Endocrine System

ENDOCRINE SYSTEM

What is the endocrine system? Second great controlling system of the

body Body system that contains internal

organs that secrete hormones.

So, what is a hormone? Slowly acting chemical messenger that is

released into the blood

So, where do hormones work? So glad you asked that question! Target cells or target organs

Location where a given hormone affects

What do hormones do? Hormones cause certain changes. What are these changes?

Changes in plasma membrane permeability or electrical state

Synthesis of proteins or certain regulatory molecules (enzymes) in the cell.

Activation or inactivation of enzymes Stimulation of mitosis

In English please… Hormones control all activities in the

body They alter or change functions of cell to

get a response

3 types of hormones Steroidal Hormones

Insoluble in water, carried in the blood and released near the vicinity of the target cell

Nonsteriodal hormones Unable to enter target cells and instead bind

to receptors situation on the target cell’s plasma membrane

Prostaglandins act locally, affecting only the organ where

they are produced

What controls hormones? Negative feedback

The chief means of regulating blood levels of nearly all hormones

Triggered by some internal or external stimulus

Rising hormone levels inhibit further hormone release

In other words, a stimuli triggers hormone production… then that hormone may either stimulate or inhibit other hormones

Major Endocrine Organs Pituitary Thyroid Parathyroid Adrenal Pineal Thymus Pancreas Gonads

Pituitary Structure

Size of grape Located at the

base of the brain Attached to the

hypothalamus 2 parts

Anterior pituitary Posterior pituitary

Function Often called the

“master gland” because of its great influence on the body organs

Hormones of the Anterior Pituitary Gland

Prolactin (PRL) Stimulates milk production in women after childbirth Can affect sex hormone levels in men and women

Growth hormone (GH) Stimulates growth in childhood Important for maintaining healthy body composition In adults, important for muscle mass, bone mass,

and fat distribution Adrenocorticotrophin (ACTH)

Stimulates production of cortisol (“stress hormone”) by adrenal gland. Helps maintain blood pressue and blood glucose levels

More… Thyroid stimulating hormone (TSH)

Stimulates thyroid to produce thyroid hormones Thyroid hormones – regulate metabolism,

energy, growth, and development Lutenizing homone (LH)

Regulates testosterone in men and estrogen in women

Follicle Stimulating hormone (FSH) Promotes sperm production in men Stimulates ovaries to release eggs (ovulate) in

women

Posterior Pituitary Hormones

Oxytocin Causes milk letdown in nursing mothers and

contractions during childbirth Antidiuretic hormone (ADH)

Regulates water balance If not secreted properly can lead to kidney

problems and too much sodium

Thyroid Gland Structure

Small gland in back of neck

In front of trachea and below Adam’s apple

Function Controls

metabolism

Thyroid Gland Hormones Thyroxin

Increase rate at which cells release energy from carbs

Calcitonin Regulates the blood concentration of calcium

Thyroid Disorders Hypothyroidism

Stunted growth Mental retardation Sluggish Weight gain in adults

Hyperthyroidism (Grave’s disease) Restlessness Weight loss Anxiety Can cause Goiter (enlarged thyroid)

Parathyroid gland Structure

Behind thyroid Four tiny glands

Function Help maintain

calcium and phosphorus levels

Parathyroid Hormones Parathyroid hormone (PTH)

Takes calcium from bones to make it available in the blood

Parathyroid disorders Hyperparathyroidism

Can be caused by a tumor Increases PTH secretion Bones soften Too much calcium can cause kidney stones

Hypoparathyroidsm Too little PTH Too little calcium affects nervous system

Adrenal Glands Structure

2 organs… 1 located above each kidney

Function Outer portion

called adrenal cortex and are essential for life

Inner portion is the adrenal medulla and are not essential for life

Hormones of the Adrenal Medulla

Epinephrine & Norepinephrine Increased heart rate, breathing rate, elevated

blood pressure (fight or flight response to stress)

Hormones of the Adrenal Cortex

Aldosterone Helps kidneys conserve sodium and excrete

potassium, maintaining blood pressure Cortisol

Keeps blood glucose stable Adrenal Sex Hormones

Androgens (male) and estrogens (women)

Adrenal Disorders Cushing’s Syndrome

Hypersecretion of cortisol Blood glucose remains high, retains too much

sodium, puffy skin, masculinzing effects in women

Addison’s Disease Hyposecretion Decreased blood sodium, dehydration, low

blood pressure, increased skin pigmentation

Pancreas Structure

Large gland behind stomach

Function Helps body

maintain healthy blood sugar levels

Contains islands of cells called islets of Langerhans which secrete glucagon and insulin

Hormones of Pancreas Glucagon

Stimulates liver to break down glycogen, raises blood sugar

Insulin Decreases blood sugar concentrations, affects

the uptake of glucose cells

Disorders Related to the Pancreas

Diabetes Mellitus Results from an insulin deficiency, blood sugar

rises and excess is excreted in the urine Type I

Insulin dependent; often inherited immune disorder that destroys pancreatic cells

Type II Can be controlled with diet and exercise

Hypoglycemia Low blood sugar; can be caused by too much

insulin

Pineal Gland Located between the cerebral

hemispheres Secretes melatonin Important for maintaining Circadian

rhythums (light and dark activity)

Thymus Gland Large in young children Gradually shrinks with age Secretes thymosins – important to

immune function

Reproductive Glands Testes and ovaries Testosterone, progesterone, estrogen