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Endocrine System Notes.docx

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Kinesiology 3222A/B
Dan Belliveau

Anatomy Study Notes: Endocrine 1 THE ENDOCRINE SYSTEM Lecture 7: Endocrine System Endocrine System - Integration and regulation of body systems - Most cells of body are affect by hormones - Mostly of epithelial origin - Hormones can alter metabolism / regulate growth & development / influence reproductive processes - Hormones rely upon receptors to initiate actions Two Kinds of Glands - Exocrine o Secret products into ducts that deliver to body cavities/outer surface o Dont have hormones o Example: gall bladder (secretes bile) - Endocrine o Duct-less o Secrete specific chemicals (hormones) o Released directly into interstitial fluid surrounding cells o Taken up by rich vascular & lymphatic drainage that surrounds organs blood carries them throughout body o Hormones released into whole body but only specific target organs respond Pure Endocrine Organs ONLY MAKE HORMONES: - Pineal gland - Parathyroid gland - Adrenal gland - Thyroid gland - Pituitary gland Mixed Endocrine Organs: - Will secrete some hormones just not primary role - Hormones produced though, are very important - Organs dispersed through body o Cranial cavity o Thyroid gland in neck o Abdominal o Etc Anatomy Study Notes: Endocrine 2 Hormonal Chemistry - Amino acid o Derived from amino acids o Most hormones are peptide based o Molecular size varies greatly From amino acid to proteins o Affect target cell by binding to receptor Hormones bind to receptor surface found in plasma membrane of cell - Steroids o Derived from cholesterol o Only gonadal and adrencortical produce steroid hormones o Lipid soluble because of cholesterol Plasma membrane made up of lipids o Diffuse into target cells through plasma membrane o Bind intracellular receptor to transmit signals (receptor inside cell) Comparing Nervous and Endocrine Systems Characteristic Nervous System Endocrine System Mediator Neurotransmitters Hormones molecules Site of Action Synapse between one axon Hormones released into and dendrite or target cell circulation, travel and bind to receptors in membrane of cell Types of target All muscle cells, smooth Almost all cells cells muscles, organs, other neurons Time until Action Milliseconds (very fast) Epinephrine=seconds, Growth hormones (hours, days) Duration of action Impact of neural impulse= Seconds, hours, days milliseconds Hormonal Action - Alter cell activity - Response depends on target cells 1. Alters plasma membrane (allow cell to be more permeable or to secrete) 2. Stimulates protein synthesis (Growth hormone muscle and bone building) 3. Activates/deactivates enzymes (changing cellular processes) 4. Induces secretary activity (Insulin and glucagon release glucose) 5. Stimulates mitosis (cell division) Target Cells - Hormones displace specificity due to receptors Molecular triggers - Activation depends on three factors Anatomy Study Notes: Endocrine 3 1. Blood level of hormones (Enough hormones circulating blood to activate cell?) 2. Number of receptors on cell 3. Affinity between hormone and receptor (may prevent sufficient binding) Hormonal Regulation - Negative Feedback o Homeostatic o Target cell secretions - Neural impulses o Autonomic nervous system o Releasing factors from neurosecretory cells o Can override homeostatic balance Epinephrine over rides mechanisms of other things - Positive Feedback o Infrequent o Example: at birth uterus contraction stimulate oxytocin oxytocin stimulates more contractions o When no more contraction, naturally shuts off Regulatory Stimuli - Humoral o Changing blood levels of molecules o Circulating levels of hormones humoral level o EXAMPLE: Cells within parathyroid gland measure levels of calcium detect low calcium levels release parathyroid hormones acts on bone, recovers levels of calcium o Humoral levels being measure: calcium - Neural o Nerves stimulate hormone release o Neural impulses - Hormonal o Release in response to hormones from other endocrine organs o Where hormones 1 binds to cell a, cell a produces hormone 2, hormone 2 binds to cell baction tropic effect o EXAMPLE: Hypothalamus produces hormones affect pituitary to produces hormones hormones affects glands/other organs to produce hormones Anatomy Study Notes: Endocrine 4 Summary - Imbalance - Stimulates endocrine gland to secrete hormones o Amino acids (bind to receptor cells) o Steroids (intracellular) - Creates stimulus action (receptor binding) - Action returns system to balance Lecture 8: The Pituitary Gland (Hypothalamus) The Pituitary Gland (Hypothalamus) - Hypophyseal Fossa (Sphenoid) - Connected to Hypothalamus through Infundibulum - Secretes 9 hormones - Major Lobes: Posterior and Anterior Lobes Posterior Lobe (Neural Tissue) - Nerve fibers and axon terminals o Cell bodies located in hypothalamus o Paraventricular & supraoptic nuclei - Not a true endocrine gland o Does not synthesize hormones (just stores & releases them) - Maintains connection via hypothalamic-hypophyseal tract bundles of axons o Begins in hypothalamus, ends in capillaries near posterior pituitary - Within tract o Axons from SON (supraoptic nucleus) ADH
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