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Chapter 15

Endocrine System

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Points to Ponder

What is the endocrine system? Compare and contrast exocrine and endocrine

glands.

What are steroid and peptide hormones?

Name the major glands and their functions in theendocrine system.

What is diabetes (Type 1 and 2) and how mightyou prevent Type 1?

How do the endocrine nervous systems workwith the rest of the systems in the body tomaintain homeostasis?

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Endocrine system

Mostly comprised of glands

Secretes hormones that move throughthe bloodstream to target cells

Results in a slow but a prolongedresponse

15.1 Endocrine glands

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Endocrine system


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What is a target cell?


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Exocrine vs. endocrine glands

Exocrine glands secrete their products into

ducts that carry these products to other

organs or outside the body

Endocrine glands secrete their products

directly into the bloodstream


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What are hormones?

Hormones are chemical signals that promotescommunication between cells, body parts and evenindividuals

Hormones: Prostaglandins: local hormones affect neighboring cells and thus

are not carried in the bloodstream

Pheromones: chemical signals that influence the behavior ofother individuals

Peptide hormones: bind to a receptor in the plasma membranecausing the formation of cAMP which activates a cascade ofenzymes

Steroid hormones: lipids that enter a cell and affect gene activityand thus protein synthesis


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Action of peptide hormones15.1 Endocrine glands

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Action of steroid hormones


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Major glands of the endocrine system

1. Hypothalamus2. Posterior pituitary gland

3. Anterior pituitary gland

4. Thyroid gland

5. Parathyroid glands6. Adrenal glands

7. Pancreas

8. Testes

9. Ovaries

10.Thymus gland

11.Pineal gland

15.2 Hypothalamus and pituitary gland

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1. Hypothalamus

Regulates internal environment through

the autonomic nervous system

Helps control heartbeat

Helps control body temperature

Helps control water balance

Controls glandular secretions


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2. Posterior pituitary gland

Stores antidiuretic hormone (ADH) and

oxytocin that are produced by the

hypothalamus

ADH: regulates water balance byreabsorbing water into the bloodstream

Oxytocin: causes uterine contractions

during childbirth and allow milk to bereleased during nursing


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3. Anterior pituitary gland

Controlled by hypothalamic-releasing andhypothalalmic-inhibiting hormones

Hormones produced by the anterior pituitary:1. Thyroid-stimulating hormone (TSH): stimulates the thyroid to

produce thyroid hormones2. Adrenocorticotropic hormone (ACTH): stimulates the adrenal

cortex to produce cortisol

3. Gonadotropic hormones: stimulate gonads to produce sex cellsand hormones

4. Prolactin (PRL): stimulates mammary glands to develop andproduce milk only after childbirth

5. Melanocyte-stimulating hormone (MSH): causes skin cells toproduce melanin

6. Growth hormone (GH): promotes skeletal and muscular growth


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The hypothalamus and pituitary15.2 Hypothalamus and pituitary gland

1 2 H h l d i i l d

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What happens when the body

produces too much or too little GH? Pituitary dwarfism too little GH is producedduring childhood that results in small stature

Giantism too much GH is produced duringchildhood that results in poor health

Acromegaly overproduction of GH as an adultthat results in larger than normal feet, hands,and face


15 2 H th l d it it l d

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What happens when GH is produced in

improper results during childhood?


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What happens when GH is produced in

high amounts during adulthood?


15 3 Th id d th id l d

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4. Thyroid gland

A large gland located below the larynx

Iodine is needed in the diet to allow the thyroid

gland to produce its hormones

It produces:

Thyroid hormone (TH): regulates metabolism Calcitonin: helps lower blood Ca2+ levels by

stimulating the deposition of calcium in the bones

15.3 Thyroid and parathyroid glands

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Thyroid abnormalities

Simple goiter thyroid enlarges due to lack of iodine in thediet

Hypothyroidism low blood levels of thyroid hormonesA. Congenital hypothyroidism: thyroid does not develop properly

and is characterized in a short, stocky person that may bementally retarded

B. Myxedema: hypothyroidism in adults characterized by lethargy,weight gain, loss of hair, cold intolerant and thick, puffy skin

