Brief Endocrinology 2015. The Endocrine System Exocrine glands - transport their hormones to target...

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Brief Endocrinology 2015

Transcript of Brief Endocrinology 2015. The Endocrine System Exocrine glands - transport their hormones to target...

Page 1: Brief Endocrinology 2015. The Endocrine System Exocrine glands - transport their hormones to target tissues via ducts. Endocrine Are ductless & secrete.

Brief Endocrinology

2015

Page 2: Brief Endocrinology 2015. The Endocrine System Exocrine glands - transport their hormones to target tissues via ducts. Endocrine Are ductless & secrete.

The Endocrine System

• Exocrine glands - transport their hormones to target tissues via ducts.

• Endocrine• Are ductless &

secrete hormones into bloodstream

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Endocrine glands: are those glands that has no ducts so called (ductless) and secret its products (Hormones) directly to the blood as the thyroid and pituitary glands

The functions of the body are regulated by the nervous and the endocrine

system.

A hormone :-

A hormone is a chemical messenger, secreted from endocrine glands, released directly into the blood transported by the circulation to the tissues upon which they exert their effects and exerts a regulatory effect on the body cells

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Hormones•Hormones are made by the gland’s cells, possibly stored, then released

•Circulate throughout the body vasculature, fluids

•Influences only specific tissues:

•target cells that have a receptor for that particular hormone

•A hormone can have different effects on different target cells: depends on the receptor

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Target Cell

• A target cell is only a target cell

if it is has a functional receptor

(a protein) for the hormone.

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What is a “receptor”?• It is a protein made by the target cell (protein

synthesis after gene expression)

• The protein is made, then inserted into plasma

membrane, or found in cytoplasm or

nucleoplasm

• The active site on the protein “fits” the hormone

• Acts to convert the signal into a response

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Chemical characteristics of hormones

• 1-Proteins and Polypeptides, including hormones secreted by the anterior and posterior pituitary gland, the pancreas (insulin and glucagon), the parathyroid gland (parathyroid hormone), and many others.

• 2- . Steroids hormones:-are derived mainly from cholesterol secreted by the adrenal cortex (cortisol and aldosterone), the ovaries (estrogen and progesterone), the testes (testosterone), and the placenta (estrogen and progesterone

• 3-. Derivatives of the amino acid

• Tyrosine, secreted by the thyroid (thyroxine and triiodothyronine) and the adrenal medullae (epinephrine and norepinephrine)

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Regulation of hormone secretion

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Regulation & Communication

Nervous system •System of neurons transmits “electrical” signal to target tissue• release neurotransmitters into a

synapse, affecting postsynaptic cells

Endocrine system• The collection of endocrine glands

makes up the endocrine system.• Glands release hormones into the

blood stream to target cells

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Comparison between endocrine and nervous systems

1. Nervous system

2. “wired”3. Chemical

signal at target cell

4. Rapid5. Brief

duration

1.Endocrine system

2.“Wireless”3.Chemical

signal at target cell

4.Slow5.Long

duration

Page 11: Brief Endocrinology 2015. The Endocrine System Exocrine glands - transport their hormones to target tissues via ducts. Endocrine Are ductless & secrete.

Functional Classification of hormones•Trophic hormone: Acts on another endocrine gland to

stimulate secretion of its hormone. Called trophic hormones; ‘trophic’ means “feed”.

•For example, thyrotropin, or thyroid-stimulating hormone (TSH), stimulates the secretion of thyroid hormones. Adrenocorticotropin, or

adrenocorticotropic hormone (ACTH), stimulates the adrenal cortex to secrete the hormone cortisol. Both trophic hormones are produced by

the pituitary gland; in fact, many trophic hormones are secreted by the pituitary. The pituitary gland is sometimes referred to as the “Master gland” because its hormones regulate the activity of other endocrine

glands.•Nontrophic hormone: Acts on nonendocrine target tissues. For

example, parathormone released from the parathyroid glands acts on bone tissue to stimulate the release of calcium into the blood.

Aldosterone released from the cortical region of the adrenal glands acts on the kidney to stimulate the reabsorption of sodium into the blood.

