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Essentials of Anatomy & Physiology

Fifth edition

Seeley • Stephens • Tate

Chapter 10

The Endocrine System

PAUL E. MANAIG,MD

1.1. Water balanceWater balance2.2. Uterine contractionUterine contraction3.3. Growth, metabolism, and milk secretionGrowth, metabolism, and milk secretion4.4. Ion regulationIon regulation5.5. Heart rate and blood pressure Heart rate and blood pressure

regulationregulation6.6. Blood glucose controlBlood glucose control7.7. Immune system regulationImmune system regulation8.8. Reproductive function controlReproductive function control

Chemical signalsChemical signalsChemical signalsChemical signalsChemical signals or Ligands

- Molecules released from one location that move to another location to produce a response.

Intracellular response – produces from one part of a cell and travel to another part of the SAME cell

Autocrine ParacrineNeuromodulators Pheromones

ReceptorsReceptorsReceptorsReceptorsChemical signals bind to proteins

and glycoproteins (RECEPTORS)Specificity – Tendency for each

receptor site to bind to a specific chemical signal and not the others.

Membrane-bound Membrane-bound receptorsreceptors

Extend across the cell Extend across the cell membrane, with their membrane, with their receptor sites outside receptor sites outside the surface of the cell the surface of the cell membranemembrane

Responds to chemical Responds to chemical signals that are large, signals that are large, and water-solubleand water-soluble

Intracellular receptorsIntracellular receptorsChemical signals Chemical signals

DIFFUSES and bind to DIFFUSES and bind to the intracellular the intracellular receptor located at the receptor located at the cytoplasm or nucleuscytoplasm or nucleus

Hormones are distributed in the blood to all parts of the body, but only its corresponding target tissue respond to each type of hormone

Influences target cells by chemically binding to their receptors.

2,000-100,000 receptors for a particular hormone Hormones that pass in the blood and act on distant

cells are called Circulating hormones or ENDOCRINE PARACRINE - Hormones that act on neighboring cells AUTOCRINE – Acts on the same cell Local hormones usually are inactivated quickly

HormonesHormonesHormonesHormones

Pituitary and Pituitary and HypothalamusHypothalamusPituitary and Pituitary and

HypothalamusHypothalamus

Pituitary gland / HypophysisPituitary gland / Hypophysis – – Small gland about the size of peaSmall gland about the size of pea Rest in the depression of sphenoid bone Rest in the depression of sphenoid bone

inferior to the hypothalamus of the inferior to the hypothalamus of the brain.brain.

Infundibulum – Stalk connecting the Infundibulum – Stalk connecting the pituitary gland to the hypothalamuspituitary gland to the hypothalamus

Once known as Once known as “Master Gland”“Master Gland”

Pituitary and HypothalamusPituitary and HypothalamusPituitary and HypothalamusPituitary and Hypothalamus

1. Growth hormone2. Thyroid-Stimulating Hormone (TSH)3. Adrenocorticotropic Hormone (ACTH)4. Gonadotropins

a. Leutinizing hormone (LH)b. Interstitial Cell-stimulating hormone

(ISCH)5. Prolactin6. Melanocyte-Stimulating Hormone

Hormones of the Anterior PituitaryHormones of the Anterior PituitaryHormones of the Anterior PituitaryHormones of the Anterior Pituitary

1. Growth Hormone1. Growth HormoneStimulates the growth of bones, muscles, and other Stimulates the growth of bones, muscles, and other

organs by increasing protein synthesis.organs by increasing protein synthesis.Resist protein breakdown during periods of food Resist protein breakdown during periods of food

deprivationdeprivationSecretion of growth hormone is controlled by 2 hormones Secretion of growth hormone is controlled by 2 hormones

from the hypothalamus (releasing and inhibitory hormone)from the hypothalamus (releasing and inhibitory hormone)Daily peak levels during sleep, also increases during Daily peak levels during sleep, also increases during

fasting and exercisefasting and exerciseDwarfismDwarfismGigantismGigantism

• In gigantism - ACROMEGALY - facial features and hands become abnormally large

• Somatomedins – Protein chemical signal which together with Growth hormone to bind to the receptors of bone and cartilage tissues to stimulate growth

2. Thyroid-Stimulating Hormone 2. Thyroid-Stimulating Hormone (TSH)(TSH)

Binds on Membrane-bound receptors Binds on Membrane-bound receptors of the of the thyroid glandthyroid gland, causes to , causes to secrete thyroid hormones.secrete thyroid hormones.

