Special Circulations Flashcards
Where do you see Active VD response
skin muscle = high
kidney = low - at rest is already maximally dilated
Muscle - What happens to CO with exercise
increases
20-25 L/min with exercise
Muscle - Where is most of CO going with exercise
to muscle - 80 to 85% of it
As inc exercise intensity - CO to viscera diminishes
As inc exercise intensity - CO to heart and brain stays the same
As inc exercise intensity - CO to skin increases and then kind of narrows off
Muscle - Weight
30kg
Muscle - At rest receives how much blood flow? and with exercise?
Rest = 2-4 ml/min or 15-20% of CO Exercise = 400 ml/min or 85% of CO
Maximal amount of flow that muscle can receive in limited buy
Cardiac Output
If didn’t matter, would want CO of 90L/min - this would rupture aorta
If we activate sympathetic NS
Decrease in blood flow of about 70-80%
If block sympathetic NS
Would see double or tripling in BF from rest
Inc 200-300%
Fibers types and blood flow
The more oxidative the tissue, the more flow that it will get
Capillaries with muscle
Very dense capillary unit, only heart has mroe
density of this matches the oxidative potential of the fiber
with exercise training = inc in number of capillaries per muscle fiber and inc mitochondria
Blood flow control has both neural and local component in skeletal muscle
Contains both alpha and beta ARs (alpha= constrict, beta = dilate) and with this alpha wins
Blood flow control has both neural and local component in skeletal muscle - Neural
EPI and NE = cause VD of muscle by binding to beta
Blood flow control has both neural and local component in skeletal muscle - Local
Metabolic vasodilation
And shear stress and muscle pump
How does blood flow to muscle increase during exercise
Muscle has greatest absolute increase in total NE spillover - we have overshadowed the inc in SNA during exercise, as you inc exercise you are inc spill over
Functional Sympatholysis - overshadow SNA during exercise
Splanchnic weight
Weight = 1.5 kg
Liver receives blood from
Hepatic Artery
Portal Vein
Haptic Artery vs. Portal Vain
Hepatic artery has autoregulatory mechs
Portal vein does not (more ANS)
Splanchnic Circulation - Extrinsic
Highest density of Alpha - can constrict down very well
Highest density of Beta too - during stress will VD
NO PARASYMP HERE
Splanchnic - Redistribution of flow
Splanchnic circulation is a huge resdistributor of blood flow
- it receives high BF
- has little metabolic activity - doesnt really need the flow so is the best place to take it away from
Splanchnic circulation and compliance
It is very compliant
Compliance primarily impacts venous circulation
27% of CO
Max flow = 2.5L/mn
Other that is very compliant?
Skin
9% of CO
Max flow = 8 L/min
Splanchnic and Skin
Will accommodate large change in volume with a very small pressure
If you constrict Splanchnic or Skin
Upstream pressure will inc
Downstream pressure will dec - this drop in pressure will mobilize a large amount of flow - this is what initially happens during exercise
If you constrict muscle
You aren’t mobilizing hardly any flow - it is not as compliant
Compliant circulation - if you dilate a compliant circulation you will
dec SV and venous return back to the heart
Compliant circulation - if you constrict a compliant circulation you will
you are liberating more volume back to heart - it inc venous return, SV and CO
When flow goes back through circulation again (from heart) will go to where least resistance - the muscle
Constriction of compliant vessels
Dilation of noncompliant vessels
VC of compliant –> inc flow back to heart
After you will get less flow back to the constricted area and more flow back to the dilated - noncompliant area - more flow and more pressure here
Constriction of noncompliant vessels
Dilation of compliant vessels
Flow gets caught up in the dilated compliant vessel and less will go back to the heart
Basic Renal Process
Filters
Secretes
Reabsorbs
Renal Circulation: Blood Flow -
Highly overperfused
Renal Circulation - Resting Blood Flow, Max Blood Flow
Resting = 1.2 L/min = 22% CO
Max blood flow = 1.2 L/min
Renal Weight
0.3 kg
Flow Control - Renal
Does not have alpha but does have beta Ars
Dec 20-30% with SNA
Regulated by autoregulatory control - myogenic and metabolic
Cerebral Circulation -
Comes through carotid and basilar to circle of willis
Enclosed in cranial vault - so is non compressible
Cerebral - Resting Blood Flow and CO
750 mL/min
12-15% CO
Cerebral - Max blood flow
about 2 L/min
Constant blood flow sure to incompressibilty - vault prevents tissue from
Cerbral Flow Control
Unaffected by ANS
Controlled exclusively by autoregulation
Myogenic, metabolic and starling resistor
Cerebral - Starling Resistor
As tissue pressure increases, transmural pressure of vessels will decrease
Autoregulatory resistors are subject to this
If tissue pressure inc too much, you will not get flow to the brain
Cerebral and gases
Sensitive to changes in blood gases
Small changes in PCO2 will have large changes in cerebral blood flow
Cerebral - Cushing Reflex
Cerebral ischemia activates the cushing reflex
Inc in intracranial press –> dec in blood flow –> hige SNS –> inc in MAP –> inc CNS flow
Coronary Blood Flow -
Receives 250mL/min (5% of CO)
Coronary - Capillary
Has very dense capillary network (10x as many as skeletal muscle)
During exercise - what happens to coronary BF
increases as HR increases - up to 1200 mL/min
Coronary BF can inc to 1L/min during max exercise
Control of Coronary Blood Flow
Powerfully regulated by autoregulation
- metabolic control
Increased O2 will math increased flow
Little to no influence of symp NS
Atherosclerosis starts with
Endothelial dysfunction
and ends with plaque - thickening of intima space and change ind diameter of the vessel
Why are plaques dangerous
Unstable, can rupture and cause MI or stroke
Plaque will compromise flow to areas downstream from it and tissues will become ischemic
Thrombus
platelets held together with fibrin strands
Emobolus
when thrombus separates from wall and floats in circulation
Results of plaque –>
Will weaken the vascular wall and an aneurysm can develop
Myocardial Infarction
Death of myocardial cells due to O2 deprivation
Disrupts the depolarization and can lead to Vtach or Vfib
Causes of MI
Coronary Artery Disease - plaque formation - thormbus Will see drop in CO and MAP Compensate with baroreflex --> SNA will inc to bring CO back up --> it iwll vasoconstrict --> you are now inc workload of already damaged heart though --> not good
Left Heart Failure
Dam = jxn LV and aorta Upstream = pulmonary circulation Downstream = systemic circulation
Right Heart Failure
Dam = lung or jxn RV and pulmonary aorta Upstream = venous return in RA Downstream = left heart
Etiology of Heart Failure
Drop in CO Baroreflex kicks in to bring pressure up SNA - contractillity, inc HR Stressing an already damaged heart vasoconstriction --> inc afterload --> working heart too hard
