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Information about Carotid Body

Section of part of human glomus caroticum. Highly magnified. Numerous bloodvessels are seen in section among the gland cells.
Diagram showing the origins of the main branches of the carotid arteries.
Latinglomus caroticum
subject #277 1281
Dorlands/Elsevier g_07/12394794
The carotid body (or carotid glomus) is a small cluster of chemoreceptors and supporting cells located near the bifurcation of the carotid artery.

It measures changes in the composition of arterial blood flowing through it, mainly the partial pressure of oxygen, but also of carbon dioxide. Furthermore, it is also sensitive to changes in pH and temperature.

Composition

The carotid body is made up of two types of cell: type I (glomus) cells, and type II (sustentacular) cells. Glomus cells are derived from neural crest,[1] which, in turn are derived from neuroectoderm. They release a variety of neurotransmitters, including acetylcholine, ATP, and dopamine that trigger EPSP's in synapsed neurons leading to the respiratory center.

Type II cells resemble glia and act as supporting cells.

Function

The carotis body functions by a stimulus, in this case mainly O2 partial pressure, is detected by the type I (glomus) cells, and triggers an action potential in an afferent nerve fiber, which relays the information to the central nervous system.

Stimulus

While the central chemoreceptors in the brainstem are highly sensitive to CO2 the carotid body is a peripheral chemoreceptor that mainly provides afferent input to the respiratory center that is highly O2 dependent. However, the carotid body also senses increases in CO2 partial pressure and decreases in arterial pH, but to a lesser degree than for O2

The output of the carotid bodies is low at an oxygen partial pressure above about 100 mmHg (torr) (at normal physiological pH), but below this the activity of the type I (glomus) cells increases rapidly.

Detection

The mechanism for detecting reductions in PO2 is not well understood. There may be a heme-containing protein in the glomus cell which responds to the loss of complexed oxygen by reducing the probability of potassium channels being open. Another possibility is that low PO2 inhibits NADPH oxidase in mitochondria. This would increase the ratio of reduced glutathione to oxidised glutathione, which blocks potassium channels.

An increased PCO2 is detected because the CO2 diffuses into the cell, where it increase the concentration of carbonic acid and thus protons. These protons displace calcium from high-conductance calcium channels, reducing potassium current.

Arterial acidosis (either metabolic or from altered PCO2) inhibits acid-base transporters (e.g. Na+-H+) which raise intracellular pH, and activates transporters (e.g. Cl--HCO3-) which decrease it. Changes in proton concentration caused by acidosis (or the opposite from alkalosis) inside the cell stimulates the same pathways involved in PCO2 sensing.

Action potential

The type 1 (glomus) cells in the carotid (and aortic bodies) are derived from neuroectoderm and are thus electrically excitable. A decrease in oxygen partial pressure, an increase in carbon dioxide partial pressure, and a decrease in arterial pH can all cause depolarization of the cell membrane, and they effect this by blocking potassium currents. This reduction in the membrane potential opens voltage-gated calcium channels, which causes a rise in intracellular calcium concentration. This causes exocytosis of vesicles containing a variety of neurotransmitters, including acetylcholine, noradrenaline, dopamine, substance P, and met-enkephalin. These act on receptors on the afferent nerve fibres which lie in apposition to the glomus cell to cause an action potential.

Relay

The feedback from the carotid body is sent to the respiratory centers in the medulla oblongata via the afferent branches of the glossopharyngeal nerve (IX). These centers, in turn, regulate breathing and blood pressure.

Disorders

A paraganglioma is a tumor that may involve the carotid body.

References

1. ^ Gonzalez C, Almaraz L, Obeso A, Rigual R (1994). "Carotid body chemoreceptors: from natural stimuli to sensory discharges". Physiol. Rev. 74 (4): 829–98. PMID 7938227. 

