Clin Phys Week 12 FINISHED Flashcards
What is the arterial pressure in the lungs compared to the rest of the body?
24-28mmHg vs 120-180mmHg
What does low levels of oxygen in the lungs cause?
Vasoconstriction
What does high levels of oxygen in the lungs cause?
Vasodilation
What is small vessel coronary circulation influenced by?
Aortic pressure
Pumping activity of the ventricles
What happens to the blood flow in the heart during ventricular systole?
Coronary vessels compress
Myocardial blood flow ceases
Stored myoglobin supplies sufficient oxygen
What happens to the heart during ventricular diastole?
Oxygen and nutrients are carried to the heart
How is the blood flow to the brain controlled?
Metabolic controls
Myogenic controls
What are the metabolic controls of the blood supply to the brain?
Decreased pH and Increased CO2
= causes vasodilation
What are the myogenic controls of the blood supply to the brain?
Protects the brain from damaging changes in blood pressure.
- decreases in MAP cause cerebral vessels to dilate to ensure adequate perfusion
- increased in MAP cause cerebral vessels to constrict
What is the blood brain barrier? What is it maintained by?
Refers to a permeability barrier between cerebrospinal fluid and blood.
Is maintained by tight junctions between endothelial cells in brain capillaries.
Tight junctions are reinforced by astrocytes (connective tissue cells)
What is the function of the blood brain barrier?
Maintain stable environment or neurons (homeostasis)
Prevents escape of neurotransmitters from CNS into periphery
Prevents entry of toxic substances from blood to brain
What is CSF?
A selective filtrate of the plasma
Formed in the choroid plexus in the cerebral ventricles
Also have blood-csf barrier (not so tight in hypothalamus, thirst reflex)
