Physiological basis for Cushing reflex
Cushing reflex (Cushing effect, Cushing reaction, Cushing phenomenon, Cushing response)
- Increase systolic blood pressure and reduce heart rate ( bradycardia) due to increased intracranial pressure
Cerebral blood flow depends on
- Local constriction and dilation of cerebral arteriols
- Intracranial pressure
- Mean arterial pressure
- Mean venous pressure
- Viscosity of blood
Physiological changes in increase intracranial pressure
- When intracranial pressure increase , cerebral blood flow decreases
- Decreased cerebral blood flow lead to ischemia ( increase Co2 , decrease O2 )
- Hypoxia and hypercapnea Stimulate vasomotor center
- It leads to increased Sympathetic discharge
- Therefore Increase heart rate, the vessels constrict ( vasoconstriction )
- Increase heart rate and vasoconstriction increase cardiac output ( CO = SV × HR)
- Therefore blood pressure increase ( BP = CO × TPR)
- Increase blood pressure stimulates bareoreceptor and inhibit sympathetic discharge ( baroreceptor reflex )
- Due to reduce sympathetic discharge heart rates reduces ( baradycardia )
Labels: CVS, CVS SEQs, Physiology SEQ