Epinephrine Podcast Transcript

1.      What gland is it produced in?

a.      The inner region, adrenal medulla, of the adrenal glands located on top of both kidneys.

2.      Chemical Pathway – what does this mean/Structure etc.

a.      Cells in the nervous and endocrine system work together in an environment of what our senses perceive as danger, stress, or threat, initiating the fight or flight response.

This elicits instantaneous and simultaneous responses throughout the body

b.      Sensory nerve cells pass the signal to the hypothalamus in the brain. Neurosecretory cells in the hypothalamus transmit a signal to the pituitary gland compelling the cells there to release a chemical messenger into the bloodstream. Simultaneously, the hypothalamus transmits a nerve signal down the spinal cord. The adrenal gland will receive both the chemical messenger and the nerve impulse.

c.      The adrenal glands (located on top of the kidneys) receive the signals initiated by cells in the hypothalamus, activating the release of epinephrine into the bloodstream.

d.      When chemical messengers arrive via the bloodstream, they dock on to receptors and begin cell signaling that results in the production of cortisol. Cortisol is released into the blood stream, resulting in an increase in blood pressure, increase in blood sugar levels, and suppression of the immune system and digestive system.

3.      Water soluble or Fat soluble and Structure – type and contrast it with the opposite type.

a.      Epinephrine is a water-soluble molecule derived from amino acids (the building blocks of protein). These hormones are stored in endocrine cells until they are needed. They act by binding to protein receptors on the outside surface of the cell. The binding alerts a second messenger molecule inside the cell that activates enzymes and other cellular proteins or influences gene expression.

b.      Most water-soluble hormones can travel freely in the blood because they "like" water. They are repelled by lipid and fatty structures such as the membranes that surround a cell and its nucleus. Because of this repulsion, these hormones generally bind to receptor sites on the outside of the cell and signal from there.

c.      Fat-soluble hormones, like the sex hormone steroids estrogens and androgens, are fat soluble and water repellent. They "like" lipid or fatty structures (such as those surrounding cells and are repelled by watery areas). Steroids generally travel to their target cells attached to a special carrier protein that is water soluble. (such as, sex steroid hormone binding globulin and serum albumin). The hormones detach before passing into the cell where they bind to receptors.

4.      Type of cellular receptor

a.      Epinephrine, which binds to two types of GPCRs, is important in mediating the body’s response to stress, when all tissues have an increased need for glucose and fatty acids. These principal metabolic fuels can poured into the blood in a matter of seconds by the breakdown of glycogen in the liver and of triacylglycerol in adipose storage cells.

b.      “In mammals, the liberation of glucose and fatty acids can be triggered by binding of epinephrine (or norepinephrine) to β-adrenergic receptors on the surface of hepatic (liver) and adipose cells. Epinephrine bound to similar β-adrenergic receptors on heart muscle cells increases the contraction rate, which increases the blood supply to the tissues. Epinephrine bound to β-adrenergic receptors on smooth muscle cells of the intestine causes them to relax. Another type of epinephrine receptor, the α2-adrenergic receptor, is found on smooth muscle cells lining the blood vessels in the intestinal tract, skin, and kidneys. Epinephrine bound to α2 receptors causes the arteries to constrict, cutting off circulation to these peripheral organs. These diverse effects of epinephrine are directed to a common end: supplying energy for the rapid movement of major locomotor muscles in response to bodily stress. As discussed in more detail later, β- and α-adrenergic receptors are coupled to different G proteins. Both β1- and β2-adrenergic receptors are coupled to G proteins (Gs), which activate adenylyl cyclase. In contrast, α1 and α2 receptors are coupled to two other G proteins, Gq and Gi, respectively. Gi inhibits adenylyl cyclase, and Gq stimulates phospholipase C to generate IP3 and DAG as second messengers.”

5.      What type of feedback loop is it?

a.      Positive.

6.      Action of hormone or its function – specific

a.      It regulates heart rate, blood vessel, air passage diameters, and metabolic shifts. It also controls our instinctive fight or fight response.

b.      After epinephrine is released, the supply of oxygen and glucose to muscles and the brain is increased. There is a rise in stroke volume (the volume or quantity of blood pumped by a ventricle due to a single heartbeat) and the heart rate increases. The hormone also dilates the pupils and constrict the arterioles present in the skin. The secretion of adrenaline also brings up the sugar level in the blood as well as suppressing the function of the immune system and digestive system.

7.      What is this regulated by?

a.      Epinephrine is regulated by the central nervous system. The sympathetic nervous system and the Adrenocorticotropic hormone both play important roles in the synthesis of epinephrine.