45 lectures ppt

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 45Chapter 45

Hormones and theEndocrine System


Overview: The Body’s Long-Distance Regulators

• Las hormonas animales son señales químicas que son secretadas al sistema circulatorio y se encargan de llevar mensajes regulatorios dentro del cuerpo

• Las hormonas llegan a todas las partes del cuerpo, pero solo responden las células blanco

– Tienen receptores específicos


• La metamorfosis de los insectos está regulada por hormonas


Concept 45.1: The endocrine system and the nervous system act individually and together in regulating an animal’s physiology

• Los animales tienen dos sistemas de comunicación y regulación interna: el sistema nervioso y el sistema endocrino


• El sistema nervioso lleva señales eléctricas de alta velocidad a través de células especializadas llamadas neuronas

• El sistema endocrino secreta hormonas que coordinan respuestas más lentas pero más duraderas


Overlap Between Endocrine and Nervous Regulation

• Ambos sistemas trabajan juntos para mantener la homeostasis, el desarrollo, y la reproducción

• Células nerviosas especializadas llamadas células neurosecretoras liberan neurohormonas a la sangre

• Tanto las hormonas endocrinas como las neurohormonas trabajan como reguladores de larga distancia de muchos procesos fisiológicos


Control Pathways and Feedback Loops

• Hay tres tipos de trayectos de control hormonal: endocrino, neurohormonal, y neuroendocrino

• Una característica común es un “feedback loop” que conecta la respuesta al estímulo inicial

• La retroalimentación negativa regula muchos de los trayectos hormonales importantes en la homeostasis

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Targeteffectors

Response

Simple endocrine pathway

Glycogenbreakdown,glucose releaseinto blood

Liver

Bloodvessel

Pancreassecretesglucagon ( )

Endocrinecell

Low bloodglucose

Receptorprotein

Stimulus

Pathway Example

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Targeteffectors

Response

Simple neurohormone pathway

Stimulus

Pathway Example

Suckling

Milk release

Smooth musclein breast

Neurosecretorycell

Bloodvessel

Posterior pituitarysecretes oxytocin( )

Hypothalamus/posterior pituitary

Sensoryneuron

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Targeteffectors

Response

Simple neuroendocrine pathway

Stimulus

Pathway Example

Milk production

Bloodvessel

Hypothalamus

Sensoryneuron

Mammary glands

Endocrinecell

Bloodvessel

Anteriorpituitarysecretesprolactin ( )

Hypothalamussecretes prolactin-releasinghormone ( )

Neurosecretorycell

Hypothalamicneurohormonereleased inresponse to neural andhormonalsignals


Concept 45.2: Hormones and other chemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses

• Hormonas llevan la información via la sangre hacia las células blanco a través del cuerpo

• Tres clases de moléculas trabajan como hormonas en los vertebrados:

– Proteínas y péptidos

– Aminas derivadas de aminoácidos

– Esteroides


• Signaling by any of these hormones involves three key events:

– Reception

– Signal transduction

– Response


Cell-Surface Receptors for Water-Soluble Hormones

• The receptors for most water-soluble hormones are embedded in the plasma membrane, projecting outward from the cell surface

Animation: Water-Soluble Hormone

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SECRETORYCELL

Hormonemolecule

Signal receptor

VIABLOOD

VIABLOOD

TARGETCELL TARGET

CELLSignaltransductionpathway

OR

Cytoplasmicresponse

DNA

NUCLEUS

Nuclearresponse

Receptor in plasma membrane Receptor in cell nucleus

DNA

NUCLEUS

mRNA

Synthesis ofspecific proteins

Signaltransductionand response

Signalreceptor

Hormonemolecule

SECRETORYCELL


• Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm or a change in gene expression

• The same hormone may have different effects on target cells that have

– Different receptors for the hormone

– Different signal transduction pathways

– Different proteins for carrying out the response


• The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress

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Different receptors different cell responses

