sympathetics
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Main transmitter of cholinergic sympathetic nerves?
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Acetylcholine
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Where are cholinergic receptors found? (2)
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Skeletal muscle & skin --> mediate anticipatory vasodilation
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Do parasympathetics display divergence?
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No: one preganglionic --> one postganglionic
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Long or short postganglionics in sympathetic & parasympathetic?
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Sympathetic = long
Parasympathetic = short |
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Main transmitter of parasympathetic cholinergic nerves?
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Acetycholine
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What are peptidergic nerves?
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Nerves that release peptides
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At high concentrations epinephrine stimulates? and at low?
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high concentrations --> alpha receptors
low concentrations --> beta |
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Serotinin is released from?
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aggregating platelets
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What do seritonin & histamine do?
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Stimulates receptors on endothelium & VSM
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Where is histamine released from?
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mast cells
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ADH (vasopressin) released in response to?
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Hemorage or dehydration
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ADH release inhibited by?
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ethanol
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ADH acts on?
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Receptors of endothelium & VSM
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hydrogen acts as a vasodilator/constrictor?
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Vasodilator
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Alkalosis stimulates?
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Vasoconstriction
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What is hypoxia?
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Oxygen partial pressure below normal
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Hypoxia dilates or constricts? & does what to metabolism?
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Hypoxia --> vasodilator
Powerful inhbiitor of metabolism |
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What is hypercapnia?
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CO2 partial pressures above normal & powerful vasodilator
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Main goal of all cardiovascular reflexes is to?
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Maintain constant arterial pressure via carefully metered changes in: stroke volume, heart rate & peripheral vascular resistance
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Mean arterial pressure is equal to?
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MEAN ARTERIAL PRESSURE=
STROKE VOLUME x HEART RATE x PERIPHERAL VASCULAR RESISTANCE |
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carotid sinus senses?
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high pressure
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High pressure detected by carotid sinus sends impuslves to ____ via which nerve?
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carotid sinus --> glossopharyngeal nerve --> medulla
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Aortic arch senses?
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high pressure
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High pressure detected by aortic arch sends impusles to ____ via which nerve?
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aortic arch --> vagus nerve --> medulla
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baroreceptors in atria sense? send it to medulla via which nerve
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low pressure--> vagus --> medulla
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Increased medullary input from low pressure receptors accelerate ___ to heart but ____ to kidneys?
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Accelerate sympathetic to heart but decrease to kidneys
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Carotid body chemoreceptors stimulated by?
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Decreased PO2 & weakly stimulated by increased PCO2
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Aortic & carotid body chemoreceptors impulses travel same/different path as baroreceptors?
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same path
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increased chemoreceptor input does what?
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Increases respiratory drive via increasing motor to respiratory muscles
& increase sympathetic to heart & vessels |
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Chemoreceptors in in floor of medullary ventricle strong stimulated by?
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Decreases in pH or increases in CO2
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Medullary centers regulated blood pressure via short/long term influences on vascular resistance & short/long term influences on blood volume?
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blood pressure --> short term
blood volume--> long term |
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What is blood flow autoregulation?
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Ability of an organ to maintain constant blood flow in face of changing perfusion pressure
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Why is autoregulation critically important?
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Enables organs to maintain constant flow during conditions in which blood flow demand is so high that arterial pressure falls
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