Control of blood pressure is crucially dependent on the integrity of a small region of the brainstem called the ventrolateral medulla. Within this part of the brain are the cells that control the heart, blood vessels, swallowing, breathing and many other functions of the body that are not noticed at a conscious level; such unconscious activities are known as "'Autonomic'".
One of these regions is the Rostral Ventrolateral Medulla (RVLM) is also known as the pressor area of the medulla

Medulla oblongata

The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...

 (medulla pressor). It receives inhibitory GABAergic input from the caudal ventrolateral medulla (CVLM). The RVLM is the primary regulator of the sympathetic nervous system

Sympathetic nervous system

The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...

, sending excitatory fibers (catecholaminergic) to the sympathetic preganglionic neurons in the spinal cord, via reticulospinal tract

Reticulospinal tract

The reticulospinal tract is an extrapyramidal motor tract which travels from the reticular formation.-Functions:...

.

The RVLM is notably involved in the baroreflex

Baroreflex

The baroreflex or baroreceptor reflex is one of the body's homeostatic mechanisms for maintaining blood pressure. It provides a negative feedback loop in which an elevated blood pressure reflexively causes heart rate to decrease therefore causing blood pressure to decrease; likewise, decreased...

.

Physostigmine

Physostigmine

Physostigmine is a parasympathomimetic alkaloid, specifically, a reversible cholinesterase inhibitor. It occurs naturally in the Calabar bean....

, a choline-esterase inhibitor, elevates endogenous

Endogenous

Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...

 levels of acetylcholine

Acetylcholine

The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...

by stimulation of the RVLM .