Cholinergic receptors

Cholinergic receptors are receptors on the surface of cells that get activated when they bind a type of neurotransmitter called acetylcholine.

There are two types of cholinergic receptors, called nicotinic and muscarinic receptors - named after the drugs that work on them.

The nervous system is divided into the central nervous system, so the brain and spinal cord, and the peripheral nervous system, which includes all the nerves that connect the central nervous system to the muscles and organs.

The peripheral nervous system is divided into the somatic nervous system, which controls skeletal muscles, and the autonomic nervous system, which is further divided into the sympathetic and the parasympathetic, and controls internal organs.

Neurons are the main cells of the nervous system. They’re composed of a cell body, which contains all the organelles, and nerve fibers, which are projections that extend out from the neuron cell body.

Nerve fibers are dendrites that receive signals from other neurons, and axons that send signals along to other neurons.

Where two neurons come together is called a synapse; that’s where an axon releases neurotransmitters that bind to receptors present on the cell membrane of the dendrites or the cell body of the next neuron in the series.

Now the autonomic nervous system - so both sympathetic and parasympathetic - is made up of a relay that includes two neurons: preganglionic neurons, which have their cell bodies in nuclei throughout the spinal cord, and postganglionic neurons, which have their cells bodies in ganglia out of the spinal cord.

Axons of preganglionic neurons exit the spinal cord to reach the ganglia and synapse with postganglionic neurons. Then, the axons of postganglionic neurons exit the ganglia to reach the organs and synapse with the target organ cells.

Let’s zoom into the synapses. In the sympathetic nervous system, preganglionic and postganglionic neurons release different neurotransmitters.