See also

External links

Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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A chemosensor, also known as chemoreceptor, is a cell or group of cells that transduce a chemical signal into an action potential. Or, more generally, a chemosensor detects certain chemical stimuli in the environment.
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Bifurcation refers to the main body of one item splitting into two parts.

Bifurcation may also refer to:
  • Bifurcation (law), the division of issues in a trial
  • Bifurcation (accounting),to divide into separate parts or accounts

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In human anatomy, the common carotid artery is an artery that supplies the head and neck with oxygenated blood; it divides in the neck to form the external and internal carotid arteries.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
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    pH is a measure of the acidity or alkalinity of a solution. Aqueous solutions at 25 ℃ with a pH less than seven are considered acidic, while those with a pH greater than seven are considered basic (alkaline). The pH of 7.
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    trillion fold).]]

    Temperature is a physical property of a system that underlies the common notions of hot and cold; something that is hotter generally has the greater temperature. Temperature is one of the principal parameters of thermodynamics.
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    The neural crest, a transient component of the ectoderm, is located in between the neural tube and the epidermis (or the free margins of the neural folds) of an embryo during neural tube formation.
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    Neuroectoderm (or neural ectoderm) is the term for ectoderm which receives inhibitory signals from proteins such as noggin, which leads to the development of the nervous system from this tissue.
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    Neurotransmitters are chemicals that are used to relay, amplify and modulate signals between a neuron and another cell. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions:

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    The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. It is a chemical transmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans.
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    Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer. In this role, ATP transports chemical energy within cells for metabolism.
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    Dopamine is a hormone and neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In chemical structure, it is a phenethylamine.
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    Glial cells, commonly called neuroglia or simply glia (greek for "glue"), are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system.
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    In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.
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    torr (symbol: Torr) is a non-SI unit of pressure defined as 1/760 of an atmosphere. It was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644.
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    A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as
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    complex in chemistry usually is used to describe molecules or ensembles formed by the combination of ligands and metal ions. Originally, a complex implied a reversible association of molecules, atoms, or ions through weak chemical bonds.
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    The NADPH oxidase (nicotinamide adenine dinucleotide phosphate-oxidase) complex is an enzyme complex

    Subunits

    It is made up of six subunits. These subunits are:

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    This article is about the physical mechanism of diffusion. For alternative meanings, see diffusion (disambiguation).


    Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
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    Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3. It is also a name sometimes given to solutions of carbon dioxide in water, which contain small amounts of H2CO3.
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    Proton

    The quark structure of the proton.
    Composition: 2 up, 1 down
    Family: Fermion
    Group: Quark
    Interaction: Gravity, Electromagnetic, Weak, Strong
    Antiparticle: Antiproton
    Discovered: Ernest Rutherford (1919)
    Symbol: p+
    Mass: 1.
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    BK channels, also called Maxi-K or slo1 channels, are large conductance Ca2+ and voltage-activated K+ channels, which allow K+ to leave the cytoplasm under physiological conditions when activated by membrane potential and/or intracellular Ca
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    MeSH D000138
    For acidosis referring to acidity of the urine, see renal tubular acidosis.
    Acidosis is an increased acidity (i.e. an increased hydrogen ion concentration). If not further qualified, it refers to acidity of the blood plasma.
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    Metabolic acidosis
    Classification & external resources

    Davenport diagram
    ICD-10 E 87.2
    ICD-9 276.2

    DiseasesDB 92
    MedlinePlus 000335
    eMedicine emerg/312   med/1458 ped/15

    In medicine, metabolic acidosis
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    The introduction to this article provides insufficient context for those unfamiliar with the subject matter.
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    Alkalosis refers to a condition reducing hydrogen ion concentration of arterial blood plasma (alkalemia). Generally alkalosis is said to occur when arterial pH exceeds 7.45. The opposite condition is acidosis.
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    In biology, depolarization is a decrease in the absolute value of a cell's membrane potential. Thus, changes in membrane voltage in which the membrane potential becomes less positive or less negative are both depolarizations.
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