Endocrine System

Endocrine SystemOverview: Purpose, Basic StructuresEndocrine SystemWhat is the function of the endocrine system?To coordinate body functions by facilitating communication between cells in response to environmental and cellular signals.Purpose?Control development and growth (childhood and adolescence)Regulates blood pressure, heart rateResponds to danger, stressRegulates metabolismHelps fight infectionControl human reproductionWhats a gland?Group of cells that manufacture secretions2 types of glandular secretionsExocrine deposited into body cavities, surface of skin through ductsEndocrine sent directly into bloodstreamCoordinate body functionsHow do they do this?Intracellular communicationEndocrine glands: respond to signals from the environment, other cellsSignals varyEnvironmental (gases, gravity, nutrients, sunlight, temp)Cellular (hormones) originate inside the bodyImportant to noteAlmost any organ can produce endocrine secretionsEndocrine system composed of 10 endocrine glandsEndocrine glands

Endocrine glands a.k.a. ductless glandsSecretions enter blood directly through capillariesDont direct secretions to any particular part of the body Yet not every cell of the body responds to these secretionsHow does a cell know if it is supposed to respond?Receptors!Special surface molecules (often proteins) that permit cell to detect various types of stimuliCells with receptors sensitive to endocrine secretions are called target cellsTarget cellsGenetically programmed to modify their metabolism when they detect a specific endocrine secretion.SoOnly target cells will respond to the particular secretionReview: Answer these questionsWhat glands comprise the endocrine system? What do they produce?Once endocrine secretions are released, where are they deposited? How does this differ from exocrine secretions?Endocrine secretions are what type of signals?Hormone FunctionGuiding QuestionsWhat is the function of a ligand? How do hormones work?What is an effector?What is the function of carrier proteins?What is the function of a ligand?Ligand: general name for a group of chemicals that attach to receptors.Hormones are a type of ligandFor a ligand to propagate a chemical change, it must have the proper shape to fit into the receptorWhen bound to the receptor it causes many chemical reactions within the cell.How do hormones work?Hormones are released from a gland. They bind to a receptor either on the inside or the outside of the target cell depending on the location of the receptor.Activates one of several chemical reactions in the cell.Receptors that are on the surface of the cell = surface receptorReceptors that are located within the cell = internal receptors

16What is an effector?The target cellthe cell a hormone attaches to initiate a biological changeWhat is the function of carrier proteins?To bring hormones that use internal receptors to the target cellOROnce inside the cell, to bring hormones to the receptor

Endocrine secretionsGuiding QuestionsHow are endocrine glands different from exocrine glands?How do endocrine secretions know where to go once theyre secreted?How are autocrine secretions different from paracrine secretions?Do endocrine secretions usually target cells that are close to the point of origin of the secretion or far from it?What type of feedback loop does the endocrine system use to control the body? Give an example of one.

How are endocrine glands different from exocrine glands?Exocrine: secretions are deposited into body cavities or onto the surface of the skin via ductsEndocrine: secretions are sent directly to the bloodstream

How do endocrine secretions know where to go once theyre secreted?Secretions travel to every part of the body, but only target cells (cells with the correct receptor for the secretion) react.

How are autocrine secretions different from paracrine secretions?Autocrine: interact with the cells that created it. Cells control their own activity. They do not travel in the bloodParacrine: secretions travel short distances to target cells.Most important function: coordinate cells within an organ.Pheromones: leave the body and signal the cells of other organisms.

Do endocrine secretions usually target cells that are close to the point of origin of the secretion or far from it?Bothit depends on the function of the secretion.

What type of feedback loop does the endocrine system use to control the body? Give an example of one.Negative feedback loopA signal that inhibits an endocrine gland by preventing further secretion of a particular hormone.Similar to temperature control in a building

Negative feedback continuedAnimationThyroxine

An Example of negative feedback in the role of the thyroid in maintaining body temperature at 37C.:The hypothalamus of the brain detects a drop in blood temperature. The hypothalamus stimulates the pituitary to secrete TSH (thyroid-stimulating hormone). This hormone stimulates the thyroid to increase its secretion of thyroxine. The higher concentration of thyroxine increases metabolism and heat production increases. The blood is warmed back to normal temperature. Hypothalamus detecting raised blood temperature and reduces its stimulation of the pituitary. High thyroxine levels inhibiting the release of TSH from the pituitary. The increased level of thyroxine leads to the limitation or reduction of its secretion. Bodys metabolism slows down as a result of less thyroxin. The bodys temperature goes down.

