Endocrine System

By Dr. Shamanthakamani By Dr. Shamanthakamani NarendranNarendran

Endocrine SystemEndocrine System

The endocrine system is made up of the cells, tissues, and The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluidsorgans that secrete hormones into body fluids

INTRODUCTIONINTRODUCTION Endocrine means ‘Endocrine means ‘secreting internally’secreting internally’.. Indeed, the endocrine system is made up Indeed, the endocrine system is made up

of glands whose secretions enter the blood of glands whose secretions enter the blood stream.stream.

Hence these glands are different from Hence these glands are different from those whose secretions are released on those whose secretions are released on the surface of the body, like the sweat the surface of the body, like the sweat glands or the tear secreting glands.glands or the tear secreting glands.

The endocrine glands are sometimes The endocrine glands are sometimes referred to as ‘referred to as ‘ductlessductless’ glands.’ glands.

This is to differentiate them from another This is to differentiate them from another set of glands (set of glands (exocrineexocrine).).

Exocrine glands have a duct or tube which Exocrine glands have a duct or tube which carries the secretions to the place where it carries the secretions to the place where it should act.should act.

In contrast, the secretions of endocrine In contrast, the secretions of endocrine glands (glands (ductlessductless) enter the blood stream ) enter the blood stream directly.directly.

These secretions are called These secretions are called hormoneshormones..

Characteristically, hormones travel in the Characteristically, hormones travel in the blood stream far from the gland which blood stream far from the gland which secreted them.secreted them.

Hormones act on an organ/structure which Hormones act on an organ/structure which is called the is called the target organtarget organ..

ENDOCRINE GLANDS (DUCTLESS)

EXOCRINE GLANDS (WITH DUCT)

HORMONE

• BLOOD STREAM

• DISTANT ACTION

SECRETIONS

• LOCAL ACTION

BLOOD VESSEL

DUCT

The endocrine system is concerned with The endocrine system is concerned with the maintenance of homeostasis or the maintenance of homeostasis or internal balanceinternal balance

Glands comprising the endocrine system;Glands comprising the endocrine system; Pituitary Pituitary brain brain Thyroid & parathyroid Thyroid & parathyroid neck neck Adrenal glands Adrenal glands top of each kidney top of each kidney Pancreas Pancreas abdomen abdomen Gonads Gonads pelvis (ovaries & testes) pelvis (ovaries & testes) Thymus Thymus chest chest Pineal Pineal brain brain

THE SYSTEM IS LARGELY CONTROLLED THE SYSTEM IS LARGELY CONTROLLED BY HYPOTHALAMUS & HENCE IS BY HYPOTHALAMUS & HENCE IS LINKED TO THE AUTONOMIC NERVES LINKED TO THE AUTONOMIC NERVES SYSTEMSYSTEM

This control mechanism has This control mechanism has threethree levels. levels. HypothalamusHypothalamus Pituitary glandPituitary gland Other glands (thyroid, adrenals, etc.)Other glands (thyroid, adrenals, etc.)

The hypothalamusThe hypothalamus has many essential has many essential functions, one of these is regulation of the functions, one of these is regulation of the endocrine system.endocrine system.

It controls the endocrine glands through It controls the endocrine glands through releasing hormonesreleasing hormones..

This mechanism regulates the secretions This mechanism regulates the secretions of almost all the other glands.of almost all the other glands.

Exceptions are: a small part of the pituitary Exceptions are: a small part of the pituitary gland, the gland, the posterior pituitaryposterior pituitary, and the , and the pancreas.pancreas.

The releasing hormones pass (like other The releasing hormones pass (like other hormones) via the blood stream to the hormones) via the blood stream to the pituitary gland which is the next level of pituitary gland which is the next level of controlcontrol..

The The pituitarypituitary (the (the anterior partanterior part) receives ) receives releasing hormones from the releasing hormones from the hypothalamus.hypothalamus.

In response to these releasing hormones In response to these releasing hormones (RH), the pituitary secretes stimulating (RH), the pituitary secretes stimulating hormones (SH).hormones (SH).

There is a specific SH for each gland (i.e. There is a specific SH for each gland (i.e. separate SH for thyroid/adrenal glands/and separate SH for thyroid/adrenal glands/and for gonads.for gonads.

