Introduction to endocrine systems Flashcards
At what concentration is a hormone secreted?
low concentration
Where is a hormone secreted from?
cell or group of cells
How does is a hormone transported?
via bloodstream (circulatory system)
Why does a hormone only act on specific cells?
Only acts on target cells because they have the correct, complementary membrane protein receptor (that is functional)
Example of a disease where the receptors to a hormone are damaged?
type 2 diabetes
significance of diastema
no contact points so interproximal caries is approached differently. Masticatory mucosa between teeth is non-keratinised so it will become keratinised.
What determines how long a hormone persists?
clearance, half-life of hormone, absence of carrier, enzymes that breakdown hormone (e.g. in blood, liver)
Examples of steroid hormones
cortisol, aldosterone, testosterone, oestrogen, progesterone
What are steroid hormones based on?
cholesterol ring structure
How can non-steroid hormones be divided?
amino acid derivatives, peptides, glycoproteins
Examples of non-steroid hormones that are amines
adrenaline, noradrenaline, melatonin
List of endocrine glands
hypothalamus, pituitary, thyroid, parathyroid, pancreas (islets), adrenal (supra-renal), GIT endocrine cells, gonads, placenta, pineal gland, thymus
How can hormones be classified?
Steroid or non-steroid
What are gonads?
ovaries and testes
Two types of amino acid derivatives of non-steroid hormones
amines and iodinated amino acids
Why is adrenaline considered both a neurotransmitter and hormone?
released into the bloodstream as well as in synapses
Examples of iodinated amino acids that are non-steroid hormones
triiodothyronine, tetraiodothyronine (thyroxine)
Examples of non-steroid peptide short chain hormones
antidiuretic hormone, oxytocin, melanocyte stimulating hormone, somatostatin, thyrotropin releasing hormone, gonadotropin releasing hormone, atrial natriuretic hormone
Examples of non-steroid peptide long chain hormones
growth hormone, prolactin, PTH, calcitonin, adrenocorticotropic hormone, insulin, glucagon, GIT hormones (secretin, CCK, gastrin)
Which types of hormones need to be modified? (not produced in their final form)
long chain peptide (non-steroid) hormones
Name given to inactive precursor form of many peptide hormones
pro-hormone
How are active hormones produced (from pre-prohormones)
the pre-prohormone is converted to pro-hormone in the endoplasmic reticulum. The prohormone is packaged in Golgi apparatus and converted to active hormone that is secrete from vesicles
Example of a pro-hormone
proinsulin
Why are some peptide hormones produced in an inactive form (e.g. proinsulin)
damage to the pancreas will release proinsulin instead of insulin. Proinsulin is not as effective so hypoglycaemia is avoided
Why can hypoglycaemia be fatal?
Can starve the brain
Which type of diabetic patients are more at risk of hypoglycaemia?
Type 1 diabetes - inject insulin without eating. Need to ensure timing of appointment suits patient’s mealtimes
Examples of glycoproteins (non-steroid) hormones
Follicle stimulating hormone (FSH), luteinizing hormone (LH), thyroid stimulating hormone, chorionic gonadotrophin
What is a glycoprotein?
A protein with carbohydrate groups attached to amino acids
Examples of hormone-like substances that have a paracrine (local) effect
prostagrandins, leucotrienes, thromboxanes
Functions of ‘local tissue’ hormones
blood flow regulation, homeostasis, mucosal protection (stomach), inflammation
How do steroid hormones act?
Pass through the plasma membrane and bind to intracellular receptors
How do non-steroid hormones act?
Via second messengers (non-steroid hormones cannot pass plasma membrane)
Example of common second messengers
cAMP and Ca2+
Overview of hormone action
- Synthesis
- storage
- released in response to stimulus
- transported in blood
- act on target cells (2nd messengers)
- metabolised and/or excreted
Which organs have a role of removing hormones?
Kidneys (excrete), Liver (metabolise)
How are most hormone systems regulated?
Negative feedback
Example of negative feedback involving PTH
When there is a low plasma conc of Ca2+, PTH is secreted by the parathyroid glands. PTH acts on target cells which increases plasma Ca2+ conc
Term used to describe excess secretion
hypersecretion
Term used to describe decreased secretion
hyposecretion
What feature can alter the sensitivity of target cells?
The number of membrane receptors
Term used to describe a cell that has an increased number of receptors
upregulation
Term used to describe a cell that has decreased number of receptors
downregulation
Effect of upregulation
do not need much hormone to cause the same response
effect of downregulation
need more hormone to cause the same response
Effect of having a prolonged high concentration of cortisol
leads to downregulation of cortisol receptors therefore a higher concentration of cortisol is required to cause the same response
Examples of medications that can cause downregulation of cortisol receptors
corticosteroids, corticotherapy
3 potential causes of hyperfunction
excess production/secretion, upregulation of receptors, failure to metabolise hormone (clearance)
3 potential causes of hypofunction
decreased production/secretion, downregulation of receptors, non-functioning receptors (e.g. type 2 diabetes which leads to hypersecretion of insulin so B cells are overloaded)
