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Chapter 7

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John Gibson

on 5 December 2014

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Transcript of Chapter 7

Endocrine Systems
Components of The Endocrine System
Endocrine gland
Target tissue
Hormone Structure and Synthesis
Derived from cholesterol
Not all steroids have the same function
Interact directly with the DNA
activate gene signaling cells to make proteins
or to degrade proteins
Can have very complex structures with 100's of amino acids
Interact with the cell membrane to activate a secondary signaling system
Derived from individual amino acids
epinephrine (adrenaline)
norepinephrine (noradrenaline)
Thyroid Hormones
Hormone Release
Hormones are synthesized in their respective glands, then stored and released with the appropriate stimulus
hormone is secreted into the blood and transported
hormone is released into an area close to the target cell
hormone is released by a cell and interacts with the same cell
Hormone Degradation
Half life
the amount of time for the concentration of a hormone to diminish by half
Many hormones will bind to proteins in the blood to lengthen their half life
Once a hormone has interacted with its target cell it is broken down
Some hormones will release a burst of hormones when stimulated
hormonal secretion will follow both positive and negative feedback
Circadian Rhythms
Some hormones have a circadian rhythm
Typically related to light and dark cycles
Example: SCN
1st and 2nd sleep
Hypothalamus and Pituitary Gland
Hypothalamus Releasing and Inhibiting Hormones
Growth Hormone
Releasing And Inhibiting Hormones
The hypothalamus will release hormones that will either stimulate or inhibit the release of hormones in the pituitary gland
Thyroid-releasing hormone (TRH) --> Thyroid-stimulating hormone (TSH)-->Thyroid Hormones
Thyroid Hormones --> Thyroid-inhibiting hormone --> stops the release of TSH
Growth Hormone
Stimulates protein synthesis with active muscle cells
Stimulates the release of triglycerides in fat cells
Inhibits uptake or accumulation of lipids from circulation
Release in a pulsatile manner, mostly when sleeping
Growth hormone releasing hormone (GHRH)-->GH--> IGF --> Somatostatin (hypothalamus) --> inhibits GH
Ghrelin from the stomach stimulates the release of GH
Highest when sleeping, after resistance exercise
declines with age
Exercise increases GH ability to interact with tissue
Proopiomelanocortin Peptides
Stimulation of the hypothalamus causes POMC to be enzymatically cleaved
Adrenocorticotropin (ACTH)
Melanocyte-stimulating hormones (MSH)
Thyroid Stimulating Hormone
Stimulates the release of Cortisol
Increases in response to stress and intense exercise
Stimulates the release of melanin from melanocytes in the skin
changes the pigment of the skin
stimulates aldosterone secretion from the adrenal glands
helps glucose, sucrose, and albumin cross the blood brain barrier
Helps with mood, memory, arousal, fear
strain of opioids
has an analgesic effect
increases in response to pain, trauma, higher exercise intensities and stress
TRH-->TSH-->Thyroid hormone
Stimulates the release of sex hormones (Testosterone in men, Estrogen in women)
hCG from the placenta during pregnancy
hCG Diet
500 calories a day, injectable hCG
Compared to only 500 calories a day... no difference
Most gain the weight back plus more
Primary regulators of sex-related physiological function
Estrogen and the Menstrual Cycle
Masculinization of the brain
Influences the development of secondary sex characteristics in young boys
stimulates muscle, bone, strength and libido in men
High levels of testosterone results in higher levels of estrogen
Levels of testosterone in men and women
Women: 6-86 ng/dl
Men: 270-1100 ng/dl
Produced in the testes in men and in the ovaries and adrenal cortex in women
Women rely on GH and IGF for anabolic actions
Acute exercise (both aerobic and anaerobic) increases testosterone and receptors on target tissue
Extreme endurance activity reduces testosterone
Estrogen and the Menstrual Cycle
The menstrual cycle is the process of preparation for pregnancy each month
Usually lasts for 28 days (21-35)
Menstruation typically lasts 3-5 days
Menstrual disorders
Premenstrual Syndrome (PMS)
Exercises role in menstrual disorders
Menstrual Cycle
LH stimulates the release of estradiol
allows the lining to grow and thicken
Spike in FSH, LH and drop in estradiol causes the release of the egg
If fertilization doesn't occur menstruation will occur, causing the lining of the uterus to be removed.
Painful periods with severe cramping
caused from a release of higher levels of prostaglandins
cause uterine contractions
Could also be caused by
uterine fibroids
Lack of a menstrual period
Women have never had a period
absence of menstrual period for at least 6 months
extreme weight loss
eating disorders
excessive exercise is likely not related
more likely due to insufficient nutrients
Prolonged menstrual bleeding
Very heavy bleeding lasts longer than 7 days with large clots in the flow
cause by
hormonal imbalances
uterine fibroids
Could be due to lower levels of progesterone
Exercise and Menstrual Disorders
Exercise likely doesn't play a role in menstrual disorders
Menstrual disorders are commonly found
cross country (endurance training)
dancing, gymnastics (demands for body image)
diving, gymnastics, figure skating (weight class sports, or sports where weight is vital to performance)
Recovery from menstrual disorders is usually linked to increasing caloric intake, without any change in exercise
Insulin Like Growth Factors
Peptide hormones that are very complex
We don't understand them very well
Binding proteins:
extend IGFs half life
transport to the target cell
help modulate its actions
Important anabolic actions for muscle and bone development
Higher levels of fitness and higher intake of CHO and protein are linked to higher resting levels of IGF-I
Adrenal Hormones
Adrenal Medulla
Adrenal Cortex
Adrenal Medulla
Release from the adrenal medulla is caused by the sympathetic nervous system (fast response)
Adrenergic Response (interacts with adrenergic receptors)
epinephrine (85%)
Breakdown glucose in the liver
Enhances fatty acid release
may play role in recovery and immune enhancement
Role in exercise
Role In Exercise
Catecholamines increase in response to stressors
epinephrine can elevate 30 minutes to 24 hours before exercise
Bind to sarcoplasmic reticulum causing more rapid release of calcium ---> more rapid contraction
epinephrine has a half life of 2 minutes - returns to resting levels pretty quickly
Adrenal Cortex
Endocrine stimulation
helps regulate water and electrolyte balance in blood
signals kidneys - retain Na+, release K+
Influences acid/base balance
secretion of H+ from intercalated cells in the collecting ducts of the kidneys
stimulates the posterior pituitary gland to release arginine vasopressin
causes kidneys to retain water
Interacts with almost every cell of the body
enhances enzyme activity in gluconeogenesis
stimulates the release of amino acids and fatty acids to be used in gluconeogenesis
preserve glycogen by providing substances for gluconeogenesis
Blocks protein synthesis
suppresses immune cells - anti-inflammatory
Cortisone--->reduces muscle and bone development
Cushing's Disease - excessive production of cortisol
Pancreatic Hormones
Lowers Blood Glucose (Glut 4)
Raises Blood Glucose
Main feedback pathway deals with the level of glucose in the blood
Type 1
Pancreas' beta cells don't release enough insulin
Type 2
Target cells are resistant to insulin
High intensity exercise has a greater effect than low intensity
Thyroid Hormones
Thyroxine (T4)
Triiodothyronine (T3)
Increases basal metabolic rate
Protein synthesis
increases effects of epinephrine
aids in growth and development
Full transcript