L46 - Intro To The Endocrine System Flashcards
What are the different parts of the endocrine system?
- hypothalamus
- pituitary
- pineal
- thyroid
- parathyroid
- thymus
- heart
- kidney
- adrenals
- pancreas
- gonads
What are the endocrine functions?
- reproduction
- growth and development
- maintenance of internal environment
- regulation of energy
What are endocrine glands like?
- ductless
- richly vascularised
- secrete messengers into circulation
- primary (pituitary, thyroid, adrenals)
- secondary (brain, heart, kidney, GI tract)
Endocrine glands
What are the different mechanisms of cell to cell signalling?
- intacrine
- autocrine
- paracrine
- endocrine
- neuroendocrine
What are hormones produced by? Released into?
- glands
- directly into circulation
What are hormones like?
- bind to specific, high affinity receptors on/in target cells
- single hormone may have dif tissue-specific effects
- single function may be regulated by dif hormones
What are the 3 major chem classes of hormones?
- amino acids / amines
- peptides/proteins
- steroids
What are the amine hormones?
- catecholamines from tyrosine (adrenaline,nora)
- thyroid hormones from tyrosine (thyroxine, trioodothyronine)
- (indoleamines from tryptophan, melatonin)
What is the adrenal catecholamine synthesis?
- tyrosine to L-DOPA by tyrosine hydroxylase
- then to dopamine by dopa decarboxylase
- then to noradrenaline by dopamine-B-hydroxylase
- then to adrenaline by phenylethanolamine N-methyl transferase
What is the thyroid hormone synthesis?
- tyrosine + mono-iodotyrosine (MIT) = di-iodotyrosine (DIT)
- DIT + DIT = Thryoxine (T4)
- DIT + MIT = Triiodothyronine (T3)
What is the specific steroid hormone synthesis?
- cholesterol to pregnenolone
- pregnenolone - dehydroepiandrosterone - androsenedione
- pregnenolone - 17-hydroxyprogesterone - cortisol
- progesterone - corticosterone - aldosterone
What are the different peptide hormones?
- short a/a chains (ADH, oxytocin 9AA)
- polypeptides (insuline 135AA, prolactin 198AA)
What are the protein hormones?
- thryoid stimulating hormone
- folicle stimulating hormone
- growth hormone
What is the synthesis of peptide and protein hormones?
- cleave off the non functional part of the chain
- leaves the functional
- packaged into hormone
What is the transport of hormones like in the blood?
- water soluble hormones (lipophobic) - a/a, peptide hormones exc. thryoid
- lipid soluble (lipophilic) - steroid and thyroid hormones
What does the abiliity of a cell to respond to a hronone dependent on?
- the presence of receptors for that hormone on/in the target cell
- inc - up-regulation
- dec - down-regulation
What can hormone receptors be?
- cell surface receptors - water soluble hormones
- intracellular receptors - lipid soluble hormones
What do cell surface receptors do?
- activate intracellular cascades
- GPCRs // adrenaline, insulin
What do intracellular receptors do?
- hormones act specific ones
- activate gene transcription
- //corticosteroids
What are the 2 patterns of hormone release?
- short, simple ones
- long, complex ones
What is the short and simple hormone release?
- stimulus to endocrine cells
- cause hormone release
- act on target cells
- bring about response
What is the long and complex hormone release?
- stimulus sensed by hypothalamic neurone
- regulatory hormone release
- acts on pituitary gland
- causes hormone release 1
- acts on endocrine cells
- causes hormone release 2
- acts on target cells
- brins about response
What is endocrine communication like?
- from glands to effector via circulation
- relatively slow transfer
- long lasting
- all cells contacted, specifity conferred by receptors
- slow maintenance of cellular homeostasis
