The Endocrine The Endocrine SystemSystem

Mrs. HartleyMrs. Hartley

Anatomy and PhysiologyAnatomy and Physiology

2004-20052004-2005

FunctionsFunctions

Works with nervous system to control body Works with nervous system to control body activitiesactivities

Primary role is to help maintain homeostasisPrimary role is to help maintain homeostasis Communication using chemicals called Communication using chemicals called

hormoneshormones Regulate processes including metabolism, Regulate processes including metabolism,

growth and development, reproduction, and growth and development, reproduction, and regulation of stressregulation of stress

Control of these processes is essential to Control of these processes is essential to survivalsurvival

Composition of Endocrine Composition of Endocrine SystemSystem

Composed of organs that produce and Composed of organs that produce and secrete hormonessecrete hormones

Perform a secretory function therefore Perform a secretory function therefore are referred to as are referred to as glandsglands

Two types: endocrine and exocrine Two types: endocrine and exocrine glandsglands

Nervous vs. EndocrineNervous vs. Endocrine

Often work togetherOften work together Parts of the nervous sytem stimulate or Parts of the nervous sytem stimulate or

inhibit the release of hormones and vice-inhibit the release of hormones and vice-versaversa

Endocrine system typically acts more Endocrine system typically acts more slowly than the nervous systemslowly than the nervous system

Endocrine GlandsEndocrine Glands

Secrete products into Secrete products into extracellular space extracellular space surrounding the cellssurrounding the cells

Products = hormones that Products = hormones that enter bloodstreamenter bloodstream

Pituitary gland, thyroid gland, Pituitary gland, thyroid gland, parathyroid glands, adrenal parathyroid glands, adrenal glands, pancreas, and gonads glands, pancreas, and gonads are primary endocrine glandsare primary endocrine glands

Pineal and thymus gland play Pineal and thymus gland play small rolesmall role

Hormones received by Hormones received by kidneys, stomach, small kidneys, stomach, small intestine, placentaintestine, placenta

HormonesHormones

Chemical units produced by endocrine glandsChemical units produced by endocrine glands Means by which glands provide control of body Means by which glands provide control of body

activitiesactivities Hormones are released into the bloodstream Hormones are released into the bloodstream

which in turn delivers to all body cellswhich in turn delivers to all body cells The cells that recognize a particular hormone The cells that recognize a particular hormone

will be the one to respond (target cell)will be the one to respond (target cell)

Hormonal ActionHormonal Action

ReleasedReleased in very small in very small quantitiesquantities

Diffuse through bloodstreamDiffuse through bloodstream Will have an effect only on a Will have an effect only on a

particular type of cell called particular type of cell called the the target celltarget cell

Effect limited to target cell Effect limited to target cell because of protein molecules because of protein molecules acting as receptors that are acting as receptors that are specific to a particular specific to a particular hormonehormone

Cells other than the target cell Cells other than the target cell are not affected by a hormone are not affected by a hormone because they lack appropriate because they lack appropriate receptorsreceptors

Hormonal Action Cont.Hormonal Action Cont.

Hormone unites with receptor and exerts it’s effect Hormone unites with receptor and exerts it’s effect (generally altering metabolic processes)(generally altering metabolic processes)

May change rate of activity, rate of protein synthesis, May change rate of activity, rate of protein synthesis, rate of secretion, etc largely determined by the nature rate of secretion, etc largely determined by the nature of the hormoneof the hormone

LIPID BILAYERLIPID BILAYER

Water Soluble HormonesWater Soluble Hormones

Include molecules that are composed of amino acidsInclude molecules that are composed of amino acids Cannot pass through the lipid plasma membraneCannot pass through the lipid plasma membrane How can they produce an effect on the cell then? They How can they produce an effect on the cell then? They

must use a second messenger system located in the must use a second messenger system located in the cell.cell.

