coronary circulation and temperature regulation

Question 1

what does the phasic blood flow thru coronary circulation do at delta P1? when is P1?

Answer 1

-P1 is when the AV is closed and ventricles are in diastole and ventricles are filling

Question 2

what is delta P2?

Answer 2

• 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

Question 3

what is delta P3

Answer 3

• 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

Question 4

what is delta P4

Answer 4

• 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

Question 5

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?

Answer 5

• during diastole
• during systole
• at the end of isovolumic contraction

Question 6

how is the coronary circulation different on the right side than the left?

Answer 6

• compressive forces smaller (smaller afterload)
• pressure grad remains relatively stable throughout events of cardiac cycle
• results in better perfusion of RV

Question 7

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?

Answer 7

• 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

Question 8

what are the steps by which working harder can change the vascular tone

Answer 8

increase metabolism via work
increase hypoxia (decrease pO2)
increase atp turnover
increase cell adenosine accum
increase vasodilation

Question 9

how does core temp compare to skin temp

Answer 9

• 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

Question 10

what are the four mechanisms for heat transfer

Answer 10

radiation, conduction, convention, evaporation

Question 11

radiation

Answer 11

• infrared heat rays- electromagnetic

- relies on gradient ;therefore if body temp>environmental temp, heat radiated away from body

Question 12

Conduction
what is it?
what has better conduction?-air or water

Answer 12

• 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

Question 13

convention

Answer 13

• cools/heats by wind

- loss of heat greater in water

Question 14

Evaporation

Answer 14

• 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

Question 15

how does the peripheral nervous system react to cold?

Answer 15

-vasoconstriction reducing the amount of thermal conductivity exchange between the environment and us

Question 16

in terms of temperature regulation, what does the anterior hypothalamic preoptic area do? what about sensory receptors in the skin?

Answer 16

• has heat sensitive (sweating, cutaneous vasodilation) and cold sensitive neurons
• sensory receptors-more for the cold- initiates shivering, inhibits sweating and elicits vasoconstriction

Question 17

what do deep temperature sensory receptors do?

Answer 17

• sense cold and hot but mostly cold

- spinal cord, abdominal cav, great veins

Question 18

what does the posterior hypothalamus do?

Answer 18

relay station for sensory inputs from periphery and anterior hypothal
integrates response to warm or cool the body

Question 19

what occurs in the body when we are too hot

Answer 19

vasodilation of cutaneous vessels
sweating
decreased heat production-inhibit shivering/thermogenic rxns

Question 20

what occurs when we are too cold?

Answer 20

• cutaneous vasoconstriction
• piloerection = chills
• increase thermogen-shivering, stim of heat production, thryroxine secretion

Question 21

what is the process of shivering entail?

Answer 21

1) get signal from dorsamedial portion of the hypothalamus
2) activate body temp falls
3) transmission of signal to spinal cord
4) get TWO STEP ACTION A) increase skeletal muscle tone to reader shivering signal
B) temp drops enough to initiate muscle shaking

Question 22

how do we stimulate heat production

Answer 22

• chemical thermogenesis- sympathetic nervous system increases cell metabolism
  -it uncouples oxidatitive phosphorylation to release energy in the form of heat rather than ATP
  = MAIN HEAT REGULATORY MECH IN INFANTS

Question 23

what are two chemical thermoregulation strategies

Answer 23

• activate SNS to alter oxidative phos to render heat instead of ATP
  or
  -thryroxine secretion

Question 24

thyroxine secretion

Answer 24

• chemical thermoreg strategy
• increase thryroid activity and secretion of thyroxine
• increase cell metab = heat

Question 25

what can an over reaction to heat do?

Answer 25

• vasodilation can cause decreased B.P
• perspiration- can cause electrolyte and water imbalance
• cardiac probs- heat increases permeability of heart cells
• increased HR