Endocrine System & Appetite Flashcards
Describe the main features of control systems in the body
1) stimuli,
2) receptor
3) afferent pathway (hormonal, nervous),
4) control centre,
5) efferent pathway,
6) effector
How are inputs from a control system interpretted?
Set point of a control system can vary = inputs are interpreted by ‘suprachiasmatic nucleus’ = small group of neurones in brain e.g. circadian rhythm
What does the pineal gland do?
Secretes melatonin = controls circadian rhythm
Define the term hormone
Chemical signals prod in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues
List the communication processes involving hormones
Autocrine = acts back on origin.
Paracrine = adjacent cells via intestinal fluid.
Endocrine = bloodstream.
Neurocrine = originates in neurone, down axons, bloodstream.
What are osmoreceptors?
Located in the hypothalamus - Monitor osmotic pressure of blood plasma
What is osmolarity vs osmolality?
Osmolarity = number of osmole per L.
Osmolality = number of osmole per Kg
Outline plasma glucose homeostasis
Meal = insulin from pancreas = glycogenesis in liver – glucose uptake GLUT4 = plasma glucose declines = glucagon released = glucogenolysis in liver = plasma glucose increase
List the major endocrine gland
Hypothalamus, pituitary gland, thyroid gland, pineal gland, parathyroid gland, thymus, pancreas, adrenal gland, testis/ovary
List the classes of chemical substances which can act as hormones
Peptide = short chain AA, water sol (insulin, glucagon).
Amines = aromatic AA, adrenal are water sol, thyroid are lipid sol (A, NA, thyroid, melatonin).
Glycoproteins = carb side unit, water sol (LH, FSH, TSH).
Steroids = cholesterol derived, lipid sol (cortisol, aldosterone, testosterone)
Describe how hormones are transported and act upon target cells
Some travel blood in solution. MOST bind specific carrier proteins, travel in blood, then bind specific receptors for hormone on cell = GPCR, tyrosine kinase = cellular response
What 3 factors determine hormone levels in the blood?
1) rate of prod,
2) rate of delivery (higher blood flow),
3) rate of degradation (metabolized)
Briefly how does a tyrosine kinase receptor work when a hormone binds?
Hormone binds = dimerization = autophosphorylation = recruitment of adapter proteins + signalling complex = activate of protein kinase = phosphorylation of target proteins = cellular response
Briefly explain the stages of hormones binding intracellular receptors
Lipid sol hormones diffuse across PM.
Type I = bind cytoplasmic receptor, enters nucleus, binds DNA.
Type II = enters nucleus, binds pre-bound receptors on DNA. Receptor bind hormone response element = expression of new protein
Describe in outline the control of appetite.
Satiety centres = appetite control centre = in hypothalamus = contains arcuate nucleus = stim neurones promote (NPY/AgRP)/inhib neurones promote satiety (α-MSH/β-endorphin) = control appetite
