Study Guide Exam II Pet 3322 Anatomy and Physiology I February 21 2013 The Endocrine System An Overview 1 Define an endocrine gland and list the major endocrine glands of the body and their locations An endocrine gland secrete their products hormones into the interstitial fluid surrounding the secretory cells rather than into ducts It uses hormones produced by glandular structures to produce their effects Interacts with the nervous system to coordinate and integrate the activity of body cells Also called ductless glands They produce hormones and lack ducts They release their hormones into the surrounding tissue fluid Pituitary Gland hypophysis master endocrine gland hypothalamus controls it Peas shaped structure that lies in the hypophseal fossa of the sella turcica of the sphenoid bone Attaches to the hypothalamus by a stalk the infundibulun Thyroid Gland butterfly shaped located on the anterior neck on the tranchea just infereior to the larynx Right and left laternal lobes connected by an isthmus anterior to the trachea 50 have third lobe called the pyramidal lobe Parathyroid Gland tin yellow brown Nearly hidden from view in the posterior aspect of the thyroid gland Usually one superior and inferior on each lateral thyroid lobe Adrenal Gland Paired Pyramid shaped organs perched atop the kidneys where they are enclosed in a fibrous capsule and a cushion of fat suprarenal glands Retrperitoneal space Pineal Gland Tiny pine cone shaped hanfs from the rood of the third ventricle in theof the brain at the midline part of the epithalamus Endocrine glands are ductless glands that produce and release hormone to the blood through diffusion Endocrine glands may be strictly endocrine such as the pituitary thyroid parathyroid adrenal pineal and thymes or they may be organs that have hormone production as one of many functions such as the pancrease gonads hypothalamus and others Hormones 2 Define a hormone and describe the chemical categories of hormones A hormone is a chemical messenger released into the blood to be transported throughout the body a mediator molecule that is relased in one part of the body but regulates the activity of cells in other parts of the body Lipid Soluble Hormones Steroid hormones dirived from cholesterol Gonadal and adrenocortical Thyroid hormones T3 and T4 Nitric oxide Water Soluble Hormones Amine hormones Catecholamines epinephrine norepinephrine and dopamine histmine serotanin and melatonin Peptide hormones and protein hormones amino acid polymers Eicosanoid hormones leukotrienes and prostaglandins inflammation A Hormones Hormones are long distance chemical signals that are secreted by the cells to the extracellular fluid and regulate the metabolic functions of other cells Most hormones are amino based but gonadal and adrenocortical hormones are steroids derived from cholesterol B Mechanisms of Hormone Action Hormones typiclally produce changes in membrane permeability or potential stimulate synthesis of proteins or regulatory molevules actrivate or deactive enzymes induce secretory actiry or stimulate mitosis Nearly all amino acid based hormones exert their effect thourhg and intracellular second messenger that is activated when a hormone binds to a membrane receptor Steroid hormones are lipid soluble and diffuse into the cell where they can bind to intraceulluar receptors migrate to the nucleus and activate specific target sequences of DNA 3 Explain the relationship of hormones to target cells and the types of changes that result in target cells in response to hormone stimulation A hormone is distributed throughout the body of the blood The target cells are the only cells which respond to it to do their functions Hormones circulate to all tissues but only activates cells regerred to as target cells Target cells must have specific receptors to which the hormone binds Theses receptors may be intracelluar or located on the plasma membrane Target cell activation depends on three factors o Blood level of the hormone o Relative number of receptors on the target cell o The affinity of those receptors for the hormone Up regulation is when target cells form more receptors in response to the hormone Down regulation is when target cells lose receptors in response to the hormone Permissive affect the actions of some hormone on target cells require a stimultaneous or recent exposer to a second hormone Synergistic effect the effect of two hormones acting together is greater or more extensive than the effect of each hormone acting alone Antagonistic effect when one hormone opposes the actions of another hormone Target Cell Specificity Cells must have specific membrane or interacellular receptors to which hormones can bind Target cell respond depends on three factors blood levels of the hormone relative number of target cell receptors and affinityh of the receptor for the hormone Target cells can change their sensitivity to a hormone by changing the number of receptors 4 Describe the second messenger systems used by amino acid based hormones Second messenger systems activated when a hormones binds to a plasma membrane receptor activate G proteins within the cell that alter enzyme activity An example is cyclic AMP 1 Hormone first messenger binds to receptor 2 Binding causes the receptor to change shape allowing it to bind a nerby inactive G protein acts like a light switch 3 Activated G proein moving along the plasma membrane binds to effector enzyme adenylate cyclase Some G proteins stimulate while other inhibit The GTP bound to the G protein is hydrolyzed to GDP and the G protein becomes inactive once again 4 cAMP free to diffuse thru the cell triggers cascade of chemical reactions becingin with the activation of protein kinase A translates the presence of the first messenger the water soluble hormone into a response inside the cell 5 Explain the mechanism of intracellular activation used by steroid hormones and thyroid hormone Lipid soluble hormones bind to receptors inside the target cells they diffuse into the cell where they bind to intracellular receptors migrate to the nucleus and activate specific target sequences of DNA Direct gene activaiton mechanism of steroid hormones soluble hormones steroid or thyroid hormome diffuses through the plasma membrane of the target cell and binds to a receptor chaperionin complex in the nucleus Once hormone is bound the chaperonin dissociates from the receptor and the hormone A lipid recepotr complex binds to a specific sequence
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