Endocrine System (2)

ENDOCRINE

SYSTEM

ENDOCRINE

Secretions enter interstitial

fluid and then

bloodstream

Stay in the body: ENDO -

Examples: all hormones such

as growth hormone, insulin,

adrenalin, estrogen

EXOCRINE

Secrete substances that

enter ducts

Ultimately exit the body

(exo-)

Examples: mucus, saliva and

other digestive secretions,

sweat, tears

HORMONES

Intercellular chemical signals

“hormon” – set into motion

Lipid-soluble Steroids, such as testosterone, estrogens

Thyroid hormones: T3 and T4

Water-soluble Amino acid derivatives, such as epinephrine,

norepinephrine

Peptides: antidiuretic hormone (ADH), oxytocin

Proteins: insulin and growth hormone

ENDOCRINE GLANDS

PITUITARY GLAND

HYPOTHALAMUS AND PITUITARY

Hypothalamic cells synthesize

Many releasing and inhibiting hormones

Two hormones (oxytocin and ADH) that are then stored

and released from the posterior pituitary

Anterior pituitary synthesizes 7 hormones

Regulate growth, development, metabolism and

homeostasis

PITUITARY GLAND

PITUITARY GLAND

ANTERIOR PITUITARY

HORMONES

GROWTH HORMONE (GH)

CELLS Somatotropes

STRUCTURE Polypeptide

REGULATED BY • GH- releasing hormone (GHRH)

• Somatostatin (inhibiting hormone)

TARGET TISSUE Most tissues

FUNCTION • promotes growth of bone and cartilage

• increases protein synthesis

• promotes lipid breakdown to fatty acids

• increases blood glucose concentration

PROLACTIN

CELLS Lactotropes

STRUCTURE Protein

REGULATED BY • Prolactin – releasing

• Prolactin inhibitory factor (PIF)

TARGET TISSUE Female: ovary and mammary glands

Male: testis

FUNCTION • stimulates milk production and secretion

• prolongs progesterone secretion

• increases sensitivity to LH in males

ADRENOCORTICOTROPHIC

HORMONE (ACTH)

CELLS Corticotropes

STRUCTURE Polypeptide

REGULATED BY • Corticotropin releasing hormone (CRH)

TARGET TISSUE Adrenal cortex

FUNCTION • stimulates secretion of cortisol

• increases skin pigmentations at high conc

MELANOCYTE – STIMULATING

HORMONE

CELLS Corticotropes

STRUCTURE Protein

REGULATED BY • Prolactin – releasing

• Prolactin inhibitory factor (PIF)

TARGET TISSUE Mammary glands

FUNCTION • stimulates milk secretion

LUTEINIZING HORMONE (LH)

FOLLICLE STIMULATION HORMONE (FSH)

CELLS Gonadotropes

STRUCTURE Glycoproteins

REGULATED BY • Gonadotrohic releasing hormone (GnRH)

TARGET TISSUE Ovary and testis

FUNCTION • LH• promotes ovulation and progesterone production

• testosterone synthesis and support for sperm cell

production

• FSH• promotes follicle maturation and estrogen secretion

• sperm cell production

THYROID – STIMULATION HORMONE

CELLS Tyrotropes

STRUCTURE Glycoprotein

REGULATED BY • Thyrotropin – releasing hormone

TARGET TISSUE Thyroid gland

FUNCTION • increases thyroid hormone secretion

• Thyroxine

• Triiodothyronine

PITUITARY GLAND

POSTERIOR PITUITARY

HORMONES

ANTIDIURETIC HORMONE (ADH)

ORIGIN Hypothalamus (supraoptic nuclei)

STRUCTURE Peptides

REGULATED BY • Osmotic changes in blood (Na+)

TARGET TISSUE Kidneys

FUNCTION • promote reabsorption of water into the blood

circulation

• potent vasoconstrictor

OXYTOCIN

ORIGIN Hypothalamus (paraventricular nuclei)

STRUCTURE Polypeptides

REGULATED BY • sucking reflex communicated via

hypothalamus

TARGET TISSUE Uterus and mammary gland

FUNCTION • increase uterine contractions

• increases milk “let-down”

THYROID GLAND

THYROID GLAND

Structure and function

Follicular cells produce hormones and

store them in follicles Thyroxine (T4)

Triiodothyronine (T3)

Parafollicular cells produceCalcitonin (CT)

PARATHYROID GLAND

PARATHYROID GLAND

Small round masses in posterior of thyroid gland

Release parathyroid hormone (PTH)

Increases blood Ca2+ in 3 ways

Increases number and activity of osteoclasts that break down bone

Slows loss of Ca2+ and Mg2+ in urine

Promotes production of calcitriol (vitamin D) increases rate of Ca2+, Mg2+ and HPO4

2- absorption in GI tract increase blood Ca2+

ADRENAL GLAND

Chromaffin cells

produce catecholamines

Epinephrine

Norepinephrine

Dopamine

Reinforce the effect of the sympathetic division

ADRENAL MEDULLA

MINERALOCORTICOIDS

Major hormone: Aldosterone

Function:

regulate blood volume and blood levels of

K+ and Na+

part of renin-angiotensin-aldosterone

pathway

ADRENAL CORTEX

GLUCOCORTICOIDS

Major hormone: cortisol

Function:

Increases rate of protein breakdown

Stimulates liver formation of glucose

Breaks down triglycerides in adipose

Anti-inflammatory effects

Inhibit white blood cells

ADRENAL CORTEX

ANDROGENS

Small amount secreted from adrenal cortex in

both females and males

At puberty, in both genders, androgens

stimulate axillary and pubic hair growth

contribute to adolescent growth spurt

ADRENAL CORTEX

PANCREAS

Endocrine

Islets of langerhans

α - glucagon

β - insulin

γ - somatostatin

PANCREAS

Low blood glucose stimulates glucagon release

Glucagon stimulates liver to release glucose increased blood glucose

High glucose levels stimulate insulin release

Insulin increases glucose transport into skeletal muscle and adipose cells decreased blood glucose

Insulin promotes amino acid uptake, protein synthesis, and lipid storage

INSULIN AND GLUCAGON

GONADS: OVARIES AND TESTES

Produce gametes: sperm and oocytes

Produce hormones

Testosterone in males

Estrogen and progesterone in females

Regulated by

GnRH from hypothalamus

FSH + LH from anterior pituitary

PINEAL GLAND

Small gland attached to roof of third ventricle of

brain

Produces melatonin

Sets body’s biological clock

More released in darkness, less in sunlight

THYMUS GLAND

Thymus: thymosin

Development of

T-cells

Help protect the

body against

infection