The Endocrine System (the second messenger system of the body)

• The Endocrine System(the second messenger system of the body)

I. Hormones:

A.Endocrine system produces hormones (chemical messages) that are important in maintaining homeostasis & regulating reproduction, metobolic rate, growth & development plus it mobilizes the immune system.

I. Hormones:

B. A Hormone is a chemical messenger produced by a cell that causes specific changes in the cellular activity of other cells (target cells).

Overview of the Endocrine System • The Role of Target Cell Receptors in Hormonal

Action

Figure 10-2

• Classes of Hormone Receptor–Extracellular Receptors

• Located in cell membrane• Targeted by

–Amino acid derivatives–Peptides–Eicosanoids

• Operates through a second messenger such as cyclic-AMP

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Overview of the Endocrine System

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-3(a)1 of 7

Membranereceptor

Hormone-receptorcomplex

First messengers(E, NE, peptide hormones,and eicosanoids)

Cellmembrane

G protein(inactive)

G protein(activated)

Activatesadenylatecyclase

CytoplasmATP cAMP

Acts assecond

messenger

Activates kinase

Alterations inenzyme activity;

opens ion channels

TARGET CELLRESPONSE

Nuclear envelope

Nuclear pore

Nucleus

DNA

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-3(a)2 of 7

Membranereceptor

G protein(inactive)

Cytoplasm

Nuclear envelope

Nuclear pore

Nucleus

DNA

Cellmembrane

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-3(a)3 of 7

Membranereceptor

Hormone-receptorcomplex

First messengers(E, NE, peptide hormones,and eicosanoids)

Cellmembrane

G protein(inactive)

Cytoplasm

Nuclear envelope

Nuclear pore

Nucleus

DNA

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-3(a)4 of 7

Membranereceptor

Hormone-receptorcomplex

First messengers(E, NE, peptide hormones,and eicosanoids)

Cellmembrane

G protein(inactive)

G protein(activated)

Activatesadenylatecyclase

Cytoplasm

Nuclear envelope

Nuclear pore

Nucleus

DNA

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-3(a)5 of 7

Membranereceptor

Hormone-receptorcomplex

First messengers(E, NE, peptide hormones,and eicosanoids)

Cellmembrane

G protein(inactive)

G protein(activated)

Activatesadenylatecyclase

CytoplasmATP cAMP

Acts assecond

messenger

Activates kinaseNuclear envelope

Nuclear pore

Nucleus

DNA

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-3(a)6 of 7

Membranereceptor

Hormone-receptorcomplex

First messengers(E, NE, peptide hormones,and eicosanoids)

Cellmembrane

G protein(inactive)

G protein(activated)

Activatesadenylatecyclase

CytoplasmATP cAMP

Acts assecond

messenger

Activates kinase

Alterations inenzyme activity;

opens ion channels

Nuclear envelope

Nuclear pore

Nucleus

DNA

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 10-3(a)7 of 7

Membranereceptor

Hormone-receptorcomplex

First messengers(E, NE, peptide hormones,and eicosanoids)

Cellmembrane

G protein(inactive)

G protein(activated)

Activatesadenylatecyclase

CytoplasmATP cAMP

Acts assecond

messenger

Activates kinase

Alterations inenzyme activity;

opens ion channels

TARGET CELLRESPONSE

Nuclear envelope

Nuclear pore

Nucleus

DNA

C. Unlike exocrine glands that release their products at the body’s surface or into body cavities through ducts, the endocrine glands do not secrete substances into ducts instead their hormones are secreted directly into the surrounding extracellular space & then diffuse into nearby capillaries & are transported throughout the body in the blood.

• D. The endocrine & nervous systems often work together to maintain homeostasis.

• E. The nervous system uses neurotransmitters to act on cells (which is usually short-lived) to maintain homeostasis

• F. The endocrine system uses hormones (whose effects last longer than neurons) to produce homeostasis.

