The Endocrine

System

…….hormonal control of homeostasis

Compare Nervous /hormonal

Functions of Endocrine System

Mechanism of action

The Major Endocrine Glands

Pineal Body

Pituitary

Thyroid ParathyroidsThymus

Adrenals Pancreas

Testes Ovaries

Thyrotrophin (the Thyroid Stimulating Hormone -TSH) Regulates the activity of the thyroid gland

Adrenocorticotrophin (ACTH) Regulates the function of the adrenal cortex of the

adrenal glands

Gonadotrophins a) Follicle Stimulating Hormone (FSH)b) Lutenising Hormone (LH) Regulate the reproductive organs

(gonads)

FSH ♀ regulates the development of ovarian

follicles and secretion of oestrogen

FSH ♂ regulates the

production of sperm in men

The Anterior Pituitary –Trophic Hormones

LH ♀ stimulates ovulation and formation of the

corpus luteum that secretes oestrogen and progesterone.

LH ♂ Stimulates

testosterone secretion in the male

Melanocyte Stimulating Hormone (MSH) Stimulates the production and release of melanin

by melanocytes in skin (basal layer).HYPERSECRETION - unnaturally dark skinHYPOSECRETION - prone to sunburn

The Anterior Pituitary –Other Hormones

Prolactin Enlarges the mammary glands and stimulates milk

production HYPERSECRETION - over production of milk and

enlargement of breasts (also occurs in men) HYPOSECRETION - under production or no

production of milk

Human Growth Hormone (HGH) Regulates growth during pregnancy. HYPERSECRETION causes gigantismHYPOSECRETION causes dwarfism

The Posterior Pituitary Hormones

VasopressinAnti Diuretic Hormone (ADH)

Regulates the body fluidsHYPERSECRETION - high blood pressureHYPOSECRETION- low blood pressure

Oxytocin Regulates the release of milk in

lactating women Induces uterine contractions in

labour Has a role in orgasm and inducing

'pair bonding'…ie. Love!)

The Thyroid Hormones Thyroxine

Increases the metabolic rate HYPERSECRETION -

Hyperthyroidism - HYPOSECRETION -

Hypothyroidism

Calcitonin Lowers blood calcium and

phosphorus levels maintains dense bones by

inhibiting osteoclast activity.

HYPERSECRETION - leads to low blood calcium levels

Thyronine Reduces the metabolic rate

Parathormone Increases blood calcium and phosphorus

levels by stimulating osteoclast activity, enhancing calcium reabsorption (kidneys) and enhances absorption of calcium in the intestines

HYPERSECRETION - Softened bones from lack of calcium

HYPOSECRETION - Low blood calcium levels

The Parathyroid Hormones

Insulin Lowers blood glucose levels by

increasing glucose transport into the body cells and increasing glycogen synthesis in liver and muscle cells

HYPERSECRETION - HypoglycaemiaHYPOSSECRETION - Hyperglycaemia • low levels of insulin leads to diabetes

mellitus type 2 (NIDDM), no insulin leads to diabetes mellitus type 1 (IDDM)

The Pancreatic Hormones

Glucagon Raises blood glucose levels by

inhibiting glucose uptake and liberating glucose stored as glycogen.

The Thymus Hormones

Thymic Factor (TF) & Thymic humoral factor (THF) Involved in the activation of T lymphocytes (T-

cells)HYPOSECRETION - increased susceptibility to disease

Adrenal Cortex

Aldosterone Increase reabsorption of mineral salts (sodium

etc) in the renal tubules

HYPOSECRETION - Addison's Syndrome (dehydration, weight loss, hypoglycaemia, hypotension)

The Adrenal Hormones

Adrenal Medulla

Adrenaline (aka epinephrine or nor-adrenaline)

Affects the heart; breathing centre of brain; arterioles of skin and digestive tract; muscles of the gut, muscles of the body, liver.

Secreted during fear, fight, flight response to danger

HYPERSECRETION - stress / anxiety disorders, digestive disorders, CV disorders, skin disorders, immune weakening etc

The Pineal Hormones

Seratonin Regulates Mood, sexuality and body

rhythms (responds to sunlight)HYPERSECRETION - ecstasyHYPOSECRETION - depression,

Seasonal Affective Disorder (SAD)

Melatonin Regulates sleep/wake or circadian

rhythms Stimulated by darkness and inhibited

by light

The GonadsTestes

Testosterone Regulates the production and

maturation of sperm; Responsible for the secondary

male sexual characteristics

Ovaries

Progesterone

Prepares the endometrium for implantation and pregnancy

Oestrogen Matures the ovum for release; Responsible for the secondary

female characteristics