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37 Cards in this Set
- Front
- Back
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Hormonal System
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- Involves hormones (chemical impulses)
- Hormones are transported by the blood - Information transfer is slow - Responses may be short or long lived - Always involuntary - Tend to affect more than one target organ |
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Intercellular Communication
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Communication between animal cells via secreted signals classified by thetype of secreting celland the route taken by the signal in reaching its target
Key Players: - Cell that sends signal - Signal (molecule) carried by the blood - Target tissue (receptor) |
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Endocrine Signaling
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Hormones are secreted into extracellular fluid by endocrine cells and reach target cells via the blood stream (or hemolymph)
- Maintains homeostasis - Regulates growth and development - Triggers physical and behavioral changes in sexual maturity and reproduction |
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Paracrine Signaling
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Cells produce and secrete local regulators, molecules that act over short distances and reach their target cells solely by diffusion
- No need for signal to travel through the blood - Paracrine = target cells lie near secreting cells - Autocrine signaling = secreting cells themselves are the target cells |
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Neuroendocrine signaling
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Specializedneurosecretorycells secrete molecules called neurohormones thattravel to target cells via the bloodstream
- Similar to endocrine signaling, except secreting cells are neurons - Neurohormones diffuse from the nerve cell endings into the bloodstream |
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Pheromones
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Members of the same animalspecies sometimes communicate with pheromones,chemicals that are released into the environment
- Pheromonesserve many functions, including marking trails leading to food, definingterritories, warning of predators, and attracting potential mates |
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Endocrine vs. Exocrine
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- Endocrine glands secrete hormones directly intosurrounding fluid --> inside body
- Thesecontrast with exocrineglands, which have ducts and which secrete substances onto bodysurfaces or into cavities --> outside body |
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The Pancreas
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Both endocrine and exocrine components:
- The exocrine pancreas, a gland behind the stomach, to raisethe pH in the duodenum and secretes digestive enzymes - The pancreas hasclusters of endocrinecells called pancreatic islets that produce glucagon and produce insulin in response to high blood sugar |
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Chemical Classes of Hormones
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Threemajor classes of molecules function as hormones in vertebrates:
– Polypeptides (proteins and peptides) --> water soluble (ex. Insulin) – Amines derived from amino acids --> some are lipid, some are water soluble – Steroidhormones --> lipid soluble |
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Water Soluble Hormones Pathway
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Bindingof a hormone to its receptor initiates a signal transduction pathwayleading to responses in the cytoplasm, enzyme activation, or a change in geneexpression
- Receptor is on the outside of the cell (on cell membrane), aiding the hormone through the membrane - Requires a second messenger to activate the signal transduction pathway leading to transcription of a gene |
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Lipid Soluble Hormones Pathway
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-Steroids,thyroid hormones, and the hormonal form of vitamin D enter target cells andbind to protein receptors in the cytoplasm ornucleus
- Protein-receptorcomplexes can act as transcription factors in the nucleus, regulatingtranscription of specific genes |
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Multiple Effects of Hormones
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Thesame hormone may have different effects on target cells that have
– Differentreceptors for the hormone – Differentsignal transduction pathways Example: epinephrine can increase blood flow to major skeletalmuscles, but decrease blood flow to the digestive tract |
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Epinephrin in the Liver
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When epinephrin activates a receptor on a liver cell, it causes glucose to be released from the cell
- Blood glucose level increases |
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Epinephrin in a Muscle Cell (Skeletal Muscle)
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When epinephrin activates a receptor on a muscle cell in wall of a blood vessel that supplies skeletal muscle, it causes the cell to relax
- Blood vessels dilate, increasing flow to skeletal muscle |
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Epinephrin in a Muscle Cell (Intestines)
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When epinephrin activates a receptor on a muscle cell in wall of blood vessel that supplies the intestines, the cell contracts
- Different hormone receptor as in skeletal muscle cell - Blood vessels constrict, decreasing flow to the intestines |
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Major Human Endocrine Glands
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- Pineal gland (sleep)
- Hypothalamus - Pituitary gland - Thyroid gland - Adrenal glands - Pancreas - Ovaries (Female) - Testes (Male) |
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Feedback Regulation
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Hormonesare assembled into regulatory pathways:
- A negativefeedback loopinhibits a response by reducing the initial stimulus, thus preventing excessivepathway activity - Positive feedback reinforces a stimulus to produce an evengreater response |
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Positive Feedback Loop: Oxytocin
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Suckling (stimulus) causes a release of oxytocin
- Oxytocin causes smooth muscle in the mammary glands, which causes milk to be released |
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Hypothalamus and Pituitary Glands
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Central to endocrine regulation
- Thehypothalamusreceives information from the nervous system and initiates responses throughthe endocrine system - Attachedto the hypothalamus is the pituitary gland,composed of the posterior pituitary and anterior pituitary |
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Posterior Pituitary Hormones
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Thetwo hormones released from the posterior pituitary act directly on non endocrine tissues:
– Oxytocinregulates milk secretion by the mammary glands, uterine muscles – Antidiuretichormone (ADH) regulatesphysiology and behavior, kidney tubules (aquaporins) |
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Anterior Pituitary Hormones
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Hormoneproduction in the anterior pituitary iscontrolled by releasing hormones and inhibiting hormones secreted by the hypothalamus
- Hormones reach the anterior pituitary via the blood, and the anterior pituitary receives the single and produces new hormones in response - Hormones released by anterior pituitary have many targets (hormone released by hypothalamus only target anterior pituitary) |
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The Thyroid
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Thyroidhormonerefers to a pair of hormones
- Triiodothyronin (T3), with three iodine atoms - Thyroxine (T4), with four iodine atoms The Thyroid gland also produces otherhormones: Calcitonin(C-Cells)andPTH (Parathyroid gland): Ca++metabolism - Bone health |
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Thyroid Regulation: A Hormone Cascade Pathway
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- Ahormone can stimulate the release of a series of other hormones, the last ofwhich activates a nonendocrinetarget cell; this is called a hormone cascade pathway
- Therelease of thyroid hormone resultsfrom a hormone cascade pathway involving the hypothalamus,anterior pituitary, and thyroid gland |
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Thyroid Regulation (cont.)
