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Cushing ReflexThe Cushing reflex, consisting of an increase in blood pressure and a lowering of the heart rate (bradycardia), is a hypothalmic response to ischaemia, usually due to poor perfusion (delivery of blood) in the brain. The ischaemia activates the sympathetic_nervous_system, causing an increase in the heart's output along with periferal constriction of the blood vessels. This accounts for the rise in blood pressure, ensuring blood delivery to the brain. The increased blood preasure also stimulates the baroreceptors (pressure sensitive receptors) in the carotides, leading to an activation of the parasympathetic nervous system, which slows down the heart rate, causing the bradycardia. Cushing reflex is usually seen in the terminal stages of an acute head injury.
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