• G. Hormones are classified into 2 basic categories: peptides (including amino acids, polypeptides, & proteins) & steroids (complex rings of carbon & hydrogen atoms) synthesized by cholesterol. Ex. Gonadal hormones & adrenocortical hormones

Now we are going to look at each gland individually:

• These next few slides will be copied onto your paper but do not have blanks to fill in

• H. Pituitary – found in sella turcia pea-size, gland. It is also called the Master Gland. The Anterior pituitary is hormone production glandular portion. Ex. GH (bone & muscle) & TSH (growth of thyroid)

• The Posterior pituitary is the neural portion & extension of hypothalamus. Ex. Oxytocin (milk release) & ADH ( increase H2O & BP)

Hormones of the Anterior Pituitary

The Pituitary Gland• Pituitary Hormones and Their Targets

Figure 10-8

Hormones of the Posterior Pituitary

• I. Thyroid-Found in anterior throat overlying inferior border of larynx. One of the largest endocrine glands & has a heavy blood supply. Ex. Thyroid hormone T3 & T4 contain iodine.

• J. T3-T4 Function to 1) accelerate cellular metabolism, 2) tissue growth, 3) skeletal reproductive & nervous system development. Calcitonin lowers blood calcium levels.

• K. Thyroid gland unique because it can store & slowly release its hormones (up to 3 months worth)

Goiter= iodine or T3 / T4

deficiency

L. Over active & under active thyroid can cause severe disturbances. Ex. Hypothroid syndrome – goiter or cretinism; Severe hyperthyroidism – Graves disease (autoimmune disorder that attacks the thyroid)-most common.

M. Parathyroid – 4 to 8 embedded in posterior aspect of thyroid gland. Ex. PTH important in controlling level of calcium in blood.

•N. Hyperparathyroidism- rare result of PTH deficiency untreated death may occur. Kidney stones, reflexes & skeletal muscle weakness.

The Parathyroid Glands

Figure 10-11

• O. Adrenal glands almond size atop the kidneys.

1. Adrenal Medulla (inner)- epinephrine & norepinephrine

2. Adrenal cortex (outer)- Makes steroid hormones called Corticosteroids. Ex. Mineralcotricoids, Glucocorticoids, & Androgens

Adrenal Medulla Produces two similar hormones 1.Epinephrine – aka Adrenaline;

associated w/the fight or flight system. Axons stimulate hormone secretion. Increases heart rate and force, releases glucose, fatty acids into blood, opens airways

Epinephrine

Adrenal Medulla Produces two similar hormones 2. Norepinephrine: aka. Noradrenaline- associated w/the rest & digest system. Is the antagonist to epinephrine. These hormones prepare the

body to deal with short-term stress

Norepinephrine – Rest & Digest

Adrenal Cortex-Mineralcorticoids(mainly aldosterone)

Produced in outer adrenal cortex

Regulate mineral content in blood, water, and electrolyte balance

Target organ is the kidney

Production stimulated by renin and aldosterone

Adrenal Cortex: Glucocorticoids (including

cortisone and cortisol)

Promote normal cell metabolism

Help resist long-term stressors

Released in response to increased blood levels of ACTH

Adrenal Cortex: Sex hormones

Produced in the inner layer of the adrenal cortexAndrogens (male hormones) and some estrogen (female hormones)

Adrenal Gland Response to Stress

• P. Pancreas- located partially behind the stomach. Mixed gland so has both endocrine & exocrine capabilities.

• Islets of Langerhans-minute clusters of cells that produce pancreatic hormones. Ex. Insulin-lowers blood sugar level & Glucagon –increases blood sugar

P. Pancreas: –Islet cells secrete insulin and glucagon

•Insulin produced by beta cells•Glucagon produced by alpha cells

–Exocrine cells secrete enzyme-rich digestive fluid

• Actions of Insulin and Glucagon–Insulin

•Lowers blood glucose concentration• Increases glucose uptake, storage, and use by target cells

•Targets liver, muscle, fat cells–Glucagon

•Raises blood glucose concentration• Increases glycogen breakdown and glucose synthesis

•Targets liver cells

The Pancreas

Figure 10-13(a)

