ANEQ305 week 7 notes
ANEQ305 week 7 notes ANEQ305
Popular in Functional Large Animal Anatomy/Physiology
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This 5 page Class Notes was uploaded by Andrew Everitt on Sunday October 9, 2016. The Class Notes belongs to ANEQ305 at Colorado State University taught by Dr. Hyungchul Han in Fall 2016. Since its upload, it has received 5 views. For similar materials see Functional Large Animal Anatomy/Physiology in Animal Science at Colorado State University.
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Date Created: 10/09/16
ANEQ305 Week 7 10-3-16 Peptide and Amine Hormones - FSH and LH - TSH - Growth Hormone - Insulin and glucagon - Vasopressin and oxytocin - PTH - Renin - Prolactin - Epinephrine and norepinephrine Prostaglandins - Name comes from fact that prostaglandins were first found in conjunction with prostate gland - There are many (20 or more) prostaglandins - Synthesized from fatty acid arachidonic acid - Short lived in blood thus has major effect locally - Causes inflammation – aspirin inhibits action of PGF - Inhibits gastric secretion Hormone characteristics - Water-soluble hormones (all peptides and catecholamines) are transported dissolved in the plasma, whereas lipid-soluble hormones are almost always transported bound to plasma proteins - Endocrine-disrupting chemicals can mimic the effects of native hormones o Dioxins, PCB (polychlorinated biphenyl), phenolics, pesticides - Hormones produce their effects by altering intracellular proteins through ion fluxes, second messengers, and transcription factors o Hydrophilic and lipophilic hormones - By stimulating genes, lipophilic hormones promote synthesis of new hormones - Hormones are greatly amplified at the target cell - The effective plasma concentration of a hormone is normally regulated by changes in its rate of secretion - The effective plasma concentration of hormone can be influenced by the hormone’s transport, metabolism and excretion o Liver is the major site for metabolic hormonal inactivation o Excreted by urinary excretion o Hydrophilic: faster secretion o Hydrophobic: slower secretion (bound to plasma protein - The responsiveness of a target cell to its hormone can varied by regulating the number of its hormone-specific receptors - Downregulation o High level of hormone is controlled by downregulation of receptors by internalization followed by degradation, causing lower receptor concentration by negative feedback mechanism - Endocrine disorders are attributed to hormonal excess, deficiency, or decreased responsiveness of the target cells o Hypo-secretion, hyper-secretion Hormone to hormone interaction o Permissiveness: one hormone is needed for other hormones to act on target cell (thyroid hormone and epinephrine) o Synergism: action of several hormones’ combined effect is greater than separate effects (FSH and testosterone) o Antagonism: presence of one hormone losses the other hormone’s receptor (progesterone estrogen) Endocrine disorders - Hyposecretion o Primary hyposecretion: abnormal gland secrete too little o Secondary hyposecretion: deficiency of tropic hormone o Genetic: inborn absence of enzyme to catalyze the hormone o Dietary: lack of precursor or component in the diet o Chemical or toxic: destroy the gland o Immunologic: autoimmune antibody self-destroy the gland - Hypersecretion o Tumors o Immunologic factors Pineal Glands - Secretes melatonin - Maintains circadian rhythms - Seasonal changes in melatonin secretion patters trigger reproduction - In mammals melatonin output is controlled by the suprachiasmasmatic nucleus (SCN) of the hypothalalmus Pituitary gland (hypophysis) - Located at the base of the brain, connected to the hypothalamus by a thin stalk, the infundibulum - Posterior pituitary o Nervous tissue - Anterior pituitary o Glandular epithelial tissue - Intermediate lobe o Absent in birds and cetaceans o Rudimentary in humans after birth o Size of intermediate lobe correlates with ability of animal to adapt to corolation of its environment Posterior Pituitary - Connects to the hypothalamus by a neural pathway o Neurosecretory neurons have cell bodies in supraoptic and para ventricular nuclei of hypothalamus - Secretes vasopressin and oxytocin - Evolutionary precursor, arginine