Glomus cell

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The carotid body is not labelled but is located within the wall of the internal carotid artery near the bifurcation of the common carotid artery. Glomus type I cells are the chemoreceptor cells found in the carotid body. Gray's Anatomy with markup showing carotid artery bifurcation.png
The carotid body is not labelled but is located within the wall of the internal carotid artery near the bifurcation of the common carotid artery. Glomus type I cells are the chemoreceptor cells found in the carotid body.

Glomus cells are the cell type mainly located in the carotid bodies and aortic bodies. Glomus type I cells are peripheral chemoreceptors which sense the oxygen, carbon dioxide and pH levels of the blood. When there is a decrease in the blood's pH, a decrease in oxygen (pO2), or an increase in carbon dioxide (pCO2), the carotid bodies and the aortic bodies signal the dorsal respiratory group in the medulla oblongata to increase the volume and rate of breathing. [1] The glomus cells have a high metabolic rate and good blood perfusion and thus are sensitive to changes in arterial blood gas tension. Glomus type II cells are sustentacular cells having a similar supportive function to glial cells. [2] [3] [4]

Contents

Structure

The signalling within the chemoreceptors is thought to be mediated by the release of neurotransmitters by the glomus cells, including dopamine, noradrenaline, acetylcholine, substance P, vasoactive intestinal peptide and enkephalins. [5] Vasopressin has been found to inhibit the response of glomus cells to hypoxia, presumably because the usual response to hypoxia is vasodilation, which in case of hypovolemia should be avoided. [6] Furthermore, glomus cells are highly responsive to angiotensin II through AT1 receptors, providing information about the body's fluid and electrolyte status. [7]

Function

Glomus type I cells are chemoreceptors which monitor arterial blood for the partial pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2) and pH.

Glomus type I cells are secretory sensory neurons that release neurotransmitters in response to hypoxemia (low pO2), hypercapnia (high pCO2) or acidosis (low pH). Signals are transmitted to the afferent nerve fibers of the sinus nerve and may include dopamine, acetylcholine, and adenosine. [8] This information is sent to the respiratory center and helps the brain to regulate breathing.

Innervation

The glomus type I cells of the carotid body are innervated by the sensory neurons found in the inferior ganglion of the glossopharyngeal nerve. [9] The carotid sinus nerve is the branch of the glossopharyngeal nerve which innervates them. Alternatively, the glomus type I cells of the aortic body are innervated by sensory neurons found in the inferior ganglion of the vagus nerve. Centrally the axons of neurons which innervate glomus type I cells synapse in the caudal portion of the solitary nucleus in the medulla. Glomus type II cells are not innervated.

Development

Development of the nervous system. The glomus type I cells of the carotid body are derived from the neural crest and can be seen in green. Neural Crest.png
Development of the nervous system. The glomus type I cells of the carotid body are derived from the neural crest and can be seen in green.

Glomus type I cells are embryonically derived from the neural crest. [2] In the carotid body the respiratory chemoreceptors need a period of time postnatally in order to reach functional maturity. [10] This maturation period is known as resetting. [11] At birth the chemorecptors express a low sensitivity for lack of oxygen but this increases over the first few days or weeks of life. The mechanisms underlying the postnatal maturity of chemotransduction are obscure. [8]

Clinical significance

Clusters of glomus cells, of which the carotid bodies and aortic bodies are the most important, are called non-chromaffin or parasympathetic paraganglia. They are also present along the vagus nerve, in the inner ears, in the lungs, and at other sites. Neoplasms of glomus cells are known as paraganglioma, among other names, they are generally non-malignant. [12]

Research

The autotransplantation of glomus cells of the carotid body into the striatum – a nucleus in the forebrain, has been investigated as a cell-based therapy for people with Parkinson's disease. [13]

Related Research Articles

Vagus nerve Tenth cranial nerve

The vagus nerve, historically cited as the pneumogastric nerve, is the tenth cranial nerve or CN X, and interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It actually comprises two nerves—the left and right vagus nerves—but they are typically referred to collectively in the singular. The vagus is the longest nerve of the autonomic nervous system in the human body and comprises sensory and motor fibers. The sensory fibers originate from neurons of the nodose ganglion, whereas the motor fibers come from neurons of the dorsal motor nucleus of the vagus and the nucleus ambiguus.

