AEMCA Practice Exam

What triggers the secretion of renin by renin-secreting cells?

1. Activation by alpha-1 adrenergic receptor stimulation

2. Reduced blood flow in the renal artery

3. Activation of ß-1 adrenergic receptors due to increased sympathetic nervous system activity

4. Increase in sodium chloride transport at the distal tubule

The correct answer is: Activation of ß-1 adrenergic receptors due to increased sympathetic nervous system activity

Renin secretion is primarily triggered by a few physiological factors, and activation of ß-1 adrenergic receptors due to increased sympathetic nervous system activity is one of the key triggers. When there is an increase in sympathetic nervous system activity, such as during times of stress or low blood pressure, norepinephrine is released. This neurotransmitter binds to ß-1 adrenergic receptors on the juxtaglomerular cells in the kidneys, which leads to the secretion of renin. Renin plays a crucial role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance. While reduced blood flow in the renal artery can also stimulate renin release by promoting renal baroreceptor activation, signaling that there is inadequate perfusion pressure, the direct activation of the sympathetic nervous system through ß-1 adrenergic receptors is a more immediate and potent stimulus for renin secretion in response to acute stress situations.