The other glands (i.e. thyroid, adrenals, The other glands (i.e. thyroid, adrenals, gonads) in response to the specific SH gonads) in response to the specific SH from the pituitary, the gland secretes its from the pituitary, the gland secretes its hormone.hormone.

These three levels of control can be These three levels of control can be understood with an exampleunderstood with an example

First level First level – hypothalamus: thyrotropin – hypothalamus: thyrotropin releasing hormone.releasing hormone.

Second level Second level – (ANT) pituitary: TSH– (ANT) pituitary: TSH Third levelThird level – thyroid gland: thyroid – thyroid gland: thyroid

hormone (thyroxine)hormone (thyroxine)

Thus the hypothalamus triggers the Thus the hypothalamus triggers the pituitary, which in turn triggers the target pituitary, which in turn triggers the target gland.gland.

HYPOTHALAMUS

TARGET GLAND(THYROID GLAND)

ANTERIORPITUITARY

OTHER STIMULI

FEEDBACK(e.g. thyroxine)

RH

SH

The hormones secreted by the target The hormones secreted by the target gland have a ‘feedback effect’ on both gland have a ‘feedback effect’ on both the pituitary and the hypothalamusthe pituitary and the hypothalamus..

This means if the thyroid gland secretes This means if the thyroid gland secretes increasedincreased amounts of thyroid hormone, amounts of thyroid hormone, this has a this has a negative feedbacknegative feedback effect on effect on both the pituitary and the hypothalamus.both the pituitary and the hypothalamus.

As a result the amount of stimulating and As a result the amount of stimulating and releasing hormones (SH, RH) releasing hormones (SH, RH) decreasesdecreases..

Thus further secretion of thyroid hormone Thus further secretion of thyroid hormone is prevented.is prevented.

This is a very important control This is a very important control mechanism.mechanism.

On the other hand, if the target gland On the other hand, if the target gland secretes secretes lessless of its hormone, the pituitary of its hormone, the pituitary and hypothalamus are stimulated to and hypothalamus are stimulated to secrete secrete greatergreater amounts of SH and RH amounts of SH and RH respectively.respectively.

The hypothalamus is stimulated by The hypothalamus is stimulated by specific factors, both inside and outside specific factors, both inside and outside the bodythe body..

The stimuli are specific for each target The stimuli are specific for each target gland.gland.

For example, in presence of cold, the For example, in presence of cold, the hypothalamus stimulates the pituitary, hypothalamus stimulates the pituitary, which activates the target gland.which activates the target gland.

Similarly there are specific stimuli which Similarly there are specific stimuli which cause the hypothalamus to secrete the cause the hypothalamus to secrete the specificspecific RH to activate the adrenal glands RH to activate the adrenal glands and the gonads.and the gonads.

PITUITARY GLANDPITUITARY GLAND

Located at the base of the brain.Located at the base of the brain. It is roughly pea sized, weighting It is roughly pea sized, weighting

approximately half a gram.approximately half a gram. The pituitary gland has been called the The pituitary gland has been called the

control centre of the endocrine system.control centre of the endocrine system. It is under the control of the hypothalamus.It is under the control of the hypothalamus. There are 3 parts or lobes: Posterior, There are 3 parts or lobes: Posterior,

intermediate, and anterior.intermediate, and anterior. The intermediate lobe is thinner than the The intermediate lobe is thinner than the

other two, and is still being investigated.other two, and is still being investigated.

POSTERIOR PITUITARYPOSTERIOR PITUITARY

The lobe stores two hormones.The lobe stores two hormones. The hormones are produced in the The hormones are produced in the

hypothalamus.hypothalamus. Their release is also controlled by the Their release is also controlled by the

hypothalamus, which sends the necessary hypothalamus, which sends the necessary nerve messages to the posterior pituitary.nerve messages to the posterior pituitary.

The two hormones are The two hormones are anti diuretic anti diuretic hormone (ADH)hormone (ADH) & & oxytocinoxytocin..

ADH controls the amount of water in the ADH controls the amount of water in the body.body.

ADHADH does this by acting on the kidneys, does this by acting on the kidneys, regulating the amount of water they regulating the amount of water they excrete or retain.excrete or retain.

