The endocrine system II Flashcards
What characteristics of a hormone does their transport in the blood depend on?
Their chemical composition and hydrophilicity
What kinds of hormones are transported dissolved in plasma?
Protein and peptide hormones
Why are protein and peptide hormones usually transported dissolved in the plasma?
They are water soluble
What are the temporal characteristics of protein and peptide hormones?
Fast acting, short half-life, rapidly eliminated
How are steroid and thyroid hormones transported in the blood?
Bound to plasma proteins
Why are steroid and thyroid hormones transported via being bound to plasma transport proteins?
They are hydrophobic and so not water soluble
If something is hydrophobic, what is is soluble in?
lipids
What are the temporal characteristics of steroid and thyroid hormones?
Slower action, longer half-life, slower elimination
What is the total hormone concentration?
Sum of free hormone and bound hormone
What can free hormones do that bound hormones cannot?
Interact with target cells and organs
What is the reversible reaction involving free hormone, carrier plasma protein and hormone-protein complex
Free hormone + Carrier plasma protein<—-> hormone-protein complex
What is the total mass of a hormone usually?
micrograms (10-6 g), nanograms (10-9 g) and picograms (10-12 g)
Difference between intracrine and autocrine hormone action
Autocrine hormones are secreted, intracrine are not
What is intracrine hormone action?
The hormone acts inside the cell from which it was produced
What is paracrine hormone action?
Hormone is secreted and acts on a neighbouring cell
What is special about intracrine hormones?
They are not secreted
What is autocrine hormone action?
Hormone is secreted and binds to the cell from which it was released
What does the location of the hormone (in or on the cell) depend on?
The water solubility of the hormone
Why do only some tissues respond to specific hormones?
They have receptor proteins in or on their cells that are specific to a certain hormone(s)
What is neuroendocrine action?
Neurons secrete endocrine hormones
What is endocrine hormone action?
Hormone is secreted and acts on a cell far away
If a hormone is water soluble, where is its receptor?
On the plasma membrane of the receptor cell
How does the signal of a water soluble hormone reach the inside of a receptor cell?
Via second messengers which are activated by the receptor on the plasma membrane
How does the receptor for water soluble hormones receive a signal from the outside and cause a 2nd messenger reaction inside the cell?
They span the plasma membrane
If a hormone is water insoluble where is its receptor?
Inside the nucleus of the receptor cell
Why can water insoluble hormones enter the receptor cells?
They are hydrophobic (so lipid soluble) and so can cross the lipid bilayer of the plasma membrane
What is a typical outcome of a water soluble hormone?
An enzyme in the cytoplasm may be activated
What is a typical outcome of a water insoluble hormone?
Transcription factors (etc) activated and so specific proteins will be synthesised
