illinois state university hormonal regulation of exercise chapter 21 and 22

Illinois State University

Hormonal Regulation of Exercise

Chapter 21 and 22


The Endocrine System

Gland Hormone Target organ or

tissue.


Hormones

Hormones can be classified as either steroidal or nonsteroidal. » Steroid hormones are lipid soluble, and

most are formed from cholesterol.» Nonsteroid hormones are proteins,

peptides, or amino acids.


Hormones

Hormones are generally secreted into the blood and then circulate through the body to exert an effect only on their target cells.


Hormones

Steroid hormones pass through cell membranes and bind to receptors inside the cell. » They use a mechanism called direct gene

activation to cause protein synthesis.


Hormones

Non-steroidal hormones cannot enter cells easily, so they bind to receptors on the cell membrane. » This activates a second messenger within

the cell which in turn can trigger numerous cellular processes.


Hormones

Secretion of most hormones is regulated by a negative feedback system.


Hormones

The number of receptors for a specific hormone can be altered to meet the body’s demands.


Hormones

Key point - the pituitary gland was once thought to be the master endocrine gland solely in control of many other glands and organs.


Control

It is now recognized that the pituitary gland is largely controlled by the hypothalamus.


Hormones

See Table 21.3 (p. 629) for listing of glands,

hormones, and major function.


Pituitary Hormones

Anterior Lobe Somatotropin (hgH) - Impacts all cells of

the body. » Major role in maturation, protein synthesis,

use of fat, and CHO sparing.


Pituitary Hormones

Anterior Lobe Andrenocorticotropin (ACTH) - Impacts

the adrenal cortex and regulates adrenal cortex hormone secretion.


Pituitary Hormones

Posterior Lobe Antidiruretic Hormone (ADH or

vasopressin) - impacts the kidneys.» Regulates water excretion and blood

pressure by vasoconstriction.


Thyroid Hormone

Thyroxine and triiodothyronine - Impact all cells in the body. » Increases rate of cellular metabolism,

increases heart rate and force of contraction.


Adrenal Hormones

Medulla Epinephrine - Impacts most cells of the

body. » Mobilizes glycogen, increases skeletal

muscle blood flow, increases heart rate and contractility, increases oxygen consumption.


Adrenal Hormones

Medulla Norepinephrine - impacts most cells of

the body through vasoconstriction which increases blood flow, increases heart rate and contractility, increases VO2.


Adrenal Hormones

Cortex Mineralcorticoids (aldosterone) - impacts

kidneys causing Na retention and K excretion.


Adrenal Hormones

Cortex Glucocorticoids (cortisol) - impacts most

cells of the body. » Controls metabolism of all fuels and has an

anti-inflammatory action.


Adrenal Hormones

Cortex Androgens and estrogens - impacts sex

organs. » Responsible for development of secondary

sexual characteristics.


Pancreatic Hormones

Insulin - impacts all cells of the body. » Regulates blood glucose levels. » Increases the utilization of glucose and the

synthesis of fat.


Pancreatic Hormones

Glucagon - impacts all cells of the body. » Increases blood glucose levels and

stimulates the breakdown of protein and fat.


Gonadal Hormones

Testes Testosterone - affects sex organs and

muscles. » Responsible for the development of male

secondary sexual characteristics.


Gonadal Hormones

Ovaries Estrogen - affects sex organs and

adipose tissue. » Responsible for the development of female

secondary sexual characteristics.


Hormones and Exercise

Catecholamines - secretion increases. » Greater increase with intense exercise.» Secrete more norepinephrine than

epinephrine.» Secretion increases less after training.» Significance - increased blood glucose.



Somatotropin - increases with exercise.» Increases more in unfit person.» Declines faster in fit person.» Significance - unknown?



ACTH-cortisol - increases with exercise.» Greater increase with intense exercise.» Increases less after submaximal exercise

training.» Significance - increased gluconeogenesis

in liver.



Testosterone - Increases with exercise.» Effect - none.» Significance - unknown?



Insulin - decreases during exercise.» Decreases less after training.» Significance - increased stimulus to utilize

blood glucose.



Glucagon - Increases with exercise.» Increases less after training.» Significance - increased blood glucose via

glycogenolysis and gluconeogenesis.



Renin-angiotensis-aldosterone - Increase with exercise.» Same after training in rats.» Significance - Na retention to maintain

plasma volume.



ADH - Increases with exercise. » Effect - none» Significance - Causes water retention to

maintain plasma volume.


Hormones and Metabolism

Plasma glucose is increased by the combined actions of glucagon, epinephrine, norepinephrine, and cortisol. » These hormones promote glycogenolysis

and gluconeogenesis, thus increasing the amount of glucose available for use as a fuel source.



Insulin helps the released glucose enter the cells where it can be used for energy production.


Insulin

But insulin levels decline during prolonged exercise, indicating that exercise facilitates the action of insulin so that less of the hormone is required during exercise than when at rest.



When CHO reserves are low, the body turns more to fat oxidation for energy, and this process is facilitated by cortisol, epinephrine, norepinephrine, and growth hormone.



Cortisol accelerates lipolysis, releasing free fatty acids into the blood so they can be taken up by the cells and used for energy production.


Cortisol

But cortisol levels peak and then return to near normal levels during prolonged exercise.


Hormones and Metabolism:

When this happens, the catecholamines and growth hormone take over cortisol’s role.



Key point - Loss of fluid (plasma) from the blood results in a concentration of the constituents of the blood, a phenomenon referred to as hemoconcentration.



Conversely, a gain of fluid into the blood results in a dilution of the constituents of the blood, which is referred to as hemodilution.


Fluid Balance and Hormones

The 2 primary hormones involved in the regulation of fluid balance are aldosterone and antidiuretic hormone (ADH).


Fluid Balance and Hormones:

When plasma volume or blood pressure decreases, Angiotensinogen II increases peripheral resistance, raising the blood pressure.



Angiotensinogen II also triggers the release of aldosterone from the adrenal cortex.


Aldosterone

Aldosterone promotes sodium reabsorption in the kidneys, which in turn causes water retention, thus increasing plasma volume.



ADH acts on the kidneys, promoting water conservation.» Through this mechanism, the plasma

volume is increased, which results in dilution of the plasma solutes.


Anabolic Androgenic Steroids

illinois state university hormonal regulation of exercise chapter 21 and 22

Documents