Autonomic nervous system Division of the peripheral nervous system supplying smooth muscle and glands

The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of internal organs. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response.

A chemoreceptor, also known as chemosensor, is a specialized sensory receptor cell which transduces a chemical substance to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis.

The control of ventilation refers to the physiological mechanisms involved in the control of breathing, which is the movement of air into and out of the lungs. Ventilation facilitates respiration. Respiration refers to the utilization of oxygen and balancing of carbon dioxide by the body as a whole, or by individual cells in cellular respiration.

Carotid body

The carotid body is a small cluster of chemoreceptor cells, and supporting sustentacular cells. The carotid body is located in the adventitia, in the bifurcation (fork) of the common carotid artery, which runs along both sides of the neck.

Chromaffin cell

Chromaffin cells, also pheochromocytes, are neuroendocrine cells found mostly in the medulla of the adrenal glands in mammals. These cells serve a variety of functions such as serving as a response to stress, monitoring carbon dioxide and oxygen concentrations in the body, maintenance of respiration and the regulation of blood pressure. They are in close proximity to pre-synaptic sympathetic ganglia of the sympathetic nervous system, with which they communicate, and structurally they are similar to post-synaptic sympathetic neurons. In order to activate chromaffin cells, the splanchnic nerve of the sympathetic nervous system releases acetylcholine, which then binds to nicotinic acetylcholine receptors on the adrenal medulla. This causes the release of catecholamines. The chromaffin cells release catecholamines: ~80% of adrenaline (epinephrine) and ~20% of noradrenaline (norepinephrine) into systemic circulation for systemic effects on multiple organs, and can also send paracrine signals. Hence they are called neuroendocrine cells.

Solitary nucleus

In the human brainstem, the solitary nucleus(SN) is a series of purely sensory nuclei forming a vertical column of grey matter embedded in the medulla oblongata. Through the center of the SN runs the solitary tract, a white bundle of nerve fibers, including fibers from the facial, glossopharyngeal and vagus nerves, that innervate the SN. The SN projects to, among other regions, the reticular formation, parasympathetic preganglionic neurons, hypothalamus and thalamus, forming circuits that contribute to autonomic regulation. Cells along the length of the SN are arranged roughly in accordance with function; for instance, cells involved in taste are located in the rostral part, while those receiving information from cardio-respiratory and gastrointestinal processes are found in the caudal part.

Paraganglioma Medical condition

A paraganglioma is a rare neuroendocrine neoplasm that may develop at various body sites. When the same type of tumor is found in the adrenal gland, they are referred to as a pheochromocytoma. They are rare tumors, with an overall estimated incidence of 1/300,000. Unlike other types of cancer, there is no test that determines benign from malignant tumors; long-term follow-up is therefore recommended for all individuals with paraganglioma.

Aortic body

The aortic bodies are one of several small clusters of peripheral chemoreceptors located along the aortic arch. They are important in measuring partial pressures of oxygen and carbon dioxide in the blood, and blood pH.

Neuroendocrine cells are cells that receive neuronal input and, as a consequence of this input, release message molecules (hormones) into the blood. In this way they bring about an integration between the nervous system and the endocrine system, a process known as neuroendocrine integration. An example of a neuroendocrine cell is a cell of the adrenal medulla, which releases adrenaline to the blood. The adrenal medullary cells are controlled by the sympathetic division of the autonomic nervous system. These cells are modified postganglionic neurons. Autonomic nerve fibers lead directly to them from the central nervous system. The adrenal medullary hormones are kept in vesicles much in the same way neurotransmitters are kept in neuronal vesicles. Hormonal effects can last up to ten times longer than those of neurotransmitters. Sympathetic nerve fiber impulses stimulate the release of adrenal medullary hormones. In this way the sympathetic division of the autonomic nervous system and the medullary secretions function together.

Inferior ganglion of glossopharyngeal nerve

The inferior ganglion of the glossopharyngeal nerve is a sensory ganglion. It is larger than and below the superior ganglion of the glossopharyngeal nerve. It is located within the jugular foramen.

Paraganglion

A paraganglion is a group of non-neuronal cells derived of the neural crest. They are named for being generally in close proximity to sympathetic ganglia. They are essentially of two types: (1) chromaffin or sympathetic paraganglia made of chromaffin cells and (2) nonchromaffin or parasympathetic ganglia made of glomus cells. They are neuroendocrine cells, the former with primary endocrine functions and the latter with primary chemoreceptor functions.

