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adam
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« Reply #2 on: May 05, 2009, 10:01:39 pm » |
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Epinephrine (adrenaline) is a stimulatory hormone that plays a large part in heart rate regulation in relation to exercise. Like you said Sasha, as you increase exercise, your body must respond to the exercise stimulus, and increasing heart rate and ventilatory rate and glycogen breakdown (depending on the intensity) is part of that. It is significant from the Nervous signal down to the muscle contraction itself.
Will some endocrine secretions are in limited supply (glands are very small), they can be (and are) extremely potent. If I remember correctly, I recall hearing that in order to gain a very small sample of pituitary secretions, hundreds of pigs' cadavers had to be opened in order to get a small drip from each of their pituitary glands.
Generally, as you increase your exercise rate, your body will increase its release of epinephrine as a coping mechanism. However, the body also works on a negative feedback system, which after a while of rising epinephrine concentration levels tells the body that it has enough to do the job. The body then relays this message back and says, "too much stimulation, concentration is too high, shut down sympathetic secretion". It will continue to do this until blood concentration levels decrease. To make this easier to understand, think of it as a big meal for lots of people. You to begin with, you have lots of empty plates. Then you begin to fill them up with food for everyone. Things go smoothly. However, after you fill up the available plates, you notice you are still making lots of food. You then have to cut back production until plates are available again. Once those plates are open again, then you can start filling them back up and you can start production again. Or it works the other way around. More and more people show up to come eat, and you cannot produce food fast enough to feed all of them. You then have to limit the number of people coming in until you get caught up. If their were no regulatory mechanisms withe epinephrine, you would not have a happy heart rate. It would beat so fast you would probably die. Or so slow you would die. In exercise, it has to be elevated and suppressed constantly to ensure proper function and balance. yes you want it higher, but your body will only allow you so much before it has to revert back to safety mode.
In some individuals, this negative feedback mechanism is hindered or affected in some way. This leads to hypersecretion. Eventually, either the gland tires out, or the body becomes less and less stimulated by the hormone secretion. Another possible problem is hyposecretion, in which the gland receives little to no signal to produce and secrete more, and then atrophies.
The endocrine system is not as easily "trainable" as other body systems mainly because it is so intricate. This is why so many athletes attempt to mimic the effects of endocrine hormones by taking things like GH, or testosterone. Only with this kind of sustained potency can they use the endocrine system to their advantage in training. Sure, you can try to get yourself pumped by getting angry before a run - like slapping yourself or something, or pretending to be chased by a dog (or actually being chased by a dog), or listening to upbeat, clear tempo'd music (which by the way has been used by music therapists and others to teach efficient motor control and movements, so it's not a false belief that listening to music can actually help you perform or run better) but eventually, your endocrine system will begin to say- "you actually don't need me as much anymore for this, so i'm not going to do anything much to help". Another reason why so many athletes turn to illegal means to try and get a bigger "hit" on their system.
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