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1. Thyroid hormone levels drop
2. Hypothalamus secretes TRH (Thyroid Releasing Hormone) into the blood. Portal vessels carry TRH to anterior pituitary 3. TRH causes anterior pituitary to secrete TSH (Thyroid Stimulating Hormone) 4. TSH is circulated throughout the body and stimulates endocrine cells in thyroid gland to secrete T3 and T4 5. Thyroid hormone levels return to normal range 6. Negative feedback loop: thyroid hormone blocks TRH and TSH release preventing overproduction of thyroid hormone |
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Disorders of Thyroid Function and Regulation
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Hypothyroidism (toolittle thyroid function) can produce symptoms such as
- Weightgain, lethargy, cold intolerance Hyperthyroidism (excessive production of thyroid hormone) can lead to - Hightemperature, sweating, weight loss, irritability, and high blood pressure |
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Malnutrition and Thyroid Function
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Malnutrition canalter thyroid function
- Insufficientdietary iodine leads to an enlarged thyroid gland, called a goiter - T3 (3 Iodine atoms) and T4 (4 Iodine atoms) |
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Evolution of Hormone Function
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Hormones are not just a “mammal thing” andover thecourse of evolution the function of a given hormone may diverge between specie
- Ex: Thyroid hormoneplays a role in metabolism across many lineages, but in frogs has taken on aunique function: stimulating the resorption of the tadpole tail during metamorphosis |
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Adrenal Hormones: Responses to Stress
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Theadrenal glands are on top of the kidneys
- Each adrenalglandactually consists of two glands: the adrenalmedulla (innerportion) and adrenalcortex (outerportion) |
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Catecholaminesfromthe AdrenalMedulla
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The adrenal medulla secretes catecholamines:
- Epinephrine(adrenaline) - Norepinephrine(noradrenaline) They aresecreted in response to stress-activated impulses from the nervous system Theymediate various fight-or-flight responses |
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Epinephrine and Norepinephrine
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Epinephrineand Norepinephrine:
- Triggerthe release of glucose and fatty acids into the blood - Increaseoxygen delivery to body cells - Directblood toward heart, brain, and skeletal muscles and away from skin, digestivesystem, and kidneys - The release of epinephrine and norepinephrine occurs in response toinvoluntary nerve signals |
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Steroid Hormones from the Adrenal Cortex
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Theadrenal cortex releases a family of steroids called corticosteroids inresponse to stress
- Thesehormones are triggered by a hormone cascade pathway via the hypothalamus andanterior pituitary (ACTH) - Humansproduce two types of corticosteroids: glucocorticoidsand mineralocorticoids |
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Glucocorticoids and Mineralocorticoids
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Glucocorticoids, such as cortisol, influenceglucose metabolism and the immune system
- Proteins and fats broken down and converted to glucose --> increased blood glucose - Partial suppression of the immune system Mineralocorticoids, such as aldosterone,affect salt and water balance - Retention of sodium ions and water by kidneys - Increased blood volume and blood pressure |
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Short Term Stress
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- "Fight or Flight" response
- Neuron releases hormone directly to adrenal gland - Adrenaline (epinephrine and norepinephrine) - Quick response |
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Long Term Stress
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- Hypothalamus releases hormone to anterior pituitary
- Anterior pituitary releases ACTH to the bloodstream - ACTH reaches the adrenal cortex and stimulates the production of glucocorticoids and mineralocorticoids |
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Glucose Homeostasis
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- Stimulus: High blood glucose levels
- Insulin produced in pancreas - Circulation of insulin throughout body via blood - Insulin reaches liver and muscle cells - Response: glucose uptake by liver and muscle cells |
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Glycosuria
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Glycosuria or glucosuria is the excretion of glucose into the urine
- Ordinarily, urine contains no glucose because the kidneys are able to reclaim all of the filtered glucose back into the bloodstream - Glycosuria is nearly always caused by elevated blood glucose levels |
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Diabetes Mellitus
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- High glucose levels in the blood
- Body is not able to produce insulin - Insulin receptors are not binding anything, so target cells in liver and muscles are not activated - No uptake of glucose in liver - Pee a lot due to high concentration of glucose in urine, more water must stay in urine to balance osmolarity equilibrium in body - Pee has glucose in it |
