Introduction to Endocrinology Flashcards
What are the characteristics of a control system?
1) Stimulus
2) Receptor
3) Communication - afferent (eg hormones, AP)
4) Control centre (determines set point, analyses afferent input and determines response)
5) Communication - efferent
6) Effector (eg muscles, glands)
What is the suprachiasmatic nucleus?
A tiny region of the brain in the hypothalamus responsible for controlling circadian rhythms.
What is a zeitgeber?
a rhythmically occurring natural phenomenon which acts as a cue in the regulation of the body’s circadian rhythms.
Which hormone is involved in setting the biological clock?
Melatonin (from pineal gland)
What are some examples of positive feedback?
Blood clotting, ovulation
What are some of the major endocrine glands?
Hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid gland, thymus, adrenal gland, pancreas, testis/ovary
What are some examples of hormones released by the heart?
ANP and BNP
What is an example of hormones released by the stomach?
Gastrin, ghrelin
What is an example of an important hormone released by the liver?
IGF1
What is an example of an important hormone released by adipose tissue?
Leptin
What is some examples of hormones released by the kidney?
Erythropoietin, renin, calcitriol
What features do the endocrine and nervous systems have in common?
1) Both secrete
2) Both can be depolarised
3) Some molecules act as both a neurotransmitter and a hormone
4) Their mechanisms of action requires interaction with specific receptors
5) Both systems work in parallel to control homeostasis
What are the classes of hormones?
Peptide/polypeptide
Amino acid derivatives (amines)
Glycoproteins
Steroids
What class is the largest group of hormones?
Peptide/polypeptide
True or False:
Peptide hormones are all lipid soluble
False
All water soluble
What are some examples of peptide/polypeptide hormones?
Insulin, glucagon, growth hormone
What are some examples of amino acid derived hormones?
Adrenaline/noradrenaline (tyrosine) Thyroid hormones (tyrosine) Melatonin (tryptophan)
Describe the solubility of adrenal medulla hormones
Water soluble
Describe the solubility of thyroid hormones
Lipid soluble
What are some examples of glycoprotein hormones?
LH, FSH, TSH
Describe the solubility of the glycoprotein hormones
All water soluble
What are steroid hormones all derived from?
Cholesterol
What are some examples of steroid hormones?
Cortisol, aldosterone, testosterone
What is the solubility of steroid hormones?
All lipid soluble
True or False:
Only the free form of a hormone is biologically active
True
What is a bound hormone?
Free hormone + binding protein
What are the roles of carrier proteins?
Increase solubility of hormone in plasma
Increase half life
Readily accessible reserve
What 3 main factors determine hormone levels in the blood?
1) Synthesis and secretion
2) Rate of delivery
3) Rate of degradation
What are some examples of cell surface receptors?
GPCRs, tyrosine kinase receptors
What is an exception to the rule that tyrosine kinase dimerise when an agonist binds?
Insulin receptor - already dimerised
What happens when an agonist binds to a tyrosine kinase receptor?
Dimerisation, autophosphorylation of specific tyrosines, recruitment of adapter proteins and signalling complex, activation of protein kinase, phosphorylation of target proteins, cell response
What happens when a lipid soluble hormone binds to a cytoplasmic receptor?
Receptor-hormone complex enters nucleus and binds to DNA
What is a hormone response element?
A hormone response element (HRE) is a short sequence of DNA within the promoter of a gene that is able to bind a specific hormone receptor complex and therefore regulate transcription.
What is the satiety centre?
Appetite control centre located in the hypothalamus
What are nuclei in the hypothalamus?
Several clusters of neurones
Which nucleus in the hypothalamus plays a central role in controlling appetite?
Arcuate nucleus
What neurones promote hunger?
Stimulatory neurones - contain NPY and AgRP
What neurones promote satiety?
Inhibitory neurones - contain POMC which yields several neurotransmitters including a-MSH and B-endorphin
What is ghrelin?
Peptide hormone released from stomach wall when empty - stimulates excitatory primary neurones in arcuate nucleus and therefore stimulates appetite
What is PYY?
Peptide hormone released by cells in the ileum and colon in response to feeding - inhibits excitatory primary neurones of arcuate nucleus and stimulates inhibitory neurones - suppresses appetite
What is leptin?
Peptide hormone released into blood by adipocytes
What two effects does leptin have in the arcuate nucleus?
1) Stimulates inhibitory neurones (POMC)
2) Inhibits excitatory neurones (AgRP/NPY)
What effect does leptin have on mitochondria?
Induces expression of uncoupling proteins, energy therefore dissipated as heat
What is amylin?
Peptide hormone secreted by beta cells in the pancreas
Supresses appetite, decreases glucagon secretion and slow gastric emptying
What is pramlintide?
Amylin analogue - treatment of type 2 diabetes
