[shalinibalan]

When our senses perceive a stress such as danger or a threat, cells in the nervous and endocrine systems work closely together to prepare the body for action. This is referred to as the fight or flight or stress response. The fight or flight response is a complicated systemic reaction. This involves some instantaneous messengers and is accompanied by physiologic changes. Epinephrine is an important chemical cell signaling molecule or messenger in the fight or flight response. Also known as adrenaline, epinephrine is an efficient messenger that signals many cell types throughout the body with many effects,

In fact, the initial sensitivity of a threat or danger is also perceived by a portion in the brain stem that begins yet another axis of communication and response involving the release of the messenger norepinephrine. Like cortisol and epinephrine, norepinephrine travels throughout the body, which triggers cell signaling in all the cell types.

In spite of their kind, or point of origin, cell signaling molecules involved in the fight or flight response work intimately .Their overall effect is an increase in circulation and energy to certain body systems and a downshift of less important ones into maintenance mode.
The response is initiated when the Sensory nerve cells perceive and pass the information of a threat, or stress, from the environment to the hypothalamus located in the brain. Neurosecretory cells in the hypothalamus transmit a signal to the pituitary gland stirring cells there to release a chemical messenger into the bloodstream. Simultaneously, the hypothalamus transmits a nerve signal down the spinal cord. Both the chemical messenger and nerve impulse will travel to the same destination, the adrenal gland.

Adrenal glands which are placed on the top of the kidneys receive nerve and chemical signals activated by cells in the hypothalamus. Nerve signals activate the release of epinephrine into the bloodstream. When they reach the blood stream the receptors on the cell initiate the process of signaling and produce cortisal . This release in the cortisal in the blood stream results in increase in blood pressure, increase in blood sugar levels, and suppression of the immune system.

When nerve cells in the hypothalamus fire, corticotrope cells in the pituitary gland are stimulated to release ACTH, (‘Adrenocorticotrophic hormone'), is a polypeptide tropic hormone which acts as a chemical messenger, into the bloodstream. When the splanchnic nerve in the hypothalamus fires, a signal is sent down the spinal cord directly to the adrenal gland.

These signaling molecules coordinate and work from every part of the boy that provides an energetic boost in a variety of ways. When the chemical messengers like epinephrine binds to receptors on liver cells, it triggers a signaling chain that produces glucose from larger sugar molecules.
Cotisol which circulate in the blood stream transform fatty acids into energy. Which in turn are rapidly excreted into the bloodstream, supplying a boost of readily available energy for muscles throughout the body, priming them for exertion.

The splanchnic nerve stimulates chromaffin cells in the adrenal gland to release epinephrine, a chemical messenger, into the bloodstream. In this way, the fight or flight response prepares the body for extreme action.