Exam1Lec4ControlofBloodFlowandTheMicrocirculation Flashcards
What are blood vessels for?
Delivery of nutrients, removal of wastes, and gas exchange
How do blood vessels nutrients to the tissues?
Microvascular exchange a consequence of vessel permeability
Are all blood vessels perfused all the time?
NO, so your body must prioritize blod flow to the metabolically active organs.
What constitutes the highest surface area?
Capillary beds
with high surfce areas you can get as much o2 into your blood quickly
Where do we see the lowest/slowest blood velocity?
Capillaries
they are known as the exchange vessels to allow tfor maxiumum exchanfe
Most of the blood volume in what?
Veins
Label capillaries, veins, and arterioles as
exchange vessels
capitance vessels
resistance vesses
capillaries-exchange vessels
veins-capitance vessels
arterioles-resistance vesses
What are the 3 types of capillaries?
- Continuous (very controlled-BBB)
- Fenestrated (most normal)
- Sinusoidal (discontinous- spleen or liver)
What do arterioles respond to?
- Tissue demand (metabolite)
- Flow and pressure inside the vessel
- neurogenic stimuli
- hormones, drugs, other chemical stimuli
arteriorles simultaneouslt control SVR (Systemic vascular resistance) and blood flow to tissues
When looking at a cross section of an arteriole, what is the order of layers from innermost to outermost?
- Endothelial cells
- SM cells ( these constrict or dilate to regulate vessel diameter)
- Nerve bundles
- CT
Give a general explanation of electrochemical coupling
There’s a membrane dep, and there is an influx of ca2+ causing muscle contraction/constriction
main thing is that calcium comes inside smooth muscle cell and causes contraction/constriction
Give a general explanation of pharmacomechanical coupling
a vasoconstrictor agonist drug binds to gpcr causing different signaling cascades and specifically IP3 open Ip3 receptors on sarcoplasmic reticulum and releases ca2+ into smooth muscle cells causing constriction
main thing is that calcium comes inside smooth muscle cell and causes contraction/constriction
Sympathetic stimulation results in what?
Vasoconstriction (arterioels can constict and shunt blood flow to the body)
for ex, in an experiment they shunted epineph and the smc consticted all the way so that rbc can’t go through
neurogenic control of arteriolar tone
Sympatheitc NS
releases____ which binds to ____ causing ____
It can also have ____ released inside the cell which then triggers the release of ____ from the SR.
NE, alpha receptors on vmsc, constriction, ip3 Ca2+
What is innervated by sympathetic ns by SNS fibers:?
arteries, arterioles, veins, and lymphatics
neurogenic control of arteriolar tone
Parasympathetics NS releases____ which binds to ____. A signaling cascade occurs and can lead to an activation of an enzyme called ____
Ach, muscarinic receptors on endothelial cells, eNOS
eNOS enzyme is going to produce ____ which then diffuses to ____ and these activate____, which then produces ____ which leads to ____.
NO, VSMC, sGC, cGMP, dilation
small fracion of vessels are innervated with parasymp fibers
In the experiment that has to do with endothelial regulation of arteriolar tone, what are the main points.
When adding CCh and ACh they both causes relaxation bc of decr tension and dilation occuring with endothelium present. If you take a helical strip, the endothelium was removed, killing endothelial cells. So when you add a higher dose of CCh it is unable to produces NO and eNOS causing constriction.
cannot dilate vessel w/o endothelial cells
Explain endothelial regulation of arterioriolar tone.
We have a ligand such as ACh, serotonin, thrombin, or bradykinin binding to a muscrinic receptor releasing Ca2+ into the endothelial cell. This release activates eNOS which needs a co-factor of eitherr Calmodulin, NADPH, FAD, BH4 to catylze a rxn of turning L-Arginine to both L-Citrulline and NO( eNOS turning to NO). NO freely diffuses into vascular smooth muscle cell activating GC with is an enzyme that converts GTP into cGMP causing relaxation.
slide 18 of lecture
cGMP activates myosin light chain phosphotase> muscle relaxation
Calcium in endothelial cell causes relaxation
Calcium in in smooth muscle cell causes constriction
What is Sidenafil?
It is a cGMP phosphodiesterase inhibitor (PDE5). It breaks down cGMP deactivating the pathway of relaxation .
turns cGMP to GTP leading to contraction remaining
Explain how arterioles contribute to myogenic response of autoregulation of blood flow
Arterioles protect capillary beds bc with an incr of pressure, the arteriole dilate transiently and then constricts to limit the amount of pressure reaching capillary beds to prevent rupturing and bledding from capillaries bc they don’t have a layer of smooth muslcle cells to expand.
For myogenic response for autoregulation, is endothelium involved?
How can this response eliminated? what is required?
- Endotheloum is not involved (kill endothelial cells and smc still does the job)
- Treatment with NO will cause smc to completely dilate, so no constric occurs
- VSMC alone is required ( no nerves )
What is the myogenic hypotheis of autoregulation?
Vascular SMC themselves contracts/constricts in response to an incr in pressure. Conversely, VSMC relaxes in response to a decr in pressure.
With incr transmural pressure, incr stretch, incr constriction
transmural pressure= (pressure inside-pressue outside)
What is active hyperemia?
Incr metabolic activity that creates byprodycrs that induce vasodilation and a subsequent incr in blood flow (hyperemia)
ex: working out; lots of reps, little weigjt, incr bf to muscles
eating a meal, decr in vaso resistnace, incr bf into gut to meet tissue needs