↑↑ TSH- Thyroid gland enlargesTSH- Thyroid gland enlarges

3. Adrenocorticotropic Hormone (ACTH)3. Adrenocorticotropic Hormone (ACTH)Binds on Membrane-bound receptors on the Binds on Membrane-bound receptors on the

cells in cells in cortex of adrenal glandscortex of adrenal glands.. Increases secretion of Cortisol Increases secretion of Cortisol

( hydrocortisone), which keeps the adrenal ( hydrocortisone), which keeps the adrenal cortex from degeneratingcortex from degenerating

Binds to melanocytes and increase skin Binds to melanocytes and increase skin pigmentation.pigmentation.

↑ ↑ ACTH - Darkening of the skinACTH - Darkening of the skin

4. Gonadotropins4. GonadotropinsLeutinizing hormone (LH)Leutinizing hormone (LH)Interstitial Cell-stimulating hormone Interstitial Cell-stimulating hormone (ISCH)(ISCH)Binds on Membrane-bound receptors of the Binds on Membrane-bound receptors of the

gonadsgonads. Regulates growth, development and . Regulates growth, development and of functions of gonadsof functions of gonads

Leutinizing hormone (LH) – Ovulation of oocytes Leutinizing hormone (LH) – Ovulation of oocytes and the secretion of estrogen and and the secretion of estrogen and progesterone from ovariesprogesterone from ovaries

Interstitial Cell-stimulating hormone (ISCH) – Interstitial Cell-stimulating hormone (ISCH) – stimulates interstitial cells of the testes to stimulates interstitial cells of the testes to secrete testosterone.secrete testosterone.

Follicle-Stimulating Hormone – Stimulates Follicle-Stimulating Hormone – Stimulates the development of follicles in the the development of follicles in the ovaries and sperm cells in the testes.ovaries and sperm cells in the testes.

5. Prolactin5. ProlactinBinds on Membrane-bound receptors in the Binds on Membrane-bound receptors in the

cells of the cells of the BreastBreast, during pregnancy and , during pregnancy and stimulates the production of milk.stimulates the production of milk.

6. Melanocyte-Stimulating 6. Melanocyte-Stimulating HormoneHormoneBinds on Membrane-bound receptors on Binds on Membrane-bound receptors on

melanocytes and causes them tomelanocytes and causes them to

synthesize melanin.synthesize melanin.

↑ ↑ ACTH - Darkening of the skinACTH - Darkening of the skin

1. Antidiuretic hormone (ADH)1. Antidiuretic hormone (ADH)Binds to Membrane-bound receptors and Binds to Membrane-bound receptors and

increases water reabsorption by kidney increases water reabsorption by kidney tubules. Resulting to less water lost in urine.tubules. Resulting to less water lost in urine.

Can cause blood vessels to constrict Can cause blood vessels to constrict (vasopressin)(vasopressin)

Hormones of the Posterior PituitaryHormones of the Posterior PituitaryHormones of the Posterior PituitaryHormones of the Posterior Pituitary

2. Oxytoxin2. Oxytoxin

Binds on Membrane-bound Binds on Membrane-bound receptors and causes Uterine receptors and causes Uterine contraction and milk ejection contraction and milk ejection (milk let-down)(milk let-down)

• Made up of 2 lobes connected by the isthmus

• Located on either side of trachea, just below the larynx

• Largest endocrine gland• Thyroid follicles – small spheres with walls

that consist of simple cuboidal epithelium• Each follicle is filled with protein to which

thyroid hormones attached.

