Ch10 Endocrine System 7e 13

7/29/2019 Ch10 Endocrine System 7e 13

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The Endocrine System

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Lecture Outline


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Endocrine Glands

o Endocrine glands are ductlesso Secrete hormones

Chemical signals that influence:

Metabolism Growth and development

Homeostasis

Categories of hormones

Peptides (proteins, glycoproteins, andmodified amino acids) most hormones

Steroid hormones


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Table 10.1 cont


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Endocrine Glands

o How Hormones Function Second messenger system

Peptide hormone binds to a receptorprotein on the plasma membrane

Peptide hormone (first messenger)activates a second messenger (cyclicAMP and calcium)

Second messenger sets in motion anenzyme cascade that leads to a cellularresponse

Change in cellular behavior

Formation of an end product that leaves the cell


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Fig. 10.2 Actionof a peptide

hormone


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Animation: How Intracellular ReceptorsRegulate Gene Transcription


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Endocrine Glands

Intracellular mechanism of hormonefunction

Steroid hormones (lipids) diffuse acrossthe plasma membrane

Once inside the cell, steroid hormonesbind to receptor proteins

Hormone-receptor complex binds to DNA,activating particular genes

Gene activation leads to production ofcellular enzymes that cause cellularchanges


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Fig. 10.3 Action ofa steroid hormone


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Animation: Mechanism of Steroid HormoneAction


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Endocrine Glands

o Hormone Control Many hormones affect concentrations of

certain substances in the blood

Other hormones are involved in normal

function of various organs Release of hormones controlled by one or

more of the following:

The nervous system

The action of other hormones Glands response directly when change in the

internal environment (humoral stimulus)

Negative feedback mechanisms


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Control of Hormonal Secretions

primarily controlled by negative feedback mechanism


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Hypothalamus and Pituitary Gland

o Hypothalamus Controls secretions of the pituitary

gland

Neurosecretory cells produce Antidiuretic hormone (ADH)

Oxytocin


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Pituitary Gland Control

Hypothalamic releasing hormones stimulate cells ofanterior pituitary to release hormones

Nerve impulses from hypothalamus stimulate nerveendings in the posterior pituitary gland to release hormones


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o Posterior pituitary Stores hypothalamic hormones antidiuretic

hormone (ADH) and oxytocin

ADH (vasopressin)

Released when neurons in the hypothalamusdetect that the blood is too concentrated with salt

Causes more water to be reabsorbed into kidneycapillaries

Raises blood pressure by vasoconstriction of blood

vessels Diabetes insipidus results from the inability to

produce ADH


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Regulation of ADH

Neurons in Hypothalamus

(nervous control)

Posterior Pituitary Gland releases

Antidiuretic Hormone

Kidney Blood vessels

Reabsorption of

water

-Vasoconstriction of blood

vessels

-Increase blood pressure

Blood is concentrated with salt /low blood pressure

Negative

Feedback

Mechanism


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Animation: Hormonal Communication


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Oxytocin

Causes uterine contraction during childbirth

Causes milk letdown when a baby is nursing

Release of oxytocin is controlled by positivefeedback


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o Anterior pituitary Controlled by hypothalamic hormones

Produces hormones that affect other

glands Thyroid-stimulating hormone (TSH)

Adrenocorticotropic hormone (ACTH)

Gonadotropic hormones

Produce hormones that do not affectthe endocrine system

Prolactin (PRL)

Growth hormone (GH)


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Fig 10.4


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Effects of growth hormone Affects the height of an individual

Pituitary dwarfism results if too little GHis produced during childhood

If too much GH is produced duringchildhood, a person can become a giant

Acromegaly results when too much GH issecreted in adulthood


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Thyroid and Parathyroid

o Thyroid Gland Two forms of thyroid hormone

Triiodothyronine (T3) contains 3 iodineatoms

Thyroxine (T4) contains 4 iodine atoms

Effects of thyroid hormone

Increase the metabolic rate

Stimulate all cells of the body


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Fig 10.4

(-)

()

()

(-)

Regulation of Thyroid Hormone Secretions

Thyrotropin- releasinghormone (TRH)

Thyroid-stimulatinghormone(TSH)

T3, T4


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Simple goiter

Often caused by alack of iodine

Thyroid enlarges in

response to constantstimulation by theanterior pituitary


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Congenital hypothyroidism Thyroid fails to develop

properly

Undersecretion of thyroidhormone

Individuals are short and

stocky Myxedema

Hypothyroidism in adults

Characterized by Lethargy

Weight gain

Loss of hair

Slower pulse rate

Lowered bodytemperature

Thick and puffy skin


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Hyperthyroidism (Graves Disease) Oversecretion of thyroid hormone

Exophthalmic goiter forms

Edema in eye socket tissues

Swelling of the muscles that move the eyes Symptoms include

Hyperactivity

Nervousness and irritability

Insomnia
https://courses.stu.qmul.ac.uk/SMD/kb/resources/endocrinologyresource/images/patgrave.jpg


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Calcitonin Helps control blood calcium levels

Secreted when the blood calcium levelsrise

Brings about the deposit of calcium in thebones


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o Parathyroid Glands

Posterior surface of the thyroid gland

Produces parathyroid hormone (PTH)

Causes blood phosphate (HPO42-) level to decrease

Causes blood calcium (Ca2+) level to increase

Promotes the release of calcium from the bones

Promotes the reabsorption of calcium by the kidneys

Activates vitamin D in the kidneys, which stimulates the

reabsorption of calcium from the intestines Hypocalcemic tetany results when there is insufficient

secretion of PTH


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Parathyroid Hormone

Mechanism by which PTH promotes calciumabsorption in the intestine


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Adrenal Glands

o Adrenal Medulla Inner portion

Under nervous control

Secretes epinephrine(adrenaline) andnorepinephrine(noradrenaline)

