Frank Amthor

A crucial aspect of neuronal function is their unique use of electricity. They use electricity both to secrete their neurotransmitters and for computation. Here's how.The membrane of the neuron contains a special kind of ion channel that is actually an active pump for ions. Ions are the charged atoms that are dissolved in fluids inside and outside the cell.

Although pain is a necessary function for preventing damage to the body, in some cases, pain itself becomes disabling. Chronic pain can occur in disease conditions such as cancer, in which case the normal function of pain that forces you to rest, protect, or not use some injured part of the body until it heals is simply inappropriate in a disease state in which destruction is occurring from the cancer all over the body that cannot be healed from rest.

The nervous system consists of the central nervous system (the brain, retina, and spinal cord), the peripheral nervous system (the sensory and motor nerve axons that connect the central nervous system to the limbs and organs). The peripheral nervous system also includes the autonomic nervous system (which regulates body processes such as digestion and heart rate), and the enteric nervous system, which controls the gastrointestinal system.

Although not located in the skin, receptors mediating proprioception (position sense) and kinesthesis (movement sense), are either free nerve endings or structures similar to mechanoreceptors like Ruffini corpuscles (refer to the first figure below) and have similar layouts as the cell bodies in the dorsal root ganglia (refer to the second figure).

The sense of pain can be reduced in several ways, including the body's own production of endorphins. Feeling pain is, well, painful. Wouldn't you be better off if you could just eliminate pain? The answer to the question of whether you would be better off without a sense of pain is a resounding no.This situation actually occurs in some people.

Most psychoactive drugs mimic the action of known neurotransmitters, but until a few decades ago, there was no known neurotransmitter that mediated the general effects of pain. Here's a mystery that puzzled researchers for a long time: Why does a substance produced by a poppy plant (morphine) relieve pain?This all changed with the discovery of endogenous opioids (that is, opioids that are developed naturally within the body).

Skin receptors allow you to respond to things that contact your skin and to be aware of what those things are. The output of most somatosensory receptors participates in at least three different kinds of neural circuits: Local reflexes are those that primarily involve contraction of a single muscle, such as a flexor like the biceps that contracts when, for example, you touch something hot.

You can detect more than just various kinds of pressure on your skin. Two other skin senses are temperature and pain. These receptors have similar structures, or, really, lack of structure. All the mechanoreceptors consist of an axon terminal with ion channel receptors embedded in some sort of structure, such as a corpuscle, disk, or myelin wrapping, that gives the receptor its particular responsiveness to different mechanical stimulation frequencies.

Somatosensory neurons, the tips of which form the mechanoreceptors, have an unusual morphology, or structure. This morphology is crucial to their function. Their morphological classification is called pseudounipolar. Although this rather unwieldy name isn't particularly illuminating about their function, understanding their structure explains some aspects about how these receptors work.