Endocrine System

Endocrine glands

secrete their hormones directly into bloodstream

Exocrine glands

send chemical substances via ducts to the outside of the body or within body cavities

9 Endocrine glands

thyroid, parathyroid (4), adrenal (1 pair), pancreas, pituitary, ovaries (1 pair), testes (1 pair), thymus gland, pineal gland

Endocrine tissue

body cells, gastrointestinal tract, kidney, placenta, skin

Hypersecretion

too much hormone produced from a diseased gland

Hyposecretion

too little hormone produced

Nonsteroid hormones

water soluble, first messenger, bind to receptors on target cell membrane, trigger release of second messengers to affect cell’s activities

Steroid hormones

lipid soluble, binds to receptors within target cell nucleus and influence cell activity by acting on DNA (slower process than nonsteroid)

Steroid hormones sencodary effect

may occur when steroid hormone bind to membrane receptors to rapidly trigger changes in target cell

Homeostatic feedback

controls hormone secretion

Negative feedback

mechanism that reverse the direction of a change in a physiological system (response to high glucose)

Positive feedback

mechanism that amplifies physiological changes (childbirth)

Prostaglandins (PGs)

powerful substances found in body tissue, aka tissue hormones (not true hormones), often produced in a tissue and diffuse a short distance

Thyroid function

3 hormones:
- thyroxine/tetraiodothyronine (T4), triiodothyronine (T3)
- aid in cells oxygen uptake, regulate metabolic rate
- calcitonin: stimulate calcium to leave blood and enter bone

Parathyroid function

parathyroid hormone (PTH): causes calcium to mobilize from bones into bloodstream

Adrenal glands (structure)

Adrenal cortex (outer)
Adrenal medulla (inner)

Adrenal cortex

secretes corticosteroids or steroids, chemicals derived from colesterol

Adrenal medulla

secretes catecholamines, chemicals derived from amino acids

Adrenal cortex hormones

Glucocorticoids (sugar): cortisol, cortisone
Mineralocorticoids (salts) : aldosterone
Sex hormones (sex): androgens and estrogen

Glucocorticoids

cortisol: influence metabolism of sugar, fats and proteins
cortisone: anti-inflammatory

Mineralocorticoids

aldosterone: regulate electrolytes, reabsorption of sodium/excretion of potassium

Sex hormones

Androgens (testosterone) and Estrogen: influence secondary sex characteristics

Adrenal medulla hormones

catecholamine hormones: sympathomimetic agents
- epinephrine: increases HR, BP, dilates bronchial tubes, releases glucose from storage
- norepinephrine: constricts vessels to raise BP

Pancreas

near/partially behind stomac, exocrine and endocrine organ

Pancreas Function

Endocrine function: islets of langerhans produce isulin and glucagon

Insulin

promotes movement of glucose into cells and storage as glycogen (lowers blood sugar)

Glucagon

promotes movement of glucose into blood by breaking down stored glycogen in liver cells (raises blood sugar)

Pituitary gland (hypophysis)

anterior lobe (adenohypophysis)
posterior lobe (neurohypophysis
hypothalamus controls secretions of pituitary via hormones

Anterior pituitary hormones

• growth hormone (GH)/Somatotropin (STH)

• thyroid-stimulating hormone (TSH)/thyrotropin

• Adrenocorticotropic hormone (ACTH)

• Gonadotropic hormones: follicle-stimulating hormone (FSH), luteinizing hormone (LH)

• prolactin (PRL)

Posterior pituitary hormones

store and release hormones synthesized in hypothalamus
antidiuretic hormone (ADH vasopressin), oxytocin (OT)

Adrenocorticotropic hormone (ACTH)/Adrenocorticotropin

stimulates adrenal cortex

Follicle-stimulating hormone (FSH)/Gonadotropin

stimulates ovaries and testes

Growth hormone (GH)/Somatotropin

stimulates growth

Thyroid-stimulating hormone (TSH)/thyrotropin

stimulates thyroid gland

Prolactin (PRL)

stimulates milk production

antidiuretic hormone (ADH)/vasopression

increases water reabsorption

Oxytocin

stimulates labor

Reproductive organs

Male: testes (testotesrone)
Female: ovaries (estrogen and progesterone)

testosterone

maintains sperm cell formation and secondary sexual characteristics

Estrogen and progesterone

maintains menstrual cycle, release of ovum, secondary sexual characteristics, preparation of uterus for pregnancy

Thymus

hormone is thymosin, plays important role in development and function of body’s immune system

Pineal gland

becomes fibrous and calcified with age, influences secretory activity related to the amount of light entering the eyes
secretes melatonin

Melatonin

inhibits ovarian activity, regulates body’s internal clock