Causes fight or flightresponses

Provide a short-termresponse to stress


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Adrenal Glands

o Adrenal Cortex Outer portion 3 layers, each

produces a different set of hormones

Under the control of ACTH Hormones

Provide a long-term response to stress

Mineralcorticoids

Glucocorticoids Male and female sex hormones

Fig 10.10 Adrenal glands. Adrenal medulla & Adrenal cortex under control of the


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g ghypothalamus and respond to stress

Left: Adrenal medulla provides a rapid butshort-term stress response

Right: Adrenal cortex provides a slower but

long-term stress response


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Adrenal Glands

Glucocorticoids (cortisol) Raises the blood glucose level in at least

2 ways: Promotes the breakdown of muscle proteins to

amino acids which pass to the bloodstream.

Liver then converts excess amino acids toglucose.

Promotes the metabolism of fatty acids insteadof carbohydrates as spares glucose for thebrain

Counteracts the inflammatory responseand can relieve swelling and pain

Can also make a person susceptible toinjury and infection


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Adrenal Glands

Mineralcorticoids (aldosterone) Targets the kidney

Promotes renal absorption of sodium andwater

Promotes renal excretion of potassium Aldosterone secretion is controlled by:

ACTH (from anterior pituitary gland)

Renin-Angiotensin mechanism


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ACTH is not the primary controller foraldosterone secretion

Renin-Angiotensin mechanism stimulatesaldosterone secretion when the blood

sodium level and blood pressure are low Renin-Angiotensin-Aldosterone system

raises blood pressure in two ways:

Angiotensin II constricts arterioles

Aldosterone causes the kidneys to reabsorbsodium

Atrial natriuretic hormone (ANH) isantagonistic to aldosterone


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Adrenal Glands

Malfunction of the Adrenal Cortex Addison Disease

Hyposecretion of adrenal cortex hormones

Excessive (but ineffective) ACTH causesbronzing of the skin

Because glucose cannot be replenished withoutcortisol, individuals are susceptible to infection

Lack of aldosterone results in the developmentof low blood pressure and possibly severedehydration

Cushing Syndrome

Hypersecretion of adrenal cortex hormones

Tendency towards diabetes mellitus

Excess aldosterone leads to hypertension


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Pancreas

o Composed of two types of tissue Exocrine secretes digestive juices

Endocrine tissue (pancreatic islets orislets of Langerhans) produces:

Insulin Secreted when blood glucose level is high

Stimulates the uptake of glucose by most bodycells

Glucagon Secreted when blood glucose levels are low

Targets liver and adipose tissue

Stimulates liver to break down glycogen toglucose


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Pancreas

o Diabetes Mellitus Insulin-sensitive body cells are unable

to take up and/or metabolize glucose

Blood glucose level is elevated(hyperglycemia)

Symptoms:

Polyphagia extreme hunger

Glycosuria glucose in the urine Polyuria excessive water loss through

urine

Polydipsia extreme thirst


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Pancreas

Two forms of diabetes mellitus Type I insulin-dependent diabetes

mellitus

Pancreas does not produce insulin

Immune cells destroy the pancreatic islets Type II non-insulin-dependent diabetes

mellitus

Normal or elevated amounts of insulin arepresent in the blood

Receptors on the cells do not respond to insulin


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Other Endocrine Glands

o Testes and ovaries Testes produce androgens

(testosterone)

Ovaries produce estrogens andprogesterone

Secretion is controlled by thehypothalamus and the pituitary


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Androgens

Increased testosterone secretion duringpuberty stimulates the growth of thepenis and the testes

Brings about and maintains the male

secondary sex characteristics Facial, axillary, and pubic hair

Enlargement of larynx and the vocal cords

Muscular strength

Stimulates oil and sweat glands of theskin


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Estrogen and Progesterone

Required for breast development

Regulation of the uterine cycle

Estrogens

Stimulate the growth of the uterus and thevagina during puberty

Necessary for egg maturation

Responsible for secondary sex characteristics

- Female body hair

- Fat distribution


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o Thymus Gland Most active during childhood Transforms lymphocytes into thymus-

derived lymphocytes (T-lymphocytes)

Epithelial cells secrete hormonescalled thymosins

o Pineal Gland

Located in the brain Produces the hormone melatonin

Melatonin is involved in daily sleep-wake cycle


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o Hormones from Other Tissues Leptin Produced by adipose tissue

Signals satiety in hypothalamus

Growth Factors stimulate celldivision and mitosis

Granulocyte and macrophage colony-stimulating factor

Platelet-derived growth factor Epidermal growth factor and nerve

growth factor

Tumor angiogenesis factor


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Prostaglandins Potent chemical signals

Act locally

Some effects of prostaglandins include:

Uterine contractions Mediate the effects of pyrogens

Reduce gastric secretion

Lower blood pressure

Inhibit platelet aggregation

h f Ch l S l


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The Importance of Chemical Signals

o Cells and organs communicatewith one another using chemicalsignals

o Chemical signals betweenindividuals

Called pheromones

Humans produce airborne chemicalsfrom a variety of areas

Eff f A i


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Effects of Aging

o Thyroid disorders Hypothyroidism

Hyperthyroidism

o Diabetes

H t i


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Homeostasis

o The endocrine system and thenervous system work together tomaintain homeostasis

o The endocrine system helpsregulate the following:

Digestion

Fuel metabolism

Blood pressure and volume

Calcium balance

Response to the external environment

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Ch10 Endocrine System 7e 13

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