ADH prevents water from being excreted.ADH prevents water from being excreted. The hypothalamus is stimulated to send a The hypothalamus is stimulated to send a

message (RELEASE ADH!) to the pituitary, message (RELEASE ADH!) to the pituitary, if blood volume decreases.if blood volume decreases.

This could happen after severe bleeding or This could happen after severe bleeding or even if we lose a lot of fluid due to diarrhea even if we lose a lot of fluid due to diarrhea or vomiting.or vomiting.

OXYTOCINOXYTOCIN causes the contractions of the causes the contractions of the uterus which are necessary for child birth.uterus which are necessary for child birth.

It is also responsible for the release of It is also responsible for the release of breast milk.breast milk.

Hence the stimuli are factors like the Hence the stimuli are factors like the pressure of the infant’s head on the uterus, pressure of the infant’s head on the uterus, or near the nipple, during breast feeding.or near the nipple, during breast feeding.

The function in men is uncertain.The function in men is uncertain.

ANTERIOR PITUITARYANTERIOR PITUITARY

Produces the hormones which it secretes Produces the hormones which it secretes (unlike the posterior pituitary).(unlike the posterior pituitary).

Trigger signals to release these hormones, Trigger signals to release these hormones, or not is sent by the hypothalamus.or not is sent by the hypothalamus.

There are 6 main hormones: Two of them There are 6 main hormones: Two of them ((growth hormonegrowth hormone & & prolactinprolactin) act directly ) act directly on body tissues or processes.on body tissues or processes.

The other four hormones are The other four hormones are Stimulating Stimulating Hormone (SH)Hormone (SH), which control the , which control the production of hormones in other glands: production of hormones in other glands: thyroid, adrenals, & gonads.thyroid, adrenals, & gonads.

GROWTH HORMONEGROWTH HORMONE controls the growth controls the growth of the body during childhood, until of the body during childhood, until adolescence.adolescence.

Too little of the growth hormone is Too little of the growth hormone is childhood leads to dwarfism. childhood leads to dwarfism.

Too much causes gigantism. Too much causes gigantism. Later on in life (adulthood), when the Later on in life (adulthood), when the

length of bones is fixed, too much of length of bones is fixed, too much of growth hormone causes thickening of the growth hormone causes thickening of the limbs and jaws, giving the person a limbs and jaws, giving the person a distorted appearance.distorted appearance.

PROLACTINPROLACTIN has the effect of enlarging the has the effect of enlarging the breasts so that milk production occurs during breasts so that milk production occurs during pregnancy.pregnancy.

THYROID STIMULATING HORMONE (TSH)THYROID STIMULATING HORMONE (TSH) promotes the secretion of the thyroid gland.promotes the secretion of the thyroid gland.

ADRENOCORTICOTROPIC HORMONE ADRENOCORTICOTROPIC HORMONE (ACH)(ACH) promotes the secretion of promotes the secretion of corticosterone by the adrenals.corticosterone by the adrenals.

GONADOTROPINSGONADOTROPINS include include FOLLICLE FOLLICLE STIMULATING HORMONE (FSH) STIMULATING HORMONE (FSH) and and LUTEINIZING HORMONE (LH)LUTEINIZING HORMONE (LH), both of them , both of them stimulate the gonads (ovaries or testis) to stimulate the gonads (ovaries or testis) to produce ova or eggs/sperms.produce ova or eggs/sperms.

The production and release of these 4 The production and release of these 4 hormones is partially controlled through a hormones is partially controlled through a negative feedback system.negative feedback system.

The presence in the blood of the hormone The presence in the blood of the hormone produced by the target gland produced by the target gland (thyroid/adrenals/gonads) will control the (thyroid/adrenals/gonads) will control the release of the Stimulating Hormone from release of the Stimulating Hormone from the pituitary.the pituitary.

This feedback also works on the This feedback also works on the hypothalamus and in this way also, hypothalamus and in this way also, ((indirectlyindirectly) on the pituitary, by altering the ) on the pituitary, by altering the secretion of hypothalamic secretion of hypothalamic releasing releasing hormoneshormones..