vasotocin, is found in many vertebrates - Without vasopressin we would never talk up water from blood - Vasopressin o Enhances retention of water by kidneys (anti-diuretic effect) o Causes contraction of arteriolar smooth muscle o Target organs - Kidney and arteriolar smooth muscle - Oxytocin o Social bonding o Contraction of uterine smooth muscle o Ejection of milk from mammary glands - Arginine vasotocin o Involved in osmoregulation o Vasoconstriction Anterior Pituitary Hormones - Growth Hormone o Stimulates growth and affects metabolism o Targets liver, muscle, and adipose tissue - Thyroid stimulating hormone o Stimulates thyroid hormone secretion by thyroid gland - Adrenocorticotropic hormone o Stimulates cortisol secretion by the adrenal cortex o Targets adrenal cortex - Follicle-stimulating hormone o Regulates gamete production o Targets gonads - Luteininzing hormone o Regulates sex hormone secretion o Ovulation and formation of corpus luteum in females o Targets gonads - Prolactin o Stimulates milk production by mammary glands o Wide range of additional actions o Targets mammary gland Hypothalamic releasing and inhibiting hormones - Hypothalamus releases hormones that release or inhibit the release of one of the 6 hormones in the anterior pituitary - Thyrotropin – releasing hormone – stimulates release of thyroid stimulating hormone - Corticotropin – releasing hormone – stimulates the release of Adrenocorticotropic hormone - Gonadotropin-releasing hormone – stimulates the release of follicle stimulating and luteinizing hormone - Growth hormone-releasing hormone - Growth hormone-releasing hormone - Prolactin-releasing hormone - Prolactin-inhibiting hormone - Releasing and inhibiting hormones reach the anterior pituitary through the hypothalamic-hypophyseal portal system - Regulation of hypophysiotropic hormone secretion o Neural input o Negative-feedback effects of anterior pituitary or target gland hormones Growth depends on: - Adequate diet o Malnourished animals do not reach full growth potential o Seasonally shortened day length reduces growth by reducing food intake - Freedom from chronic disease and stressful environmental conditions o Glucocorticoids secreted during stress inhibit growth - Growth influencing hormones o Placental hormones promote fetal growth o Growth hormone and other hormones promote growth after birth Direct effects of growth hormone - Metabolic effects o Target organs are adipose tissue, skeletal muscles and liver o Mobilizes fat stores as a major energy source o Conserves glucose for use by the brain Decreases glucose uptake by muscles and increases glucose output by the liver o Enhances immune system - Facilitates the synthesis of amino acids - Brain needs oxygen and glucose to survive - GHs growth-promoting actions are mediated by insulin-like growth factors (IGFs) GH/IGF’s growth promoting effects - Growth of soft tissues o Hypertrophy – size of cells o Hyperplasia – number of cells o Promotes uptake of amino acids into cells o Stimulates protein synthesis and inhibits protein degradation - Growth of bone o Promotes increases in bone thickness and length o Thickness depends on addition of new bone by osteoblasts o Length depends on proliferation of cartilage cells (chondrocytes) in epiphyseal plates and invasion by osteoblasts Bone growth - Cell types o Chondrocytes o Osteoclasts o Osteoblasts - Process o New cells undergo cell division o Older cells grow larger o The extracellular matrix calcifies – the chondrocyte inside dies o Dead chondrocytes are cleared by osteoclasts o Osteoblasts swarm up from diaphysis and deposit bone over persisting remains of disintegrating cartilage Regulation of growth hormone secretion - Negative feedback loop involving hypothalamus-pituitary-liver axis o IGF-I inhibits secretion of GH by somatotropes in anterior pituitary o IGF-I inhibits GHRH-secreting cells and stimulates somatostatin- secreting cells in hypothalamus - Other stimuli o Sleep o Exercise, stress and hypoglycemia o High protein meal o Ghrelin Growth Hormone administration (artificial administration) - Increase bone growth o Treatment of dwarfism in humans - Increases muscle mass o Abuse by athletes o Improved meat production in swine - Increases milk production in dairy cattle