Chapter 5 Flashcards
The role that hormones play in helping maintain plasma gluecose levels and plasma volume during exercise: 1) Definitions 2) Hormone-Receptor Interactions 3) Mechanisms of Hormone Actions 4) Sources of fuel During Exercise 5) Review of select hormones
Define Endocrine System
Releases hormones into the blood to circulate to tissues
Define Hormones
Chemical messengers which carry signals to the tissue to carry out a function. (work with receptors)
How can hormones freely circulate in the blood without affecting every tissue?
Because they bind to specific receptors (Lock & Key mechanism)
List 3 classes of Hormones…
Amino Acid derivatives
Peptides/Proteins (also created from cholesterol)
Steroids (derived from cholesterol)
What 2 factors are directly related to the effect a hormone exerts?
Blood hormone concentration
Hormone-receptor interaction
Hormone concentration is determined by:
SMPT Spenser Mooned Paul Temple
- Rate of secretion (magnitude of input, stimulatory vs. inhibitory input)
- Rate of metabolism / excretion (at the receptor and by the liver/kidneys)
- Changes in plasma volume (during exercise volume decreases)
- Quantity of transport protein (increase in transport proteins = decrease in free hormones)
In order for a tissue to be responsive to a hormone, it must have the specific receptor for that hormone.
The number of receptors on a cell can change.
What is down-regulation
A decrease in the number of receptors. (occurs because of an over-exposure of a hormone) (type 2 diabetes)
What is up-regulation?
An increase in the number of receptors (increased sensitivity)
What are the three main ways that hormones function?
- Membrane transport mechanism
- Stimulation of DNA in the nucleus
- Second messengers
Describe the Membrane Transport mechanism
It activates the carrier molecules inside the cell.
- Hormones bind to receptors on membrane
- It activates carrier molecule in or near the membrane
- Increases movement of substrates or ions from outside to inside cell
Describe the Stimulation of DNA in the Nucleus
Steroid hormones easily diffuse through the membrane (builds things)
- Steroid hormones easily diffuse through membrane (thyroid)
- Bind to protein receptors in cytoplasm
- Enters the nucleus and binds to protein joined to DNA
- mRNA
- Synthesis specific proteins
- “Slow acting” hormones
- Effects long lasting
What is a Second Messenger?
Some hormones cannot easily cross the cell membrane, so they exert their effects through a second messenger
Describe the Second Messenger
Hormones bind to a receptor an this activates a G-Protein.
The G-Protein then activates either:
1. Ion channels in the cell to allow things to enter the cell (such a calcium)
2. Enzymes
Second Messenger
They are really just a series of actions and reactions initially triggered by the binding of a hormone to a receptor.
What is a G-Protein?
It is the link between the hormone-receptor interaction on the surface of the membrane and the subsequent events inside the cell.
- it opens ion channels for Ca++ to enter cell.
- activates enzymes in membrane
Sources of CHO during exercise
Carbohydrates are stored as glycogen in the muscle and liver. Gluecose is also carried in the blood.
When and how is the Blood Gluecose source used for fuel during exercise?
It is the IMMEDIATE Source of energy.
When and how is the Muscle Glycogen source used for fuel during exercise?
It is the SECONDARY Source (it is near the muscles so it can be an immediate use for energy)
When and how is the Liver Glycogen source used for fuel during exercise?
It REGULATES BLOOD GLUECOSE LEVELS. (back up tank)
What are the 3 primary homeostatic goals during exercise?
- Maintain plasma gluecose levels
- Preserve glycogen levels
- Maintain plasma volume
What does the body do to accomplish the first two homeostatic goals? (maintain plasma gluecose levels & preserve glycogen levels)
- Mobilizes gluecose from liver glycogen
- Mobilizes FFA from adipose tissue to spare plasma gluecose and glycogen
- Synthesizes new gluecose in the liver from amino acids and lactic acid
- Blocks the entry of gluecose into cells to force the use of FFA
What are the 4 hormones that act to help maintain plasma gluecose levels and preserve glycogen levels?
- Growth Hormone
- Catecholamines: Epinephrine & Norepinephrine
- Glucagon
- Insulin
Growth Hormone
Secreted from: Anterior Pituitary Gland
Growth hormone INCREASES UPTAKE OF AMINO ACIDS and INCREASES LONG BONE GROWTH.
How does the Growth Hormone help during exercise?
- DECREASES gluecose uptake by tissue
- INCREASES FFA mobilization
- ENHANCES glueconeogenesis (liver)
Why are athletes taking growth hormone as a performance-enhancing drug?
Because of it’s role in protein synthesis. Helps to re-build connective tissue -promotes less fatigue
What is the danger to taking growth hormones as a full-grown adult?
HGH only thicken bone, not strengthen it.
What is Acromagely
Giantism
Catecholamines: Epinephrine & Norepinephrine
Secreted from: Adrenal Glands
The adrenal medulla secretes 80% EPI and 20% NEPI. NEPI is mainly excreted from the SNS
What alone does EPI do during exercise?
It responds to changes in the blood gluecose levels.
Stimulates breakdown of liver glycogen.
What 3 things do both EPI and NEPI do during exercise to help maintain homeostasis?
- Mobilization of gluecose from liver
- Mobilizes FFA from adipose tissue
- Interferes with gluecose uptake by tissues
Glucagon
Secreted from: Alpha cells in the islets of the Langerhans in the pancreas.
What 2 jobs does glucagon perform during exercise?
- Increases mobilization of substrates from storage (gluecose and FFA)
- Stimulates glueconeogenesis in the liver
Insulin (opposite of glucagon)
Secreted from: Beta cells of the islets of Langerhans
Job: Insulin promotes the storage of gluecose, amino acids, and fats
Problems of Diabetes Mellitus? (Type 1 & Type 2)
Type 1: LACK OF INSULIN production, problems with blood gluecose levels without intervention. Ketoacidosis
Type 2: LACK OF RECEPTORS FOR INSULIN. Lack of activity may cause increased storage of gluecose, amino acids and FFA. (Later stages mimic type 1)
What 2 main hormones are involved with the maintenance of plasma volume?
Antidiuretic hormone
Aldosterone
Antidiuretic Hormone
Secreted from: Posterior Pituitary Gland
Reduces water loss from the body.
Re absorption of water in the kidney tubules back to capillaries.
Aldosterone
Secreted from: Adrenal Cortex
Aldosterone levels directly impact plasma volume and blood pressure.
Impacts plasma volume and BP
(training does not affect it)
What happens during exercise to the Growth Hormone?
Increases
What happens during exercise to the Catecholamines?
Increases
What happens during exercise to Glucagon?
Increases
What happens during exercise to Insulin?
Decreases
What happens during exercise to Antidiuretic?
Increases
What happens during exercise to Aldosterone?
Increases (prolonged exercise)
