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Anatomy Chapter 18-19.docx

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Biological Sciences
Connie Soros

Chapters 18/19 Endocrine System • Basics - "slow" control system - many interactions among endocrine glands - interacts with nervous system (neuroendocrine reflexes) - acts via hormones 1. chemical secreted into the blood that acts on target cells elsewhere in the body a. only target cells have receptors for a particular hormone 2. function at very low concentrations 3. prolonged effects 4. includes neurohormones 5. tropic hormones regulate hormone secretion of other glands - general functions 1. regulate metabolism 2. H2O and electrolyte balance 3. coping with stress 4. growth and development 5. reproduction 6. RBC production 7. digestion/absorption - 3 categories of hormones - most hormone systems operate with negative feedback - diurnal (circadian) rhythms 1. hormone secretion varies throughout time (a day-days-months) a. set point changed by CNS 2. negative feedback maintains level at set point for that time 3. external cues like light/dark or activity/inactivity - endocrine disorders 1. hyposecretion (genetic, dietary, toxins, immune disorder) 2. hypersecretion (tumors) 3. abnormality of target cell (lack of receptors or lack of enzymes for reactions) - responsiveness of receptors 1. action of hormone depends on number of receptors a. hormone influences number of its own receptors (1) down-regulation (more hormone  fewer receptors) b. other hormones influence receptors of a different hormone (number of receptors or affinity) (1) permissiveness - enhances response of another hormone (2) synergism - both hormones enhance each others response (3) antagonism - inhibits response of another hormone • Pineal Gland - melatonin 1. regulates biological clock a. cued by light/dark sensed by eyes 2. may also... a. induce sleep b. inhibit sex hormones c. enhance immunity d. slow aging (antioxidant) • Hypothalamus and Posterior Pituitary (neurohypophysis) - Hypothalamus produces hormones that are stored in posterior pituitary 1. hypothalamus signals release with APs - Vasopressin (ADH) 1. conserves H O 2when osmolarity increased) 2. vasoconstrictor (when ECF/BP decreased) - Oxytocin 1. uterine contractions during childbirth a. estrogen has permissive effects b. triggered by neuroendocrine reflexes (baby's head pushing against cervix) 2. milk ejection a. triggered by baby nursing • Hypothalamus and Anterior Pituitary (adenohypophysis) - Anterior pituitary produces hormones and releases them in response to hormones from hypothalamus 1. hypothalamus secretes tropic hormones (releasing and inhibiting hormones) 2. anterior pituitary tropic hormones act on other endocrine glands a. thyroid stimulating hormone (TSH, thyrotropin) (1) growth and secretion of thyroid gland (2) thyrotropin releasing hormone (TRH) b. adrenocorticotropic hormone (ACTH, adrenocorticotropin) (1) growth and secretion of adrenal cortex (cortisol) (2) corticotropin releasing hormone (CRH) c. gonadotropins (1) secretion of sex hormones by gonads (2) gonadotropin releasing hormone (GnRH) d. growth hormone (GH, somatotropin) (1) regulates growth and metabolism (2) growth hormone releasing hormone (GHRH) and growth hormone inhibiting hormone (GHIH) 3. nontropic anterior pituitary hormone a. prolactin (PRL) (1) breast development and milk production in females (2) prolactin releasing factor (PRF) and prolactin inhibiting hormone (PIH) - Growth Hormone 1. stimulates production of somatomedins (mainly in liver) that then act on target cells (most cells) to promote growth a. growth of cells in size/number (1) stimulates protein synthesis and cellular uptake of amino acids (2) inhibits protein breakdown b. growth of bones in length/thickness 2. conserves glucose (for brain) and use fat stores a. increases blood fatty acids for muscle use b.
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