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Chapter 2

Chapter 2.docx

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Melissa Holmes

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Major Vertebrate hormones (1) Protein & Peptide (2) Steroid (3) Monoamines (4) Lipid-Based  Only 1 class of hormone produced by single endocrine gland (usually)  Hormones differentiate in: o Mode of release o Movement through blood o Location of target cell’s receptors o Manner by which interaction w. target = biological response o Glands originated o Primary physiological functions Protein & Peptide Protein vs. Peptide  Protein: made up of individual amino acid building blocks o few amino acids in length peptide hormones o Larger chains of amino acids  protein/polypeptide  Vary in sequence of amino acids (structure is never similar, like in steroid hormones) Examples  insulin, glucagon, hypothalamus neurohormones, anterior pituitary tropic hormones, leptin, inhibin, calcitonin, parathyroid hormone, gastrointestinal hormones, ghrelin, adiponectin, posterior pituitary hormones Storage/Release/Removal  Stored: in endocrine cells; released via exocytosis o Soluble in blood (no carrier proteins) o May bind to other plasma proteins (slow metabolism by peptidases – enzymes that break down peptides) in blood  Removed via degradation/excretion  Metabolism: biological half-life o Amount of time needed to remove ½ hormone from blood (radioactive tagging) o Large hormones  longer ½ lives than smaller (GH > thyrotropin-releasing hormone) Biological Functions  Single hormone (peptides)  autocrine, paracrine, endocrine functions o Eg. LEPTIN – Endocrine: produced in adipose, released in blood (hormone), regulates hypothalamus energy balance Paracrine: produced in anterior pituitary, diffuses locally, influences TSH secretion (thyroid stimulating) Autocrine: stimulates expression of self & autoreceptors Hypothalamic Hormones Overview  Hypothalamic median eminence o Releasing hormones & inhibiting hormones  Small peptides (3-44 amino acids)  Properties = neurotransmitters  Aka. special class of neurotransmitters that act in anterior pituitary Examples  Releasing Hormones (6) o Thyrotropin releasing hormone (TRH) o Somatocrinin (growth hormone releasing hormone; GHRH) o Gonandotropin releasing hormone (GnRH) o Melanotropin releasing hormone (MRH) o Corticotrophin releasing hormone (CRH) o Kisspeptin  Inhibiting Hormones (2) o Growth hormone inhibiting hormone (GHIH; aka. somatostatin) o Gonandotropin inhibitory hormone (GnIH)  Others: o Dopamine (DA)  Neurotransmitter, technically monoamine  Inhibits release of prolactin & melanotropin from anterior pituitary  Prolactin inhibitory hormone (PIH) & melanotropin inhibitory hormone (MIH) o Hypocretin (aka. orexin)  Found in cells that project to rest of brain & spinal cord  Sleep, metabolic balance, activation of SNS (sympathetic nervous system) Biological Functions  Sequence of aminos = shape of molecule o Protein hormones from one animal may not activate receptors in another animal o Injecting mammal GNRH into toad = no affects  Small variations don’t prevent biological effect (BUT body builds immunity to it) o Hormones from animals not used for humans Anterior Pituitary Hormones Overview  Protein hormones (15-220 amino acids)  If removed, sliced thin, mounted on slide & stained  pattern of cells observed  Types of cells: acidophils, basophils, chromophobes o Acidophils: stains w. acidic stains o Basophils: stains with basic stains o Chromophobes: doesn’t stain with acidic/basic  Via immunocytochemistery: o Specific types of hormones made w. 3 cell types o Acidophils & basophils  subdivided into more cell types = single hormone Examples Basophils  Luteinizing hormone (LH)  Follicle stimulating hormone (FSH)  Thyroid stimulating hormone (TSH)  Made of: 200-220 amino acids Glycoproteins: LH, FSH, TSH  10-25% of molecular structure: carbohydrate  Each glycoprotein  2 subunits (a & B) o Both subunits needed to produce biological response (no good individually) o a subunits of LH, FSH, TSH = identical o B subunits –  Specific biological function  Species specificity o LH a-subunit & TSH B-subunit combined = TSH active molecule Gonandotropins : LH & FSH  W. GNRH = stimulate steroidogenesis in gonads + dev’t & maturation of gametes  W. TRH from hypothalamus, TSH released from anterior pituitary & stimulates thyroid gland  thyroid hormone Acidophils  Growth hormone (GH)  Prolactin  Simple proteins (190-220 aminos) Growth Hormone  RELEASE: from ANT. Pit due to GHRH from hypothalamus  Shows most species specificity of all hormones  Stimulates somatic (body) growth (not directly) o Stimulates production of somatomedins (growth-regulating substances) by liver, kidneys, other tissues  bones can take up sulfates = growth  GH + somatomedins = protein synthehsis o GH = protein anabolism & anti-insulin  Fat mobilization, increased cell membrane permeability to increase amino acid uptake, changes in ion influx, increased blood sugar concentrations (hyperglycemia), indirect effects on thymus (immune function organ), inherent prolactin activity Human Prolactin  198 aminos, 3 disulfide bonds  RELEASE: stim
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