A&P.endocrine.17.18
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| endocrine system is composed | of glands that secrette CHEMICAL signals into the circulatory system
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| What is the EXOCRINE system? | glands that have ducts - that carry their secretions to surfaces
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| What are the secretory products of the endocrine systme called? | hormones (Gr. hormon "to set into motion"
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| Ligand (4 characteristics) | a chemical signal which: 1. produced in minute amounts by a collection of cells; 2. is secreted into interstitial spaces; 3. enters the circularoy systems, where it is transported some distance; 4. acts on specific tissues called TARGET TISSUES
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| ligand (dictionary) | a molecule that binds to a macromolecule;
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| ligase | a generic term for enzymes caltalyzing the joing of two molecules couped with the breakdown of pyrophosphate bond in ATP or a similar compound
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| hormone (dict) | a chemical substance formed in a tissue or organ & carried in the blood; stimulates or inhibits growth or function of one or more tissues
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| amplitude-modulated signals | increases or decreases in the concentration of hormones in the body fluids
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| what is the contrast between hormone signalling and nervous system action potentials? | action potential are all-or-none; carried along axons to special cells; they are FREQUENCY MODULATED
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| frequency-modulated signals | In the nervous system, all action potentials have the same "size" when they innervate muscles; it is the FREQUENCY of the signal that makes a stronger stimulus
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| are the endocrine system and nervous system independent from each other? | no, not completely- there is an intimate relationship between them & they cannot be separated either anatomically or functionally
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| neurohormones | some neurons secrete chemcial signal into the circulatory system, which function like hormones
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| do neurons ennervate endocrine glands? | yes, some do
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| neurohormone | : a hormone (as acetylcholine or norepinephrine) produced by or acting on nervous tissue [Medline]
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| autocrine | Main Entry: au·to·crine: of, relating to, promoted by, or being a substance secreted by a cell and acting on surface receptors of the same cell <autocrine stimulation of T cell growth> <autocrine growth of some breast cancers - -- compare PARACRINE
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| autocrine | chemical signals released by cells-have local effect on the same cell type
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| example of autocrine | prostagalndin-like chemicals released from smooth muscle cells & platelets in response to inflammation; cause clotting
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| paracrine | released by cells and affect other cell types locally without being transported in the blood
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| paracrine (dictionary) | relating to a kind of hormone function in which the effect of the hormone are restricted to the local environment
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| paracrine hormone (example-medline) | so·mato·stat·in: a polypeptide neurohormone that is found especially in the hypothalamus, is composed of a chain of 14 amino acid residues, and inhibits the secretion of several other hormones (as growth hormone, insulin, and gastrin)
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| Paracrine hormone (example-book) | somatostatin is released by cells in the pancreas and inhibit secretion of insulin from other cells in the pancreas
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| pheromones | special chemical signals - secreted into the environment (outside the body) modify behavior & physiology
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| pheromones (ex.) | pheromones release in urine of cats & dogs indicate fertility
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| pheromones | women - influence the length of menstrual cycles in other women
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| how are hormone secretions controlled? (3 patterns) | 1. changes in concentration of a substance (in body or area) 2. neural regulation 3. endocrine glands are controlled by other endocrine glands
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| nonhormonal regulation of hormone secretion | "changes in concentration" Ex. increased blood glucose stimulates increased insulin secretion from the pancreas or 2. decreased blood glucose inhibits insulin secretion - see figure 17.4 p. 588
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| neural control of endocrine glands | neurons release neurotransmitters that also affect endocrine glands Ex. epinephrine is released in body during stressful situations, affecting endocrine glands
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| neural control of insulin secretion | blood glucose levels can also be controlled by nervous system;acetylchoine causes depolarization of pancreatic cells
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| control of secretory activity of one endocrine gland by a another endocrine gland | another endocrine gland - secretes a hormone or a neurohormone
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| what is example of control by another endocrine gland? | thyroid-releasing hormone - see process figure 17.6
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| negative feedback (medline) | Main Entry: negative feedbackfeedback that tends to stabilize a process by reducing its rate or output when its effects are too great
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| negative feedback | homeostasis is the maintenance of a variable around an ideal normal value or "set point" -negative feedback is used to control deviations from the setpoint
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| positive feedback | when a deviation from a normal value occurs, the response of the system is to make the deviation even greater--creates a cycle that leads away from homeostasist
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| positive feedback (ex.) | when blood pressure drops, heart is disrupted due to injury, heart responsds by pumping less blood, which decreases blood pressure even further-can result in death