Thyroid GlandThyroid GlandThyroid GlandThyroid Gland

Thyroid HormonesThyroid HormonesBinds to intracellular receptors in cells and regulate Binds to intracellular receptors in cells and regulate

the rate of metabolism in the body.the rate of metabolism in the body.Participates in normal rate of growth and Participates in normal rate of growth and

development.development.HypothyroidismHypothyroidismInfants – Cretinism - Mentally retarded and short in Infants – Cretinism - Mentally retarded and short in

stature, with abnormally formed skeletal structures.stature, with abnormally formed skeletal structures.Adults – reduced rate of metabolismAdults – reduced rate of metabolismsluggishness, reduced ability to perform sluggishness, reduced ability to perform routine task.routine task.

HyperthyroidismHyperthyroidism

Elevated rate of metabolism, extreme Elevated rate of metabolism, extreme nervousness, and chronic fatigue.nervousness, and chronic fatigue.

Grave’s disease – bulging of the eyes Grave’s disease – bulging of the eyes (exopthalmia).(exopthalmia).

Thyroid gland requires iodine to synthesize Thyroid gland requires iodine to synthesize thyroid hormone.thyroid hormone.

Iodine is taken up by thyroid follicles, hormone Iodine is taken up by thyroid follicles, hormone synthesissynthesis

Thyroxine / tetraiodothyronine (T4)Thyroxine / tetraiodothyronine (T4)

Triiodothyronine (T3)Triiodothyronine (T3)

Lack of iodine results in reduced T3Lack of iodine results in reduced T3

and T4 synthesisand T4 synthesis

Para-thyroid GlandPara-thyroid GlandPara-thyroid GlandPara-thyroid Gland• Embedded in posterior wall of the thyroid glandEmbedded in posterior wall of the thyroid gland• Secretes parathyroid hormone (PTH)Secretes parathyroid hormone (PTH)

– Regulation of blood calciumRegulation of blood calcium– Increases the absorption of Ca+ from the Increases the absorption of Ca+ from the

intestine by causing an increase in active vitamin intestine by causing an increase in active vitamin D formationD formation

HyperparathyroidismHyperparathyroidismElevated Blood Ca+ results in nerve and muscle Elevated Blood Ca+ results in nerve and muscle

less excitable, resulting in fatigue and muscle less excitable, resulting in fatigue and muscle weaknessweakness

HypoparathryroidismHypoparathryroidismReduced Vitamin D formation. Nerves and muscles Reduced Vitamin D formation. Nerves and muscles become more excitable and produce spontaneous become more excitable and produce spontaneous action potential. Frequent muscle cramps or action potential. Frequent muscle cramps or

tetanustetanus

Hyperparathyroidism Hyperparathyroidism

Bones become soft, Bones become soft, deformed and easily deformed and easily fracturedfractured

1. Adrenal Medulla – Inner part1. Epinephrine (adrenaline)2. Norephinephrine

2. Adrenal Cortex – Outer part

Adrenal GlandsAdrenal GlandsAdrenal GlandsAdrenal Glands

Adrenal Medulla –Adrenal Medulla – Inner part (narrow or Inner part (narrow or middle)middle)

Secretes Epinephrine (adrenaline) and Secretes Epinephrine (adrenaline) and small amounts of Norephinephrinesmall amounts of Norephinephrine

Released in response to stimulation of Released in response to stimulation of Sympathetic nervous systemSympathetic nervous system

Fight or Flight hormonesFight or Flight hormones

Fig. 10.18

• Endocrine part consist of pancreatic islets Endocrine part consist of pancreatic islets a.k.a. “Islets of Langerhans” – has two a.k.a. “Islets of Langerhans” – has two types of cells.types of cells.

