Ch. 18 – The Endocrine System

What is the system?

• Functions– Made up of glands that produce and secrete

hormones (chemical messengers– Regulation of growth, metabolism, and sexual

development– Responses to stress and injury– Internal balance of body systems (homeostasis)

Hormones

• Are chemical messengers that act on target cells or organs

• Endocrine – secretions within the body• Exocrine – secretions outside the body (sweat)

Hormone Action

• Hormones can:– Attach to cells and cause change (water-soluble

hormones)– Diffuse into cells and cause change (steroid and

thyroid hormones)

Major Structures

Hormone Control

• The pituitary is often called the “master gland”

• It is controlled by the hypothalamus in the brain.

• Negative Feedback System– When hormone levels rise, the organ that

secretes the hormone is switched off.

Hormone Control

Anterior Pituitary Hormones

• Prolactin (PRL)• Growth hormone (GH)• Adrenocorticotropin (ACH)• Thyroid-stimulating hormone (TSH)• Luteinizing hormone (LH)• Follicle-stimulating hormone (FSH)

PRL and GH• Prolactin

– Stimulates milk production in a woman’s breasts after childbirth– Can affect sex hormone levels from the ovaries in women and

the testes in men• Growth hormone

– Stimulates growth in children– Important for maintaining healthy body composition– In adults, important for maintaining muscle mass and bone

mass– Can affect fat distribution in the body– Problems with the pituitary gland can result in dwarfism

Problems with GH

Problems with GH

Problems with GH

ACH and TSH

• Adrenocorticotropin– Stimulates production of cortisol by the adrenal

glands– Cortisol – “stress hormone” is vital to survival

• Helps maintain blood pressure and blood glucose levels

• Thyroid-stimulating hormone– Stimulates the thyroid gland to make thyroid

hormones• Regulate the body’s metabolism, energy, growth and

development, and nervous system activity

FSH and LH

• Follicle-stimulating hormone– Promotes sperm production in men– Stimulates the ovaries to release eggs (ovulate) in

women• Luteinizing hormone– Regulates testosterone in men and estrogen in

women• These are gonadotropins**FSH and LH work together to allow normal functioning of

ovaries and testes

FSH and LH

Posterior Pituitary Hormones

• Oxytocin– Causes milk letdown in nursing mothers– Causes contractions during childbirth

• Antidiuretic hormone (ADH)– Also called vasopressin– Regulates water balance– If this hormone is not secreted properly, this can lead

to problems with sodium (salt) and water balance• This could also cause the kidneys not to work well

ADH and Diuretics

• Diuretics – chemicals that increase urine production

• Many common foods and drinks contain diuretics (alcohol)– Midol relieves symptoms of bloating because it

increases urination

Thyroid Gland

• Thyroid hormones control your metabolism– Which is your body’s ability

to break down food– Store it as energy– Ability to break down food

into waste products with a release of energy in the process

Thyroid Hormones

• Thyroxin (T4) and Tri-iodothyronine (T3)– Both regulate the rate at which cells release

energy from carbohydrates• Calcitonin– Regulates the blood concentration of calcium

BMR – basal metabolic ratehttp://www.bmi-calculator.net/bmr-calculator/

Thyroid Problems

• Thyroid hormones are partly made of iodine• Iodine is essential for making thyroxin• If a person doesn’t eat enough iodine, they

can’t make thyroid hormones– The size of the follicle grows, the gland grows –

goiter– If salt wasn’t iodized, most people wouldn’t get

enough iodine

Goiter

Thyroid Problems

• Hypothyroidism– Thyroid produces less hormone than

normal– Symptoms – sensitive to cold, fatigue,

joint or muscle pain, weight gain• Hyperthyroidism

– Thyroid produces more hormone than normal

– Grave’s disease• Symptoms – bulging eyes, fatigue, weight

loss, increased sweating, heat intolerance

Hypothyroidism

Parathyroid Gland

• Located behind the thyroid• Four tiny glands that

maintain calcium and phosphate levels

• PTH – parathyroid hormone – takes calcium from the bones and makes it available in the blood

Adrenal Glands

• Located above each kidney• Epinephrine and norepinephrine

– Increase heart rate, breathing rate, elevated blood pressure (fight or flight response)

• Aldosterone– Helps maintain blood pressure

• Cortisol– Keeps blood glucose levels stable

• Adrenal sex hormones– Androgens (males) and estrogens (females)

Pancreas

• Large gland behind stomach• Glucagon– Stimulates liver to break

down glycogen, increases blood sugar concentration

• Insulin– Decreases blood sugar

concentration, affects uptake of glucose by cells

Diabetes

• Diabetes – insulin deficiency– Blood sugar increases – excess is excreted in urine– Type 1 – inherited, juvenile-onset• Caused by immune disorder that destroys pancreatic

cells– Type 2 – adult, mature-onset• Often occurs in individuals who are overweight• Can be controlled with diet and exercise• Body makes insulin, but excess fat interferes with

body's ability to use the insulin correctly

Hypoglycemia

• Insulin– Lowers blood sugar levels– Hypoglycemia can result• Can be cured with sugar injection or eating sugary

foods

This is why diabetics often carry candy with them.

Steroids• Anabolic steroids

– Artificial steroids that mimic the function of androgens (male sex hormone)• These contribute to

male characteristics such as muscle mass

– The most powerful is testosterone