3.4.1. Regional Circulation Flashcards
Distribution of BF to tissues is:
Determined by ______________.
Influenced by _______________________.
Distribution of BF to tissues is:
Determined by local metabolic factors
Influenced by different intrinsic properties of each vascular bed
What predominates cardiac output?
GI (25%)
What is the system that requires the least blood?
The heart only needs 5% of the CO. Which is three times less than the brain.
Blood flow is determined by local matabolic needs but is little affected by what?
Primarily determined by local metabolic NEEDS
However, there is little effect of local metabolites on BF
Sympathetic stimulation _____ BF through skeletal muscle, but not cerebral circulation
Sympathetic stimulation increases BF through skeletal muscle
Neural vs. local influence
Skeletal muscle Control
At rest - Regulated primarily by the neural influence
During exercise - Regulated predominantly by the local influence
Remember, BF is directly related to contractile state
What is Maximal oxygen consumption (VO2 max)?
Maximum amount of oxygen your body can utilize in one minute
Formula for aerobic endurance
VO2 = CO x (a- vO2)
[Fick equation]
Factors affecting VO2 max
Heredity, sex, age, body composition, training (5-20%), others (e.g., EPO, blood doping)
Arteriovenous anastomosis is controlled by what
SNS
In the arteriovenous anastamosis, we constrict and divert blood into the superficial capillary during what?
Constrict and divert blood into the superficial capillary during low ambient temperature
Oxygen requirements to maintain anastamoses
Very little
BF through the skin is adjusted to maintain deep body temperatures by what mechanism?
BF through the skin is adjusted to maintain deep body temperatures by regulating ordinary arterioles and arteriovenous anastomosis
Sweat glands secrete ______ which increases BF to skin and sweat glands
Sweat glands secrete bradykinin which increases BF to skin and sweat glands
Unlike humans, mice maintain temperature by regulating BF to tail and do not sweat (result = what?)
Unlike humans, mice maintain temperature by regulating BF to tail and do not sweat (result = ↑↑↑temp, ↑↑↑HR, and ↑↑↑BP)
More Fit = ____ BF and _____ in temp
More Fit = better BF and slower increase in temp
What two things happen when transitioning from rest to exercise?
Increased demand for BF in the Heart, respiratory muscles, and active skeletal muscles
Increased demand for BF to dissipate heat via cutaneous vasodilation
How does the CV system adjust to meet the demands of exercise?
↑ vascular resistance and ↓ BF to non-vital organs
↓ vascular resistance and ↑ BF to active muscles
↑ cardiac output
Adenosine causes what?
Adenosine causes transient heart block in the atrioventricular (AV) node
It also causes endothelial-dependent relaxation of smooth muscle
Mechanism of action for Adenosine
Via the A1 receptor, inhibiting adenylyl cyclase, reducing cAMP and so causing cell hyperpolarization by increasing outward K+ flux
Why do surgeons use Adenosine to test fro blockages in coronary arteries?
One of Adenosine’s actions is to cause endothelial-dependent relaxation of smooth muscle
This causes dilation of the “normal” segments of arteries, i.e. where the endothelium is not separated from the tunica media by atherosclerotic plaque
This feature allows physicians to use adenosine to test for blockages in the coronary arteries, by exaggerating the difference between the normal and abnormal segments
What cells release L-Lactate?
Optogenetically activated astrocytes release L-lactate,
Functino of L Lactate
Optogenetically activated astrocytes release L-lactate, which excites locus coeruleus (LC) neurons and triggers release of norepinephrine
LDH is responsible for what?
LDH is responsible for the conversion of NADH to NAD+ and back
The near-equilibrium between free cytosolic NADH/NAD+ and lactate/pyruvate ratios established by LDH predicts that what?
predicts that transfer of additional electrons and protons from injected lactate to NAD+ will augment the elevated blood flows in stimulated retina and cortex, whereas transfer of electrons and protons from NADH to injected pyruvate will attenuate the elevated flows.
What is one important function of NADH?
Fuels a signal cascade that increases NO radical production
NO does what?
augments blood flow in photostimulated retina and visual cortex
EDRF (endothelium-derived relaxing factor)
Promote smooth muscle relaxation
Analagous to NO
EDHF (endothelial derived hyperpolarizing factor)
Hyperpolarizes vascular smooth muscle cells, causing the cells to relax, thus allowing the blood vessel to expand in diameter
EDCF (endothelial derived contracting factor)
Endoperoxides (PGH2) and prostacyclin, which activate thromboxane-prostanoid (TP) receptors of the vascular smooth muscle cells
PGs
Prostacyclins are synthesized in the walls of blood vessels and serves the physiological function of preventing needless clot formation
