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Lecture 5

Lecture 5 - Jan 24.doc

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PSYC 342
Jens C Pruessner

PSYC 342 Lecture 5 - Jan. 24 Summary: • The endocrine systems consists mostly of glands in the body which secrete specific hormones that have a variety of effects throughout the body • These glands are mostly controlled by hormones from the Pituitary (certain glands are not con- trolled by the Pituitary) • The Pituitary hormones are mostly controlled by hormones from the Hypothalamus Differential Hormonal Action: • Two principal ways in which hormones exert their effects on behaviour: • Organizational Activation • Organizational Hormone Action: • Pre- and early postnatal development • Hormones ‘sculpt’ neural and behavioural systems • Permanent and irreversible Can only occur during critical development periods • • Lead to permanent structural and/or physiological changes • Asymmetric with regards to the sexes Activational Hormone Action: • Later in development Not permanent - only displayed when hormone is present • • No critical development periods • More subtle changes Example for Organizational Effect: Finger-length Ratio • Ratio of Index Finger (2) to Ring Finger (4) Three possibilities 2 < 4, 2 = 4, 2 > 4 • • Determined during weeks 13 to 14 during gestation Differences Between the Nervous System and the Endocrine System: • Nervous system use electricity (chemical) whereas endocrine uses hormones • Speed of nervous system is much faster than endocrine system Hormones can attach to any part of the body through the bloodstream but to activate a specific re- • action, you must propel a specific nerve • Timing and duration of activation (hormone effects last longer) • Nervous system acts on an on/off system based on action potential threshold, but even a small amount of hormones can affect the body Similarities Between the Nervous System and the Endocrine System: • They both have effects on behaviour • They both act through receptors (neurotransmitters and cell receptors) Mechanism of Hormone Action: Mediated • Receptor action on outside membrane of cell • Induce change in cell through second messenger • Changes cell metabolism and gene expression • Is true for all polypeptide hormones, monoamines, prostaglandins Mechanisms of Hormone Action: Direct • Hormone enters the cell (diffuse through cell membrane) • Intracellular receptors, form H-R (Hormone Receptor) complex • Penetrating the cell nucleus • Induce gene expression through messenger RNA • Protein synthesis at the endoplasmatic reticulum • Thyroid and steroid hormones (pass through cell membrane because of size) Receptor Up-and-Down Regulation: • Too much hormone - down regulation of receptor (decrease sensitivity to detect hormone to return back to normal) • Too little hormone - up regulation (increase sensitivity to detect hormone to return to normal) • No hormone - marked decline of receptors Types of Hormones: • Vertebrate hormones fall into four chemical classes: • Amine-derived hormones are derivatives of the amino acids tyrosine and tryptophan Peptide hormones consist of chains of amino acids. Examples of small peptide hormones are • TRH and vasopressin. Peptides composed of hundreds of amino acids are referred to as pro- teins. Examples of protein hormones include insulin and growth hormone • Steroid hormones are derived from cholesterol. The adrenal cortex and the gonads are primary sources. Examples of steroid hormones are testosterone and cortisol • Lipid and phospholipid hormones are derived from lipids such as linoleum acid and phospho- lipids such as arachidonic acid. The main class is the eicosanoids, which includes the widely- studied prostaglandins The Chemical Structure of Hormones: • Steroids • Synthesized from cholesterol • Glucocorticoids (catabolic) • Mineralocorticoids (catabolic) • Sex Steroids (anabolic) • Estrogens • Progestagens • Non-Steroids • Can take three forms • Peptides/Proteins • A
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