Lec15 - The Endocrine System.doc

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22 Apr 2012
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The Endocrine System
1 Topics
Types of cell signalling
oFour types of cell signalling (major)
oFour types of hormones (major)
Types of hormones
Hormone receptors
Major endocrine glands
Major hormones
The hypothalamus and pituitary
The thyroid gland
The adrenal gland
The pancreas / insulin and diabetes
The pineal gland
Atrial natriuretic peptide
2 Adrenal Gland
Nervous System:
oNeural networks / rapid signalling
Endocrine System
oEndocrine glands secrete hormones that mediate slower, but longer-
lasting responses
oEndocrine system functions more as a regulatory than a command
system
Secretes hormones that move through blood or extracellular fluid
Response can be very rapid (e.g. adrenalin)
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Or very slow (e.g. changes in protein synthesis or gene
transcription)
Adrenal gland has two parts:
oOuter cortex
Produces steroid hormones
oInner medulla
Releases adrenaline
Part of fight or flight response
The more cortisol you have, the more rapidly you age
3 Circulating Hormones
Classic endocrine hormonal response
oEndocrine gland that contains cells which synthesize and secrete
hormones
oHormones diffuse through extracellular fluid and they circulate in the
blood
oMove through blood to these target cells and activates their receptors
4 Neurocrine Endocrine Signaling
Hormones can also originate / move from nerves
oReferred to as neurohormones
Rather the cell of a gland producing and secreting hormones they have a nerve
doing this function
oFrom the nerve it is transported through extracellular fluid and blood
Hormones acts on target tissues
Hypothalamus has neurons which produces two hormones:
oADH
oOxytocin
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oThe axons from these cells are found on the nerve terminals (posterior
pituitary)
5 Paracrine and Autocrine Signaling
Paracrine endocrine signalling
oAn endocrine releases hormones
oHormones don’t travel through the blood
Instead they moves through one cell type to another cell type in
the extracellular fluid (short distances)
Autocrine endocrine signalling
oCell releases hormones
oHormones feeds back and has an effect on the same cell that released it
This can occur in nerves
o-e.g. acetylcholine (paracrine manner)
Released and travels to target cell via extracellular fluid
o–e.g. dopamine (autocrine manner)
Released and travels to target receptor on the same cell
You can often have an autocrine effect on the cell which either inhibits or
accelerates the release of the paracrine substance
o–i.e. release hormones that:
Inhibits release of paracrine substance
Accelerates release of paracrine substance
6 Cell Signalling Regulations
Four major methods of signalling
oClassical endocrine signalling
Release of hormone (from endocrine cell) transported in blood
binds to receptor protein response
oNeuroendocrine (Neurocrine) signalling
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