Unit IV: Regulation Endocrine System

1. Unit IV: RegulationEndocrine System Chapter 16 pp. 541-551; 560

2. 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

3. Endocrine Glands

4. Endocrine vs. Exocrine Glands • Exocrine glands • ducts carry secretion to a surface or organ cavity • extracellular effects • Endocrine glands • no ducts, hormones • intracellular effects

5. Endocrine Glands Hormone • Receptors located on cell membrane • Alters activity of enzymes Protein receptor G protein (inactive) G protein activated Ca2+ as 2nd messenger cAMP as 2nd messenger system Ca2+ Hormone Hormone Hormone G protein activated G protein activated G protein activated cAMP cAMP ATP AMP Ca2+ Ca2+ Ca2+ Reduced enzyme activity Calmodulin Opens ion channels Activates enzymes Activates enzymes

6. Endocrine Glands Thyroid hormone Steroid hormone • Receptors located in ICF • Alters activity of specific genes Transport Diffusion Target cell response Target cell response Alteration of activity ↑ATP production Alteration of cellular structure or activity Receptor Translation Translation Receptor CYTOPLASM Transcription Transcription Receptor Gene activation Receptor Gene activation Nuclear pore Binds to DNA Binds to DNA

7. Nervousvs. Endocrine Systems • Communication • nervous - electrical • endocrine - only chemical • Speed and persistence of response • nervous - reacts quickly; stops quickly • endocrine - reacts slowly • Adaptation to long-term stimuli • nervous - response declines • endocrine - response persists • Area of effect • nervous - targeted and specific • endocrine - general, widespread effects Neurotransmitter Nerve impulse Neuron Target cells (a) Nervous system Endocrine cells Target cells Hormone in bloodstream (b) Endocrine system

8. Hypothalamus • Shaped like a flattened funnel, forms floor and walls of third ventricle of brain • Regulates primitive functions from water balance to sex drive • Many functions carried out by pituitary gland • Hypophyseal portal system • Hypothalamo-hypophyseal tract Paraventricular nuclei Supraoptic nuclei Neurosecretory neurons Hypophyseal Portal System HYPOTHALAMUS MEDIAN EMINENCE Portal vessels Infundibulum Posterior lobe of pituitary gland Anterior lobe of pituitary gland Hypophyseal veins

9. 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

10. Hypothalamus Pituitary/Hypophysis Hormones Indirect Control through Release of Regulatory Hormones Direct Release of Hormones Growth hormone- releasing hormone (GH-RH) Sensory stimulation Osmoreceptor stimulation Gonadotropin- releasing hormone (GnRH) Corticotropin- releasing hormone (CRH) Thyrotropin- releasing hormone (TRH) Prolactin- inhibiting hormone (PIH) Adrenal cortex Anterior lobe of pituitary gland Posterior lobe of pituitary gland ADH ACTH Adrenal glands GH Kidneys TSH OXT Liver MSH PRL LH Thyroid gland Males: Smooth muscle in ductus deferens and prostate gland FSH Somatomedins Females: Uterine smooth muscle and mammary glands Corticosteroids Melanocytes (uncertain significance in healthy adults) Ovaries of female Bone, muscle, other tissues Testes of male Mammary glands Thyroid hormones Inhibin Testosterone Estrogen Progesterone Inhibin

11. Growth Hormone (Somatotropin) • Promotes tissue growth • stimulates liver to produce IGF-I and II • protein synthesis • proteins synthesized • enhances amino acid transport into cells • lipid metabolism • stimulates FFA and glycerol release from adipocytes • CHO metabolism • glucose sparing effect • Electrolyte balance • promotes Na+, K+, Cl- retention, Ca 2+ absorption Stimulation GH-IH GH-RH Inhibition Anterior lobe Epithelia, adipose tissue, liver GH Liver Somatomedins Stimulates growth of skeletal muscle, cartilage, and many other tissues

12. 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

13. 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

14. Thymus • Involution after puberty • Regulate development and activation of T-lymphocytes • Thymopoietin, thymosins, and thymulin