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.