coronary circulation and temperature regulation Flashcards
what does the phasic blood flow thru coronary circulation do at delta P1? when is P1?
-P1 is when the AV is closed and ventricles are in diastole and ventricles are filling
what is delta P2?
- cooresponds to tail end of isovolumic contraction, ventricle is filled which increases coronary artery pressure, AV is NOT open yet
- INCREASE IN CORONARY ARTERY PRESSURE BECAUSE INCREASE IN LV PRESSURE
- seeing as flow = p/R and keeping R constant, we see that there is very little pressure change in the aorta with the AV closed
what is delta P3
- it is the ejection phase of systole, av is open, release of blood into aorta generates a pressure grad
- if look at flow= p/R keeping R constant, we see that the increase in pressure causes an increase in flow thru coronaries
what is delta P4
- when the AV closes and there is a start of ventricular valve filling
- holding R constant we see that Flow= P/R will elicit a flow thru the left coronaries as the change in P from systole to diastole is significant
when is the LV maximally perfused by the coronaries? when is it minimally? where is the lowest point of the coronary perfusion to the LV?
- during diastole
- during systole
- at the end of isovolumic contraction
how is the coronary circulation different on the right side than the left?
- compressive forces smaller (smaller afterload)
- pressure grad remains relatively stable throughout events of cardiac cycle
- results in better perfusion of RV
when the coronary perfusion is the lowest (ie in isovolumic contraction) what is occurring with the wall tension of the ventricle? what occurs if the heart gets bigger?
- wall tension is the highest
- the wall tension gets bigger and that means that we are starting the cardiac cycle at a very low coronary perf
what are the steps by which working harder can change the vascular tone
increase metabolism via work increase hypoxia (decrease pO2) increase atp turnover increase cell adenosine accum increase vasodilation
how does core temp compare to skin temp
- basal core temp is constant and within +/-1 F except in case of fever
- basal temp will vary with stress and activity
- changes with circadian rhythm, lutal phase (increases), exercise and age
- skin changes widely
what are the four mechanisms for heat transfer
radiation, conduction, convention, evaporation
radiation
- infrared heat rays- electromagnetic
- relies on gradient ;therefore if body temp>environmental temp, heat radiated away from body
Conduction
what is it?
what has better conduction?-air or water
- requires contact with heat source
- conductivity- is the rate of transfer of heat by conduction
- water
- thermal conductivity varies in skin- vasoconstriction in the cold = decreased conductivity
convention
- cools/heats by wind
- loss of heat greater in water
Evaporation
- only mechanism that can continue when the ambient temp exceeds body temp
- regulated by sympathetic NS- sweat glands that cool body temps
- cooling cant occur if evaporation does not occur; therefore can’t cool if dripping sweat
- this is why humidity is harsh- because it decreases evaporation
how does the peripheral nervous system react to cold?
-vasoconstriction reducing the amount of thermal conductivity exchange between the environment and us