Hormones Secreted by the Pituitary GlandHormones Secreted by the Pituitary Gland

THYROID GLANDTHYROID GLAND

Butterfly shaped gland located at the base of the neck just below the larynx.

It is composed of 2 lobes, jointed together by a horizontal bridge.

In adults it weighs approximately 20 g. The gland secretes thyroxine. Thyroxine controls the metabolic rate, i.e.

the speed at which cells consume and process food an oxygen.

Another secretion is calcitonin, which helps deposition of calcium in the bones.

THYROXINETHYROXINE

……increases the amount of energy used by increases the amount of energy used by the cell and increases heat production.the cell and increases heat production.

……stimulates bone growth.stimulates bone growth. ……is essential for normal brain is essential for normal brain

development. It is also necessary for the development. It is also necessary for the brain to function normally in adulthood.brain to function normally in adulthood.

IodineIodine is essential for thyroxine formation. is essential for thyroxine formation. A lack of iodine in the diet will result in A lack of iodine in the diet will result in

thyroid malfunction.thyroid malfunction. IodineIodine is present in sea food, sea water, is present in sea food, sea water,

salt, & is deficient in the soil in hilly areas.salt, & is deficient in the soil in hilly areas.

WHAT HAPPENS WHEN WHAT HAPPENS WHEN THYROXINE IS DEFICIENTTHYROXINE IS DEFICIENT

BEFORE BIRTHBEFORE BIRTH Physical growth is retardedPhysical growth is retarded Mental retardationMental retardation They are called They are called cretinscretins and the condition and the condition

is called is called cretinismcretinism..

AFTER BIRTHAFTER BIRTH Metabolic rate is decreased.Metabolic rate is decreased. Person gains weight.Person gains weight. Body temperature decreases.Body temperature decreases.

Mental processes and reflexes slow down Mental processes and reflexes slow down – an example of a reflex is that if we reach – an example of a reflex is that if we reach out for something which is burning hot then out for something which is burning hot then we withdraw our hand hurriedly.we withdraw our hand hurriedly.

In case of thyroid deficiency the speed with In case of thyroid deficiency the speed with which we withdraw our hand, slows down.which we withdraw our hand, slows down.

IF A PERSON WITH THYROID IF A PERSON WITH THYROID DEFICIENCY IS EXAMINED – WE FINDDEFICIENCY IS EXAMINED – WE FIND

Lower metabolic rate.Lower metabolic rate. Lower temperatureLower temperature Gain in body weight, and a puffy Gain in body weight, and a puffy

appearance. This swelling does not ‘pit’ on appearance. This swelling does not ‘pit’ on pressure.pressure.

Mental processes slowed downMental processes slowed down Heart rate decreases.Heart rate decreases.

WHAT HAPPENS WHEN THYROXINE IS WHAT HAPPENS WHEN THYROXINE IS SECRETED IN INCREASED AMOUNTSSECRETED IN INCREASED AMOUNTS

Metabolic rate increasesMetabolic rate increases Body temperature is raised.Body temperature is raised. Body weight is reduced.Body weight is reduced. Mental processes are speeded up. The Mental processes are speeded up. The

reflex responses are also quicker than reflex responses are also quicker than normal. Some persons are anxious and normal. Some persons are anxious and irritable.irritable.

Heart rate increasesHeart rate increases

Decreased levels of thyroxin causes a Decreased levels of thyroxin causes a decrease in the cellular respiration rate.  cells decrease in the cellular respiration rate.  cells produce less energy and become less active. produce less energy and become less active.

PARATHYROID GLANDSPARATHYROID GLANDS There are 4 parathyroid glands.There are 4 parathyroid glands. These glands are very small.These glands are very small. They are present on the back surface of They are present on the back surface of

the thyroid gland.the thyroid gland. ParathormoneParathormone, which is secreted by the , which is secreted by the

parathyroids regulates the level of calcium parathyroids regulates the level of calcium in the blood.in the blood.

Hence it functions along with calcitonin Hence it functions along with calcitonin which is secreted by the thyroid gland.which is secreted by the thyroid gland.

In case too much of parathormone is In case too much of parathormone is secreted, calcium is removed from the secreted, calcium is removed from the bones.bones.

PARATHYROID GLANDSPARATHYROID GLANDS1. Attached to or embedded in

the back surface of the thyroid gland, two in each lobe.

