Area postrema

Area postrema is a part of the medulla oblongata, a structure in the brainstem. It is one of the circumventricular organs (CVOs) in the brain, which are regions that allow substances in the blood to affect brain function directly. The area postrema is located in the fourth ventricle, near the obex.

Structure

The area postrema is a small, rounded structure that is part of the dorsal medulla. It is located in the floor of the fourth ventricle, near the midline. The area postrema is made up of a dense network of capillaries and neurons. These neurons are unique in that they lack a blood-brain barrier, which allows them to directly sense substances in the bloodstream.

Function

• The primary function of the area postrema is to act as a chemoreceptor trigger zone (CTZ). This means that it can detect toxins and other harmful substances in the blood and cerebrospinal fluid. When these substances are detected, the area postrema triggers a vomiting reflex to expel them from the body. This makes the area postrema an important part of the body's defense mechanism against poisoning.

• In addition to its role in vomiting, the area postrema also plays a role in regulating body fluid balance, cardiovascular function, and hormone secretion. It is also involved in the control of food intake and energy balance.

Clinical significance

Because of its role in detecting toxins, the area postrema is a target for antiemetic drugs, which are used to treat nausea and vomiting. However, its lack of a blood-brain barrier also makes it vulnerable to damage from substances in the blood, including drugs and toxins.

See also

• Chemoreceptor trigger zone
• Vomiting center
• Circumventricular organs