6. Endocrine System Continued

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來自 University of Colorado Boulder 的課程

Science of Exercise

634 個評分

University of Colorado Boulder

Science of Exercise

634 個評分

Learners who complete Science of Exercise will have an improved physiological understanding of how your body responds to exercise, and will be able to identify behaviors, choices, and environments that impact your health and training. You will explore a number of significant adjustments required by your body in order to properly respond to the physical stress of exercise, including changes in carbohydrate, fat and protein metabolism, nutritional considerations, causes of muscle soreness & fatigue, and the effectiveness and dangers of performance enhancing drugs. Active learning assessments will challenge you to apply this new knowledge via nutrition logs, heart rate monitoring, calculations of your total daily caloric expenditure and body mass index (BMI). Finally, learners will examine the scientific evidence for the health benefits of exercise including the prevention and treatment of heart disease, diabetes, cancer, obesity (weight loss), depression, and dementia.

從本節課中

Physiological Systems During Exercise

In this module you will learn how a number of key physiological systems (muscular, respiratory, cardiovascular, endocrine and immune systems) are regulated during exercise to help maintain homeostasis. These adjustments are critical for exercise to continue for any significant duration. This will include: how the respiratory system adjusts during exercise to ensure proper oxygen delivery and carbon dioxide removal from active muscles; how the cardiovascular system responds to ensure adequate blood flow to various organs, including muscle, during exercise; how the endocrine system plays a major role in regulating key biochemical and physiological responses to exercise and; how exercise influences the immune system and your ability to fight infections.

1. Skeletal Muscle Structure & Function9:34

2. Respiratory System Responses to Exercise10:44

3. Cardiovascular System Responses to Exercise7:45

4. Cardiovascular System Continued9:44

5. Endocrine System Responses to Exercise8:35

6. Endocrine System Continued7:12

7. Immune System Responses to Exercise10:42

與講師見面

Robert Mazzeo, Ph.D.
Associate Professor
Department of Integrative Physiology

In this second video on the endocrine system,

I will examine three additional hormones that play a critical role

in the adjustments made by the body in response to exercise.

I will begin by discussing the many contributions of epinephrine and

norepinephrine.

These hormones are released from the adrenal glands and more specifically,

the adrenal medulla.

I will conclude the video examining the role of the growth hormone plays during

both exercise as well as into the post-exercise recovery period.

Based on their structure, epinephrine and norepinephrine belong to the chemical

family of catecholamines which also includes the neurotransmitter dopamine.

Since epinephrine and norepinephrine are synthesized in the adrenal glands

they are also commonly referred to as adrenaline and noradrenaline.

Norepinephrine also functions as the major neurotransmitter for

the sympathetic nervous system, which as we discussed in the cardiovascular system

videos, plays an important role in the regulation of cardiac output and

blood flow during exercise.

The adrenal glands are located on top of the kidneys.

Shown here are the sympathetic nerve fibers

directly enervating the adrenal medulla.

Thus, whenever sympathetic nerve activity is increased, as during exercise,

the adrenal medulla releases epinephrine and norepinephrine into the blood Where

these hormones will have a tremendous impact on a number of biochemical and

physiological adjustments necessary to sustain exercise.

This sympathetic nervous system adrenal access is responsible for

the fight or flight response which occurs when you're frightened or nervous.

It originates from the animal kingdom, when a predator spots a prey.

One animal gets excited for a chance at its next meal

while the other animal is frightened, not wanting to become the next meal.

Both reactions elicit a large sympathetic response.

These stress hormones can actually prepare the body for

exercise prior to taking the first step.

Shown here are the many biochemical and

physiological variables affected by these hormones.

You may have felt your heart pounding in your chest when you become frightened or

nervous.

This is the fight or flight response in action.

This table demonstrates the many physiological and

metabolic effects of epinephrine required for exercise.

As discussed in our cardiovascular videos, epinephrine plays a major

role in many physiological adjustments, including an increase in heart rate and

stroke volume, and thus cardiac output and an increase in local muscle blood flow.

All of these adjustments contribute to the increase in the delivery of oxygen and

fuel to the working muscles.

From a metabolic standpoint,

epinephrine regulates the breakdown of glycogen in both muscle and liver.

As well as stimulates fatty acid mobilization from adipose tissue.

Together, these metabolic functions ensure that the working muscles

have adequate fuel for ATP production.

During the course of a graded exercise test to exhaustion, blood epinephrine and

norepinephrine levels will increase exponentially

as maximal oxygen cup consumption is reached.

This represents the progressive increase in sympathetic nerve activity,

resulting in adrenal medullary release of epinephrine and norepinephrine.

Not surprisingly, as shown here, the epinephrine response to submaximal

exercise will be dependent upon the exercise intensity.

The greater the exercise intensity, the greater is the sympathetic nerve activity

and thus, epinephrine release from the adrenal medulla.

Before moving on to the next hormone I cannot emphasize enough the critical role

that both the sympathetic nervous system and the adrenal medullary hormones,

epinephrine and norepinephrine play in regulating multiple physiologic and

metabolic adjustments necessary to sustain physical activity.

Next, I will discuss the contribution of the growth hormone,

both during exercise, as well as into the post exercise recovery period.

The growth hormone is synthesized and secreted by the anterior pituitary gland.

While the growth hormone's major effect is to promote protein synthesis in

all tissues, during exercise it also plays a role in the mobilization and

utilization of free fatty acids.

During exercise, there was a slow or

delayed response of growth hormone released into the blood.

As just mentioned this will assist with the mobilization and

utilization of free fatty acids.

However, notice that after relatively high-intensity exercise,

growth hormone levels continue to rise and

can remain elevated up to over one hour post exercise.

As discussed in the video on protein metabolism,

there is a very significant increase in the rate of protein synthesis

during the period immediately following exercise.

This is a crucial time for the initiation of training adaptations for

both endurance and strength training.

The elevation in growth hormone is primarily responsible for the regulation

of this increase in protein synthesis during this post-exercise period.

Many studies but not all suggest that as a result of training

the growth hormone responds to endurance training is more robust.

This has potential implications for

not only future training adaptations but for healthy aging as well.

The implications for aging will be discussed in module four.

For now, understand that both the frequency and

magnitude of growth hormone release from the anterior pituitary gland

decreases with advancing age and sanitary men and women.

This can directly impact an individual's ability to maintain muscle mass and

strength as we get older and threaten one's independence and quality of life.

In summary, shown here is the typical response of the hormones that I have

discussed in this and the previous video.

Other hormones, such as cortisol, contribute to the adjustments made by

the body during the stress imposed by a single bout of excercise.

However, I have covered the five major players when it comes to the regulation of

the critical biochemical and physiological adjustments necessary to sustain exercise.

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