On top of the adrenal gland, there is the adrenal medulla. Norepinephrine (noradrenaline) and epinephrine (adrenaline) are produced by this gland. They circulate in the bloodstream, depending on their need. Blood pressure, heart rate, and breathing are managed by these glands. In emergency situations, adrenaline is required to increase blood flow to the brain and other organs. It is norepinephrine that triggers the fight-or-flight response when we feel threatened.
During the early stages of the development of the sympathetic nervous system, the adrenal medulla is an important component. The cells are called chromaffin or pheochrome cells because, when catecholamines are oxidised to melanin, storage granules stain brown with chromic acid. Paraganglia can be found in these cells, which are located on both sides of the aorta.
This cell population is concentrated near the second-rate mesenteric artery, where the cells form an organ known as Zuckerkandl, which undergoes involution during the first year of life. These cells are responsible for the production of norepinephrine, epinephrine, and dopamine in the paraganglia and adrenal medulla. A large number of pores fill the adrenal medulla, which is connected to thoughtful ganglia and organised in sporadic patterns.
Adrenal Medulla Structure
The adrenal medulla is made up of randomly shaped cells that are arranged around veins. These cells are personally associated with the autonomic sensory system’s sympathetic division (ANS). Unlike the preganglionic nerves, the preganglionic autonomic nerve strands of the focal sensory system lead directly to the adrenal medullary cells.
In addition to regulating energy availability, pulse rate, and basal metabolic rate, the adrenal medulla also regulates heart rate. Recent research suggests the adrenal medulla may receive input from higher-request brain areas, such as the prefrontal cortex, and sensory and motor cortex, which suggests a role for these brain structures in psychosomatic disorders.
Development of the Adrenal Medulla
The neural crest generates postganglionic sympathetic cells called chromaffin cells. A postganglionic sympathetic neuron is part of the autonomic sensory system that has lost its axons and dendrites, but still receives innervation from a preganglionic fibre that is attached to it. Norepinephrine and epinephrine are transported into circulation by cells forming groups around fenestrated vessels.
As a group of neuron cells in our bodies, the adrenal medulla is thought to be an adjusted ganglion of sympathetic sensory cells.
Functions
The adrenal medulla cells release hormones, rather than delivering a synapse. Throughout the body, tyrosine is converted primarily into epinephrine, norepinephrine, and dopamine in the adrenal medulla.
- It is possible for hormone delivery to occur quickly due to the direct control of the chromaffin cells by the ANS, explicit in the sympathetic division.
- The catecholamines, adrenaline and noradrenaline, are released into the blood as a result of stress or danger.
- Adrenaline increases pulse and circulatory strain, expands smooth muscles (bronchioles and slims), and stimulates digestion, which are all signs of instinctive reaction.
- Nerve impulses influence the arrival of catecholamines, and catecholamine receptors are widely scattered throughout the body.
Adrenal Medulla Hormones and Their Functions
Adrenal medulla cells integrate and release epinephrine and norepinephrine. The proportion of these two catecholamines varies greatly between species: in humans, felines, and chickens, epinephrine accounts for approximately 80%, 60%, and 30% of catecholamine yield, respectively. Following delivery into the bloodstream, these chemicals bind to adrenergic receptors on track cells, where they essentially have the same effects as an immediate anxious feeling.
Physiologic Effects of Medullary Hormones
Despite their longer lasting effects, circulating epinephrine and norepinephrine releasing from the adrenal medulla have similar effects on target organs as the immediate feeling produced by sympathetic nerves. In addition, flowing hormones can have an impact on cells and tissues that are not directly innervated. Metabolic responses to medullary catecholamine release are legitimately characterised as pressure-regulating reactions. The impact can be predicted by considering what may be required. The following is a list of a few major impacts interposed by norepinephrine and epinephrine:
- In general, epinephrine acts as a beta receptor agonist to increase the rate and power of compression of the heart muscle.
- Specifically, norepinephrine causes a bindless vasoconstriction, which leads to an expanded obstruction and thus, an increased pulse.
- Expanding the bronchioles helps with respiratory ventilation.
- Fat cells experience lipolysis, allowing unsaturated fats to be used as energy in many tissues, and for the protection of decreasing blood glucose stores.
- In response to epinephrine, oxygen utilisation and heat creation increase throughout the body. The chemicals in the gastrointestinal tract also contribute to the breakdown of glycogen in the skeletal muscles to provide glucose for energy production.
- Expansion of the pupils is especially important when the ambient light is low.
- There is a tendency for non-essential processes to be hindered: gastrointestinal discharge and motor skills, for example.
Clinical Importance
Neoplasms include:
- Pheochromocytoma (normal)
A growth of the adrenal medulla that releases catecholamines. - Neuroblastoma
A neuroendocrine cancer of any part of the sensory system of the brain. - Ganglioneuroma
Cancer of the nerve cells in the fringe sensory system.
In cases of missing adrenal organs, the adrenal medulla may be poorly shaped or even absent. The whole body cannot effectively deliver epinephrine and norepinephrine because of dopamine beta-hydroxylase deficiency. This causes serious dysautonomia, however, it is often because of independent sensory system imperfections that require epinephrine and norepinephrine as synapses, with dopamine used as an inadequate substitute.
Conclusion
In the adrenal medulla, preganglionic neurons innervate attentive preganglionic cells. Chromaffin cells are found inside the adrenal medulla, and they are homologous to thoughtful neurons, which themselves develop from early peak stage brain cells. A chromaffin cell produces epinephrine (adrenaline) and norepinephrine in a much lesser degree, in addition to different synthetic compounds, for example, chromogranin, enkephalins, and neuropeptide Y, which are all delivered into the circulatory system and act as chemical messengers. The effects of epinephrine are specific to numerous types of tissues throughout the body, and it has a noticeable impact on cells with β-adrenoceptors.