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
What hormones are in the anterior pituitary?
- TSH
- ACTH
- GH
- Prolactin
- Luteinizing hormone
What is the difference between trophic hormones (ACTH, TSH, LH, etc) and prolactin & growth hormone?
- Trophic hormones cause a release of another hormones somewhere else, while the others have an effect in their own right
What happens in hypothalamo-pituitary disconnection?
All hormones decrease in their levels except ONE: prolactin
- normally, these hormones have something that releases them all the time
What is external work of metabolism?
Energy used by skeletal muscles to move
What is internal work of metabolism?
Energy used to sustain life
What determines how fast body functions are?
Thyroid hormone
Are TH lipophilic or hydrophilic?
LIPOPHILIC
How are TH transported?
In plasma bound carrier proteins
Is T3 or T4 more potent?
T3
Where does T4 get converted to T3?
In the tissues
TH: control of synthesis and release
LOOK AT DIAGRAM
What is hypothyroidism?
Thyroid gland failure or deficiency in TRH or TSH
Hypothyroidism symptoms
- Decreased metabolism
- Poor cold tolerance
- Weight gain
- Puffy face
- Cretinism or dwarfism
Is hypothyroidism reversible?
Only if treated from birth
What is hyperthyroidism?
Caused by excess THR, TSH or TH production
Hyperthyroidism symptoms
- Increased metabolism
- excessive sweating
- muscle weakness