Epinephrine

receptor

Epinephrine

receptor

Epinephrine

receptor

Vesselconstricts

Vesseldilates

Intestinal bloodvessel

Skeletal muscleblood vessel

Liver cell

Different intracellular proteins different cell responses

Glycogendeposits

Glycogenbreaks downand glucoseis releasedfrom cell


Intracellular Receptors for Lipid-Soluble Hormones

• Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus

• Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes

Animation: Lipid-Soluble Hormone


Paracrine Signaling by Local Regulators

• In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells (la respuesta es más rápida)

• Types of local regulators:

– Neurotransmitters (derivados de aa)

– Cytokines (respuesta inmunológica) and growth factors (estimulan proliferación celular y diferenciación)

– Nitric oxide (si O2 baja,

– Prostaglandins


• Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots


• Aspirin (known chemically as acetyl salicylic acid and often abbreviated as ASA) belongs to a class of medications called nonsteroidal anti-inflammatory drugs or NSAIDs. Aspirin and other NSAIDs, for example, ibuprofen (Motrin, Advil) and naproxen (Aleve), are widely used to treat fever, pain, and inflammatory conditions such as arthritis, tendonitis, and bursitis. In addition to its effects on fever, pain, and inflammation, aspirin also has an important inhibitory effect on platelets in the blood. This antiplatelet effect is used to prevent the platelets from initiating the formation of blood clots inside arteries, particularly in individuals who have atherosclerosis or are otherwise prone to develop blood clots in their arteries.


• Aspirin prevents blood from clotting by blocking the production of thromboxane A-2, a chemical that platelets produce that causes them to clump. Aspirin accomplishes this by inhibiting the enzyme cyclo-oxygenase-1 (COX-1) that produces thromboxane A-2. While other NSAIDs also inhibit the COX-1 enzyme, aspirin is the preferred NSAID for use as an antiplatelet agent because its inhibition of the COX-1 enzyme lasts much longer than the other NSAIDs. Thus, aspirin ﾕ s antiplatelet effect lasts for days while the other NSAIDs ﾕ antiplatelet effects last for only hours.

http://www.medicinenet.com/script/main/art.asp?articlekey=32482





• Aspirin will inhibit the enzyme cyclo-oxygenase and will inhibit the prostaglandin-like substance, thromboxane A2 which in turn will increase the adhesion of platelets and cause a vascular blood clot, especially in a coronary artery.


• aspirin inhibits the formation of chemicals called "prostaglandins" by blocking an essential enzyme needed for their formation. Among the many properties of prostaglandins is their ability to promote blood cells to stick together. Thus, by blocking the formation of prostaglandins, aspirin decreases the likelihood of blood clots forming in your blood vessels.Since a large number of heart attacks and strokes are directly caused by small, spontaneously forming blood clots, the ability of aspirin to prevent the formation of these small clots means that heart attacks and strokes become less likely.


• The hypothalamus and the pituitary gland control much of the endocrine system

Concept 45.3: The hypothalamus and pituitary integrate many functions of the vertebrate endocrine system

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Testis(male)

Ovary(female)

Adrenal glands

Pancreas

Parathyroid glands

Thyroid gland

Pituitary gland

Pineal gland

Hypothalamus


Relation Between the Hypothalamus and Pituitary Gland

• The hypothalamus, a region of the lower brain, contains neurosecretory cells

• The posterior pituitary, or neurohypophysis, is an extension of the hypothalamus

• Hormonal secretions from neurosecretory cells are stored in or regulate the pituitary gland

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Mammary glands,uterine muscles

Hypothalamus

Kidney tubules

OxytocinHORMONE

TARGET

ADH

Posteriorpituitary

Neurosecretorycells of thehypothalamus

Axon

Anteriorpituitary


• Other hypothalamic cells produce tropic hormones, hormones that regulate endocrine organs