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Major Endocrine Glands1. Hypothalamus2. Pituitary Gland3. Thyroid Gland4. Parathyroid Glands5. Thymus Gland6. Adrenal Glands 7. Pancreas8. Ovaries9. Testes10. Pineal Gland 12

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Major endocrine glands in the body

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•Hypothalamus is located at the base of the brain. It controls the autonomic nervous system and the endocrine systems. The hypothalamus controls the endocrine system by controlling the pituitary gland. Secretes releasing hormones to cause the pituitary to release its hormones andSecretes inhibiting hormones to turn off secretion of pituitary hormones

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Hypothalamus Hormones• Growth Hormone Releasing Hormone (GH-RH) stimulate GH secretion

• Prolactin Releasing Hormone (PRL-RH) stimulate PRL secretion

• Thyroid Stimulating Hormone Releasing Hormone (TSH-RH) stimulate TSH

secretion

• Adrenocorticotropic Hormone Releasing Hormone (ACTH-RH) stimulate ACTH

secretion

• Melanocyte Stimulating Hormone Releasing Hormone (MSH-RH) stimulate MSH

secretion

• Follicle Stimulating Hormone Releasing Hormone (FSH-RH) stimulate FSH

secretion

• Luteinizing Hormone Releasing Hormone (LH-RH) stimulate LH secretion

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The Adenhypophysis•Growth hormone (GH) Causes the body to grow

•Prolactin (PRL): Stimulates lactation (milk production) in females

–Stimulated lacrimation (desire to cry) , Decreased in adolescent males so it decreases desire to cry

•Thyroid Stimulating Hormone (TSH): Causes the thyroid gland to release thyroid hormone

•Adrenocorticotropic hormone (ACTH) :Acts on adrenal cortex to stimulate the release of cortisol ,Helps people cope with stress

•Melanocyte-stimulating hormone (MSH):Darkens skin pigmentation

–Increases during pregnancy: Also has effects on appetite and sexual arousal

•Follicle-stimulating hormone (FSH) :Present in males and females, affects both, Stimulates maturation of sex cells

•Luteinizing hormone (LH) :Induces ovulation in females–Induces testosterone in males 17

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Two divisions:

• Anterior pituitary(adenohypophysis)

• Posterior pituitary(neurohypophysis)

Sits in hypophyseal fossa: depression in sella turcica of sphenoid bone

Pituitary secretes 9 hormonesThe Pituitary

1. TSH2. ACTH3. FSH4. LH5. GH6. PRL7. MSH

8. ADH (antidiuretic hormone), or vasopressin9. Oxytocin

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The first four are “tropic” hormones, they regulate the function of other hormones

________

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Hormones secreted by the pituitary gland

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Anterior pituitary hormonesAnterior pituitary hormones

FSH & LH GH

Anterior Pituitary

GonadsThyroid gland

Mammary glands

Adrenal cortex

TSH Prolactin ACTH

+ + + +

Most tissues

+

protein synthesis;

Lipolysis; &

blood glucose

+ T4;

+ T3

+ thyroid

growth

+ milk;

+ breast dvlp.

regulate ♂

reproductive

system

glucocorticoids estrogen;

progeterone;

+ testosterone

+ gametes; + ovulation;

+ corpus Lut.

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The Neurohypophysis

• This is a continuation of the brain; cell bodies of special

neurons in the hypothalamus have axons which go to

the neurohypophysis and synapse on capillaries there.

Instead of releasing neurotransmitter, they release

hormones.

• Oxytocin: Childbirth contractions, milk letdown

• Antidiuretic hormone (ADH)

– Signals kidneys to increase water reabsorption

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Humoral Stimulation• Something in the blood is being monitored. When the level of

that substance is too high or low, it stimulates the release of the hormone.

• Examples are insulin, glucagon, parathyroid hormone, and aldosterone.

• When you eat, glucose gets high, releases insulin, which tells cells to take in the sugar. Excess sugar is then converted to glycogen, which is the storage form.

• When glucose is low, glucagon is released, glycogen is broken back down to glucose and released into the blood.

• When blood calcium is low, parathyroid gland hormone tells the intestinal cells to absorb more calcium, and kidneys to reabsorb more Ca++, and stimulates osteoclasts to degrade bone matrix so calcium goes into blood.

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Neuronal Stimulation• Examples are oxytocin, ADH (neurohypophysis

hormones) and Epinephrine (adrenal medulla hormone)

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Hormonal Stimulation • This is when one endocrine gland releases a

hormone that stimulates another endocrine gland to release its hormone.

• Examples are any of the hypothalamus or anterior pituitary hormones, and also the adrenal cortex (steroid) hormones (except aldosterone) and thyroid hormone.

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Hormonal regulation of hormone secretion

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• Short feedback loop:– Retrograde transport of blood from anterior pituitary to the hypothalamus.

• Hormone released by gonads (estrogen) inhibits anterior pituitary hormone FSH.

• Long feedback loop– Hormone released by gonads (Testosteronee) inhibits anterior

hypothalamic hormone as GnRH

Negative feed back: a hormone from a peripheral

gland, for example, testosterone binds to its receptor on

cells in the hypothalamus and pituitary gland, and inhibit the

secretion of the tropic hormones: FSH

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Positive feed back: a hormone from a peripheral gland, for example, estrogen, binds to its receptor on cells in the hypothalamus and adenohypophysis, and has the effect of increasing secretion of tropic hormones LH