Most common is cyclic AMPMost common is cyclic AMP Hormone (first messenger) activates second Hormone (first messenger) activates second

messenger which in turn exerts the effect in the cell.messenger which in turn exerts the effect in the cell. Examples: epinephrine, norepinephrine (NE), Examples: epinephrine, norepinephrine (NE),

antidiuretic hormone (ADH), oxytocin (OT), calcitonin antidiuretic hormone (ADH), oxytocin (OT), calcitonin (CT), and parathyroid hormone (PTH)(CT), and parathyroid hormone (PTH)

Lipid-Soluble HormonesLipid-Soluble Hormones

Include mainly steroid hormonesInclude mainly steroid hormones Can pass directly through the bilayer by diffusion to the Can pass directly through the bilayer by diffusion to the

target cell easilytarget cell easily Binds to receptor in cell which binds to the DNA of the Binds to receptor in cell which binds to the DNA of the

nucleusnucleus ““Turns on” the synthesis of specific protein molecules Turns on” the synthesis of specific protein molecules

by DNAby DNA Activate genes to synthesize new proteins and Activate genes to synthesize new proteins and

enzymesenzymes Examples: aldosterone, cortisol, testosterone, Examples: aldosterone, cortisol, testosterone,

estrogen, thyroxineestrogen, thyroxine

ProstaglandinsProstaglandins

Chemicals with regulating effect on cellsChemicals with regulating effect on cells Act only on nearby cells whereas hormones Act only on nearby cells whereas hormones

can travel distances, often called “local can travel distances, often called “local hormones”hormones”

Interact with hormones to regulate activitiesInteract with hormones to regulate activities Reduce blood pressure and open airways OR Reduce blood pressure and open airways OR

stimulate smooth muscle contraction for the stimulate smooth muscle contraction for the opposite effectopposite effect

Hormonal ControlHormonal Control

How does an endocrine gland “know” How does an endocrine gland “know” how much hormone to produce and how much hormone to produce and release? - - Feedback is provided by way release? - - Feedback is provided by way of chemical signals sent to the endocrine of chemical signals sent to the endocrine glandgland

Two systems: negative and positive Two systems: negative and positive feedbackfeedback

Negative Feedback Negative Feedback SystemsSystems

Provides a response Provides a response in the opposite in the opposite direction to that of direction to that of the stimulusthe stimulus

Signal is secreted by Signal is secreted by the hormone or its the hormone or its products which products which exerts the negative exerts the negative effect on the effect on the endocrine glandendocrine gland

IncreasedBlood level

Ca2+

Stimulates Parathyroid

gland

Decreased bloodLevel Ca2+

Ca2+ Blood levelRises above

normal

Inhibits Parathyroid

Gland

DecreasedBlood Level

Ca2+

HOMEOSTASISNORMAL BLOOD

LEVEL Ca2+

HOMEOSTASISNORMAL BLOOD

LEVEL Ca2+

Positive Feedback Positive Feedback SystemsSystems

Regulate hormone secretion by providing Regulate hormone secretion by providing a response in the same direction as the a response in the same direction as the stimulusstimulus

Endocrine gland increases its rate of Endocrine gland increases its rate of hormone release and more responses hormone release and more responses are stimulatedare stimulated

Cause extreme conditions in the body Cause extreme conditions in the body therefore quite unstable and uncommontherefore quite unstable and uncommon

Positive-feedback mechanism of labor1. The baby moves deeper into the mother's pelvic region. (See

handout, Figure 29.16)

2.Special sensory nerve cells that are pressure receptors in the cervix are stimulated and send nerve impulses to the

hypothalamus.

3. Specialized neurosecretory cells in the hypothalamus make oxytocin hormone that travels down long extensions of these cells into the posterior pituitary where it is stored. (See Fig. 5.3, p.

76 and read the text section titled Posterior Pituitary on p. 77.)

4. The posterior pituitary releases oxytocin hormone into the blood.

5. Oxytocin hormone stimulates the uterus muscle lining, the myometrium, to contract.

6. Uterine contraction pushes the baby deeper into the birth canal and pressure receptors in the cervix are again triggered.... see #2.

This positive feedback loop continues until the baby is born.

--> When doctors induce labor, the woman receives several doses of a synthetic oxytocin to get the positive feedback loop of labor

going.

FYIFYI

What triggers the start of the labor What triggers the start of the labor positive-feedback loop?positive-feedback loop?

Doctors do not know, however, it has Doctors do not know, however, it has been the generally accepted hypothesis been the generally accepted hypothesis that the baby sends out the initial that the baby sends out the initial message. Most recently, scientists have message. Most recently, scientists have discovered a protein released by the discovered a protein released by the baby's lungs that acts as a hormone baby's lungs that acts as a hormone signaling mom to begin labor.signaling mom to begin labor.