2. Produces parathyroid hormone (PTH) regulates the calcium levels in the blood by increasing the reabsorption of calcium in the kidneys and by increasing the uptake of calcium from the digestive system.

ADRENAL GLANDS (CORTEX & MEDULLA)

1. One gland is located on top of each kidney.

2. Composed of two very different types of tissue

a. Outer - The adrenal

cortex

    b. Inner - The adrenal

medulla

ADRENAL GLANDSADRENAL GLANDS

The adrenal (suprarenal) glands are a pair The adrenal (suprarenal) glands are a pair of glands placed on top of each kidney, of glands placed on top of each kidney, rather like a cap.rather like a cap.

Each gland is composed of two distinct Each gland is composed of two distinct parts: the central adrenal medulla and the parts: the central adrenal medulla and the surrounding adrenal cortex.surrounding adrenal cortex.

The two parts have separate functions, The two parts have separate functions, which influence one another.which influence one another.

ADRENAL MEDULLAADRENAL MEDULLA

The adrenal medulla produces the The adrenal medulla produces the hormones hormones adrenalinadrenalin and and noradrenalinnoradrenalin..

These are known as the ‘fight or flight’ These are known as the ‘fight or flight’ hormones.hormones.

The release of these hormones is The release of these hormones is controlled by the sympathetic nervous controlled by the sympathetic nervous system.system.

Their effects are similar to those of Their effects are similar to those of sympathetic nerve stimulation.sympathetic nerve stimulation.

ADRENAL CORTEXADRENAL CORTEX

Produces several hormones called Produces several hormones called steroidssteroids..

These hormones are released as soon as These hormones are released as soon as stress is encountered.stress is encountered.

It is not actually known It is not actually known whywhy these these hormones are essential for the stress hormones are essential for the stress response.response.

One belief is that they facilitate the action One belief is that they facilitate the action of adrenalin and noradrenalin.of adrenalin and noradrenalin.

These hormones have various functions:These hormones have various functions: Increase the blood sugar levels.Increase the blood sugar levels. Control the use of salt in the body.Control the use of salt in the body. Distribution of fat.Distribution of fat. Reduce sensitivity (allergic) reactions.Reduce sensitivity (allergic) reactions. Antiinflammatory action. [inflammation = a Antiinflammatory action. [inflammation = a

reaction of the body to injury, irritation, & reaction of the body to injury, irritation, & infection]infection]

The hypothalamus triggers the secretion of The hypothalamus triggers the secretion of the pituitary SH for the adrenal cortex, in the pituitary SH for the adrenal cortex, in respond to: pain, injury, & emotions.respond to: pain, injury, & emotions.

These steroids have therapeutic use These steroids have therapeutic use because of their because of their antiinflammatoryantiinflammatory and and antiallergicantiallergic actions. actions.

They are used for various diseases, such They are used for various diseases, such as arthritis, asthma, and certain skin as arthritis, asthma, and certain skin diseases.diseases.

It is essential to know that steroids have It is essential to know that steroids have serious side effects on prolonged use.serious side effects on prolonged use.

SIDE EFFECTSSIDE EFFECTS DiabetogenicDiabetogenic: Due to their effect of : Due to their effect of

increasing blood sugar levels, prolonged increasing blood sugar levels, prolonged usage can lead to diabetes.usage can lead to diabetes.

HypertensionHypertension: Due to salt and water : Due to salt and water retention, the blood pressure rises.retention, the blood pressure rises.

Protein breakdownProtein breakdown: Leads to thinning of : Leads to thinning of skin, with skin, with bruisesbruises and and striaestriae..

Redistribution of fatRedistribution of fat: Leads to : Leads to characteristic appearance called characteristic appearance called buffalo buffalo humphump and and moon facemoon face..

OsteoporosisOsteoporosis: Since excess of steroids : Since excess of steroids causes softening and demineralization of causes softening and demineralization of the bones.the bones.

Poor wound healing and increased Poor wound healing and increased susceptibility to infections.susceptibility to infections.

Increase in facial hair and acne.Increase in facial hair and acne.

GONADSGONADS

Are the reproductive glands – the testes in Are the reproductive glands – the testes in males, and ovaries in female.males, and ovaries in female.

