Intro To The Endocrine System + Endocrine Control Of Appetite Flashcards
What is homeostasis?
It is the maintenance of a dynamic equilibrium of conditions to maintain a stable internal environment in the body
What is a homeostatic mechanism?
Mechanisms which counteract changes in the internal environment
What are the 3 key characteristics of a control system?
Receptor detects stimulus
Control centre determines set point and determines response
Effector enacts response
Give 4 types of receptor:
Chemoreceptors (chemicals)
Thermoreceptors (temperature)
Proprioceptors (position)
Nociceptors (pain)
What is an important feature of the biological rhythms of the body?
The set point of the control centre is not fixed, it can vary
What is the biological clock in the brain called?
Suprachiasmatic nucleus (small group of neurones in brain)
How is jet lag caused?
Mismatch between environmental cause and body clock
What hormone is responsible for setting the biological clock (Circadian rhythm) in the body?
Melatonin
What gland produces melatonin?
Pineal gland
What is negative feedback?
Response in a way to reverse the direction of change
What is positive feedback?
Response which changes the variable even more in the direction of change
Stimulus is enhanced
What % of a man’s body mass is water?
60%
What is the amount of water which the average 70kg man has?
42L
How much of the 42L of water in the average 70kg man is Intracellular?
28L
How much of the 42L of water in the average 70kg man is extracellular?
14L
How much of the 14L of extracellular water in the average 70kg man is interstitial fluid?
11L
How much of the 14L of extracellular water is blood plasma in the average 70kg man?
3L
How many litres of blood are there in the average 70kg man?
5L
3L Blood plasma
2L of blood cells
What is an Osmole?
The amount of a substance that dissociates in solution to form one mole of osmotically active particles
What is osmolarity?
The number of osmoses per LITRE of solution
What is Osmolality?
The number of osmoles per Kg of solution
What is the difference between Osmolarity and Osmolality?
Osmolarity concerns LITRES of solution
Osmolality concerns KG of solution
What hormone is essential in water/fluid homeostasis?
ADH (Antidiuretic hormone)
What affect does ADH have on the body?
Increases water reabsorption in the kidney so less water is lost from the body.
Increases number of aquaporins in the Distal Convoluted Tubule and collecting duct of the kidneys nephrons
When is ADH released?
When osmoreceptors in the hypothalamus detect the blood has a HIGH Osmolality
Where is ADH produced?
Where is ADH stored and secreted from?
Hypothalamus
Posterior pituitary
What hormones regulate plasma glucose homeostasis?
Insulin
Glucagon
What should the concentration of plasmas glucose be?
5mmol/L
What is the definition of a hormone?
They are chemical signal produced in endocrine glands or tissues that travel in the bloodstream to cause own effect on other tissues
What other organs and tissues release hormones that aren’t glands?
Heart
Liver
Stomach
Placenta
Adipose
Kidney
What important hormones does the heart produce?
ANP and BNP
Regulate BP
What important hormone does the Liver produce?
IGF1
What important hormones does the stomach produce?
Gastrin and Ghrelin
What important hormones does the placenta produce?
Inhibit, placental lactogen
What important hormone does Adipose produce?
Leptin
What important hormones does the Kidney produce?
Erythropoietin, Renin, calcitriol
What are the 4 methods of hormone communication?
Autocrine
Paracrine
Endocrine
Neurocrine
What is Autocrine hormonal communication?
Hormone signal acts back on the cell of origin
What is Paracrine hormonal communication?
Hormone carried to adjacent cells not in the blood
What is Endocrine hormonal communication?
Hormone is secreted into the blood and transported to a remote site/distant target
What is Neurocrine hormonal communication?
Hormone originates in a neurone, it is released into the bloodstream after travelling down the axon of the neurone a distant target
What is the difference between the endocrine system and the nervous system?
Signal: Hormones V Neurotransmitters + action potentials
Nature: Chemical V Chemical and electrical
Conveyance: Bloodstream V Synapses + Axons
Mediators: Receptors V Receptors
Speed: Slow V Fast
What are the 4 classifications of hormone?
Peptide/Polypeptide
Amino acid derivatives (Amines)
Glycoproteins
Steroids
Which 2 classifications of hormone are all water soluble?
Peptide
Glycoprotein
Which classification of hormone is only lipid soluble?
Steroids
Which classification of hormone can be both water soluble or lipid soluble?
Amino acid derivatives (Amines)
Give 3 examples of peptide hormones
Insulin
Glucagon
Growth hormone
Give 3 examples of glycoprotein hormones
LH
FSH
TSH
Give 3 examples of amino acid derived hormones
Adrenaline
Noradrenaline
Thyroid hormones
Give 3 examples of steroid hormones
Cortisol
Aldosterone
Testosterone
What precursor are steroid hormones all synthesised from?
Cholesterol
If a hormone is not water soluble (is lipid soluble) how is it transported in the blood?
Bound to carrier proteins
Which of the 2 is biologically active? The free form of the hormone or the bound hormone?
Free hormone is biologically active
What 3 factors determine hormone levels in the blood?
Rate of production
Rate of delivery
Rate of degradation
How do water soluble hormones exert their actions on a cell?
Bind to cell surface receptors:
-G protein coupled receptors
-tyrosin kinase receptors
How do lipid soluble hormones exert their affects on a cell?
Bind to Intracellular receptors (on DNA in nucleus)
Which hormones act faster and why?
Water soluble or lipid soluble?
Water soluble since they bind to receptors on the cell surface membrane
When does somebody gain body weight?
When energy intake exceeds energy expenditure
What is the cluster of neurones in the brain called that control appetite?
Arcuate nucleus
Where is the arcuate nucleus located in the brain?
Hypothalamus
What are the 2 types of neurone found in the arcuate nucleus?
Stimulatory
Inhibitory
What do stimulatory neurones in the arcuate nucleus do and how do they do this?
Promote hunger
Contain NPY (Neuropeptide Y) and AgRP (Agouti-related peptide)
What do inhibitory neurones in the arcuate nucleus do and how do they do this?
Promote satiety
Contain POMC which makes alpha MSH and Beta endorphin
What does ghrelin do and where is it produced?
Simulates appetite
Produced in stomach when stomach is empty
What type of hormone is ghrelin?
Peptide
What does PYY (Peptide tyrosine tyrosine) do and where is it produced?
Suppresses appetite
Made by ileum and colon
What does leptin do and where is it produced?
Suppresses appetite
Released by adipocytes
How does leptin suppress appetite?
Simulates inhibitory neurones
Inhibits excitatory neurones
Induces expression of uncoupling proteins in mitochondria
What does insulin do?
Suppress appetite
What does amylin do and where is it produced?
Suppresses appetite
Beta cells of oancreas