Ortostasis

Ortostasis refers to the physiological response of the body to standing upright. It is a complex process involving multiple bodily systems that work together to maintain blood pressure and adequate blood flow to the brain when transitioning from a lying or sitting position to a standing one. This transition typically causes a pooling of blood in the lower extremities due to gravity.

To counteract this, the body employs several mechanisms. The autonomic nervous system plays a crucial role, triggering an increase in heart rate and a constriction of blood vessels, particularly in the legs and abdomen. This reduces the amount of blood that pools and helps to push it back towards the heart and brain. Baroreceptors, specialized pressure-sensing nerve endings in the arteries, detect changes in blood pressure and send signals to the brainstem to initiate these compensatory responses.

A failure or delay in these compensatory mechanisms can lead to orthostatic hypotension, a condition characterized by a significant drop in blood pressure upon standing. Symptoms of orthostatic hypotension can include dizziness, lightheadedness, blurred vision, and even fainting (syncope). Various factors can contribute to orthostatic hypotension, including dehydration, certain medications, underlying medical conditions, and aging. Maintaining proper hydration and understanding individual responses to postural changes are important for managing ortostasis.