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Endocrine I and II

QuestionAnswer
Secretagogues Inhibitors of positive effectors
Tropic factor Hormone is released and does not have direct effect
Trophic factor Hormone has direct effect
Describe negative feedback from T3 and T4 T3 and T4 are secreted from thyroid and when levels rise they will send feedback for the pituitary to shut TSH release down
Lipophillic It can get through the plasma membrane easily and will interact with receptors in cytoplasm or nucleus (steroid type hormones: not stored)
Hydrophilic hormones Hormone has to interact with a surface receptor. In many cases they are stored in granules as pre or pro form
Basophils FSH, LH, ATCH and TSH
Responsibilities of Pituitary/hypophysis Water homeostasis, Blood pressure, growth, development, reproduciton
Downward growth of diencephalon Responsible for forming the infundibulum and posterior region of pituitary
Upward growth (Rathke's pouch) Form anterior region of pituitary
Which region has direct neuoronal likange? Posterior (Pars nervosa)
Supraopticular nucleus and paraventricular nucleus Cell bodies will synthesize hormones that will undergo fast axonal transport into posterior lobe of pituitary. The tract: hypothalamohypophyseal tract
Posterior lobe hormones Oxytocin and ADH(vasopressin): structurally 9 amino acids differing by 2 amino acids
Oxytocin and ADH actions Oxytocin is important for contraction. ADH is important for water homeostasis
Herring bodies Storage sites along the tract. Neurophysin in storage vesicle which if defective can lead to defective packaging of oxytocin or vasopressin
Pituicytes At the end of nerve terminal, glial cells, supporting cells that have a clamp like structure over the terminus of the axonal end. Herring bodies and pituicytes are regulating the release of granules
Anterior lobe hormones Growth hormone, Prolactin, FSH, LH, ACTH, TSH
Acidophils Growth hormones and Prolactin
Chromophobes Resting cells that stain clear
Pre-cursor for ACTH and MSH Pro-opimelanocortin
Control for release of hormones in Anterior lobe Neurons sitting in the hypothalmus. Short axons that don't go all the way down. There is a capillary plexus that can take up inhibitory or releasing hormones and travel down the portal vessel
Portal vessel damage Decreased release of hormones because it is under the positive regulator of gonadotropin
How is the thyroid gland arranged? In follicles
What hormones does the thyroid produce? T3 and T4
What do follicular cells surround? Colloid which is composed of Thgb (660 AAs) 130 of the AAs tyrosine
What is located at the basal surface of the thyroid? G protein (7 transmembrane receptor).
Describe the mechanism for producing Thgb G protein-TSH binds-activates adenyl kinase-cAMP- kinase-production of Thgb
What happens when we need thyroid hormone It is stored in the colloid then gets endocytosed into follicular cell, chopped up then released into interstitium and then into vasculature
What happens when Thgb is in circulation? Iodide gets taken up through Na/I symporter then delivered to colloid. Iodide is converted to Iodine by thyroid peroxidase
After Thgb is iodinated what happens? It gets endocytosed into an endosome, fused with a lysosome and then the large Thgb is hydrolyzed into free AAs and thyroid hormone
T4 vs T3 80% T4. T3 is more potent and active
How is T4 converted to T3? T4 is taken up to target tissues and there is a deiodinase enzyme which removes one of the iodines and you get T3
Negative feedback of T3 and T4 T3 and T4 send feedback to the pituitary to inhibit TSH secretion and also negative feedback to hypothalmus to inhibit TRH
Name ways to form a Goiter Lack of T3/T4 production so no negative feedback. Inactive thyroid peroxidase so no iodination of Thgb. Without sufficient iodine prese
Congenital hypothyroidism Defect in an iodine transporter
Hashimoto's Thyroiditis Destroys thyroid peroxidase. Body tries to make more T3, T4 to make up
Grave's disease Antibody forms against TSH receptors. It mimics TSH, is not regulated and constantly activates the TSH receptor
Adenoma of the Pituitary Constantly producing TSH
Follicular cell morphology Resting gland= squamous. Active gland=cuboidal and columnar
Leakage of Thgb into systemic circulation Is minimum but in some disease states it is in increased amounts in cancers
Parafollicular cells (c-cells) Clear cells because they don't pick up stain. Euchromatic nucleus. Generates calcitonin. Calcitonin responds to high calcium
Parathyroid glands: Chief cells Chief cells: PTH release. Ca can inhibit PTH. If Ca is low it won't inhibit PTH.
Oxyphils increases as person ages, very eosinophilic
Adrenal gland Salt balance, metabolism of carbohydrates proteins and fats, secondary sex characteristics
Zona Glomerulosa 15% of cortex, aldosterone
Zona Fasiculata 80% of cortex, arranged in columns. Secretes cortisol in response to ACTH
Zona Reticularis 5% of cortex, steroid secreting cells, mitochondria
Medulla Chromaffin cells: produce catecholamins Epi and NE
Chromaffin cells Post-synaptic sympathetic cells because they lack axon. Upon stimulation they secrete the granular content right into the interstitial tissue and into capillaries. Epi/NE are packaged with another carrier called chromatogranins
Synthesis of Epi L-Dopa-NE-(methyl transferase)-Epi. Methyl transferase is regulated in presence of glucocorticoids/cortisol
Pineal Gland In dark: Converts serotonin to melatonin. It is under control of PVN and stimulates the release of NE which leads to synthesis of Melatonin