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19 Cards in this Set
- Front
- Back
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List the 'vasodilator substances' released from the 'tissue' (rather than from the endothelium).
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-adenosine
-adenosine phosphate compounds -CO2 -H+ (can be contained in lactic acid) -K+ -histamine |
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What stimulates the release of these substances from the tissues?
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O2 deficiency
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What theories are present to explain the increase in local tissue blood flow in response to increasing demand?
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1-Vasodilator substance theory
2- Oxygen lack theory (or nutrient lack theory) |
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What is Reactive hyperemia?
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: the observed phenomenon in which there is an ↑ in local tissue blood flow following blocking that flow for a certain period of time.
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What is Active hyperemia?
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the ↑ in blood flow in a tissue because of its increased activity e.g. in exercising muscles
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Define Autoregulation.
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: is the act of maintaining a constant blood flow via changing the vascular resistance in face of changes in the arterial perfusion pressure at constant levels of tissue metabolism
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Tell me the arterial pressure range over which the autoregulation mechanims work?
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70-175 mmHg (Guyton)
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How is autoregulation achieved?
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1-Metabolic theory
2-Myogenic theory |
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What is the half-life of NO?
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6 seconds!
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Tell me what is the average coronary blood flow?
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250 mls/min
or 80 mls/min/ 100 g of heart muscle (represents 5% of the total CO) |
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What is the arterial oxygen extraction percentage in the coronary circulation?
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70-80 %
(compared to 25% for the rest of the body) |
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Describe Gregg Effect.
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states that the ↑ in coronary blood flow independently ↑ the myocardial tissue oxygen demand/consumption due to the full coronary arteries splinting the heart and ↑ing the end-diastolic fiber length and contractility.
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What does the left coronary artery supply?
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1- the anterior and lateral walls of the left ventricle
2-the anterior two thirds of the inter-ventricular septum |
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What does the right coronary artery supply?
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1- the right ventricle
2-the posterior wall of the left ventricle 3-the posterior one third of the inter-ventricular septum |
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Describe the venous drainage of the heart?
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1- coronary sinus
2- anterior cardia vein 3- Thebesian veins |
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What is the coronary perfusion pressure?
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Coronary perfusion pressure= Aortic diastolic pressure - LVEDP
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What are the determinants of coronary blood flow?
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1- Coronary perfusion pressure
2- Perfusion time 3- Radius of the coronary vessels |
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What determines the radius of the coronary vessels?
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1- the vasomotor tone
2- any deposits inside the vessels |
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What is the average systolic time in the cardiac cycle?
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200 ms
Systolic time is usually fixed at the above number, with diastole occupying the remainder of the time |
