The endocrine system

What is an endocrine gland?

Endocrine: secretes substance into blood

Exocrine: secretes substance into a duct (ex: sweat)

ENDOCRINE GLANDS

1. PITUITARY GLAND

a. Growth Hormone (GH)

Hypersecretion = gigantism (children) or acromegaly (adults)

b. Prolactin (PRL) Stimulates milk production after

childbirth

c. Adrenocorticotropic hormone (ACTH)• Tropic hormone• Stimulates cortex of

adrenal gland

Hormones of adrenal cortex(corticosteroids)1. Mineral corticoids – regulate mineral content

of blood, like sodium and potassium

2. Glucocorticoids – regulate metabolism and resistance to stress

Ex: cortisone

3. Androgens (sex hormone)1. In puberty: stimulate axillary/pubic hair

growth/growth spurt 2. Insignificant effect in males after puberty3. In females: libido and converted into estrogens

d. Thyroid-stimulating hormone (TSH) Tropic hormone Growth & activity of thyroid gland:

– 1. Calcitonin (not influenced by TSH)• Decreases blood calcium levels by causing

calcium to be deposited in the bones.• Stimulus?• Target?

– 2. Thyroid hormone Controls rate at which glucose is “burned”

(oxidized) Targets every cell

What is a tropic hormone?

a. A synthetic (“man-made”) hormone

b. Hormones that affect the gonads

c. Hormones of the thyroid gland

d. A hormone that triggers another endocrine gland to secrete its hormones

e. Gonadotropic hormones - tropic hormones

a. function: regulate activity of gonads

b. types:

1. Follicle-stimulating hormone (FSH): egg/sperm development

2. Luteinizing hormone (LH): sex hormone synthesis; ovulation

f. Oxytocin- causes contractions for birth

g. Antidiuretic hormone (ADH) Diuresis = urine production causes kidneys to reabsorb

water from the forming urine stimulus? caffeine inhibits ADH

secretion

Which of the following is NOT a hormone secreted by the pituitary gland?a. Prolactin

b. Adrenocorticotropic hormone

c. Growth hormone

d. Calcitonin

What does sterility mean?

What effect would LH and FSH have on this?

summary

Pituitary gland – considered the “master” gland

We covered 7 hormones it produces Extra credit assignment: write a story

about a character that does not have a pituitary gland. Due: by the 11th (Monday)

POSTERIOR OF THYROID

2. PARATHYROID GLAND

2. PARATHYROID GLAND

Found posterior side of thyroid

1. Parathyroid hormone (PTH)• Regulator of calcium homeostasis in blood.• Responds to LOW levels of Ca2+

• targets the skeleton• Hyposecretion: muscles uncontrollably spasm

fatal• Hypersecretion: massive bone destruction

3. ADRENAL GLANDS

ADRENAL GLANDS: SUPERIOR TO KIDNEYS

Hormones of adrenal cortex(corticosteroids)1. Mineral corticoids – regulate mineral content of

blood, like sodium and potassium Ex: aldosterones

2. Glucocorticoids – regulate metabolism and resistance to stress

Ex: cortisone

3. Androgens (sex hormone)1. In puberty: stimulate axillary/pubic hair growth/growth

spurt 2. Insignificant effect in males after puberty3. In females: libido and converted into estrogens

SKIP

Problems with adrenal cortex Hyposecretion Addison’s disease, fatal without

treatment– Weight loss – Muscle weakness – Fatigue that gets worse over time – Low blood pressure – Patchy or dark skin

Hypersecretion of glucocorticoids Cushing’s syndrome, fatal without treatment

– Weight gain, particularly around your midsection and upper back

– Fatigue – Rounding of your face (moon face) – Fatty pad or hump between your shoulders (buffalo

hump) – Pink or purple stretch marks (striae) on the skin – High blood pressure, diabetes, bone loss

SKIP

Adrenal cortex – see pituitary notes

•adrenal medulla

a. Epinephrine

b. Norepinephrine

Augments fight-or-flight

4. PANCREAS

a. Insulin – • Responds to rising blood glucose levels• Hyposecretion high blood glucose levels ….

Diabetes mellitus (classic symptoms: polyuria (frequent urination), polydipsia (increased thirst) and polyphagia (increased hunger)

– Type I – failure to make insulin– Type 2 – insulin resistance– Gestational – during pregnancy

b. Glucagon• responds to low blood glucose levels.• target: liver

5. PINEAL GLAND

a. Melatonin- regulates day-night cycles

                                                                                       

                                                   

Taken on a strict schedule, melatonin can help reduce jet lag. (But was that West Coast or London time?)

Copyright 1997 Smithsonian Magazine All rights reserved.

6. THYMUS

Produces thymosin – regulates maturation of some white blood cells; important for immune system

7. GONADS

7A) OVARIES

1. Estrogens – • stimulate secondary sex characteristics in

females• brings about menstrual cycle

2. Progesterone- • brings about menstrual cycle. • quiets muscles of uterus during pregnancy

Hyposecretion of either: infertility

7b) Testes

1. Testosterone• cause growth and maturation of reproductive

system• secondary sex characteristics; sperm

production in adult • Hyposecretion = infertility

testes

                                                                                  

8. PLACENTA (Temporary organ)

1. human chorionic gonadotropin (hCG) – stimulates ovary to continue producing estrogen and progesterone

2. Estrogen & progesterone (3rd month)

3. Relaxin – relaxes pelvis

Aging and the endocrine glands

Late middle age: efficiency of ovaries begins to decline menopause

GH declines = muscles atrophy Mildly hypothyroid Less able to resist stress/infection (due to

thymus, glucocorticoids of adrenal and melatonin from pineal)

Some decline in insulin production diabetes

(not responsible for this slide)

How hormones work

2 categories of hormones– Soluble in lipids

• Most attached to transport protein in blood• Ex: Thyroid hormone, sex hormones

– Soluble in water• Travel by themselves in blood• Ex: epinephrine/norepinephrine, ADH, oxytocin,

GH, insulin

Lipid-soluble hormones: stimulate synthesis of new proteins

Diffuse through lipid bilayer (cell membrane)

Binds to receptors in cytoplasm or nucleus

Triggers gene on/off synthesis of new protein that alters the cell’s activity

VIDEO CLIP

MECHANISM OF ACTION OF LIPID-SOLUBLE HORMONES

Water-soluble hormones: modify existing proteins

Binds to receptor on cell membrane Activates G protein (membrane protein) that

eventually causes ATP to convert to cyclic AMP (the second messenger).

Cyclic AMP activates one/more protein kinases (enzyme that adds a phosphate group – phosphorylates – to other cellular proteins).

Phosphorylated proteins cause physiological response

Enzyme phosphodiesterase inactivates AMP

Water-soluble hormone action

Water-soluble hormone action