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Unit IV: Regulation Endocrine System Chapter 16 pp. 541-551; 560 Overview of Cell Communications Mechanisms: – gap junctions • pores in cell membrane allow signaling chemicals to move from cell to cell – neurotransmitters • released from neurons to travel across gap to 2nd cell – paracrine (local) hormones • secreted into tissue fluids to affect nearby cells – hormones • chemical messengers that travel in the bloodstream that exert an influence on target cells Endocrine Glands Endocrine vs. Exocrine Glands • Exocrine glands – ducts carry secretion to a surface or organ cavity – extracellular effects • Endocrine glands – no ducts, hormones – intracellular effects Endocrine Glands • Receptors located on cell membrane • Alters activity of enzymes Hormone Protein receptor G protein (inactive) G protein activated Ca2+ as 2nd messenger cAMP as 2nd messenger system Ca2+ Hormone Hormone G protein activated G protein activated cAMP Opens ion channels Hormone ATP Activates enzymes cAMP G protein activated AMP Reduced enzyme activity Ca2+ Ca2+ Ca2+ Calmodulin Activates enzymes Endocrine Glands • Receptors located in ICF • Alters activity of specific genes Thyroid hormone Steroid hormone Transport Diffusion Target cell response Target cell response Alteration of cellular structure or activity ↑ATP production Receptor Alteration of activity Translation Receptor Translation CYTOPLASM Transcription Transcription Receptor Receptor Nuclear pore Gene activation Binds to DNA Gene activation Binds to DNA Nervous vs. Endocrine Systems 1. Communication – nervous - electrical – endocrine - only chemical 2. Speed and persistence of response – nervous - reacts quickly; stops quickly – endocrine - reacts slowly Neurotransmitter Nerve impulse Neuron 3. Adaptation to long-term stimuli (a) Nervous system – nervous - response declines – endocrine - response persists 4. Area of effect (b) Endocrine system – nervous - targeted and specific – endocrine - general, widespread effects Target cells Endocrine Target cells cells Hormone in bloodstream Hypothalamus • Shaped like a flattened funnel, forms floor and walls of third ventricle of brain Hypophyseal Supraoptic Paraventricular nuclei nuclei Neurosecretory neurons HYPOTHALAMUS Portal System • Regulates primitive functions from water balance to sex drive • Many functions carried out by Portal vessels pituitary gland – Hypophyseal portal system – Hypothalamo-hypophyseal tract Infundibulum Posterior lobe of pituitary gland Anterior lobe of pituitary gland Hypophyseal veins Hypothalamic Hormones •Transported to posterior lobe of pituitary –Antidiuretic hormone (ADH) –Oxytocin (OXT) •Stimulate the anterior pituitary to release its hormones –Thyrotropin-releasing hormone release of TSH & PRL –Corticotropin-releasing hormone release of ACTH –Gonadotropin-releasing hormone release of FSH & LH –Growth hormone-releasing hormone release of GH •Inhibit the anterior pituitary from releasing its hormones –Prolactin-inhibiting factor inhibits release of PRL –Somatostatin /GH-IH inhibits release of GH & TSH Pituitary/Hypophysis Hormones Hypothalamus Indirect Control through Release of Regulatory Hormones Corticotropinreleasing hormone (CRH) Growth hormonereleasing hormone (GH-RH) Thyrotropinreleasing hormone (TRH) Adrenal cortex Gonadotropinreleasing hormone (GnRH) Prolactininhibiting hormone (PIH) Anterior lobe of pituitary gland GH TSH Liver Thyroid gland PRL Kidneys OXT FSH MSH LH Somatomedins Corticosteroids Bone, muscle, other tissues Thyroid hormones Mammary glands Osmoreceptor stimulation Posterior lobe of pituitary gland ADH ACTH Adrenal glands Direct Release of Hormones Sensory stimulation Testes of male Inhibin Testosterone Ovaries of female Estrogen Progesterone Males: Smooth muscle in ductus deferens and prostate gland Females: Uterine smooth muscle and mammary glands Melanocytes (uncertain significance in healthy adults) Inhibin Growth Hormone (Somatotropin) Promotes tissue growth – stimulates liver to produce IGF-I and II Stimulation GH-IH • protein synthesis GH-RH Inhibition – proteins synthesized – enhances amino acid transport into cells Anterior • lipid metabolism lobe – stimulates FFA and glycerol Epithelia, release from adipocytes adipose tissue, GH liver • CHO metabolism Liver – glucose sparing effect • Electrolyte balance Somatomedins – promotes Na+, K+, Cl- retention, Stimulates growth of skeletal muscle, Ca 2+ absorption cartilage, and many other tissues Growth Hormone and Aging • Childhood and adolescence – bone, cartilage and muscle growth – Stimulates growth at epiphyseal plates • Adulthood – increase osteoblastic activity and appositional growth – aging of tissues • Levels of GH – higher during deep sleep, after vigorous exercise, after high protein meals – lower after high CHO meals Pineal Gland • • • • Peak secretion ages 1-5; by puberty 75% lower Produces serotonin by day, converts it to melatonin at night May regulate timing of puberty in humans Melatonin in SAD & PMS – by phototherapy Thymus • Involution after puberty • Regulate development and activation of T-lymphocytes – Thymopoietin, thymosins, and thymulin