Somatic nervous systemThe somatic nervous system (SNS), or voluntary nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles. The somatic nervous system consists of nerves carrying afferent nerve fibers, which relay sensation from the body to the central nervous system (CNS), and nerves carrying efferent nerve fibers, which relay motor commands from the CNS to stimulate muscle contraction. The a- of afferent and the e- of efferent correspond to the prefixes ad- (to, toward) and ex- (out of).
Adrenal medullaThe adrenal medulla (medulla glandulae suprarenalis) is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of chromaffin cells that secrete catecholamines, including epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine, in response to stimulation by sympathetic preganglionic neurons. The adrenal medulla consists of irregularly shaped cells grouped around blood vessels.
SudomotorSudomotor function refers to the autonomic nervous system control of sweat gland activity in response to various environmental and individual factors. Sweat production is a vital thermoregulatory mechanism used by the body to prevent heat-related illness as the evaporation of sweat is the body’s most effective method of heat reduction and the only cooling method available when the air temperature rises above skin temperature. In addition, sweat plays key roles in grip, microbial defense, and wound healing.
Periaqueductal grayThe periaqueductal gray (PAG, also known as the central gray) is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for descending pain modulation. It has enkephalin-producing cells that suppress pain. The periaqueductal gray is the gray matter located around the cerebral aqueduct within the tegmentum of the midbrain. It projects to the nucleus raphe magnus, and also contains descending autonomic tracts.
Pupillary responsePupillary response is a physiological response that varies the size of the pupil, via the optic and oculomotor cranial nerve. A constriction response (miosis), is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/opioids or anti-hypertension medications. Constriction of the pupil occurs when the circular muscle, controlled by the parasympathetic nervous system (PSNS), contracts, and also to an extent when the radial muscle relaxes.
ArterioleAn arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries. Arterioles have muscular walls (usually only one to two layers of smooth muscle cells) and are the primary site of vascular resistance. The greatest change in blood pressure and velocity of blood flow occurs at the transition of arterioles to capillaries. This function is extremely important because it prevents the thin, one-layer capillaries from exploding upon pressure.
Small fiber peripheral neuropathySmall fiber peripheral neuropathy is a type of peripheral neuropathy that occurs from damage to the small unmyelinated and myelinated peripheral nerve fibers. These fibers, categorized as C fibers and small Aδ fibers, are present in skin, peripheral nerves, and organs. The role of these nerves is to innervate the skin (somatic fibers) and help control autonomic function (autonomic fibers). It is estimated that 15–20 million people in the United States have some form of peripheral neuropathy.
Ciliary muscleThe ciliary muscle is an intrinsic muscle of the eye formed as a ring of smooth muscle in the eye's middle layer, uvea (vascular layer). It controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humor into Schlemm's canal. It also changes the shape of the lens within the eye but not the size of the pupil which is carried out by the sphincter pupillae muscle and dilator pupillae. The ciliary muscle develops from mesenchyme within the choroid and is considered a cranial neural crest derivative.
Electrochemical skin conductanceElectrochemical skin conductance (ESC) is an objective, non-invasive and quantitative electrophysiological measure. It is based on reverse iontophoresis and (multiple) steady chronoamperometry (more specifically chronovoltametry). ESC is intended to provide insight into and assess sudomotor (or sweat gland) function and small fiber peripheral neuropathy. Currently, ESC measurement can be obtained with the use of a medical device, called Sudoscan. No specific patient preparation or medical personnel training is required.
Purinergic signallingPurinergic signalling (or signaling: see American and British English differences) is a form of extracellular signalling mediated by purine nucleotides and nucleosides such as adenosine and ATP. It involves the activation of purinergic receptors in the cell and/or in nearby cells, thereby regulating cellular functions. The purinergic signalling complex of a cell is sometimes referred to as the “purinome”. Purinergic receptors, represented by several families, are among the most abundant receptors in living organisms and appeared early in evolution.