Session 6- Intro to the Endocrine system- Endocrine control of appetite Flashcards
What are the characteristics of a control system
Stimulus
Receptor
Control centre
Effector
What are zeitgebers
Cues from the environment that keep the body on a 24 hour cycle
- light
- temperature
- social interaction
- exercise
- eating/drinking pattern
Negative feedback
• Response in a way to reverse the direction of change • Most common form of feedback in physiological Short loop systems
Positive feedback
• Response in a way so as to change the variable even more in the direction of the change (Rare, few examples). • Used when rapid change is desirable.
Examples of positive feedback
Ovulation
Blood clotting
What is osmolarity
Numbers of osmoles per litre of solution
Volume
What is osmolality
The number of osmoles per Kg of solution
Mass
What happens when there is high blood osmolality
Body needs to conserve water
Detected by osmoreceptors in hypothalamus-
This creates thirst
Posterior pituitary secretes more ADH
Increased reabsorption of H2O from urine into blood in collecting duct in the kidney
What happens when there is low osmolality
Body needs to excrete water
Detected by osmoreceptors in hypothalamus
Posterior pituitary secretes less ADH
Decreased reabsorption of H2O from urine into blood in collecting ducts in the kidney
Peptide hormones
Largest group
Short chains of amino acids
Water soluble
Examples of peptide/polypeptide
Insulin
Glucagon growth hormone
Amino acid derivative hormones - amines
Synthesised from aromatic amino acids
Water soluble- adrenal medulla hormones
Lipid soluble- thyroid hormones
Examples of glycoprotein hormones
Luteinizing hormone
Follicle stimulating hormone
Thyroid stimulating hormone
Example of amine hormones
Adrenaline
Noradrenaline
Thyroid hormones
Melatonin
Glycoproteins
Large protein molecules
Often made up of subunits
Carbohydrate side chain
Water soluble
Steroids
All derived form cholesterol
Steroid genie tissues convert cholesterol t different hormones
Lipid soluble
Example of steroid hormones
Cortisol
Aldosterone
Testosterone
Role of carrier proteins
Increase solubility of hormone in plasma
Increase half-life
Readily accessible reserve
What three factors determine hormone levels in the blood
Rate of production
Rate of delivery
Rate of degradation
How does the tyrosine kinase domain work
• Dimerisation (except insulin receptor which is
already dimerised)
•Autophosphorylation of specific tyrosines
• Recruitment of adapter proteins and signalling
complex
• Activation of protein kinase (e.g. PKB)
• Phosphorylation of target proteins
• Cellular response
What is faster lipid or water soluble
Water
How do type 1 lipid soluble hormones work
Cytoplasmic receptor binds hormone and receptor hormone complex enters nucleus and binds to DN
Receptor binds to specific DNA sequence called a hormone response element (HRE) in promoter region of specific genes
How do type 2 lipid soluble hormones work
Hormone enters nucleus and binds to pre-bound receptor on DNA- thyroid hormone. Binding relieves repression of gene transcription
Receptor binds to specific DNA sequence called a hormone response element (HRE) in promoter region of specific genes
Where is the appetite control centre located
Hypothalamus- arcuate nucleus
Which primary neurone promotes hunger
Stimulators neurones-
-neuropeptide Y (NPY)
-Agouti-related peptide (AgRP)
Which primary neurones promote satiety
Inhibitory neurones
-pro-opiomelanocortin (POMC)
-this yields alpha-MSH and beta-endorphin
What does ghrelin do
Stimulates appetite
Released from stomach wall when empty
Filling of stomach prevents its release
What is pyy
Peptide tyrosine tyrosine
Short peptide hormone released by cells in the ileum and colon In response to feeding
What dos PYY do
Inhibits the excitatory primary neurones of the acrucuate nucleus and simulates inhibitory neurones
Suppress appetite
What does leptin do
Stimulates inhibitory neurones
Inhibits the excitatory neurones in arcuate nucleus
OVERALL SUPPRESS APPETITE
What is leptin
Peptide hormones released into blood by adipocytes
What is Amylin
Peptide hormone also secreted by beta cellls in pancreas
What does amylin do
Known to suppress appetite by decreasing glucagon secretion and slow gastric emptying
