Endocrine system I - Hormones Flashcards
Examples of neurontransmitters;
noradrenaline
acetylcholine
Examples of neuroendocrine
Oxytocin & ADH
Examples of endocrine
Insulin
TSH
Thyroxine
Cortisol
Intracellular messages systems: simple step by step
Secreting cell > Blood vessel > target cell (neurotransmitter gets transferred)
From secreting cell >target cell. What is this type of regulation called?
Paracrine
e.g. glucagon, somatostatins
Autocrine =
chemical released by same cell is taken in by its own use - own function
e.g. prostaglandins
What are hormones + example;
chemical substances that act like messenger molecules in the body
e.g.
GIT
Thymud
Adipocyte
Placenta
Kidney
Heart
Properties and functions of hormones;
1) “yo arouse” or “excite”
2) glands secretes hormones directly into blood stream (ductless)
3) Carried to target cells/tissure (away from endocrine gland - INTERNAL to body)
Endocrine gland
Sylvia gland
Internal to the body
Function - secrete hormone
List 4 types of hormone=
- Peptide hormones
- steroidal hormones
- Tyrosine containing hormone
- Eicosanoids
DIFFERENT - [structure, storage, transportation, function]
List 4 types of hormone=
- Peptide hormones
- steroidal hormones
- Tyrosine containing hormone
- Eicosanoids
DIFFERENT - [structure, storage, transportation, function]
- Peptide hormones
Size and structure
Location of secretion
Synthesis
Release
Transport
Chemical structure : chains of amino acids
[small chains e.g. TRH: contains 3aas / large chains e.g. LH/FSH 80aas]
Mostly secreted from hypothalamus, pituitary, pancreas and GIT
Synthesis (like any other protein synthesis): transcription/translation-preprohormone-prohormone-hormone-secretory granules/vesicles STORED IN CELLS
RELEASE STIMULI : Exocytosis
Transport : Hydrophilic, freely circulate in the blood vessel
No plasma protein binding
Short half-life; minutes
- Steroidal hormones
Chemical structure
Synthesis
Release
Transport
Chemical structure : cholesterol as the base
cortisol, aldosterone (adrenal cortex) & sex hormones (gonads)
Synthesis : like any steroidal synthesis
Enzymatic conversion of precursor (cholesterol base) molecules into hormone
Not stored in the cells
Release :
Stimulus increase precursor level and enzyme activation
Simple diffusion across membrane
Transport :
Lipophilic
Binds with Plasma protein
Half-life: hours to days
Peptide hormones, why not bind to any plasma protein in order to increase its half life?
Mostly protein, not freely moving to bind
Where does steroidal hormone bind to?
Binding/carrier plasma protein IN the blood vessel
- Tyrosine containing
Chemical structure
Synthesis
Release
Transport
Chemical structure : tyrosine as the base
thyroid hormones and catecholamines (adrenal medulla)
Synthesis : Thyroxine < Tyrosine > Epinephrine
Release : Stimulus required
Simple diffusion across membrane
Transport : Binds with Plasma protein (Weak and reversible bonds)
Half-life: hours to days
- Eicosndoids
Chemical structure
Synthesis
Release
Transport
Chemical structure : Polyunsaturated fatty acid derivatives
Eg; prostaglandins, leukotrienes, prostacyclins and thromboxanes
Synthesised by stereo- and regio-specific peroxidation of arachidonic acidby three enzyme families namely lipoxygenases, cyclooxygenases, and cytochrome P450
Release
Stimulus required
Poorly diffuse through cell membrane
Transport
Eicosanoids require transporter (anionic)
Half-life: in seconds: rapidly inactivated: Limited to autocrine and paracrine effects
- Peptide hormone FUNCTION
for example hormone binds to G-protein receptor [ACTH, glucagon] > signal transduction > physiological response
hormone [insulin, growth hormone] > receptor > tyrosine kinase > signal transduction > physiological response
- Steroidal hormonal FUNCTION (& thyroid hormones)
- Intracellular receptors & transcription factors
Glucocorticoid receptor - Cortisol
Mineralocortioid receptor - Aldorsterone
Androgen receptor - Testosterone
Steroidal hormone step by step = specific proteins & biological effect
Hormone > diffusion> nuclear receptor (in nucleus) > DNA > mRNA > specific proteins & biological effects
Hormone > Cytosolic receptor > into nucleus > DNA > mRNA > specific proteins & biological effects
Hormonal homeostasis:
feedback regulation types?
- OUTCOME (Y) of a PROCESS (X) acts to regulate the RATE of the PROCESS
Process (x) > [+] Outcome (y) < [-] Process (x) =
-ive feedback : OUTCOME -ively controls PROCESS (maintain a set-treshold)
Process (x) > [++] Outcome (y) < [+] Process (x) = +ive feedback : outcome amplifies the PROCESS
Hormonal Homeostasis types;
(a) Simple Feedback Axis
(b) Hypothalamus-Pituitary- Axis
(c) Neuroendocrine reflux’s
(a) Simple Feedback Axis
Endocrine Gland > Hormone > Target cells (glucose-induced insulin secretion
(b) Hypothalamus-Pituitary- Axis
Higher centres tress > Hypothalamus > releasing hormone (CRH) > Anterior Pituitary > trophic hormone (ACTH) > target cells (bret tissue) / Peripheral Endocrine Gland > Hormone (cortisol) > Target cells (response)
Endocrine / Hormonal Disorders
- Can be too much secretion
- Could need a specific hormone in the circulation
- Tumour
Hormone released from peripheral gland we refer to them as a _________ _________
primary defect
What’s responsible for stress?
Cortisol
If releasing less > e.g. tumour in adrenal gland > cortisol level goes low in blood > more ACTH
Problem is with peripheral endocrine gland
How can cortisol be tested?
In urine
High amount of ACTH > effect on cortisol
Increased amount
Primary defect
CRH
ACTH
Secondary defect
ACTH
CORTISOL
Exception = e.g. lung cancer [ectopic] = need _____
ACTH > acts on peripheral gland to release more cortisol
Ectopic producing tumour =
Small cell lung tumour,
pancreatic, ovarian
1) Hyper-secretion
2) Hypo-secretion
3) dysfunction/impaired receptors
1) Hormone excess (hyper-secretion)
- Tumour or immunological factor (Graves disease)
2) Lack of hormone (hypo-secretion)
- Genetic, immunological attack, destruction by disease, surgical removal (Type 1 diabetes mellitus)
3) Decreased target-cell responsiveness
- At level of receptor or downstream enzyme (Type 2 diabetes mellitus)
Tumour in peripheral gland
Primary
pituitary or ectopic
Secondary
