A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the eye.

Function There are about 1.2 to 1.5 million retinal ganglion cells in the human retina.

The ganglion cells give information about ambient light levels, and react sluggishly compared to the rods and cones.

The adrenal medullary cells are controlled by the sympathetic division of the autonomic nervous system.

Cluster headache belongs to a group of primary headache disorders, classified as the trigeminal autonomic cephalalgias or (TACs).

This can mean a loss or impairment in controlling bowel and bladder, sexual function, digestion, breathing and other autonomic functions.

In fact, these adrenal medullary cells are modified postganglionic neurons, and preganglionic autonomic nerve fibers lead to them directly from the central nervous system.

History Sympathectomy developed in the mid 19th century, when it was learned that the autonomic nervous system runs to almost every organ, gland and muscle system in the body.

Many chemical mediators are involved, including cortisol and adrenalin from the adrenal glands, other hormones and neurotransmitters (such as serotonin and noradrenalin), and responses from the autonomic and immune systems.

A variety of medications may be administered, with the overall aim of ensuring sleep, amnesia, analgesia, relaxation of skeletal muscles, and loss of control of reflexes of the autonomic nervous system.

Pathways to the CNS The sensory modality that is detected by the afferent fibers is an important factor to consider because it determines the pathway that the dorsal root ganglion neurons will take within the central nervous system.

In the case of diabetic autonomic neuropathy, it is due to the failure of the heart and arteries to appropriately adjust heart rate and vascular tone to keep blood continually and fully flowing to the brain.

It is via those nerves of the autonomic nervous system that the brain is able to make adjustments in the body in response to changing conditions in the environment, fluctuating emotional states, level of exercise, and other factors to maintain the body's homeostasis.