Coronary Circulation Flashcards

1
Q

Describe the coronary pressure during ventricular filling (P1)

A

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

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2
Q

Describe the coronary pressure during Isovolumic contraction (P2)

A

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!!!
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3
Q

Descrive the coronary pressure during Ejection phase of Systole

A

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

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4
Q

Describe the coronary pressure during Ventricular diastole

A

During ventricular diastole, the pressure gradient becomes large again
- Coronary blood flow INCREASES to its HIGH VALUE

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5
Q

When is perfusion of the left ventricle highest?

A

during diastole!

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6
Q

Describe the Sympathetic Biphasic regulation of the coronary blood flow

A

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

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7
Q

Describe the effects of a bigger heart on coronary blood flow

A

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

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8
Q

Describe Radiation

A
  • 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)
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9
Q

Describe Conduction

A
  • 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)
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10
Q

Describe Convection

A

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
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11
Q

Describe EVAPORATION

A

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)
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12
Q

Describe the feedback regulation of body temp. for HOT

A

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

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13
Q

Describe shivering

A

Cold response: Sympathetic stimulation of skeletal muscles
Phase 1 = get set phase
phase 2 = (tempt gets low enough) start signal to begin active shivering

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14
Q

Describe Arrector pili muscles

A

Cold response: sympathetic stimualtion of arrector pili muscles
- gives goose bumps

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15
Q

Describe the stimulation of TRH release

A

Long term adaption (weeks) to the cold
- TRH –> Anterior pituitary stimualtion –> TSH release –> Thyroid activation –> release of T3 and T4 –> ACTIVATION OF CELLULAR METABOLISM

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16
Q

Describe Chemical thermogenesis in cold temp response

A

Stimulated by SNS to increase cellular metabolism

  • uncouple oxidative phosphorylation to release energy in heat rather than ATP production
  • especially efficient in brown fat (infants)
17
Q

Describe responses to heat

A
  • Perspiration = dehydration, loss of water, electrolytes
  • Cardiac Problems = heat increases permeability of cardiac cells
  • -> increased HR accelerates slope of pacemaker potential
  • Decreased Blood pressure = excessive cutaneous vasodilation
  • Excessively excessive heat can damage cells (increased cellular permeability