Adrenaline is both a hormone and a neurotransmitter. How ?
(I will mark you brainliest if you answer it correctly and in details.)
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Epinephrine / adrenaline is more of a hormone than a neurotransmitter. Its designation as a neurotransmitter may be archaic.
Hormones are molecules used for signaling by being released into the bloodstream. Neurotransmitters are molecules used for direct signaling between neurons, usually by physical contact at a synapse.
This is the ideal model, anyway. It is true 99% of the time, however there are exceptions.
Epinephrine / adrenaline is extra confusing because of its "sister molecule" norepinephrine / noradrenaline, which is a neurotransmitter. These molecules are nearly identical, except one has an extra carbon (C) in one place. So epinephrine / adrenaline is released by the adrenal gland into the bloodstream as a hormone whereas norepinephrine / noradrenaline is released by neurons in the brain as a neurotransmitter.
On top of that, both molecules are detected by the same receptors, called "alpha" and "beta" receptors (hence "beta-blocker" drugs for heart disease). Neurons use these receptors to listen for the neurotransmitter norepinephrine, whereas other cells in the body use these same receptors to listen for the hormone epinephrine.
And if that weren't enough, these two molecules have dual names for historical reasons. In Britain, they are called adrenaline and noradrenaline, and in the U.S. and internationally, they are called epinephrine and norepinephrine.
So here is a picture of the situation (arrow shows molecule).
Now the exceptions:
1- Norepinephrine is also released as a hormone by the adrenal glands. What is released is 80% epinephrine and 20% norepinephrine.
2- Sometimes neurotransmitters are released into neural tissue with no specific target and no synapse, called "volume transmission" (e.g. dopamine, serotonin, norepinephrine, ...)
3- In the hypothalamus, hormones are used as quasi-neurotransmitters to signal the neighboring pituitary gland using special short-distance blood vessels that only go a few millimeters.
4- There is some evidence that epinephrine could be used in rare circumstances as a neurotransmitter, e.g. within the retina neural circuit.
Hope it helps !
Hormones are molecules used for signaling by being released into the bloodstream. Neurotransmitters are molecules used for direct signaling between neurons, usually by physical contact at a synapse.
This is the ideal model, anyway. It is true 99% of the time, however there are exceptions.
Epinephrine / adrenaline is extra confusing because of its "sister molecule" norepinephrine / noradrenaline, which is a neurotransmitter. These molecules are nearly identical, except one has an extra carbon (C) in one place. So epinephrine / adrenaline is released by the adrenal gland into the bloodstream as a hormone whereas norepinephrine / noradrenaline is released by neurons in the brain as a neurotransmitter.
On top of that, both molecules are detected by the same receptors, called "alpha" and "beta" receptors (hence "beta-blocker" drugs for heart disease). Neurons use these receptors to listen for the neurotransmitter norepinephrine, whereas other cells in the body use these same receptors to listen for the hormone epinephrine.
And if that weren't enough, these two molecules have dual names for historical reasons. In Britain, they are called adrenaline and noradrenaline, and in the U.S. and internationally, they are called epinephrine and norepinephrine.
So here is a picture of the situation (arrow shows molecule).
Now the exceptions:
1- Norepinephrine is also released as a hormone by the adrenal glands. What is released is 80% epinephrine and 20% norepinephrine.
2- Sometimes neurotransmitters are released into neural tissue with no specific target and no synapse, called "volume transmission" (e.g. dopamine, serotonin, norepinephrine, ...)
3- In the hypothalamus, hormones are used as quasi-neurotransmitters to signal the neighboring pituitary gland using special short-distance blood vessels that only go a few millimeters.
4- There is some evidence that epinephrine could be used in rare circumstances as a neurotransmitter, e.g. within the retina neural circuit.
Hope it helps !
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Yea, it is both. Adrenaline is same substance whether it is a hormone or a neurotransmitter. They are two separate chemical messengers with some overlap as some molecules can act as both hormones and neurotransmitters. One example of this overlap is norepinephrine which can be released into the bloodstream by the adrenal glands as a hormone or can be released by sympathetic nerve endings as a neurotransmitter.
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