• Tropic hormones are secreted into the blood and transported to the anterior pituitary, or adenohypophysis

• The tropic hormones of the hypothalamus control release of hormones from the anterior pituitary

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Neurosecretory cells of the hypothalamus

Endocrine cells of theanterior pituitary

Portal vessels

Pituitary hormones(blue dots)

Pain receptorsin the brain

Endorphin Growth hormone

BonesLiver

MSH

Melanocytes

Prolactin

Mammaryglands

ACTH

Adrenalcortex

TSH

ThyroidTestes orovaries

FSH and LH

TARGET

HORMONE

Hypothalamicreleasinghormones(red dots)

Tropic Effects OnlyFSH, follicle-stimulating hormoneLH, luteinizing hormoneTSH, thyroid-stimulating hormoneACTH, adrenocorticotropic hormone

Nontropic Effects OnlyProlactinMSH, melanocyte-stimulating hormoneEndorphin

Nontropic and Tropic EffectsGrowth hormone


Posterior Pituitary Hormones

• The two hormones released from the posterior pituitary act directly on nonendocrine tissues

• Oxytocin induces uterine contractions and milk ejection

• Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys


Anterior Pituitary Hormones

• The anterior pituitary produces both tropic and nontropic hormones


Tropic Hormones

• The four strictly tropic hormones are

– Follicle-stimulating hormone (FSH)

– Luteinizing hormone (LH)

– Thyroid-stimulating hormone (TSH)

– Adrenocorticotropic hormone (ACTH)

• Each tropic hormone acts on its target endocrine tissue to stimulate release of hormone(s) with direct metabolic or developmental effects


Nontropic Hormones

• Nontropic hormones produced by the anterior pituitary:

– Prolactin

– Melanocyte-stimulating hormone (MSH)

– -endorphin


• Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates

• MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals

• Endorphins inhibit pain


Growth Hormone

• Growth hormone (GH) has tropic and nontropic actions

• It promotes growth directly and has diverse metabolic effects

• It stimulates production of growth factors


Concept 45.4: Nonpituitary hormones help regulate metabolism, homeostasis, development, and behavior

• Many nonpituitary hormones regulate various functions in the body


Thyroid Hormones

• The thyroid gland consists of two lobes on the ventral surface of the trachea

• It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4)


• The hypothalamus and anterior pituitary control secretion of thyroid hormones through two negative feedback loops

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Hypothalamus

TRH

Anteriorpituitary

TSH

Thyroid

T3 T4


• Thyroid hormones stimulate metabolism and influence development and maturation

• Hyperthyroidism, excessive secretion of thyroid hormones, can cause Graves’ disease in humans


• The thyroid gland also produces calcitonin, which functions in calcium homeostasis


Parathyroid Hormone and Calcitonin: Control of Blood Calcium

• Two antagonistic hormones, parathyroid hormone (PTH) and calcitonin, play the major role in calcium (Ca2+) homeostasis in mammals

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STIMULUS:Rising blood

Ca2+ level

Thyroid glandreleasescalcitonin.

Calcitonin

StimulatesCa2+ depositionin bones

ReducesCa2+ uptakein kidneys

Blood Ca2+

level declinesto set point

Homoeostasis:Blood Ca2+ level

(about 10 mg/100 mL)

STIMULUS:Falling blood

Ca2+ level

Blood Ca2+

level risesto set point

StimulatesCa2+ releasefrom bones

PTH

Parathyroidgland

Stimulates Ca2+ uptake in kidneys

Activevitamin D

IncreasesCa2+ uptakein intestines


• Calcitonin stimulates Ca2+ deposition in bones and secretion by kidneys, lowering blood Ca2+ levels

• PTH, secreted by the parathyroid glands, has the opposite effects on the bones and kidneys, and therefore raises Ca2+ levels

• PTH also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food


Insulin and Glucagon: Control of Blood Glucose

• The pancreas secretes insulin and glucagon, antagonistic hormones that help maintain glucose homeostasis

• Glucagon is produced by alpha cells

• Insulin is produced by beta cells

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Beta cells ofpancreasrelease insulininto the blood.