Q. Pineal Gland: located in the 3rd ventricle of the brain secretes Melatonin associated w/sleep & wake cycles.

R. Inhibits reproductive functionS. Protects neural tissue from free

radicals

T. Its’ complete function is still unclear.

Q. Pineal Gland: located in brain

Thymus Gland Located posterior to the sternum

Largest in infants and children

Produces thymosin

Matures some types of white blood cells

Important in developing the immune system

Reproductive Glands: Ovaries Estrogen Hormone:

Produced by Graafian follicles or the placenta

Stimulates the development of secondary female characteristics

Matures female reproductive organs

Helps prepare the uterus to receive a fertilized egg

Helps maintain pregnancy

Prepares the breasts to produce milk

Reproductive Glands: Ovaries

Progesterone

Produced by the corpus luteum

Acts with estrogen to bring about the menstrual cycle

Helps in the implantation of an embryo in the uterus

Reproductive Glands: Testes

Interstitial cells of testes are hormone-producing

Produce several androgens (sex hormones)

Reproductive Glands: Testes Testosterone (hormone) is the most

important androgen

Responsible for adult male secondary sex characteristics

Promotes growth and maturation of male reproductive system

Required for sperm cell production

Other Hormone Producing Tissues & Organs:

Parts of the small intestine Secretes hormones to control digestion

Parts of the stomach

–Kidneys Secretes three hormones• Calcitriol—Stimulates calcium and phosphate absorption in

intestine• Erythropoietin (EPO)—Stimulates red blood cell production by

bone marrow• Renin—Enzyme that leads to angiotensin II that triggers

aldosterone from adrenal cortex

Other Hormone Producing Tissues & Organs:

Heart Specialized muscle cells secrete atrial natriuretic peptide (ANP) to lower blood volume or blood pressure

• Adipose tissue (fat cells)– Secretes leptin to control appetite– Secretes resistin to reduce insulin response Many other areas have scattered

endocrine cells

Endocrine Functions of the Placenta

Produces hormones that maintain the pregnancy

Some hormones play a part in the delivery of the baby

Produces HCG in addition to estrogen, progesterone, and other hormones

Patterns of Hormonal Interaction

• Kinds of Interaction between Hormones–Antagonistic (opposing effect)

• E.g., calcitonin versus PTH–Synergistic (additive effect)

• E.g., hGH and cortisol on glucose sparing–Permissive effect

• E.g., epinephrine and thyroid hormones–Integrative effect

• E.g., calcitriol and PTH on calcium levels

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Patterns of Hormonal Interaction

• Hormones Needed for Normal Growth–Growth Hormone–Thyroid Hormones–Insulin–Parathyroid Hormone–Calcitriol–Reproductive Hormones

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Patterns of Hormonal Interaction

• Hormones and Stress• Stress—Any condition that threatens

homeostasis• General Adaptation Syndrome to stress

–Alarm phase (sympathetic ANS response)

–Resistance phase (glucocorticoid response)

–Exhaustion phase (organ system failure)Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Development of the Endocrine System Most endocrine organs operate

smoothly until old age Menopause is brought about by lack

of efficiency of the ovaries Problems associated with reduced

estrogen are common Growth hormone production declines

with age Many endocrine glands decrease

output with age

• The information on the next slides will be found on your notes papers

II. Hormone Action• C. Hormones activate target cells by 1 of

2 methods, depending upon the chemical nature of the hormone:

• 1) peptide hormones {water soluble} that bind to a receptor protein on the plasma membrane of the cell. The receptor protein, then stimulates the production of a second messenger (either cAMP or calcium.)

II. Hormone Action

• 2) steroid hormones {lipid soluble} that diffuse through the plasma membrane of the target cell & bind to receptor protein present in the cytoplasm that activates a DNA segment that turns on specific genes

III. Control of Hormone Production

• A. Endocrine glands release hormones in response to 1 or more of the following stimuli:

• 1. Hormones form other endocrine glands

• 2. Chemical characteristics of the blood

• 3. Neural stimulation

III. Control of Hormone Production• 4. most hormone production is regulated by

negative feedback system. • a. negative feedback: hormones

secretion is triggered by some internal or external stimulus, then rising hormones levels inhibit further hormone release resulting in blood levels of many hormones varying only within a very narrow margin.