Pituitary GlandPituitary Gland

Aka hypophysisAka hypophysis Located at base of brainLocated at base of brain Connected to hypothalamusConnected to hypothalamus Two portions: anterior lobe 75% and Two portions: anterior lobe 75% and

glandular; posterior composed of nerve glandular; posterior composed of nerve tissuetissue

Release of hormones regulated by Release of hormones regulated by hypothalamushypothalamus

Anterior/Posterior Anterior/Posterior HormonesHormones

Growth Hormone (GH)Growth Hormone (GH) Prolactin (PRL)Prolactin (PRL) Thyroid-stimulating Thyroid-stimulating

hormone (TSH)hormone (TSH) Adrenocroticotropic Adrenocroticotropic

hormone (ACTH)hormone (ACTH) Follicle-Stimulating Follicle-Stimulating

hormone (FSH)hormone (FSH) Luteinizing hormone Luteinizing hormone

(LH)(LH)

Oxytocin (OT)Oxytocin (OT) Antidiuretic hormone Antidiuretic hormone

(ADH)(ADH) **Stored but not **Stored but not

produced here!!!produced here!!!

Thyroid GlandThyroid Gland

Prominent organ in Prominent organ in neck made of two neck made of two large lobeslarge lobes

Hormones: Thyroxine Hormones: Thyroxine (T4), Triiodothyronine (T4), Triiodothyronine (T3), and Calcitonin (T3), and Calcitonin (CT)(CT)

Parathyroid GlandsParathyroid Glands

Four or five pea-Four or five pea-shaped masses of shaped masses of glandular epitheliumglandular epithelium

Secrete one Secrete one hormone called hormone called parathyroid hormone parathyroid hormone (PTH)(PTH)

Adrenal GlandsAdrenal Glands

Paired, triangular Paired, triangular masses that lie on masses that lie on each kidneyeach kidney

Two areas: inner Two areas: inner medulla and outer medulla and outer cortexcortex

Function as distinct Function as distinct glandsglands

Hormones of Hormones of Medulla/CortexMedulla/Cortex

MedullaMedulla EpinephrineEpinephrine NorepinephrineNorepinephrine

CortexCortex Steroid hormonesSteroid hormones Mineralocorticoids: Mineralocorticoids:

aldosteronealdosterone Glucocorticoids: cortisol, Glucocorticoids: cortisol,

corticosterone, cortisonecorticosterone, cortisone Sex hormones: Sex hormones:

androgens and androgens and estrogensestrogens

PancreasPancreas

Part of endocrine and Part of endocrine and digestive systemdigestive system

Alpha cells secrete the Alpha cells secrete the hormone glucagonhormone glucagon

Beta cells secrete the Beta cells secrete the hormone insulinhormone insulin

http://cal.man.ac.uk/studhttp://cal.man.ac.uk/student_projects/2000/mnbyent_projects/2000/mnby7lc2/factors_affecting_se7lc2/factors_affecting_secretion.htmcretion.htm

GonadsGonads

Sex organsSex organs Produce the sex cells Produce the sex cells

and secrete primary and secrete primary sex hormonessex hormones

Females = ovaries Females = ovaries which secrete which secrete estrogens and estrogens and progesteroneprogesterone

Males = testes which Males = testes which secrete testosteronesecrete testosterone

Pineal GlandPineal Gland

Small structure in Small structure in cranial cavity cranial cavity associated with brainassociated with brain

Secretes one Secretes one hormone called hormone called melatoninmelatonin

Thymus GlandThymus Gland

Prominent in infants Prominent in infants but diminishes in size but diminishes in size with advancing agewith advancing age

Soft, irregulary Soft, irregulary shaped structure on shaped structure on the top of the heartthe top of the heart

Early, secretes Early, secretes thymosinthymosin

Assignment: Create a Assignment: Create a powerpoint presentation for powerpoint presentation for your assigned hormonesyour assigned hormones

Presentation must answer the following questions:Presentation must answer the following questions: From where does the hormone come?From where does the hormone come? What effects do these hormones have on the human body?What effects do these hormones have on the human body? What organs do the hormones target?What organs do the hormones target? Why are these hormones important to homeostasis in the Why are these hormones important to homeostasis in the

body?body? What are the feedback mechanisms and antagonistic What are the feedback mechanisms and antagonistic

hormones?hormones? What happens when this gland does not work properly?What happens when this gland does not work properly? What can be medically done to correct malfunctions?What can be medically done to correct malfunctions?

Presentation must include at least three Presentation must include at least three illustrations/diagramsillustrations/diagrams