The 3 main hormones produced by the The 3 main hormones produced by the gonads are testosterone, estrogen, and gonads are testosterone, estrogen, and progesterone.progesterone.

Both men and woman have all 3 Both men and woman have all 3 hormones.hormones.

In men testosterone is predominant, In men testosterone is predominant, whereas in women estrogen and whereas in women estrogen and progesterone are mainly produced.progesterone are mainly produced.

Testosterone is concerned with Testosterone is concerned with development of the secondary sexual development of the secondary sexual characteristics in males (facial hair, characteristics in males (facial hair, deepening of the voice).deepening of the voice).

Estrogen has the same function Estrogen has the same function (development of secondary sexual (development of secondary sexual characteristics) in females.characteristics) in females.

Both estrogen and progesterone play a Both estrogen and progesterone play a role in menstruation and pregnancy.role in menstruation and pregnancy.

Estrogens are required for the development of ova and for the formation of the physical characteristics (secondary sex characteristics).

These characteristics include the development of the female reproductive system, the menstrual cycle begins, widening of the hips, and development of the breast. Puberty.

Progesterone prepares the uterus for the arrival of a developing embryo - or controls the menstrual cycle.

Male gonads or testes produce sperm, and sex hormones that affect cells throughout the body. Testes produce Androgens or the male sex hormone. It regulates male secondary sex characteristics.

Androgens: the development of physical (secondary sex) characteristics associated. Puberty. These characteristics include the growth of facial hair, increase in body size, and deepening of the voice.

PANCREAS Located in the abdominal cavity. It is not primarily an endocrine gland, the

main function being to produce digestive juices.

The hormone producing portion of the pancreas consists of clusters of cells that resemble islands, called islets of langerhans, function as an endocrine gland.

Each islet is composed of beta cells which secretes insulin, and alpha cells which secretes glucagon, both concerned with control of blood sugar levels.

These two hormones, insulin and glucagon regulate the metabolism of blood glucose (sugar) and the hormones have opposite effects. (Antagonistic hormones)

Insulin stimulates its target cells to take up and use glucose. This action lowers blood glucose levels.  "Use or store"

INSULININSULIN

A very important hormone.A very important hormone. It reduces the blood sugar level.It reduces the blood sugar level. It does this by causing sugar to enter the It does this by causing sugar to enter the

cells, and helping the cells to ‘burn’ the cells, and helping the cells to ‘burn’ the sugar in the blood, and convert it into sugar in the blood, and convert it into energy.energy.

Insufficiency of insulin results in Insufficiency of insulin results in Diabetes Mellitus in which the blood Diabetes Mellitus in which the blood sugar level is raisedsugar level is raised..

An increase in blood sugar level is strong An increase in blood sugar level is strong stimulus for insulin secretion.stimulus for insulin secretion.

GLUCAGONGLUCAGON

Raises blood sugar levels by increasing Raises blood sugar levels by increasing the breakdown of sugar stores in the liver.the breakdown of sugar stores in the liver.

Exercise, infections, and other stresses Exercise, infections, and other stresses stimulate the secretion of glucose.stimulate the secretion of glucose.

PINEAL GLANDPINEAL GLAND

Is a tiny gland (approx. 5-8 mm by 3-5 mm)Is a tiny gland (approx. 5-8 mm by 3-5 mm) This gland begins to stop functioning This gland begins to stop functioning

before puberty.before puberty. It secretes It secretes melatoninmelatonin, which is secreted in , which is secreted in

greater amounts in the dark.greater amounts in the dark. Melatonin is believed to inhibit gonadal Melatonin is believed to inhibit gonadal

development.development. The function of the pineal gland is still The function of the pineal gland is still

being investigated.being investigated.

THE PINEAL GLAND

Located near the base of the brain.

Secretes Melatonin.

Melatonin increases at night and decreases in the day. This cyclic release helps regulate sleep.

THYMUSTHYMUS The thymus gland is located beneath the

sternum (breastbone) and between the lungs.

The thymus produces cells (The thymus produces cells (lymphocyteslymphocytes/ / T-cells) which play a role in the body’s ) which play a role in the body’s defense. defense.

