Lecture 5 & 6: Endocrinology Flashcards
What is the endocrine system for?
Maintaining homeostasis
What is quicker: nervous or endocrine system?
NERVOUS
Why is the nervous system limited?
- Nerves do not have direct connection with whatever it is controlling (it must pass through an axon to connect)
Functions of the endocrine system
- Regulate metabolism
- Allow body to cope with stress
- Regulate growth
- Control reproduction
- Control digestion
What is a hormone?
Something that floats around the blood (thus can get around the whole body)
- Blood acts as the connection
What are some tissues that are involved in the endocrine system?
- Brain
- Hypothalamus
- Pituitary
- Pineal gland
- Pancreas
- Gonads
- Kidneys
- Liver
What are hydrophilic hormones made from?
Protein
Can hydrophilic hormones pass through the cell membrane?
NO - they act on receptors that are on the surface of the cells
What happens when a hydrophilic hormone acts on a receptor on the cell membrane?
1) Change cell permeability/receptor
2) Activate second-messenger response
Do hydrophilic hormones have a long half life? Why/why not?
NO - their are vulnerable to being broken down as they are floating around the cell
How are lipophilic hormones transported around the blood?
They bind to a carrier protein (some that is not bound will be dissolved (free hormone) - which is the only physiologically active part)
Can free lipophilic hormones pass through the cell membrane?
YES
Where do free lipophilic hormones bind?
To a specific receptor in the target cell (cell nucleus)
Why are lipophilic hormones hard to store?
They can dissolve out of the cell
Do hydrophilic or lipophilic hormones have a long-term effect?
LIPOPHILIC as they are not broken down easily and last a long time in the blood
Compare/contrast lipophilic and hydrophilic hormones
Hydrophilic: - Likes water - Cannot pass plasma membrane - Fast onset, short-acting - Acts on outside of cell - Can dissolve in blood Lipophilic: - Hates water - Can diffuse across membrane - Slower onset, longer-acting - Act on inside of cell - Can't easily float around blood
How can hormone activity be regulated?
- Secretion
- Transport
- Metabolism
- Excretion
- Target cell responsiveness
How can hormone activity be regulated by secretion?
Two control pathways:
1) Central regulation
2) Direct regulation
What is central regulation?
- Controlled by the brain
- Affected by negative-feedback loops, neuroendocrine reflexes
- Can be fast, slow or long term response
What is direct regulation?
Endocrine cells respond directly to changes in extracellular fluid levels of substances
- Very rapid response to critical needs
How can hormone activity be regulated by target cell responsiveness?
- Amplification of hormones effects via second messenger cascade
What is the first sign of pituitary tumor?
Decreased vision - tumor is pushing against optic chiasm
What hormones are in the posterior pituitary?
- Oxytocin
- Vasopressin
How does hypothalamus - pituitary work?
- Hormone is released into BS and taken to APG
- Releasing or inhibiting factor of hormone acts on cells in APG
- Those cells produce a hormone that goes back to the blood and to the rest of the body
