Endocrine System Flashcards
Which tissues are glucose dependent?
CNS, brain
What is hypoglycaemia?
When blood glucose <3.0mM
What are the acute effects of hypoglycaemia?
Trembling, weakness, tiredness, headache, sickness, sweating, tingling around lips, palpitations, changes in mood, slurred speech, staggering walk
What is hyperglycaemia?
When blood glucose is >7.0mM
Which systems can be affected in hyperglycaemia?
CNS, CVS and renal systems
What are the effects of hyperglycaemia?
Polyuria, polydipsia, increased non-enzymatic glycosylation of plasma proteins
What are the effects of insulin?
Increases glucose uptake, promotes glycogenesis, promotes lipogenesis, promotes amino acid uptake
What are the effects of glucagon?
Gluconeogenesis is stimulated, glycogenolysis is stimulated, lipolysis is stimulated
What are the metabolic effects of feeding?
Absorption of glucose, amino acids and lipids - increased levels in blood. Stimulates release of insulin
What are the metabolic effects of fasting?
Insulin secretion depressed, glucagon secretion stimulated
How is secretion of hormones controlled?
Change in a parameter regulated by the hormone, concentration of hormone itself or another hormone.
What is the role of osmoreceptors?
Monitor osmolality and Na+ conc
What does the magnitude of response to a hormone rely on?
Concentration of active hormone, responsiveness of target tissues, receptor number
What types of hormones are there?
Polypeptide, glycoprotein, amino acid derivatives and steroids
Where are hormones inactivated?
In the liver, kidney and in some target tissues.
Define the term hormone
Chemical messenger that travels via the bloodstream
What types of hormones are there?
Polypeptide, glycoprotein, amino acid derivatives and steroid hormones
Describe and give examples of polypeptide hormones
Short or long chain(s) of amino acids e.g. insulin, glucagon, growth hormone etc
Describe and give examples of glycoprotein hormones
Large protein molecules with carbohydrate side chains. e.g. anterior pituitary hormones (LH, FSH, TSH)
Describe and give examples of amino acid derivative hormones
Small molecules synthesised from amino acids e.g. adrenaline, and thyroid hormones
Describe and give examples of steroid hormones
Derived from cholesterol e.g. cortisol, aldosterone, testosterone, oestrogen
What effects can hormones have?
Can change the activity of enzymes or other functional proteins (e.g. membrane transport) , can effect gene expression
Describe the binding of a hydrophilic hormone
Binds to receptors on the surface of the cell which can trigger a second messenger (e.g. cAMP)
Describe the basic outline of a negative feedback mechanism
Effector opposes the stimuli - when the hormone levels rises in the blood then it’s production will be inhibited.
How can one hormone control the release of another?
Controlling hormone is called the trophic hormone - mostly secreted from anterior pituitary gland
What are the main hormones that the anterior pituitary gland secretes?
TSH, ACTH, GH, LH, FSH, prolactin
Where do releasing or inhibiting hormones come from?
Nerve cells in the hypothalamus and travel to the gland via hypophyseal portal vessels
Give examples of hormones that the hypothalamus releases
TRH, CRH, SRH, somatostatin
How are steroid hormones inactivated?
Relatively small change in chemical structure which increases their water solubility thus enabling them to be excreted from the body in the urine or via bile
How are protein hormones inactivated?
Undergo extensive chemical changes and are degraded to amino acids that are reused
How is insulin stored?
In beta-cells storage granules as a crystalline-zinc complex
What are the short term effects of insulin?
Anabolic - clears absorbed nutrients from the blood following a meal
How is glucagon synthesised?
Pre-proglucagon - undergoes post-translational processing to produce glucagon.
What are the short term effects of glucagon?
Catabolic - binds to a G-protein coupled receptor (GPCR) thus activating adenylate cyclase which increases cAMP intracellularly. High levels of cAMP activate PKA - phosphorylates shizz
What are the long term effects of insulin?
Effects cell growth/cell division which relates to its ability to stimulate protein synthesis and DNA replication.
How is insulin synthesised?
Pre-proinsulin has its signal peptide removed in ER - pro-insulin goes to trans surface of Golgi - storage vesicles - proteolysis removes a C-peptide from near the middle (good indicator of insulin)
Describe the structure of insulin
2 polypeptide chains, covalently linked by two disulphide bridges, 3rd disulphide bond is in the A chain
Describe the structure of glucagon
Single chain polypeptide, flexible 3D structure that takes up active conformation on binding to receptor
