If a masked person with a shotgun were to barge into the classroom one day and b

Question

If a masked person with a shotgun were to barge into the classroom one day and begin firing wildly and ultimately take me hostage, your body would have a strong immediate response of the release of adrenaline. Explain the effect this will have on heart cells, skeletal muscle cells, liver cells, fat cells, pancreas cells, vascular smooth muscle cells, and smooth muscle cells in the lungs. Describe the basic signal transduction pathway being used in these responses, explain why each of these cellular responses are so important in meeting with the event you have just encountered, and explain how the timing of each cellular response is important as well.

Explanation / Answer

Adrenaline: A stress hormone produced within the adrenal gland that quickens the heart beat, strengthens the force of the heart's contraction, and opens up the bronchioles in the lungs, among other effects. The secretion of adrenaline is part of the human 'fight or flight' response to fear, panic, or perceived threat. Also known as epinephrine.

When our senses perceive an environmental stress such as danger or a threat, cells in the nervous and endocrine systems work closely together to prepare the body for action. Often referred to as the fight or flight or stress response, this remarkable example of cell communication elicits instantaneous and simultaneous responses throughout the body.

Sensory nerve cells pass the perception of a threat, or stress, from the environment to the hypothalamus in the brain. Neurosecretory cells in the hypothalamus transmit a signal to the pituitary gland inciting 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.

Sitting atop the kidneys, the adrenal glands receive nerve and chemical signals initiated by cells in the hypothalamus. Nerve signals activate the release of epinephrine into the bloodstream.

When chemical messengers arrive via the bloodstream, they dock on to receptors and begin a cell signaling cascade that results in the production of cortisol. Cortisol is released into the blood stream where it begins signaling cascades in several cell types, resulting in an increase in blood pressure, increase in blood sugar levels, and suppression of the immune system.

Signaling molecules from several origins work to provide an energetic boost in a variety of ways. When epinephrine binds to receptors on liver cells, it triggers a signaling cascade that produces glucose from larger sugar molecules. Circulating cortisol sets fatty acids free to be transformed into energy. These molecules are rapidly excreted into the bloodstream, supplying a boost of readily available energy for muscles throughout the body, priming them for exertion.
In the lungs, epinephrine binds to receptors on smooth muscle cells wrapped around the bronchioles. This causes the muscles to relax, dilating the bronchioles and allowing more oxygen into the blood. At the sino-atrial node of the heart, epinephrine stimulates pace maker cells to beat faster. This increases the rate at which other chemical signals, glucose and oxygen are circulated to the cells that need them. Epinephrine also contracts specific types of muscle cells below the surface of the skin, causing beads of perspiration and raised hairs at the surface.

The fight or flight response is a complicated systemic reaction. These are just some of the instantaneous messengers and physiologic changes involved.

In fact, the initial perception of a threat or danger is also received by an area 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, triggering cell signaling cascades in a number of cell types.

Regardless of their kind, or point of origin, cell signaling molecules involved in the fight or flight response work closely together. Their overall effect is an increase in circulation and energy to certain body systems and a downshift of less important ones into maintenance mode. In this way, the fight or flight response prepares the body for extreme action.

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