Chapter 13
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Chapter 13. The Endocrine System. Chapter Outcomes. Explain how the endocrine system contributes to homeostasis Compare the nervous & endocrine systems Identify the principal endocrine glands and the hormones they secrete

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Chapter 13

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Chapter 13

Chapter 13

The Endocrine System

Chapter outcomes

Chapter Outcomes

  • Explain how the endocrine system contributes to homeostasis

  • Compare the nervous & endocrine systems

  • Identify the principal endocrine glands and the hormones they secrete

  • Explain how the endocrine system allows the body to sense and respond to the internal environment

Chapter outcomes1

Chapter Outcomes

  • Explain the relationship between negative feedback and hormonal regulation

  • Explain how the endocrine system is involved in seasonal affective disorder and the sleep-wake cycle

  • Describe the structure of the anterior and posterior pituitary and explain how they are regulated

Chapter outcomes2

Chapter Outcomes

  • Explain how human growth hormone contributes to growth and development

  • Evaluate the use of hormone therapy

  • Describe the structure and regulation of the thyroid gland

  • Describe the physiological effects of hormonal imbalances

Chapter outcomes3

Chapter Outcomes

  • Explain how the nervous and endocrine system act together to regulate stress response

  • Identify and describe the actions of epinephrine and norepinephrine in the human body

  • Describe the effects of cortisol and aldosterone on the body during long term stress response

Chapter outcomes4

Chapter Outcomes

  • Describe the physiological effects of chronic stress or an imbalance in the stress hormones

  • Describe the structure of the pancreas and its role in homeostasis

  • Explain how insulin and glucagon regulate levels of blood glucose

  • Describe the physiological effects of diabetes and how the condition occurs

Nervous vs endocrine systems

Nervous vs. Endocrine Systems

  • Both the nervous and endocrine systems regulate homeostasis in the body

  • Endocrine responses are often slower, but have longer lasting effects than nervous system responses

  • Often both the nervous and endocrine systems work together to regulate responses

Our chemical messengers

Our Chemical Messengers

  • Hormones are chemicals that are produced by cells in one part of the body and affect other parts of the body

  • These hormones can be classified as either steroid or protein hormones

  • Not all hormones affect all cells – most cells have special receptor sites for various types of hormones

Steroid hormones

Steroid Hormones

  • Steroid hormones diffuse through the cell membrane

  • They attach to receptor sites in the cytoplasm of cells

  • This hormone-receptor complex moves into the nucleus, activating a gene and producing the required protein

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Animation of Steroid Hormone Action

Protein hormones

Protein Hormones

  • Protein hormones cannot diffuse through the cell membrane, but rather attach to receptor sites on the membrane

  • This hormone-receptor complex triggers the production of an enzyme (adenyl catalase)

  • This enzyme converts ATP to cyclic AMP

  • The cyclic AMP turns on enzymes in the cytoplasm so that they carry out their functions

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An Animation of Protein Hormone Action

Negative feedback

Negative Feedback

  • We do not want constant hormone production in the body

  • Once the hormone produces its desired effect, hormone production must be decreased

Ex testosterone feedback

Ex: Testosterone Feedback

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  • The regulation of hormone levels is important to the human body

  • Many different diseases are caused by an imbalance of hormones

Seasonal affective disorder

Seasonal Affective Disorder

  • Melatonin is a hormone that lets the body know when to sleep or wake up (light inhibits its secretion)

  • However, if people do not receive enough light, too much melatonin is produced – and the person feels fatigued

Circadian rhythm

Circadian Rhythm

  • To an extent, melatonin levels regulate our circadian rhythm (the body’s internal clock)

  • In teens, this rhythm shifts by several hours

  • As a result, teenagers often feel awake at night and sleepy in the morning

The pituitary the master gland

The Pituitary – The “Master Gland”

  • The pituitary controls other glands

  • It is attached to the hypothalamus in the brain

  • The posterior lobe of the pituitary stores and releases hormones

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  • The anterior lobe produces its own hormones

  • The cells of the pituitary react to stimulus from the hypothalamus

Growth hormone

Growth Hormone

  • Regulates human growth

  • Effects are most pronounced in cartilage and bone cells

  • If GH production continues after growth plates have fused, other bones will grow

  • This results in acromegaly

Andre roussimoff

Andre Roussimoff

  • Professional wrestler

  • Grew to over 7 feet tall and over 500 lbs.

  • Died of congestive heart failure

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  • Other growth hormone disorders include dwarfism (where insufficient GH is produced) and gigantism (where excess levels of GH are present in childhood, but drop off when bone growth is complete)

The thyroid gland

The Thyroid Gland

  • The primary function of the thyroid gland is to regulate metabolism

  • It produces a hormone called thyroxine



  • Thyroxine accelerates the rate of sugar oxidation in cells

  • Thyroxine production is regulated in a feedback loop which includes the pituitary hormone TSH

Thyroxine feedback loop

Thyroxine Feedback Loop

Iodine and thyroxine

Iodine and Thyroxine

  • Iodine is an important component of the thyroxine molecule

  • Without iodine, the thyroid cannot produce thyroxine

  • This means that the production of TSH cannot be turned off

  • Continual stimulation of the thyroid by TSH causes the thyroid to become enlarged