26Types of hormonesWhat do hormones do, again?Signals a cell to alter its metabolism but must be programmed to do soHormones can be many thingsAgonists chemicals that act as hormones (phytoestrogens from food that act like certain hormones)Antagonists chemicals that block the actions of hormonesA.k.a. mimics/hormone disruptorsGuiding QuestionsWhat is the function of a hormone?What is an agonist? What is its function?What is an antagonist? What is its function?What are the two types of hormones? What are their functions?

2 types of hormones: Peptide biological molecule made of amino acid chains (named for the peptide bond in proteins)Produced on-demandSignaled by internal/external cuesLipid made from existing lipids in body, taken in through dietBody converts cholesterol to a particular hormoneCan be interconverted, tooPeptide hormones1 many amino acids (polypeptide)Effects usually rapidOften involved in immediate changes in metabolism, but some permanentEx. Growth hormoneBind to surface receptors (cant enter cell through membrane)Broken down by enzymes to prevent accumulation in bloodSome taken in, where they bind to internal receptorsLipid hormonesFluid regulation, sexual reproduction2 types:Hormone-like lipidsSingle chain of fatty acids (ex. prostaglandins, a signaling hormone)SteroidsMore complexSpecific signalingNot water soluble; carried via carrier moleculesCan move across cell membrane easily, interacting w/ DNABroken down by enzymes to prevent accumulationCan cause metabolic problems, cancer if levels too highTwo kinds of lipid hormones:Hormone-like Lipids: single chain of fatty acidProstaglandinsProduced by any cellImmune system control and blood pressure regulationSteroids: made from cholesterol molecules

Cortisol (pic 2) testosterone (pic 3)33The endocrine glandsGuiding Questions Part 1How many distinct endocrine glands are there?Which gland is the master gland?Describe the anatomy, and the location, of the pituitary gland.What are releasers and how do they function?How is the posterior pituitary controlled?Where is the pineal gland located, and what hormones does it produce?Guiding Questions, Part 2Describe the anatomy of the adrenal gland and name its parts.Describe the location and the function of the adrenal gland. Where is the thyroid located? How does it control metabolic rate?Is the pancreas an endocrine gland and/or an exocrine gland? Describe the cellular organization of the pancreas. What cells are responsible for the endocrine role of the pancreas? What endocrine secretions do these cells produce, and what is the purpose of those secretions?Where is the pancreas located?Guiding Questions, Part 3!Where is the thymus gland? What does it secrete? What does the thymus gland control?What are gonads? What do they do?Identify the female gonads, their location, and what they produce.Identify the male gonads, their location, and what they produce.Describe the function of testosterone, estrogen, and progesterone.

The Endocrine Glands Pituitary and PinealMaster endocrine gland Its hormones control most of the other endocrine glands intimately linked to the overall coordination of the bodys organ systems.

The pineal gland is responsible for producing melatonin and serotonin.38The pituitary gland is actually two glands joined together: the anterior and posterior pituitary. The anterior pituitary is controlled by releasers from the hypothalamus; the posterior pituitary is controlled by nerve cells from the hypothalamus.

Melatonin A hormone responsible for regulating the bodys daily rhythmsSerotonin A hormone involved with digestion, appetite, moods, and sleepAnterior PituitaryControlled by releasing hormones, produced by hypothalamusResponds to various signals from parts of the bodyExternal and internalReleasing hormones travel from hypothalamus to anterior pituitary via capillaries

Posterior PituitaryGets information from nerve cells of the hypothalamusCarry information from brain directlyPineal GlandSmall structureAbove and behind hypothalamusProduces melatonin (regulates body rhythms)Related to day length, mood/depression (SAD)and serotoninInvolved in appetite, emotions, mood, sleep

The Endocrine Glands - AdrenalThe adrenal glands are made up of an outer cortex and an inner medulla.

The adrenal cortex produces corticosteroids and androgens. The adrenal medulla produces adrenaline and noradrenaline.

42Corticosteriods: gluococorticosteroids and mineralocorticosteroidsGluococorticosteroids regulate metabolism and inhibit release of adrenocorticotropic hormone from the anterior pituitaryMineralocorticosteroids regulate the balance of electrolytes and water in the body

Androgens: The primary androgen is DHEA, a steroid agent related to male hormones.

