L25 Flashcards
(45 cards)
Homeostasis
The presense of a stable internal environment
What happens when homeostasis is disturbed?
Receptors detect the change and relays info to the control centre which determines if change is required –> message sent to effectors
Can the receptors for increase and decrease be the same?
Yes but not always
What is a difference between set point and normal range
Set pt is universally determined and normal range is what an individual fluctuates around the set point because our set points are rarely static
*Each individual has their own unique normal range
Characteristic of an individuals normal range and the population range
*Individuals range is narrower than the population range due to variation
*Most individuals have a set point that is within the population reference range
*If you go out of your normal range, you can exhibit symptoms of disease
What is neural signalling?
APs in neurons and neurotransmitters at synapse
*need cells to be lined up for signal transmission
*Has the fastest transmission speed to minimise response delays
*Good for brief responses
What is endocrine signalling?
Hormones released into the blood
* Relatively slow but lasts longs
*Reaches receptors all around the body
Which glands secrete hormones?
Endocrine glands through exocytosis using vesicles
What must the distant target tissue have?
the appropriate receptors
What does the hypothalamus do?
Links neural to endocrine system and controls the secretion of a lot of endocrine glands
Where is the thyroid gland found?
Wrapped around the throat at the bottom of the neck
What do the adrenal glands consist of?
Adrenal cortex and medulla
What is a hormone?
A chemical messenger that must pass through the blood, affects cells with specific receptors for that hormone
What is a receptor?
Its a protein that can be on the target cell plasma membrane or inside the cell
How to classify hormones?
By what they dissolve in
Water soluble hormones
*Mostly peptides
* Make up 75% of all hormones
*Some catecholamines incl. adrenaline and nor-adrenaline
*Made and stored until required, released through exocytosis as they are hydrophilic and cant diffuse through the membrane
*Travels dissolved in the blood
*2nd messengers
*Milliseconds to minutes
Fat soluble hormones
Steroids and thyroid hormones incl. T3 and T4
*Steroids created from cholesterol as required
*Thyroid hormones made in thyroid cells and stored until needed (unusual)
*Travels in the blood bound to a carrier protein
*Alters gene transcription
*Hours to days
What is a catecholamine?
A single modified amino acid that is H2O soluble
Why are fat soluble hormones not stored?
They would just pass through the membrane as they are lipid soluble
Where are the receptors of H2O soluble hormones?
They cannot pass through the membrane so the receptors are on the surface (plasma mem)
Where are the receptors of lipid soluble hormones?
They can pass through mem so receptors are in the cytoplasm or the nucleus
Cellular response to H2O soluble hormones
Hormone attaches to external domain of the receptor –> G protein activated on the internal domain –> G protein activates/deactivates the second messenger pathway production/reduction (AMP/cAMP OR Ca2+) –> downstream protein pathways activated/deactivated
Cellular response to lipid soluble hormones
Hormone dissociates from carrier protein –> enters cell and binds to receptor in cyto then taken to nucleus or directly goes to nucleus –> the complex acts as a transcription factor for specific mRNA –> mRNA is translated to make protein –> protein mediates cell specific response
Most common ways hormones are maintained
negative feedback
*Reduce change until stimulus is removed
*directly inhibit further release
positive feedback
*Amplify change until desired outcome is reached