Introduction to the Endocrine System and Appetite Flashcards
Where is the hormone melatonin produced?
Pineal Gland
Fraction of body fluid as intracellular fluid
2/3
Fraction of body fluid as extracellular fluid
1/3
Where is the osmotic pressure of blood plasma monitored?
In the hypothalamus by osmoreceptors
Osmolarity
The number of osmoles per litre of solution (volume)
Osmolality
The number of osmoles per kilogram of solution (mass)
Osmole
The amount of substance that dissociates in solution to form one mole of osmotically active particles
When is serum osmolality useful?
When investigating hyponatraemia
What is ADH and where is it secreted from?
Antidiuretic Hormone
Posterior Pituitary
The major endocrine glands (10)
Hypothalamus Pituitary Pineal Thyroid Parathyroid Thymus Adrenal Pancreas Ovary Testis
Which other organs and tissues release hormones and what are those hormones?
Heart - ANP & BNP Liver Stomach - Gastrin, Ghrelin Placenta Adipose - Leptin Kidney - Erythropoietin, Renin, Calcitriol
Mechanisms of hormones
Autocrine
Paracrine
Endocrine
Neurocrine
Classifications of hormones (4)
Peptide - Insulin, GH (water soluble)
Amino acid derivatives - adrenaline, noradrenaline, thyrid hormones (adrenal medulla water soluble, thyroid lipid soluble)
Glycoproteins - LH, FSH, TSH (water soluble)
Steroids - all derived from cholesterol, cortisol, aldosterone (lipid soluble)
Roles of carrier proteins
- Increase solubility of hormone in plasma
- Increase half life
- Readily accessible reserve
What do water soluble and lipid soluble hormones bind to?
Water soluble - cell surface receptors
Lipid soluble - intracellular receptors
Tyrosine Kinase Receptor process
- Dimerisation (except insulin receptor which is already dimerised)
- Autophosphorylation of specific tyrosines
- Recruitment of adaptor proteins and signalling complex
- Activation of protein kinase
- Phosphorylation of target proteins
- Cellular response
Types of lipid binding
Type I - Cytoplasmic receptor binds hormone and receptor hormone complex enters nucleus and binds to DNA
Type II - Hormone enters nucleus and binds to prebound receptor on DNA e.g. thyroid hormone. Binding relieves repression of gene transctiption
What does the receptor bind to in lipid soluble hormones?
Specific DNA sequence called a hormone response element (HRE) in promoter region of specific gene
BMI in obese
> 30kg/m^-2
Where is the appetite control centre?
Hypothalamus, contains several clusters of neurones referred to as nuclei
Which nucleus plays a central role in controlling appetite?
Acuate nucleus
Two types of primary neurones in the acuate nucleus
stimulatory - contain peptide Y (NPY) and Agouti-related peptide (AgRP)
Inhibitory - contain pro-opiomelanocortin (POMC) which yields several neurotransmitters including a-MSH and B-endorphin
Ghrelin
Released from stomach wall when empty
Stimulates excitatory primary neurones in arcuate nucleus
PYY
Peptide tyrosine tyrosine
Released by cells in the ileum and colon in response to feeding
Inhibitits excitatory primary neurones of the arcuate nucleus and stimulates inhibitory neurones
Leptin
Released into blood by adipocytes
- Stimulates inhibitory (POMC) neurones
- Inhibits excitatory (AgRP/NPY0 neurones
Induces expression of ucoupling proteins in mitochondria, energy dissipated as heat
Insulin
Stimulates appetite by similar mechanism as leptin, less important than leptin in this respect
Amylin
Secreted by beta cells in pancreas
Supresses appetite
Decreases glucagon secretion and slows gastric emptying
Pramlintide is an amylin analogue approved for treatment of Type 2 diabetes
