Chapter 7b Introduction to the Endocrine System 2013 Pearson Education Inc Neurohormones Major Groups Adrenal medulla Catecholamines Hypothalamus Posterior pituitary is neural tissue Anterior pituitary is endocrine tissue 2013 Pearson Education Inc Figure 7 8a ESSENTIALS The Pituitary Gland The pituitary gland sits in a protected pocket of bone connected to the brain by a thin stalk HYPOTHALAMUS ANTERIOR POSTERIOR Infundibulum is the stalk that connects the pituitary to the brain Sphenoid bone Posterior pituitary is an extension of the neural tissue Anterior pituitary is a true endocrine gland of epithelial origin Figure 7 8c ESSENTIALS The Pituitary Gland The posterior pituitary is an extension of the brain that secretes neurohormones made in the hypothalamus HYPOTHALAMUS Neurohormone is made and packaged in cell body of neuron Vesicles are trans ported down the cell Vesicles containing neurohormone are stored in posterior pituitary POSTERIOR PITUITARY Vein Neurohormones are released into blood Oxytocin Vasopressin Ile Gln Tyr Asp Cys Cys Phe Gln Tyr Asp Cys Cys Gly Pro Leu Gly Pro Arg Mammary glands and uterus Kidneys Figure 7 8c ESSENTIALS The Pituitary Gland Slide 1 HYPOTHALAMUS Neurohormone is made and packaged in cell body of neuron 2013 Pearson Education Inc POSTERIOR PITUITARY Figure 7 8c ESSENTIALS The Pituitary Gland Slide 2 HYPOTHALAMUS Neurohormone is made and packaged in cell body of neuron Vesicles are trans ported down the cell POSTERIOR PITUITARY 2013 Pearson Education Inc Figure 7 8c ESSENTIALS The Pituitary Gland Slide 3 HYPOTHALAMUS Neurohormone is made and packaged in cell body of neuron Vesicles are trans ported down the cell Vesicles containing neurohormone are stored in posterior pituitary POSTERIOR PITUITARY 2013 Pearson Education Inc Figure 7 8c ESSENTIALS The Pituitary Gland Slide 4 HYPOTHALAMUS Neurohormone is made and packaged in cell body of neuron Vesicles are trans ported down the cell Vesicles containing neurohormone are stored in posterior pituitary POSTERIOR PITUITARY Vein Neurohormones are released into blood 2013 Pearson Education Inc Figure 7 8b ESSENTIALS The Pituitary Gland The anterior pituitary is a true endocrine gland that secretes six classic hormones Neurohormones from the hypothalamus control release of the anterior pituitary hormones The hypothalamic hormones reach the anterior pituitary through a specialized region of the circulation called a portal system HYPOTHALAMUS Neurons synthesizing trophic neurohormones release them into capillaries of the portal system Portal vessels carry the trophic neurohormones directly to the anterior pituitary where they act on the endocrine cells Endocrine cells release their peptide hormones into the second set of capillaries for distribution to the rest of the body Capillary bed Artery POSTERIOR PITUITARY Capillary bed ANTERIOR PITUITARY Veins Prolactin Gonadotropins LH FSH TO TARGET ORGANS GH TSH ACTH Mammary glands Musculoskeletal system Thyroid gland Adrenal cortex Ovary Testis Gonads Figure 7 9 ESSENTIALS Hormones of the Hypothalamic Anterior Pituitary Pathway Endocrine Control A trophic hormone controls the secretion of another hormone Hypothalamic hypophyseal portal system Three integrating centers Hypothalamic stimulation from CNS Anterior pituitary stimulation from hypothalamic trophic hormones Endocrine gland stimulation from anterior pituitary trophic hormones except prolactin 2013 Pearson Education Inc Figure 7 10 The Growth Hormone Pathway Hypothalamic growth hormone releasing hormone GHRH stimulates growth hormone GH secretion Growth hormone acts directly on many body tissues but also influences liver production of insulin like growth factors IGFs or somatomedins another group of hormones that regulate growth HYPOTHALAMUS Hypothalamus ANTERIOR PITUITARY T T GHRH GH cells in anterior pituitary GH Liver IGFs Bone and soft tissue Growth Figure 7 11a 1 of 2 In complex endocrine pathways the hormones of the pathway serve as negative feedback signals k c a b d e e f e v i t a g e n p o o l t r o h S Stimulus Hypothalamus IC1 Trophic hormone H1 Anterior pituitary IC2 Trophic hormone H2 Endocrine gland IC3 Hormone H3 Target tissue Response L o n g l o o p n e g a t i v e f e e d b a c k Figure 7 11b 2 of 2 Control Pathway for Cortisol Secretion Cortisol is a steroid hormone secreted by the adrenal cortex ACTH corticotropin or adrenocorticotropic hormone CRH corticotropin releasing hormone Hypothalamus CRH Anterior pituitary ACTH Adrenal cortex Cortisol Target tissue L o n g l o o p n e g a t i v e f e e d b a c k To target tissue Response FIGURE QUESTION Draw in the short loop negative feedback for this pathway Combined effect is greater than the sum of individual Hormone Interactions Synergism effects Permissiveness Antagonism Need second hormone to get full effect One substance opposes the action of another Competitive inhibitors vs functional antagonism Glucagons oppose insulin 2013 Pearson Education Inc Figure 7 12 Synergism Glucagon Epinephrine Cortisol 250 200 150 100 L d g m l e s o c u g d o o B l Glucagon Epinephrine Epinephrine Glucagon Cortisol 0 1 3 2 4 Time hours 5 Endocrine Pathologies Hypersecretion excess hormone Caused by tumors or exogenous iatrogenic treatment Negative feedback Hyposecretion deficient hormone Caused by decreased synthesis materials or atrophy without a troph nourishment Absence of negative feedback not much hormone produced to start w 2013 Pearson Education Inc Figure 7 13 Exogenous hormone has the same negative feedback effect as endogenous hormone CRH Hypothalamus ACTH Anterior pituitary Exogenous cortisol Cortisol Adrenal cortex Target tissue Response Pathologies Abnormal Receptors Down regulation Decreased number of receptors Hyperinsulinemia Receptor and signal transduction abnormalities Testicular feminization syndrome when fetus developing gonads not develop properly like penis b c lack of receptors female w o uterus and ovaries Pseudohypothyroidism you have same amount of hormones but cell can t respond properly to hormone it counts as not enough 2013 Pearson Education Inc Figure 7 14 Primary and secondary hypersecretion of cortisol Primary Hypersecretion Due to Problem with Adrenal Cortex Secondary Hypersecretion Due to Pituitary Problem Secondary Hypersecretion Due to Hypothalamic Problem Hypothalamus CRH Hypothalamus CRH HYPERSECRETING TUMOR IN HYPOTHALAMUS CRH Anterior pituitary ACTH PATHOLOGY IN ANTERIOR PITUITARY ACTH Anterior pituitary ACTH