Cardioinhibition

Cardioinhibition refers to a reflex that causes a temporary decrease in heart rate and cardiac output. It is a protective mechanism that can be triggered by various stimuli, such as pain, emotional stress, or a sudden drop in blood pressure. The reflex involves the autonomic nervous system, specifically the vagus nerve, which plays a key role in slowing down the heart.

When cardioinhibition is activated, signals are sent from sensory receptors to the brainstem. From there, the vagus nerve transmits impulses to the sinoatrial (SA) node, the heart's natural pacemaker. This increased vagal activity reduces the rate at which the SA node fires, leading to a slower heart rate. In some cases, it can also decrease the force of the heart's contractions, further reducing cardiac output.

While cardioinhibition is a normal physiological response, excessive or prolonged episodes can be problematic. In certain medical conditions, such as vasovagal syncope, a sudden and exaggerated cardioinhibitory response can lead to a temporary loss of consciousness due to insufficient blood flow to the brain. This can be triggered by factors like standing for long periods, heat exposure, or the sight of blood. Medical evaluation is often recommended for individuals experiencing recurrent or severe episodes of cardioinhibition to rule out underlying health issues and manage symptoms.