Peripheral chemoreceptors are so named because they are sensory extensions of the peripheral nervous system into blood vessels where they detect changes in chemical concentrations. As transducers of patterns of variability in the surrounding environment, carotid and aortic bodies count as chemosensors in a similar way as taste buds and photoreceptors. However, because carotid and aortic bodies detect variation within the body’s internal organs, they are considered interoceptors. Taste buds, olfactory bulbs, photoreceptors, and other receptors associated with the five traditional sensory modalities, by contrast, are exteroceptors in that they respond to stimuli outside the body. The body also contains proprioceptors, which respond to the amount of stretch within the organ, usually muscle, that they occupy.

Central chemoreceptors of the central nervous system, located on the ventrolateral medullary surface in the vicinity of the exit of the 9th and 10th cranial nerves, are sensitive to the pH of their environment.

Pre-Bötzinger complex

The pre-Bötzinger complex (preBötC) is a cluster of interneurons in the ventral respiratory group of the medulla of the brainstem. This complex has been proven to be essential for the generation of the respiratory rhythm in mammals. The exact mechanism of the rhythm generation and transmission to motor nuclei remains controversial and the topic of much research.

Respiratory center brain region controlling respiration

The respiratory center is located in the medulla oblongata and pons, in the brainstem. The respiratory center is made up of three major respiratory groups of neurons, two in the medulla and one in the pons. In the medulla they are the dorsal respiratory group, and the ventral respiratory group. In the pons, the pontine respiratory group includes two areas known as the pneumotaxic centre and the apneustic centre.

Hypoxic ventilatory response (HVR) is the increase in ventilation induced by hypoxia that allows the body to intake and process oxygen at higher rates. It is initially elevated in lowlanders who travel to high altitude, but reduces significantly over time as people acclimatize. In biological anthropology, HVR also refers to human adaptation to environmental stresses resulting from high altitude.

Fish are exposed to large oxygen fluctuations in their aquatic environment since the inherent properties of water can result in marked spatial and temporal differences in the concentration of oxygen (see oxygenation and underwater). Fish respond to hypoxia with varied behavioral, physiological, and cellular responses in order to maintain homeostasis and organism function in an oxygen-depleted environment. The biggest challenge fish face when exposed to low oxygen conditions is maintaining metabolic energy balance, as 95% of the oxygen consumed by fish is used for ATP production releasing the chemical energy of O2 through the mitochondrial electron transport chain. Therefore, hypoxia survival requires a coordinated response to secure more oxygen from the depleted environment and counteract the metabolic consequences of decreased ATP production at the mitochondria. This article is a review of the effects of hypoxia on all aspects of fish, ranging from behavior down to genes.

Intermittent hypoxia


Intermittent hypoxia (also known as episodic hypoxia) is an intervention in which a person or animal undergoes alternating periods of normoxia and hypoxia. Normoxia is defined as exposure to oxygen levels normally found in earth's atmosphere (~21% O2) and hypoxia as any oxygen levels lower than those of normoxia. Normally, exposure to hypoxia is negatively associated to physiological changes to the body, such as altitude sickness. However, when used in moderation, intermittent hypoxia may be used clinically as a means to alleviate various pathological conditions.

Cell-based therapies for Parkinsons disease Treatment method for Parkinsons disease

Cell-based therapies for Parkinson's disease include various investigational procedures which transplant specific populations of cells into the brains of people with Parkinson's disease. The investigation of cell transplantation therapies followed the discovery that the death of dopaminergic neurons in the substantia nigra pars compacta resulted in the motor symptoms of the disease. Thus, cell transplantation has focused on various dopamine producing cells throughout the body.

