Coronary Circulation Flashcards
Describe the coronary pressure during ventricular filling (P1)
During ventricular filling, the outlet pressure is HIGH; the inlet pressure is LOW, generating a large pressure gradient to perfuse the coronary circulation
- Coronary blood flow is high
Describe the coronary pressure during Isovolumic contraction (P2)
During isovolumic contraction, the coronary artery pressure increases dramatically, as the ventricle is filled and wall tension is being generated
- Also at this time (ventricular systole), AORTIC PRESSURE IS LOW
- CORONARY BLOOD FLOW IS VERY VERY LOW!!!
Descrive the coronary pressure during Ejection phase of Systole
During ejection phase of systole, the AORTIC VALVE is opened and blood causes an increase in aortic pressure, generating a pressure gradient
- CORONARY BLOOD FLOW INCREASES TO a moderate level
Describe the coronary pressure during Ventricular diastole
During ventricular diastole, the pressure gradient becomes large again
- Coronary blood flow INCREASES to its HIGH VALUE
When is perfusion of the left ventricle highest?
during diastole!
Describe the Sympathetic Biphasic regulation of the coronary blood flow
PHASE 1) DIRECT EFFECT - immediate vasoconstriction due to activation of ALPHA adrenergic receptors on the vascular smooth muscle cells
PHASE 2) INDIRECT EFFECT - stimulation also will cause INCREASE in myocardial metabolism and will elicit metabolic vasodilation as described above
Describe the effects of a bigger heart on coronary blood flow
If the Heart gets bigger:
- WALL TENSION INCREASES so we are starting the cardiac cycle at a tension that produced a very low blood flow in the normal heart THEREFORE you get POOR PERFUSION
Describe Radiation
- Infrared heat rays (electromagnetic waves) (ex: a fire)
- Heat gradient: body temp > environmental temperature, heat radiated away from body
- Clothing can affect heat ray absorption (aka light color can reflect heat rays)
Describe Conduction
- Based on direct contact between 2 objects
- Heat transfer will be DOWN the thermal gradient
- Conductivity: Rate of transfer of heat by conduction (to air = low conductivity; to water = high conductivity)
- Thermal conductivity of skin varies with cutaneous flow (heat: vasodilation = increased conductivity) (Cold: Vasoconstriction = decreased conductivity)
Describe Convection
Loss by currents:
- Cooling by wind: warmed air adjacent to skin quickly blown away so continues the process of convection
- Loss is greater in water: harder to heat up a layer of water surrounding skin
- Also moves DOWN the thermal gradient
Describe EVAPORATION
SWEATING: Only physiological principle
- Only mechanims that can CONTINUE when the ambient temp. exceeds body temp.
- CHOLINERGIC SYMPATHETIC fibers activated
- Non-thermoregulatory (‘nervous’) sweating is through activation of a few alpha 1 receptors on sweat glands (circulating epi/ne)
- The water mus actually evaporate to provide COOLING (energy transfer) (humidity reduces evaporation)
Describe the feedback regulation of body temp. for HOT
1) Normal core temp.
2) increased/decreased body temp (excercising, environment, etc)
3) activation of heat/cold receptors
4) hypothalamic activation (heat-loss center)
5) cutaneous vasodilation/vasoconstriction
6) Sweat response/skeletal muscle activation (shivering)
7) Body temperature reduced/increased
8) return to normal
Describe shivering
Cold response: Sympathetic stimulation of skeletal muscles
Phase 1 = get set phase
phase 2 = (tempt gets low enough) start signal to begin active shivering
Describe Arrector pili muscles
Cold response: sympathetic stimualtion of arrector pili muscles
- gives goose bumps
Describe the stimulation of TRH release
Long term adaption (weeks) to the cold
- TRH –> Anterior pituitary stimualtion –> TSH release –> Thyroid activation –> release of T3 and T4 –> ACTIVATION OF CELLULAR METABOLISM
