Cardiac Reflexes

Question 1

Baroreceptor Reflex

Answer 1

Baroreceptors located in internal carotid and aortic arch - respond rapidly to changes in systemic BP. Increased baroreceptor stretch causes decreased sympathetic outflow resulting in vasodilation, decreased HR, decreased inotropy which all decrease systemic BP towards normal

Question 2

Chemoreceptor reflex

Answer 2

Located in carotid and aortic bodies detect decreased arterial O2, and increased CO2 which results in increases in systemic BP. Do not respond strongly until BP <80 mmHG

Question 3

Bezold-Jarisch Reflex

Answer 3

Decrease in left ventricular volume activates receptors that cause paradoxical bradycardia - decreased HR allows more time for ventricular filling, more time in diastole equals more time the left ventricle is perfused

Question 4

Bainbridge Reflex

Answer 4

Stretch receptors located in the atria cause increased HR when they are stretched - prevents accumulation of blood in the atria, veins, and pulmonary circulation

Question 5

CNS Ischemic Reflex

Answer 5

Chemoreceptors located in the medullary vasomotor center cause profound outflow of sympathetic NS impulses in response to accumulation of CO2. Does not occur until MAP reaches 50 mmHg, and is most prominent at MAP of 15-20 mmHg

Question 6

Cushing’s Reflex

Answer 6

Response to elevated ICP when it is close to MAP - hypertension, bradycardia, and irregular respirations

Question 7

Alterations in BP in response to breathing

Answer 7

Spontaneous inspiration causes an increase in BP due to negative intrathoracic pressure increasing venous return. PP inspiration causes decreased BP due to positive intrathoracic pressure decreasing venous return