The endocrine system essentially consists of many ___________ glands
The endocrine system essentially consists of many ductless glands
How is the specificity of signalling achieved in the endocrine system?
- Chemically distinct hormones
- Specific receptors
- Distinct distribution of receptors across target cells
Why is specificity of signalling required in the endocrine system?
Hormones in the blood stream can reach any tissue
(and only "need" to act on certain tissues)
What are the 4 main secretion types from endocrine glands?
- Modified amino acids
Give an example of a modified amino acid secretion from an endocrine gland?
- Thyroxine (T4)
- Triiodothyronine (T3)
Give an example of a steroid hormone
What do all steroid hormones originate from?
Give an example of a peptide hormone
- Adrenocorticotropic hormone (ACTH)
- Anti-diuretic hormone (ADH)
Peptide hormines come from _________ ___________ proteins
Peptide hormines come from larger precursor proteins
Give an example of a protein hormone
What are the 7 main endocrine organs?
- Pituitary gland
- Thyroid gland
- Parathyroid glands
- Adrenal glands
What is autocrine signalling?
When a cell is both the originator and recipient of the signal
What is paracrine signalling?
Signalling molecules travel short distances by diffusion and act on cells close by
(they do not enter systemic circulation)
What is endocrine signalling?
Hormone is released into the circulation and reaches the target organ this way
Hormones can only function in one of the following three ways, autocrine, paracrine or endocrine. True or false?
(hormones can function in more than 1 way)
Why do receptors for endocrine hormones have very high affinity for hormone?
Organ function is regulated at very low hormone concentrations
Endocrine hormones have high ________
Endocrine hormones have high potency
Due to the scarcity of the endocrine hormone signal, what does the target cell do to combat this?
Signal transduction pathways amplify the original signal
The onset and duration of hormone action is fairly consistent.
True or false?
It is highly variable froms seconds to days
The onset and duration of hormone action depends on deactivation of enzyme, but which two locations does this mainly occur at?
- Enzyme mediated deactivation in the liver
- Deactivation at the site of action
Which two categories of functions can hormones have?
Are amines either presynthesised or synthesised and secreted on demand?
When would amines be released?
In response to stimuli by Ca2+ dependent exocytosis
What are the three key characteristics of amines?
- Water soluble
- Released on demand
Are peptides and proteins either presynthesised or synthesised and secreted on demand?
When would peptides and proteins be released?
In response to Ca2+ dependent mechanisms
In terms of peptides and protein hormones, what is the general term given to enzymes which alter the precursor to the mature hormone?
Cholesterol is converted to steroid hormones via which intermediate?
Are steroids either presynthesised or synthesised and secreted on demand?
Synthesised and secreted on demand
How do steroid hormones travel in the plasma and why?
Via steroid binding proteins
They are very sparingly soluble in water (mostly hydrophobic)