Role of Epinephrine: Hormone and Neurotransmitter in Physiological Responses

Epinephrine Action

vasoconstriction and bronchodilationIncrease in HR and Contractility

Epinephrine, also known as adrenaline, is a hormone and neurotransmitter that is released by the adrenal glands in response to stress, excitement, and physical activity. It has several actions in the body, ranging from increasing heart rate and blood pressure to opening up the airways in the lungs.

One of the main actions of epinephrine is its ability to stimulate the sympathetic nervous system, which is responsible for the so-called “fight or flight” response. Epinephrine mediates this response by binding to specific receptors on cells throughout the body, including the heart, blood vessels, and airways.

In the heart, epinephrine causes an increase in heart rate, contractility, and cardiac output, which helps to increase blood flow and oxygen delivery to the muscles during physical activity. In the blood vessels, epinephrine causes vasoconstriction of some vessels (increasing blood pressure) while causing vasodilation of others, primarily in skeletal muscle (which allows more blood to flow to the muscles during exercise).

In the lungs, epinephrine binds to beta-2 receptors on smooth muscle cells, causing them to relax and allowing the airways to open up. This is important because it allows for increased oxygen exchange during physical activity.

Epinephrine also has metabolic effects, including increasing blood glucose levels (by stimulating glycogenolysis and gluconeogenesis) and promoting the breakdown of fat cells (lipolysis).

In summary, epinephrine is an important hormone and neurotransmitter that mediates many physiological responses in the body. Its actions include increasing heart rate and blood pressure, opening up the airways in the lungs, and promoting the breakdown of fats and the release of glucose in the blood.

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