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Lecture 4

Lecture 4 - Jan 19.doc

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McGill University
PSYC 342
Jens C Pruessner

PSYC342 Lecture 4 - Jan. 19 Hormones & Endocrine Systems: Overview • Three different communication systems • The nervous system (uses neurotransmitters) • The endocrine system (uses hormones) • The immune system (uses cytokines, fights infections and disease) Interacting: Nervous system controls hormonal release and cytokine release; hormones can af- • fect neuronal firing • Similarities and Differences • The endocrine system: Overview • HT hormones • PT hormones Functional Organization of the Nervous System: • Hierarchical • Evolutionary newer additions took over control from previous additions and became their new mas- ters • Results in increased environmental control • Intellect, cognition, reasoning - neocortex • Functions of the older structures? Reasons for use of Neurotransmitter in the NS: • Up and down regulation of activation • Possible through use of neurotransmitter • Centralize neurotransmitter • Failsafe mechanism • Development and learning • Neurotransmitter helps establish new connections • You can up regulate to signify importance • Centralized control Understood as subserving centralize control • Excursion: Multiple Sclerosis and the Immune system: • Inflammatory disease (traditional hypothesis) • Disease of the myelin sheath; attacks and destroys them resulting in reduce processing of elec- trical signals through neurons • Stops perception and motor functions • Impaired veinous drainage in the brain (vascular hypothesis) • Higher pressure in NS causes the disease • Time and future research will tell what’s the correct approach The Endocrine System: • Endocrine means ‘the internal secretion of a biologically active substance’ • Gland has something to do with hormone; it produces and secretes a hormone The Definition of a Hormone: • Chemical messenger effective in minute quantities • Synthesized in ductless (no tubing) glands • Secreted into and transported by blood • Acts on receptors located far away from synthesis • Exerts a specific regulatory effect on target cells • Slower than neurons; timing is not an issue for hormones • Does not target a specific area but rather diffuses throughout the body Exceptions to the Rule (Hormones): • Some hormones not synthesized in ductless glands • Hormones sometimes act as neurotransmitters (paracrine function) • Can influence cell that released them (autocrine function) • Can get feedback from body • Hormones can generalized effects, or different effects depending on the specific receptor type Two Chemical Classes of Hormones: • Amino acids and peptides • Peptides can’t get to the brain unless already there • Steroid hormones (four-ringed chemical base) • Already in the brain Overview of the Endocrine System: The Endocrine Control Center • Hypothalamus and Pituitary (most important hormonal control center) • Within the diencephalon, just inferior to the thalamus • Control a number of endocrine glands, and a range of physiological activities • Major point of interaction of nervous system and endocrine system • Part of limbic system; thus takes part in relay center Corticotropin Releasing Hormone (CRH): • Synthesized in the anterior portion of the PVN (Paraventricular Nucleus) of the hypothalamus • Stimulates the secretion of Adrenocorticotropic Hormone (ACTH) from the Pituitary • CRH releases ACTH Gonadotropin Releasing Hormone (GnRH): • Synthesized within the preoptic area of the Hypothalamus • Controls the release of luteinising hormone (LH) and follicle-stimulating hormone (FSH) • One or two GnRH? Growth Hormone Releasing Hormone (GHRH): • Secreted within the ventromedial nucleus and the arcuate nucleus of the Hypothalamus • Stimulates Growth Hormone secretions from the Pituitary Thyrotropin Releasing Hormone (TRH): • Synthesized in the PVN and anterior PVN of the Hypothalamus • Stimulates cells in the anterior pituitary gland to produce and release thyroid-stimulating hormone (TSH) Dopamine: • Neurons located in the arcuate nucleus of the Hypothalamus • When released act as primary prolactin-inhibitory hormone in the Pituitary • Strange thing is that it is a neurotransmitter - one of six classes of neurotransmitters that deals with motor functions and reward functions Somatostatin: • Also referred to as GH-IH • Secreted by the PVN of the HT • Inhibits GH and TSH • Has also inhibitory effects on insulin, glucagon, and secretin production Oxytocin and Vasopressin: • Synthesized in the supraoptic nuclei and in the lateral and superior PVN • Transported to the posterior pituitary (by tube) and released there • Location is different • When you want CNS, you release from hypothalamus • Rest of body, release from pituitary gland • Transported to pituitary so they go to blood stream (PNS) • Vasopressin also referred to as antidiuretic hormone • Regulates water balance, blood pressure, memory (?) • Oxytocin: uterine contractions, parental behaviours, attachment bonds, trust The Pituitary: • Also called the Hypophysis • Attached to the HT by the hypohyseal stalk (infundibulum) • Anterior pituitary (adenohypohysis) • Production of hormones triggered by production of hormones released in the
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