Insulin

Liver takesup glucoseand stores itas glycogen.

STIMULUS:Rising blood glucose

level (for instance, aftereating a carbohydrate-

rich meal)

Blood glucose leveldeclines to set point;stimulus for insulinrelease diminishes.

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

STIMULUS:Dropping blood glucoselevel (for instance, after

skipping a meal)

Blood glucose levelrises to set point;

stimulus for glucagonrelease diminishes.

Liver breaksdown glycogenand releasesglucose into theblood.

Body cellstake up moreglucose.

Alpha cells of pancreasrelease glucagon into the blood.

Glucagon


Target Tissues for Insulin and Glucagon

• Insulin reduces blood glucose levels by

– Promoting the cellular uptake of glucose

– Slowing glycogen breakdown in the liver

– Promoting fat storage


• Glucagon increases blood glucose levels by

– Stimulating conversion of glycogen to glucose in the liver

– Stimulating breakdown of fat and protein into glucose


Diabetes Mellitus

• Diabetes mellitus is perhaps the best-known endocrine disorder

• It is caused by a deficiency of insulin or a decreased response to insulin in target tissues

• It is marked by elevated blood glucose levels


• Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells

• Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors


Adrenal Hormones: Response to Stress

• The adrenal glands are adjacent to the kidneys

• Each adrenal gland actually consists of two glands: the adrenal medulla and adrenal cortex


Catecholamines from the Adrenal Medulla

• The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)

• These hormones are members of a class of compounds called catecholamines

• They are secreted in response to stress-activated impulses from the nervous system

• They mediate various fight-or-flight responses


Stress Hormones from the Adrenal Cortex

• Hormones from the adrenal cortex also function in response to stress

• They fall into three classes of steroid hormones:

– Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system

– Mineralocorticoids, such as aldosterone, affect salt and water balance

– Sex hormones are produced in small amounts

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Stress

Hypothalamus

Anterior pituitary

Blood vessel

ACTH

ACTH

Releasinghormone

Nervecell

Nerve cell

Long-term stress response

Effects ofmineralocorticoids:

1. Retention of sodium ions and water by kidneys

2. Increased blood volume and blood pressure

Effects ofglucocorticoids:

1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose

2. Immune system may be suppressed

Short-term stress response

Effects of epinephrine and norepinephrine:

1. Glycogen broken down to glucose; increased blood glucose

2. Increased blood pressure

3. Increased breathing rate4. Increased metabolic rate

5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity

NervesignalsSpinal cord

(cross section)

Adrenalgland

Kidney


Gonadal Sex Hormones

• The gonads, testes and ovaries, produce most of the sex hormones: androgens, estrogens, and progestins


• The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system

• Testosterone causes increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks


• Estrogens, most importantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics

• In mammals, progestins, which include progesterone, are primarily involved in preparing and maintaining the uterus


Melatonin and Biorhythms

• The pineal gland, located in the brain, secretes melatonin


• Light/dark cycles control release of melatonin

• Primary functions of melatonin appear to relate to biological rhythms associated with reproduction


Concept 45.5: Invertebrate regulatory systems also involve endocrine and nervous system interactions

• Diverse hormones regulate homeostasis in invertebrates

• In insects, molting and development are controlled by three main hormones:

– Brain hormone stimulates release of ecdysone from the prothoracic glands

– Ecdysone promotes molting and development of adult characteristics

– Juvenile hormone promotes retention of larval characteristics

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Brainhormone (BH)

Brain

Neurosecretorycells

Corpuscardiacum

Corpusallatum

Prothoracicgland

Ecdysone

EARLYLARVA

LATERLARVA PUPA ADULT

Juvenilehormone(JH)

LowJH

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