Vascular System Flashcards
Hyperemia
Excess supply of blood
Reactive Hyperemia
Myogenic & metabolic mechanism
Active Hyperemia
Metabolic mechanism
Angiogenesis
Growth of more capillaries - increase in s.a. - increased potential for greater flow
Angiogenic Factors causes & examples
Decrease in O2 levels - increase in angiogenic factors
VEGF (vascular endothelial growth factor) makes endothelial cells grow, migrate & invade
Anatomy of LHS coronary circulation
- Left main coronary
- LAD (left anterior descending artery) travels along intraventricular groove
- Circumflex artery travels posteriorly
Anatomy of RHS coronary circulation
Right coronary artery runs posteriorly between RA & RV
During systole
Marked compression of microvasculature (system of tiny blood vessels)
Higher HR –>
Higher heart rate –> reduction in diastole –> mechanical reduction in time available for flow
Intramural pressure is greatest in
Endocardium
Blood flow equal between epi & endo
Despite intramural P greatest in endo - blood flow equal between epicardium & endocardium:
Higher vessel density in endocardium
Major inducer of vasodilation in heart circulation
Adenosine
How does Adenosine regulate VD:
Low levels of Ado - stimulate release of NO
Higher levels of ado - act directly on SMC
Effect of sympathetic activation on coronaries
Sympathetic (norepinephrine) activation results in VD in coronaries
Speed Up Diffusion
1) Thinner walls (thinner the membrane - faster diffusion rate)
2) Small molecular weight molecules (such as O2 & CO2 able to diffuse quicker)
3) Increase Pressure (increase O2 conc. - increase partial P of O2 across membrane - therefore faster diffusion rate)
4) Expand surface area (larger surface area
- higher diffusion rate)
Functional Sympatholysis
Decreased VC during increase in sympathetic activity
1) Directly constricts via alpha 1 adrenoreceptor
2) Increased metabolic rate due to inotropy (increased strength of contraction), HR increases via beta-adrenoreceptors –> Functional Sympatholysis (overrides alpha 1)
Primary role of cutaneous circulation
Heat exchange: mainly regulated by sympathetic activity controlled by hypothalamic thermoregulatory centers
What holds the majority of blood volume in skin
Venous plexus
Cardiac % - in cutaneous regulation
Low temp - 0-3%
Severe heat stress - can increase to 50%
2 Stages of Vasodilation in Cutaneous Circulation
1 - Passive: reduction in sympathetic adrenergic activity - decrease in norephinerine - AVs dilate - increase flow
2 - Active: sympathetic cholinergic activity - acetylcholine stimulates VD
Villi are supplied by what order arterioles & capillaries
Villi are supplied by 3rd order arterioles & capillaries
Intestinal Circulation primary function
Nutrient & water absorption
Capillaries in hepatic circulation termed
Sinusoids
Cerebral perfusion pressure
Cerebral perfusion pressure = MAP - ICP
Two systems in Pulmonary circulation:
1 - Bronchial system: supplies nutrients for lungs
2 - Pulmonary system: supplies blood for gas exchange
Pulmonary circulation haemodynamics & regulation
low pressure
low resistance
high compliance
T/F: pulmonary circulation has autoregulation
F - does not have autoregulation of flow but does have autoregulation of pressure
Coronary circulation: (1) Sympathetic, (2) Metabolic, (3) autoregulation control
1- Sympathetic control = weak
2 - metabolic control = strong
3 - autoregulation = strong
Cerebral circulation (1) sympathetic, (2) metabolic & (3) autoregulation
1) sympathetic control = weak
2) metabolic control = strong
3) autoregulation = strong
Skeletal muscle: 1 - sympat., 2- metabolic, 3 - autoregulation
1 - sympathetic control = moderate
2 - metabolic control = strong
3 - autoregulation = moderate
Cutaneous circulation: 1 - sympathetic, 2 - metabolic, 3- autoregulation
1- sympathetic control = strong
2 - metabolic control = weak
3 - autoregulation = weak
Intestinal circulation: 1 - sympathetic, 2 - metabolic, 3 - autoregulation
1 sympathetic control = strong
2 metabolic control = moderate
3 autoregulation = moderate
Renal circulation - 1: sympathetic, 2: metabolic, 3: autoregulation
1 - sympathetic = strong
2 - metabolic = weak
3 - autoregulation = strong
Pulmonary circulation: 1- sympathetic, 2 - metabolic, 3 - autoregulation
1 - sympathetic control = weak
2 - metabolic control = weak (hypoxic vasoconstriction - pulmonary arteries constrict in the presence of alveolar hypoxia)
3 - autoregulation = N/A
During exercise - what mechanisms is used by skeletal muscle to increase flow
1 - Functional Sympatholysis
2 - Capillary recruitment
3 - Skeletal muscle pump
X reactive hyperemia
Interstitial hydrostatic pressure is generally very low due to mainly
Lymphatic system
Major driving force for reabsorption of fluid in the circulatory system is:
Capillary oncotic pressure
Increased sympathetic nerve activity causes the heart to experience
a - vasoconstriction
b - vasodilation
c - increased inotropy
In which organ is its blood flow phasic in nature:
Heart