  • The enlargement of the thyroid is known as goitre

  • This condition can be treated through the intake of iodine in the diet

The thyroid and blood calcium

The Thyroid and Blood Calcium

  • Calcium ions play a role in teeth and skeletal development

  • It also plays a role in blood clotting, nerve conduction, and muscle contraction

  • Blood Ca2+ levels are regulated by two hormones – PTH and calcitonin

  • Calcitonin is produced in the thyroid gland, while PTH is produced in the parathyroid glands (embedded within the thyroid)

Pth calcitonin loop

PTH – Calcitonin Loop

High Ca2+ Level

Low Ca2+ Level

Adrenal glands

Adrenal Glands

  • The adrenal glands are located on top of the kidneys

  • They actually consist of two glands in one shell

Adrenal medulla

Adrenal Medulla

  • The medulla regulates short-term stress responses

  • Produces two hormones: Epinephrine (adrenaline) and norepinephrine (noradrenaline)

  • The medulla is controlled by the nervous system

  • When released into the blood, epinephrine and norepinephrine cause a rise in blood sugar levels

  • They also increase heart rate, breathing rate, and cell metabolism

Adrenal cortex

Adrenal Cortex

  • The adrenal cortex produces sustained responses that make up long-term stress response

  • This part of the gland produces three hormone types:

  • Glucocorticoids (cortisol): Increases levels of amino acids in blood. These are converted to glucose by the liver. The release of these hormones are controlled by ACTH release from the pituitary. Excess levels of cortisol can damage the heart, impair thinking, and cause high blood pressure and diabetes

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  • Mineralcortocoids (aldosterone): These help to regulate the level of water in the body by regulating water absorption in the kidneys.

  • Sex hormones: Small amounts of sex hormones are released by the adrenal cortex.

Regulation of blood sugar

Regulation of Blood Sugar

  • The pancreas contains two types of cells

  • One set of cells produces digestive enzymes

  • The other cells, known as the Islets of Langerhans, regulate blood sugar levels through the release of hormones



  • Insulin is produced by beta cells

  • Insulin is released when blood sugar is high

  • The insulin makes body cells more permeable to glucose

  • This allows the liver to convert glucose to glycogen for storage



  • Glucagon works in a complementary fashion to insulin

  • Alpha cells release glucagon when the blood glucose level is too low

  • Glucagon promotes the conversion of glycogen to glucose

Blood sugar regulation feedback loop

Blood Sugar Regulation Feedback Loop

Diabetes mellitus

Diabetes Mellitus

  • This is a genetic disorder where the body’s islet cells are damaged and cannot produce enough insulin

  • Without enough insulin, the blood sugar level in the body rises

Symptoms of diabetes mellitus

Symptoms of Diabetes Mellitus

  • Dehydration associated with excess urine production

  • Low energy levels

Types of diabetes

Types of Diabetes

  • Diabetes can be classified as juvenile diabetes or maturity-onset diabetes

  • Juvenile diabetes (Type 1) is a genetic condition which results in damaged islet cells

  • Maturity-onset diabetes (Type 2) is due to decreased production of insulin by the islet cells as the body ages, and as a result of the body’s cells receptors refusal to respond to insulin

Management of diabetes

Management of Diabetes

  • Diabetes can be managed through the intake of drugs, such as insulin

  • Insulin may be taken via subcutaneous injections, or an automated insulin pump may be used

  • Originally, insulin from pigs and cattle was used for injections

  • Currently, biologically engineered bacteria can produce human insulin for use

Adam morrison

Adam Morrison

  • Suffers from juvenile diabetes

  • Played three seasons for Gonzaga University

  • Voted NCAA co-player of the year in 2005-2006

  • Drafted by NBA’s Charlotte Bobcats (3rd Overall in 2006)

Chapter 13

  • Adam manages his diabetes through the use of an insulin pump when off the court

  • He also uses a very strict diet to manage his blood sugar levels on game days (he always eats the same meals at the same time)

The discovery of insulin

The Discovery of Insulin

  • Doctors Frederick Banting and Charles Best tested a theory that diabetes resulted from a deficiency of hormones in the pancreas

  • They tied the pancreatic duct of dogs and noted that they began to show symptoms of diabetes

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  • Banting and Best then extracted the hormone from the islet cells and injected it into the dogs

  • The dogs recovered, indicating that this hormone was responsible for controlling blood sugar levels

  • Banting was awarded the Nobel Prize in Medicine in 1923, but Best was not included

Future possibilities

Future Possibilities

  • Islet transplant surgery is becoming a more viable solution for treatment of diabetes

  • In this surgery, the islet cells are replaced with healthy donor cells, which produce insulin

  • Currently, this surgery has about a 50% success rate 1 year after the surgery

Chapter 13

  • Stem cell research could also lead to new treatments for diabetes

  • These stem cells could possibly be used to help the body develop functioning islet cells by removing the damaged genes



  • A number of different types of cells produce prostaglandins

  • These hormones are released by cells in response to changes in the immediate environment of the cells

  • Prostaglandins alter the activity of cells to maintain homeostasis

End of chapter


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