• Alpha cells – secrete glucagonAlpha cells – secrete glucagon• Beta cells – secrete insulinBeta cells – secrete insulin• A decline in the blood glucose below the A decline in the blood glucose below the

normal range causes the nervous system tonormal range causes the nervous system tomalfunction (Glucose is the Nervousmalfunction (Glucose is the Nervoussystem’s main source of energy)system’s main source of energy)

Pancreas, Insulin, DiabetesPancreas, Insulin, DiabetesPancreas, Insulin, DiabetesPancreas, Insulin, Diabetes

InsulinInsulin – Released in response the elevated – Released in response the elevated blood glucose levels and increased blood glucose levels and increased sympathetic stimulation.sympathetic stimulation.

• The major target of insulin are the liver, The major target of insulin are the liver, adipose tissue, muscles, and the area of adipose tissue, muscles, and the area of the hypothalamus that controls the the hypothalamus that controls the appetite, satiety center.appetite, satiety center.

Diabetes Mellitus – Diabetes Mellitus – Result from: (1) secretion Result from: (1) secretion of too little insulin from pancreas, (2) of too little insulin from pancreas, (2) Insufficient numbers of insulin receptors on Insufficient numbers of insulin receptors on target cells, and (3) defective receptors target cells, and (3) defective receptors that do not respond normally to insulin.that do not respond normally to insulin.

Triad of Diabetes MellitusTriad of Diabetes Mellitus1.1. Polyuria - Polyuria - ↑ urination↑ urination2.2. Polyphagia - Polyphagia - ↑ food intake↑ food intake3.3. Polydypsia - Polydypsia - ↑ water intake↑ water intake

(Diabetes Mellitus)(Diabetes Mellitus)Hyperglycemia- Tissues cannot take up glucose Hyperglycemia- Tissues cannot take up glucose

effectively, causing blood glucose to become effectively, causing blood glucose to become very high.very high.

Polyphagia – Glucose cannot enter cells of the Polyphagia – Glucose cannot enter cells of the satiety center of the brain without insulin, the satiety center of the brain without insulin, the brain responds as if there were little blood brain responds as if there were little blood glucose, resulting in exaggerated appetite.glucose, resulting in exaggerated appetite.

Polyuria – Excess of glucose in the blood is Polyuria – Excess of glucose in the blood is excreted in the urine, thus…excreted in the urine, thus…

Polydypsia – Because of polyuria, the personPolydypsia – Because of polyuria, the personbecomes dehydrated and thirsty, thus becomes dehydrated and thirsty, thus the need to drink often.the need to drink often.

Testosterone Testosterone – Main sex hormone in – Main sex hormone in malemale

Responsible for the growth and Responsible for the growth and development of male reproductive development of male reproductive structures, muscle enlargement, structures, muscle enlargement, growth of body hair, voice changes growth of body hair, voice changes and male sexual drives.and male sexual drives.

Testes and OvariesTestes and OvariesTestes and OvariesTestes and Ovaries

Estrogen & ProgesteroneEstrogen & Progesterone• Development of female reproductive Development of female reproductive

structures and sexual characteristicsstructures and sexual characteristics• Enlarges the breast and distribute fat, Enlarges the breast and distribute fat,

which influences the shape of the hips, which influences the shape of the hips, breast, and thighs.breast, and thighs.

• Maintains menstrual cycleMaintains menstrual cycle

• Lies at the upper part of the thoracic Lies at the upper part of the thoracic cavitycavity

• Plays an important role in immune Plays an important role in immune systemsystem

• Thymosin – Helps in the development of Thymosin – Helps in the development of T-Cells (helps protect the body against T-Cells (helps protect the body against infection by foreign organism)infection by foreign organism)

• Most important in early life.Most important in early life.

Thymus GlandThymus GlandThymus GlandThymus Gland

• Small pinecone-shaped structure located Small pinecone-shaped structure located superior and posterior to the thalamus superior and posterior to the thalamus of the brain.of the brain.

• Melatonin – decrease secretion of LH Melatonin – decrease secretion of LH and FSH by decreasing release of and FSH by decreasing release of hypothalamic-releasing hormones. Acts hypothalamic-releasing hormones. Acts to inhibit reproductive systemto inhibit reproductive system

Pineal BodyPineal BodyPineal BodyPineal Body

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