Endocrine Physiology Flashcards
What is autocrine signalling?
When there is a chemical effect on the same cell(s) that secreted the signalling molecule
What is paracrine signalling?
When a chemical is secreted and taken by neighbouring target cells
What is endocrine signalling?
When chemicals are released into the bloodstream to reach various targets throughout the body (hormones_
What types of hormones have internal receptors?
- lipophilic ones ie steroids, THs
What types of hormones have external receptors?
- hydrophilic ones ie peptides
Name the central endocrine glands.
- Pituitary gland
- Pineal gland
- Hypothalamus
What is the difference between endocrine and exocrine structures within the body?
Endocrine
- ductless
- release hormones into surrounding fluid
Exocrine
- have ducts
- non-hormonal substances travel along ducts to reach other surfaces
Name two organs with both endocrine and exocrine function.
Stomach and Pancreas
What three factors stimulate hormone release?
Hormonal - stimulation from other hormones (known as tropic hormones)
Neural - stimulation comes from nerves fibres and APs
Humoral - stimulation due to certain levels of substances (eg. ions) in the blood
How can hormone interactions with the target cell be controlled?
- Amount of hormone circulating in blood
- Bond affinity with target cell receptor
- Number of receptors that target cells has for hormone uptake
What is meant by permissiveness?
A hormone must be present to allow another hormone’s effects to be permitted (eg. cortisol is needed for adrenaline).
What is synergism?
When a combination of hormones produce an effect larger than the sum of their individual effects.
What is antagonism?
When a hormone reduces the effectiveness of another.
How are hormones cleared from the bloodstream?
Usually by liver and kidneys
What is the difference between hyper- and hypo-secretion?
Hyper = too much Hypo = too little
What is the difference between primary and secondary dysfunction?
Primary = there is an abnormality present within the gland
Secondary = Gland is normal but there is too little or too much stimulation
What are the three main hormone types and their derivatives?
Peptides - derived from amino acids
Steroids - derived from cholesterols
Amines - derives from tyrosine and tryptophan
What are 5 characteristics of peptide hormones?
Any of:
- short half-life
- lipophobic (hydrophilic)
- stored in secretory vesicles
- synthesised as pre-hormone in the ER
- can’t diffuse into target cells (receptor needed)
- usually rapid effects
- common second messengers include cAMP and phosphoinositol
- signal amplification occurs due to second messengers
What are 3 characteristics of amine hormones?
- small in size (1-2 AAs)
- Tyrosine (catecholamines and THs) or tryptophan (melatonin) derivatives
- Can act either like peptides (catecholamines) or steroids (THs)
What are 5 characteristics of steroid hormones?
- derived from cholesterol
- lipophilic
- often bound to carrier proteins to extend their half life
- (most) receptors either in cytoplasm or nucleus
- effects target cells by activation of target genes, altering protein synthesis
- lipids synthesised in smooth ER of gonads, adrenals, placenta and skin
Define anabolism.
The synthesis of larger macromolecules.
Define catabolism.
The hydrolysis/oxidation of macromolecules.
What is glycogenesis and what is the consequence of this process?
- conversion of glucose to glycogen
- decreases blood glucose