Adrenaline: Hormone produced in response to exercise, fear, or stressNoradrenaline: Hormone that has a stimulatory effect on the nervous systemThe Endocrine Glands Thyroid and ParathyroidThe thyroid gland helps control the metabolic rate.

The parathyroid gland increases calcium levels in the blood.

43Thyroid hormone is actually two hormones: thyroxine (T4) and triiodothyronine (T3). Its main role is to increase the cellular metabolic rate. This speeds up the conversion of food into energy and helps elevate the body temperature.

The parathyroid hormone increases calcium in the blood by removing it from bone tissue. It also stimulates production of vitamin D, encourages the kidneys to retain calcium, and helps the digestive system absorb calcium.The Endocrine Glands Pancreas and Thymus

pancreasThe pancreas produces hormones and digestive enzymes.The thymus gland produces secretions that stimulate the immune system.44The pancreas is a dual gland with both endocrine and exocrine functions. Insulin and glucagon are the primary products of the endocrine cell clusters of the pancreas.

The thymus is the most specialized endocrine gland. It secretes thymosin which stimulates the development of white blood cells.The Endocrine Glands - GonadsGonad: An organ of the reproductive systemTestis: The male gonad; produces sperm and testosteroneOvary: The female gonad; produces eggs, estrogen, and progesterone

45Testosterone: Hormone that produces male sexual characteristics and ensures sperm maturation, responsible for muscle developmentEstrogen: Hormone primarily responsible for providing sexual characteristics of the female, essential for bone maintenanceProgesterone: Hormone that works with estrogen to produce the menstrual cycle and induce changes in the body during pregnancyWellness and illness over the life spanGuiding QuestionsEndocrine: Pathology of the Endocrine System1. How would one know if the endocrine system is affected by disease?Endocrine: Aging of the Endocrine System1. What happens to hormones as a person ages?2. What can people do to counteract the effects of an aging endocrine system?

How would one know if the endocrine system is affected by disease?Disorders result from the overproduction or underproduction of one or more hormones.Not always a simple answerA decrease in hormone production might be due to an inability to detect signals, lack of signals, diminished blood flow to the gland, or diseased endocrine cells, or tumors.Diabetes insipidus & diabetes mellitusDescriptionEffectsDiabetes insipidusInadequate production of antidiuretic hormone, caused by a malfunction of the posterior pituitary glandProduces extreme water loss resulting in frequent urination. The person has to drink a lot of water to prevent dehydration and to fight the constant feeling of thirst.Diabetes mellitusType I: Caused by decreased insulin productionType II: Bodys inability to detect insulin signalsCan be caused by viral infections, high carbohydrate diets, and obesityResults in high blood sugar and other disorders due to abnormal glucose levels. Glycosylation extra sugars stick to tissues and the immune system destroys them. Can lead to blindness, blood vessel destruction, and kidney failureGraves DiseaseInflammation of thyroid gland due to elevated thyroid hormone production (hyperthyroidism)Caused by an autoimmune disease.Results:Elevated metabolic rateFeelings of nervousness or tensionFeeling tired throughout the dayHypothyroidismThyroid gland doesnt produce enough thyroxineChildren: genetic defectAdults: thyroid or pituitary gland malfunctionResults Children: mental retardation and short statureAdults: lethargy, weight gain, dry hair and skin, sensitivity to cold

What happens to hormones as a person ages?13 weeks of developmentSex hormones assist in the formation of sex characteristicsPubertySex hormones at highest levelsAdultsTaper off after age 30 in men and age 40 in women

What happens to hormones as a person ages?ChildrenGrowth hormone, insulin, and thyroxine are important in growth.Thymus starts out very small and grows until a person reaches puberty, then it becomes smaller & less active as a person ages.Highly sensitive to small amts of chemicals that act like sex hormonesCauses defects in genitalia (males) and causes females to enter puberty sooner, may be more susceptible to breast cancer.If blood vessels are defective and prevent blood flow to a certain body part then that part may not reach normal size and function

What can people do to counteract the effects of an aging endocrine system?HRT-hormone replacement therapyEstrogen=most commonNatural (phytoestrogens) or prescriptionsMany physicians believe its difficult to regulate hormone levels using oral supplements.

When a person agesDecrease in size of endocrine glands and decrease in hormone productioncan be accelerated in people with cardiovascular problems and diabetesDiminished blood flow through capillariesReduce atmospheric gases, hormones and nutrients needed for hormone productionUptake of nutrientsEach gland ages individually