References

  1. ↑ Lahiri S, Semenza G, Prabhakar NR, eds. (2003). Oxygen sensing : responses and adaptation to Hypoxia. New York: Dekker. pp. 200, 232. ISBN   978-0824709600.
  2. 1 2 Pearse AG, Polak JM, Rost FW, Fontaine J, Le Lièvre C, Le Douarin N (1973). "Demonstration of the neural crest origin of type I (APUD) cells in the avian carotid body, using a cytochemical marker system". Histochemie. 34 (3): 191–203. doi:10.1007/bf00303435. PMID   4693636. S2CID   25437552.
  3. ↑ Lawson, W (January 1980). "The neuroendocrine nature of the glomus cells: an experimental, ultrastructural, and histochemical tissue culture study". The Laryngoscope. 90 (1): 120–44. doi:10.1288/00005537-198001000-00014. PMID   6243386. S2CID   13149248.
  4. ↑ Eyzaguirre, C; Fidone, SJ (November 1980). "Transduction mechanisms in carotid body: glomus cells, putative neurotransmitters, and nerve endings". The American Journal of Physiology. 239 (5): C135-52. doi:10.1152/ajpcell.1980.239.5.C135. PMID   6108075.
  5. ↑ Pardal, R.; Ludewig, U.; Garcia-Hirschfeld, J.; Lopez-Barneo, J. (11 February 2000). "Secretory responses of intact glomus cells in thin slices of rat carotid body to hypoxia and tetraethylammonium" (PDF). Proceedings of the National Academy of Sciences. 97 (5): 2361–2366. Bibcode:2000PNAS...97.2361P. doi: 10.1073/pnas.030522297 . PMC   15806 . PMID   10681419.
  6. ↑ Wang, ZZ; He, L; Stensaas, LJ; Dinger, BG; Fidone, SJ (February 1991). "Localization and in vitro actions of atrial natriuretic peptide in the cat carotid body". Journal of Applied Physiology. 70 (2): 942–6. doi:10.1152/jappl.1991.70.2.942. PMID   1827111.
  7. ↑ Allen, A. M. (1 August 1998). "Angiotensin AT1 receptor-mediated excitation of rat carotid body chemoreceptor afferent activity". The Journal of Physiology. 510 (3): 773–781. doi:10.1111/j.1469-7793.1998.773bj.x. PMC   2231066 . PMID   9660892.
  8. 1 2 Carroll, JL; Kim, I (15 November 2005). "Postnatal development of carotid body glomus cell O2 sensitivity". Respiratory Physiology & Neurobiology. 149 (1–3): 201–15. doi:10.1016/j.resp.2005.04.009. PMID   15886071. S2CID   25277654.
  9. ↑ Gonzalez, Constancio; Conde, Silvia V.; Gallego-Martín, Teresa; Olea, Elena; Gonzalez-Obeso, Elvira; Ramirez, Maria; Yubero, Sara; Agapito, Maria T.; Gomez-Niñno, Angela; Obeso, Ana; Rigual, Ricardo (2014). "Fernando de Castro and the discovery of the arterial chemoreceptors". Frontiers in Neuroanatomy. 8: 25. doi: 10.3389/fnana.2014.00025 . ISSN   1662-5129. PMC   4026738 . PMID   24860435.
  10. ↑ Hempleman, SC; Pilarski, JQ (31 August 2011). "Prenatal development of respiratory chemoreceptors in endothermic vertebrates". Respiratory Physiology & Neurobiology. 178 (1): 156–62. doi:10.1016/j.resp.2011.04.027. PMC   3146631 . PMID   21569865.
  11. ↑ Carroll, JL; Kim, I (1 January 2013). "Carotid chemoreceptor "resetting" revisited". Respiratory Physiology & Neurobiology. 185 (1): 30–43. doi:10.1016/j.resp.2012.09.002. PMC   3587794 . PMID   22982216.
  12. ↑ Anne Marie McNicol (2010). "Chapter 12: Adrenal medulla and paraganglia". Endocrine Pathology: Differential Diagnosis and Molecular Advance (Springer ed.). p. 281.
  13. ↑ Mínguez-Castellanos, Adolfo; Escamilla-Sevilla, Francisco; Hotton, Gary R.; Toledo-Aral, Juan J.; Ortega-Moreno, Angel; Méndez-Ferrer, Simón; Martín-Linares, José M.; Katati, Majed J.; Mir, Pablo (August 2007). "Carotid body autotransplantation in Parkinson disease: a clinical and positron emission tomography study". Journal of Neurology, Neurosurgery, and Psychiatry. 78 (8): 825–831. doi:10.1136/jnnp.2006.106021. ISSN   1468-330X. PMC   2117739 . PMID   17220289.
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