Slow wave potential
Encyclopedia
In physiology
, a slow-wave potential is a membrane potential that cycles between depolarizations and repolarizations. Slow wave potentials are generated by myocytes. Due to temporal summation, a slow-wave potential will periodically reach threshold and generate an action potential. This in turn triggers contraction of a myocyte. Since each cycle of a slow-wave potential does not always reach threshold, an action potential (AP) does not always fire as a result. Slow waves are intrinsic: they do not rely on exogenous stimulus, but they can be altered by an exogenous stimulus.
, a slow wave originates in the cells of Cajal
as the Basic Electrical Rhythm. Loss of these cells stops the propagation of a slow wave potential and thus, gut motility. A slow wave threshold
must be reached before a slow wave potential can propagate. The amplitude
and frequency
of the wave are modulated by intrinsic (Auerbach's plexus
& Meissner's plexus) or extrinsic (Sympathetic nervous system
& Parasympathetic nervous system
) innervation or by hormone
s. Excitatory compounds include acetylcholine
and Substance P
, inhibitory include vasoactive intestinal peptide
and nitric oxide
.
The frequency of slow waves also varies between sections of the intestinal tract. In small intestine
, they occur at a rate of 10–20 per minute, while in the colon
they occur at a slower rate of 3 to 8 per minute.
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
, a slow-wave potential is a membrane potential that cycles between depolarizations and repolarizations. Slow wave potentials are generated by myocytes. Due to temporal summation, a slow-wave potential will periodically reach threshold and generate an action potential. This in turn triggers contraction of a myocyte. Since each cycle of a slow-wave potential does not always reach threshold, an action potential (AP) does not always fire as a result. Slow waves are intrinsic: they do not rely on exogenous stimulus, but they can be altered by an exogenous stimulus.
In gastrointestinal smooth muscle
In the gastrointestinal smooth muscleSmooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
, a slow wave originates in the cells of Cajal
Interstitial cell of Cajal
The Interstitial cell of Cajal is a type of interstitial cell found in the gastrointestinal tract that serves as a pacemaker which creates the basal electrical rhythm leading to contraction of the smooth muscle ....
as the Basic Electrical Rhythm. Loss of these cells stops the propagation of a slow wave potential and thus, gut motility. A slow wave threshold
Slow wave threshold
In physiology, the slow-wave threshold is the potential which must be reached before a slow wave can be propagated in smooth muscle. Slow waves cause no smooth muscle contraction.-Gastrointestinal smooth muscle:...
must be reached before a slow wave potential can propagate. The amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
and frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of the wave are modulated by intrinsic (Auerbach's plexus
Auerbach's plexus
A part of the enteric nervous system, Auerbach's plexus , exists between the longitudinal and circular layers of muscularis externa in the gastrointestinal tract and provides motor innervation to both layers of the mucosa, having both parasympathetic and sympathetic input, whereas Meissner's plexus...
& Meissner's plexus) or extrinsic (Sympathetic nervous system
Sympathetic nervous system
The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...
& Parasympathetic nervous system
Parasympathetic nervous system
The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system . The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously...
) innervation or by hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s. Excitatory compounds include acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
and Substance P
Substance P
In the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...
, inhibitory include vasoactive intestinal peptide
Vasoactive intestinal peptide
Vasoactive intestinal peptide also known as the vasoactive intestinal polypeptide or VIP is a peptide hormone containing 29 amino acid residues that is produced in many tissues of vertebrates including the gut, pancreas and suprachiasmatic nuclei of the hypothalamus in the brain...
and nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
.
The frequency of slow waves also varies between sections of the intestinal tract. In small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
, they occur at a rate of 10–20 per minute, while in the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
they occur at a slower rate of 3 to 8 per minute.