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Flashcards in Hormones Deck (16)
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What is metabolism at a cellular vs organism level

- Cellular: Role and mechanism of specific enzymes, flux of metabolites through pathways, feedback regulation of metabolic pathways, transport of metabolites across organelle membranes
- Organism: Role and structure of specific tissues and organs, flux of metabolites from organ to organ, hormonal regulation of metabolism and control of body mass


What are the 2 types of hormones

- Act on cell surface receptor
- Alters activity of pre-existing enzyme or transcription / synthesised proteins
- Bind to receptors and induce conformational change that produces a second messenger
- Results in signal amplification and many targets
- Act on a nuclear receptor
- Acts internally and enters cell / nucleus
- Alters transcription of specific genes and amount of newly synthesised proteins


What are the types of mammalian hormones and how are they categorised

- Based on path from release to target or chemical structure
- Paracrine: Released into extracellular space, diffuse to neighbouring target (eicosanoids)
- Endocrine: Released into blood, carried to target cells via circulatory system (insulin / glucagon)
- Autocrine: Affect the cell where they’re produced (bind to surface receptors)


What is a peptide hormone and an example (E)

- Membrane hormone
- Insulin, glucagon and somatostatin
- Insulin: Synthesised on ribosome of B cells in islets of langerhans as preproinsulin and processed into 5.8 kDa active form, stored in secretory vesicles
- Preproinsulin: Signal sequence, C peptide, A and B chain
- Proinsulin: C peptide, A and B chain
- Mature Insulin: A and B chain


What are the effects of insulin on blood glucose

- Increase glucose uptake (muscle, adipose, liver) via GLUT4
- Increase glycogen synthesis via glucokinase (liver, muscle)
- Decrease glycogen breakdown via glycogen synthase (liver, muscle)
- Increase glycolysis / acetyl-CoA via PFK (liver, muscle)
- Increase FA synthesis via acetyl CoA carboxylase (liver)
- Increase TAG synthesis via lipoprotein lipase (adipose tissue)


What are catecholamine hormones and examples (E)

- Structurally similar to catechol
- Synthesised from tyrosine
- Epinephrine / Norepinephrine: Adrenal glands, synthesised from the AA l-tyrosine, concentrated in storage vesicles and released like peptide hormones
- Pathway: Bind to extracellular receptors to generate secondary messengers, like peptide hormones


What are eicosanoid hormones and examples (E)

- Prostaglandins, thromboxanes and leukotrienes
- Synthesis: not synthesised in advance, produced when needed from arachidonic acid via phospholipase A2
- Function: Paracrine (act nearby), role in inflammation, smooth muscle contraction, platelet function


What are steroid hormones and examples (NR)

- Cortisol, testosterone, estradiol
- Function: Bind to carrier proteins / plasma receptor to travel through the bloodstream (endocrine), enter cell nucleus; bind to nuclear receptor to alter gene expression


What is the vitamin D hormone (NR)

- Calcitrol
- Source: Obtained from food or from photolysis of 7-dehydrocholesterol in sun-exposed skin
- Structure: Calcitrol (1a,25-dihydroxycalcitrol ) - active form
- Function: Affects transcription of genes that regulate [Ca2+] and balance between Ca2+ deposition / removal from bone


What are thyroid hormones (NR)

- Structure: T3 (triiodothyronine) has three iodines at Tyr residues, T4 (thyroxine) has four iodines
- Function: Precursor thyroglobulin which yields T4 and is converted to T3, receptor-hormone complex increases expression of enzymes that yield energy


What is nitric oxide (NR)

- Structure: Free radical made from arginine and O2 by NO synthase
- Acts near its point of release, enters the target cell and activates guanylyl cyclase to increase cGMP
- Leads to activation of cGMP-dep protein kinase
- Leads to relaxation of contractile proteins in smooth muscle of BV lowers BP


What is top down hormonal signalling

- Some signals originate in the brain, and the signal is sent out to the body
- Oxytocin: Promotes contraction of smooth muscle of uterus during labor, milk release from mammary gland, social / external behaviour
- Vasopressin: Promotes water reabsorption in kidneys to maintain salt balance, constriction of BV; increases BP, social / external behaviour


What is the hypothalamic cortisol cascade

- Cascade of hormone release following CNS input to hyp
- Stimuli such as pain, fear, infection, haemorrhage and hypoglycaemia send electric signal to hyp
- Secretes ng of CTRH
- AP releases ug of corticotropin
- Adrenal gland releases mg of cortisol
- Cortisol end-product feeds back & can inhibit these steps


What is bottom up hormone signalling

- Some signals originate from elsewhere in the body and send messages to brain (epinephrine, insulin, leptin), require specific responses to fuel
- Feeding: The portal vein carries nutrients to the liver, hepatocytes turn nutrients into fuel, hepatocyte enzymes turn over quickly
- Enzymes increase or decrease with changes in diet and the needs of other tissues


What are retinoid hormones (NR)

- Intracellular (nuclear receptor)
- Regulate growth, survival and differentiation of cells via nuclear retinoid receptors
- Source: Derived from Vitamin A1 (retinol), which is derived from b-carotene
- Most active in cells experiencing rapid growth (lung, skin, immune system, cornea)


What are pituitary hormones

- Posterior: Neurohypophysis, contains the end of axons from hyp, produces short peptide hormones made in the hypothalamus (vasopressin, oxytocin)
- Anterior: Adenohypophysis, endocrine organ that receives releasing factors from hyp via blood vessels, produces long peptide hormones (tropins), activates second targets: adrenal cortex, thyroid, ovaries/testes