Unit IV: Regulation Endocrine System Chapter 16 pp ; 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 2 nd 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

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

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

Neuron Nerve impulse Neurotransmitter Target cells (b) Endocrine system (a) Nervous system Endocrine cells Hormone in bloodstream 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 3.Adaptation to long-term stimuli –nervous - response declines –endocrine - response persists 4.Area of effect –nervous - targeted and specific –endocrine - general, widespread effects

Portal vessels Hypophyseal Portal System Supraoptic nuclei Paraventricular nuclei Neurosecretory neurons HYPOTHALAMUS Infundibulum Posterior lobe of pituitary gland Anterior lobe of pituitary gland Hypophyseal veins MEDIAN EMINENCE 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

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

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

Stimulation Inhibition Stimulates growth of skeletal muscle, cartilage, and many other tissues Epithelia, adipose tissue, liver Anterior lobe GH GH-IH GH-RH Liver Somatomedins 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

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