Endocrine System

Function• Working with nervous system, endocrine

system coordinates and directs activity of body’s cells• Uses chemical messengers called hormones to

regulate and maintain body’s homeostasis

Major Organs1. Pineal2. Hypothalamus3. Pituitary 4. Thyroid5. Parathyroid6. Thymus7. Adrenal 8. Pancreas9. Gonads (Ovaries & Testes)

Pineal Gland• Found in epithalamus in brain• Hormone: Melatonin• Representative Actions: Involved in

sleep/wake patterns (daily and seasonal)• Regulated By: Light/dark cycles

Hypothalamus• Part of brain that controls pituitary gland• Hormones released by posterior pituitary;

releasing and inhibiting hormones that regulate anterior pituitary

Pituitary Gland: Posterior Lobe• Hormone: Oxytocin• Representative Actions: Stimulated contraction

of uterus and milk “letdown” reflex• Regulated By: Nervous system (hypothalamus)

in response to uterine stretching and/or suckling of baby

Pituitary Gland: Posterior Lobe• Hormone: Antidiuretic hormone (ADH)• Representative Actions: Promotes retention of

water by kidneys• Regulated By: Hypothalamus in response to

water/salt imbalance

Pituitary Gland: Anterior Lobe• Hormone: Growth hormone (GH)• Representative Actions: Stimulated growth

(especially of bones and muscles) and metabolism• Regulated By: Hypothalamic releasing and

inhibiting hormones

Pituitary Gland: Anterior Lobe• Hormone: Prolactin (PRL)• Representative Actions: Stimulates milk

production• Regulated By: Hypothalamic hormones

Pituitary Gland: Anterior Lobe• Hormone: Follicle-stimulating hormone (FSH)• Representative Actions: Stimulates production

of ova and sperm• Regulated By: Hypothalamic hormones

Pituitary Gland: Anterior Lobe• Hormone: Luteinizing hormone (LH)• Representative Actions: Stimulates ovaries and testes• Regulated By: Hypothalamic

hormones

Pituitary Gland: Anterior Lobe• Hormone: Thyroid-stimulating hormones (TSH)• Representative Actions: Stimulates thyroid

gland• Regulated By: Thyroxine in blood; hypothalamic

hormones

Pituitary Gland: Anterior Lobe• Hormone: Adrenocorticotropic hormone (ACTH)• Representative Actions: Stimulates adrenal

cortex to secrete glucocorticoids• Regulated By: Glucocorticoids; hypothalamic

hormones

Thyroid Gland• Hormone: Thyroxine (T4) and triodothyronine (T3)• Representative Actions: Stimulates metabolism• Regulated By: TSH

Thyroid Gland• Hormone: Calcitonin• Representative Actions: Reduces blood calcium

level• Regulated By: Calcium level in blood

Parathyroid Glands• Hormone: Parathyroid hormone (PTH)• Representative Actions: Raises blood calcium

level• Regulated By: Calcium level in blood

Thymus• Hormone: Thymosin• Representative Actions: “Programs” T cells• Regulated By: Not known

Adrenal Glands: Adrenal Medulla• Hormone: Epinephrine and Norepinephrine• Representative Actions: Increase blood glucose;

increase rate of metabolism; constrict certain blood vessels• Regulated By: Nervous system (sympathetic

division)

Adrenal Glands: Adrenal Cortex• Hormone: Glucocorticoids• Representative Actions: Increase blood glucose• Regulated By: ACTH

Adrenal Glands: Adrenal Cortex• Hormone: Mineralocorticoids• Representative Actions: Promote reabsorption

of Na+ and excretion of K+ in kidneys• Regulated By: Changes in blood volume or

blood pressure; K+ or Na+ levels in blood

Pancreas• Hormone: Insulin• Representative Actions: Reduces blood glucose• Regulated By: Glucose level in blood

Pancreas• Hormone: Glucagon• Representative Actions: Raises blood glucose• Regulated By: Glucose level in blood

Gonads: Testes• Hormone: Androgens• Representative Actions:

Support sperm formation; development and maintenance of male secondary sex characteristics• Regulated By: FSH and LH

Gonads: Ovaries• Hormone: Estrogens• Representative Actions:

Stimulate uterine lining growth; development and maintenance of female secondary sex characteristics• Regulated By: FSH and

LH

Gonads: Ovaries• Hormone: Progesterone• Representative Actions: Promotes growth of

uterine lining• Regulated By: FSH and LH