Hormones Flashcards
1
Q
What is metabolism at a cellular vs organism level
A
- 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
2
Q
What are the 2 types of hormones
A
Extracellular:
- 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
Intracellular:
- Act on a nuclear receptor
- Acts internally and enters cell / nucleus
- Alters transcription of specific genes and amount of newly synthesised proteins
3
Q
What are the types of mammalian hormones and how are they categorised
A
- 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)
4
Q
What is a peptide hormone and an example (E)
A
- 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
5
Q
What are the effects of insulin on blood glucose
A
- 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)
6
Q
What are catecholamine hormones and examples (E)
A
- 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
7
Q
What are eicosanoid hormones and examples (E)
A
- 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
8
Q
What are steroid hormones and examples (NR)
A
- 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
9
Q
What is the vitamin D hormone (NR)
A
- 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
10
Q
What are thyroid hormones (NR)
A
- 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
11
Q
What is nitric oxide (NR)
A
- 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
12
Q
What is top down hormonal signalling
A
- Some signals originate in the brain, and the signalis 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
13
Q
What is the hypothalamic cortisol cascade
A
- 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
14
Q
What is bottom up hormone signalling
A
- 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
15
Q
What are retinoid hormones (NR)
A
- 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)