Secretes Thymosin, an amino acid based hormone that stimulates the formation of t-cells, which help defend the from pathogens.

Like the pineal gland, the thymus also starts Like the pineal gland, the thymus also starts to decrease in size around adolescence.to decrease in size around adolescence.

PROSTAGLANDINS1. PROSTAGLANDINS are a group of hormone-like lipids, that also regulate cell activities.

2. Unlike hormones, prostaglandins are NOT produced by specific endocrine glands.

3. They are produced in small quantities by many cells throughout the body.  They act locally.

4. Relaxation of Smooth Muscles that line the air passages and blood vessels, regulation of blood pressure, contraction of the intestinal walls and the uterus, and stimulation of the body's inflammatory response to infection.

DIGESTIVE ORGANS1. Endocrine cells within the walls of some

digestive organs also secrete a variety of hormones that help digest food.

2. When food is eaten, endocrine cells in the stomach lining secrete gastrin, a hormone that stimulates other stomach cells to release digestive enzymes and hydrochloric acid (HCL).

3. Endocrine cells of the small intestine release secretin, a hormone that stimulates the release of various digestive fluids from the pancreas and bile from the liver.

DIABETES MELLITUSDIABETES MELLITUS

TYPE I OR JUVENILE ONSET

Before age 25, little or no insulin production, requires a strict diet and daily injections of insulin.

TYPE II OR ADULT ONSET

After age 40, produce normal amounts of insulin, but cells are unable to respond properly because of lack of insulin receptors, can be controlled by diet.

11. HYPOGLYCEMIA

CAUSED BY EXCESS (HIGH) INSULIN OR LOW BLOOD SUGAR,

A Disorder in which Glucose is Stored rather than being properly delivered to the cells of the body – causing cells to starve to death. This leads to a lower blood glucose concentration and subsequent release of Glucagon and Epinephrine (Adrenaline).

Symptoms of hypoglycemia include Lethargy, Dizziness, Nervousness, Overactivity, and in extreme cases, Unconsciousness (Ketoacidosis or Diabetic Coma) and DEATH.

12. HYPERGLYCEMIA

CAUSED BY LOW INSULIN OR HIGH BLOOD SUGAR.

Can cause Nausea and Rapid Breathing, possibly leading to Oxygen Deficiency, Circulatory and Nervous System Failure, Diabetic Coma, or even Death.

STRESS & HEALTHA. Factors that serve as stressors to the

body produce stress and threaten homeostasis.

B. Types of Stress

Stress may be physical, psychological, or some combination of the two.

1. Physical stress threatens the survival of tissues, such as extreme cold, prolonged exercise, or infections.

2. Psychological stress results from real or perceived dangers, and includes feelings of anger, depression, fear, and grief; sometimes pleasant stimuli cause stress.

C. Response to Stress

1. Responses to stress are designed to maintain homeostasis.

2. The hypothalamus controls the general stress syndrome, which involves increased sympathetic activity and increased secretion of cortisol, glucagon, growth hormone, and antidiuretic hormone.

FEEDBACK MECHANISMS

The endocrine system uses feedback mechanisms to respond and adjust to changes that occur in and outside the body.  In a Feedback Mechanism, the last step in a series of events controls the first step.

HOMEOSTASISHOMEOSTASIS 1. HOMEOSTASIS is defined as a STABLE internal environment.

2. ANTAGONISTIC HORMONES have opposite effect on the body.

3. To maintain homeostasis, hormone secretions must be tightly regulated.

4. Most hormones are controlled by a FEEDBACK MECHANISM.

5. NEGATIVE FEEDBACK INHIBITS further release of the initial hormone.

6. POSITIVE FEEDBACK STIMULATES further release of the initial hormone.

Insulin

secretion

Blood glucose level decreases

Blood glucose level Increases

Glycogensecretion

NEGATIVE FEEDBACK MECHANISMSRegulating Hormone Release

1. Regulates the release of 30 Hormones.

2. Involves interactions of nervous, endocrine, and circulatory systems.

3. Involves hypothalamus and anterior pituitary

A Good Example is a Thermostat, AC, etc.

Summary of Endocrine Glands and their Functions

See previous chart: Hormones Secreted by the Pituitary Gland

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