Muscarinic antagonists

Muscarinic antagonists, or antimuscarinic medications, are a class of medications that prevent muscarinic receptors of the parasympathetic nervous system from getting stimulated by acetylcholine.

Okay, first things first, the nervous system is divided into the central nervous system, so the brain and spinal cord; and the peripheral nervous system.

The peripheral nervous system can be divided into the somatic nervous system, which controls voluntary movement of our skeletal muscles; and the autonomic nervous system, which is further divided into the sympathetic and parasympathetic nervous systems, and controls the involuntary movement of the smooth muscles, and the glands of our organs.

Now, the autonomic nervous system is made up of a relay that includes two neurons.

We’ll focus on just the parasympathetic nervous system.

Signals for the parasympathetic nervous system start in the hypothalamus.

These hypothalamic neurons synapse with nuclei in the brainstem or spinal cord, which send out signals to preganglionic neurons that travel to the rest of the body.

Their targets are the parasympathetic ganglion, which consist of many postganglionic neuron cell bodies and are located nearby or directly in the target organs.

The postganglionic neurons extend the rest of the way to the target cell, where they release the neurotransmitter acetylcholine, which is why they are also called cholinergic neurons.

Acetylcholine binds to a type of receptor, known as muscarinic receptors, on the cells of target organs, which allow the parasympathetic nervous system to trigger a ‘rest and digest’ response, meaning that it keeps body-energy use as low as possible to stimulate activities like digestion.