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| hormones dissolved in blood plasma are transported in two forms | 1. free form or 2. bound to plasma proteins
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| hormones in free form | circulate & diffuse into interstitial spaces & bind to target cells - can be more easily eliminated by kidneys & liver
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| hormones bound to plasma proteins | remain in the body for a longer time; act as a reservoir for the hormone; remain at a relatively constant level for longer periods of time
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| how do hormones reach target cells? | they circulate through blood; diffuse through pores called fenestrae in the capillary endothelium
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| what are fenestrae? | capillary endothelis of organs that are regulateed by protein hormones have large pores that allow the proteins to pass through
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| half-life | length of time it takes for half a dose of a substance to be eliminated from the circulatory syste is called its half-life
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| half-life | standard measurement used by endocrinologists -predict rate hormones are eliminated by the body
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| water-soluble hormones | proteins, glycoproteins, epinephrine and norepinephrine a. degraded rapidly b. normally have concentrations that increase and decrease rapidly within the blood 3. generally regulat activities that have rapid onset and short duration
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| lipid soluble hormones | Ex. steroids and T(3) and T(4) secreted by thyroid glands
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| hormones are released from blood in four major ways: | 1. excretion 2. metabolism 3. active transport 4. conjugation (read p.593)
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| ligands | intercellular chemical symbols-bind to protein or glycoproteins and change their functions
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| hormones are a type of ligand | make up a major category of intercellular chemical signal
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| binding site | the portion of each protein or glycoprotein molecule where the chemical signal binds
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| receptor site | shape and checmial characteristics of each recepto site allow only specifi chemical signals to bind
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| specificity | binding sites have only certain types; will not bind to others-however, chemical signals can bind to a number of different receptors
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| receptor sites can be competitive | drugs with similar structures may compete - it may bind to a receptor site and activate or inhibit it
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| example of competitive receptor site | epinephrine receptors
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| down-regulation | example is cellular decrease in the number of receptors to a molecule, such as a hormone or neurotransmitter, which reduces the cell's sensitivity to the molcule - locally acting negative feedback mechanism
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| classes of receptors | 1.chemical signals that bind to membrane-bound recpetors; 2. chemical signals that bind to intracellular receptors
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| chemical signals-membrane-bound receptors | 3 types: 1.directly change permeability of plasma membran by opening or closing ion channels 2. alter activity of G proteins at inner surface of plasma membrane or 3. elater activity of intracellular enzymes
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| 1receptors that directly altermembrane permeability | ligand-gated channels - ex. sreotonin - a neurotransmitter involved in moods
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| membrane-bound receptors for g-proteins | guanine nucleotide-binding proteins -act as "molecular switches" found when adrenaline was studied - (read wiki)
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| receptors that directly alter the activity of intracellular enzymes | intracellular mediator or phosphorylated proteins activate process that produce the response of cells to chemical signals
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| what is another name for pituitary gland? | hypophysis (an undergrowth)
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| how many hormones does the pituitary gland secrete? | more than nine - antidiuretic hormone, oxytocin, growth hormone (GH, also called somatotropin) thyroid-stimulating hormone (TSH) - adrenocrticotropic hormone (
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| ACTH) lipotrpins, beta endorphins, melanocyte-stimulating hormone (MSH) Luteinizing hormone (LH) follicle stimultina hormone (FSH) and prolactin
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| where are the two major sites where the nervous and endocrine systems interact? | they hypothalamus of the brain and the pituitary gland
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| what regulates the secretory actvitiy of the pituitary gland? | the hypothalamus (the posterior pituitary is an extension of the hypothalamus)
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| what influences the activity of the hypothalamus? | hormones, sensory information that enters the nervous system and emotions
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| where is the pituitary gland? | rest in the sella turcica of the sphenoid bone (in the "pit" horse saddle of the sphenoid bone)
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| where is the pituitary gland in relation to the hypothalamus? | below or inferior to the hypothalamus and connected to it by a stalk of tissue called the infundibulum
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| infundibulum | "funnel" the funnerl-shaped, unpaired prminenc of the base of the hypothalamus behind the potic chiasm, enclosing the infundibular recess of the third ventricle and continuous below with the stalk of the hypophsis
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| "he had no funds because the inferior was bum" | the infundibulum
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| the posterior pituitary is also called | neurohypophysis (continuous with the brain)-it is an outgrowth of the brain forms the infundibulum, which enlarges to form the posterior pituitary
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| the anterior pituitary is also called | the adenohypophysis - it is derived from epithelial tissue of the embryonic oral cavity and NOT from neural tissue-this just grows back & gloms onto the posterior pituitary
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