IV. Communication b/w the Hypothalamus & Pituitary Glands

• A. Communication b/w the hypothalamus & the Anterior Pituitary Gland occurs through chemicals that are produced by the hypothalamus & delivered to the ant. pituitary through blood vessels.

IV. Communication b/w the Hypothalamus & Pituitary Glands

• B. Communication b/w the hypothalamus & the Posterior Pituitary Gland occurs through neurosecretory cells that connect the 2 glands.

V. Antagonistic Hormones• A. When the body hormone levels drop

below normal homeostasis levels the antagonistic hormones are secreted to bring the body back to homeostasis.

• B. Ex. Bundles of cells in the pancreas called the islets of Langerhans contain 2 kinds of cells alpha (secrete glucagons) & beta (secrete insulin) cells, that control blood glucose concentrations by producing the antagonistic hormones insulin & glucagon

VI. Major Endocrine OrgansGland Hormone Released Target Tissue/Organ Chief Function of

HormonePineal Melatonin Various Tissues Involved in daily

rhythms; possibly involved in maturation of sex organs

Hypothalamus Hypothalamic-releasing & release-inhibiting hormones

Anterior pituitary Regulate anterior pituitary hormones

Anterior Pituitary Growth hormone (GH) Prolactin; (LTH)Luteininzing Hormone; Follicle stimulating hormone (FSH); Adrenocorticotropic hormone (ACTH) Thyroid stimulating (TSH)MSH (Melanocyte stimulating Hormone)

Soft tissues, bonesMammary glndsOvary, testesGonadsAdrenal cortexThyroidSkin & Melanocytes

Stimulates protein synth. & bone growthStimulates milk production & secretionReg. Oogenesis & spermatogenesisSame as LHStimulate secretion of gluco-corticoidsStimulate secretion of T3 & T4

Stimulates melanin skin pigment formation.

VI. Major Endocrine OrgansGland Hormone Released Target Tissue/Organ Chief Function of

HormonePosterior Pituitary Oxytocin

Antidiuretic Hormone (ADH);

Uterus,mammary glandsKidneys, sweat glands

Uterine contractions, release of milkIncreases water retention & BP

Thyroid Thyroxin (T4)CalcitoninTriiodothyronine (T3)

All tissuesBones, kidneys, intestineBone

Increases metabolic rate; helps to result. growth & developmentLowers blood calcium levelsIncreases rate of cellular metabolism

Parathyroid Parathyroid hormone (PTH)

Bones, kidneys, intestine

Raises blood calcium levels

Thymus Thymosins T lymphocytes Stimulates maturation of T lymphocytes

VI. Major Endocrine OrgansGland Hormone Released Target Tissue/

OrganChief Function of Hormone

Adrenal Glands

Adrenal Medulla Epinephrine & Norepinephrine

Cardiac & other muscles

Stimulate “fight-or-fight” reaction; raise blood glucose lvl.

Adrenal Cortex Glucocorticoids ex. CortisolMineralcorticoids ex. AldosteroneAndrogens ex. DHEA

All tissuesKidneysSex organs, skin, muscles

Raises blood glucose levelIncrease reabsorption of Na+ & to excrete K+

Stimulate onset of puberty, female sex drive

Pancreas InsulinGlucagon

Liver, muscles, adipose tissuesLiver

Lowers blood glucose levelsIncreases blood glucose levels

VI. Major Endocrine OrgansGland Hormone Released Target Tissue/ Organ Chief Function of

HormoneGonads

Ovaries EstrogenProgesteroneRelaxinInhibin

UterusUterusPelvis, cervixpituitary

Regulates menstrual cycle, secondary sex characteristics.Reg.menstrual cycle, pregnancyDilates cervix & birth canalInhibits FSH release

Testes TestosteroneInhibin

TestesPituitary

Regult. spermatogenesis, secondary sex characteristicsinhibits FSH release

• THE END!!!!