The Endocrine System

The Endocrine System

• Chemical messages (hormones) are released into the bloodstream

• Some of the major processes controlled by hormones include…– Reproduction– Growth and Development– Body Defense– Maintaining Homeostasis– Regulating Metabolism

What are Hormones?

• Hormones are produced by specialized cells

• Cells secrete hormones into extracellular fluids (blood, lymph)

• Blood transfers hormones to target sites

• These hormones regulate the activity of other cells!

What are Hormones?

• Two major chemical classifications of hormones– Amino acid-based hormones

• Examples: proteins, peptides, amines

– Steroids: made from cholesterol

What do Hormones cause?

• Synthesis of proteins, such as enzymes

• Activation or inactivation of enzymes

• Stimulation of mitosis

• Changes in the plasma membrane

• These changes all have one common goal – to cause some larger, long-lasting change in the body!

What causes Hormones to be Released?

• Some sort of stimulus will trigger hormones to be released!– Hormonal Stimulus

• Some hormones released will stimulate other hormones to be released

What causes Hormones to be Released?

– Humoral Stimulus

• Changing blood levels of ions & nutrients will stimulate hormones to be released

• Examples: Parathyroid hormone (PTH) will cause calcium to be released from bone into blood, ADH will cause water to be reabsorbed into blood

What causes Hormones to be Released?

– Neural Stimulus• Nerve fibers stimulate

hormones to be released

• Examples: norepinephrine and epinephrine released during stress

What are some of

the major endocrine organs?

Endocrine Organs

• Hypothalamus– Found in brain– Releases hormones that regulate the pituitary

gland

Endocrine Organs

• Pituitary Gland– Hangs from hypothalamus, broken into two

lobes– Releases hormones to control other glands– Hormones released by the two lobes

include…

Pituitary Gland– Posterior Lobe

• Oxytocin: contraction of uterus, release of milk• Antidiuretic hormone (ADH): reabsorption of water

by kidneys– Anterior Lobe

• Prolactin: milk production (pro= for; lact = milk)• Follicle-Stimulating Hormone (FSH):

– In females, stimulates development of follicles in the ovaries.

» You will soon learn that a follicle consists of follicle cells and the developing egg

– In males, FSH stimulates sperm development within the testes

• Lutenizing Hormone (LH): – In females, triggers ovulation and the production of

progesterone and some estrogen– In males, stimulates testosterone production and release

of sperm

Pituitary Gland cont

• Thyroid Stimulating Hormone (TSH): stimulates thyroid gland

• Growth Hormone (GH): stimulates growth, especially of bones and muscles

Endocrine Organs

• Gigantism– Most of the tallest people in the world are so

because they have a tumor on their pituitary gland

– This causes an overproduction of GH

Leonid Stadnyk – 8 ft 5 in

Robert Wadlow – 8 ft 11 in

• Tallest man ever on record

• Lived to be only 22

Endocrine Organs

• Pineal Gland– Found in brain– Produces Melatonin, which helps establish

day/night cycle

Endocrine Organs

• Thyroid Gland– Found at base of throat – Produces Thyroid Hormone, which controls

the rate at which glucose is used & converted to body heat and energy

Endocrine Organs

• Hyperthyroidism: overactive thyroid– Produce too much thyroid hormone– Symptoms include increased heart beat,

tremors, weight loss, and diarrhea

• Hypothyroidism: underactive thyroid– Produce too little thyroid hormone– Can be brought on by iodine deficiency or

genetics– Symptoms include poor muscle tone, fatigue,

decreased heart beat, weight gain, and constipation

Thyroid Gland Continued*

• A second important hormone produced by the thyroid is called calcitonin– Causes calcium to be deposited into the

bones

*please add these notes to your packet o notes

Endocrine Organs

• Parathyroid– Tiny gland masses on the back of the thyroid

gland– Produces Parathyroid Hormone (PTH), which

controls calcium release from the bones into the blood

– *PTH is a hypercalcemic hormone (increases blood levels of calcium) whereas calcitonin is a hypocalcemic hormone.

Endocrine Organs

• Thymus– Sits right above heart in the upper chest– Produces Thymosin, which helps mature T

cells (immunity)

Endocrine Organs

• Adrenal Glands– Sits on top of the kidneys– Produce Aldosterone, which helps with water

balance of urine/blood– Produce Glucocorticoids, which increase

blood glucose levels – Produce Epinephrine/Norepinephrine, which

helps with short-term stresses– Some sex hormones also made here

Endocrine Organs

• Pancreas– Located at curvature of duodenum just

underneath the stomach– While produces enzymes that help with

digestion, it also produces hormones such as…

– Insulin, which increases ability of cells to transport glucose across their plasma membranes, thereby reducing glucose levels of blood

Diabetes• There are generally two types of diabetes

• Type 1/ Juvenile– Pancreas self-destructs, causing lack of production of

insulin.• Without insulin, sugar can not be absorbed by the body

– Symptoms of Type 1 diabetes (when not treated!) are• Very high blood sugar• Weight loss• 3 ‘Ps’

– Polydipsia - Excessive thirst– Polyphagia - Excessive hunger– Polyuria - Excessive urination

Type 1

– Treatment of Type 1 diabetes • Diet• Daily Insulin Injections

– Or --

• Insulin pump that continuously releases insulin into body.

Diabetes• Type 2 / Adult Onset

– Body cells become resistant to insulin • Or

– Pancreas is not producing enough insulin– Symptoms of Type 2 diabetes (when not treated)

are• Moderately high blood glucose levels

• Polydipsia, Polyphagia & polyuria (3Ps)– When glucose flushes out of body along with water, resulting

dehydration.

• Because glucose is unavailable, the body will use fats and proteins for energy instead which can cause weight loss.

Diabetes

– Treatment of type 2 diabetes• Diet

– Reduce the amount of sugar in diet and encourage weight loss

• Oral medications that help – increase absorption of sugar– increase production of insulin – decrease release of internal glucose stores

• Lastly, insulin injection if all above fail.

Endocrine Organs• Gonads

– Male: Testes• Produces Androgen hormones (especially

Testosterone), which promotes male sex characteristics and helps sperm production

• Stimulated to be released b/c of LH

– Female: Ovaries• Produces Estrogen, which promotes female sex

characteristics, stimulates growth of uterine lining• Stimulated to be released b/c of FSH• Produces Progesterone, which stimulates growth of

uterine lining