Hyperthyroidism excess thyroid hormones in the bloodA. Exophthalimic goiter: such as seen in Graves' disease and is

characterized by enlargement of the thyroid gland, protrusion ofthe eyes, hyperactive and suffers from insomnia

B. Thyroid tumor: can also cause hyperthyroidism


15 3 Th roid and parath roid glands

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Thyroid abnormalities


15 3 Thyroid and parathyroid glands

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5. Parathyroid glands

Small glands embedded in the surface of

the thyroid gland

Produces parathyroid hormone (PTH):

causes blood Ca2+ level to increase by

promoting osteoclast activity

Promotes reabsorption of Ca2+ by the kidneys


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Regulation of blood calcium15.3 Thyroid and parathyroid glands

15 4 Adrenal glands

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6. Adrenal glands

Glands that sit on top of the kidneys

2 parts of each gland

Adrenal medulla: controlled by the

nervous system

Adrenal cortex: portions are controlled by

ACTH from the anterior pituitary

15.4 Adrenal glands

15 4 Adrenal glands

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Adrenal medulla

Inner portion of the adrenal glands

Hypothalamus initiates stimulation of hormone

secretion in the adrenal medulla

Produces: hormones that allow a short-term

response to stress (fight or flight response) Epinephrine (adrenaline)

Norepinephrine

15.4 Adrenal glands

15 4 Adrenal glands

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Adrenal cortex

Outer portion of the adrenal glands

Produces hormones that provide a long-term responseto stress

2 major types of hormones: Mineralocorticoids :

regulate salt and water balance

e.g. aldosterone (targets the kidney)

Glucocorticoids:

regulate carbohydrate, protein and fat metabolism Suppress the bodys inflammatory response

e.g. cortisol and cortisone

15.4 Adrenal glands

15 4 Adrenal glands

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Summary of the adrenal glands

15.4 Adrenal glands

15 4 Adrenal glands

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Adrenal glands can malfunction

Addisons disease hyposecretion of

glucocorticoids by the adrenal cortex

characterized by bronzing of the skin

15.4 Adrenal glands

15 4 Adrenal glands

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Adrenal glands can malfunction

Cushing syndrome hypersecretion ofglucocorticoids by the adrenal cortexcharacterized by weight gain in the trunk of thebody but not arms and legs

15.4 Adrenal glands

15 5 Pancreas

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7. Pancreas

Fish-shaped organ behind the stomach

Composed of 2 tissues:

Exocrine: produces and secretes digestive juices

Endocrine (islets of Langerhans): produces andsecretes hormones

1. Insulin secreted when blood glucose is high and

stimulates uptake of glucose by cells (muscle and liver)

2. Glucagon secreted when blood glucose is low and

stimulates the breakdown of glycogen in the liver

15.5 Pancreas

15 5 Pancreas

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Regulation of blood glucose15.5 Pancreas

15 5 Pancreas

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Health focus: What is diabetes?

Inability to control blood glucose levels

There are two types: Type 1 and Type 2

18 million people in the US have diabetes

General symptoms: Frequent urination

Unusual hunger and/or thirst

Unexplained change in weight

Blurred vision

Sores that heal slowly or not at all Excessive fatigue

Long-term effects are blindness, loss of limbs, nerve deterioration,kidney and cardiovascular disease

15.5 Pancreas

15.5 Pancreas

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Diabetes: Understanding the 2 types

Type 1:

Usually early-onset

Autoimmune disorder that

tends to run in families

Pancreatic cells areattacked and cannot

produce insulin

Need insulin injections

Type 2:

Usually adult-onset and

most common type

Tends to occur in obese,

sedentary people Cells do not respond to

insulin

Usually diet and exercise

are important for controlling

this and may even preventthis!

15.5 Pancreas

15.6 Other endocrine glands

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8. Testes

Gonads found in males

Produce androgens (e.g. testosterone)

Stimulates growth of the penis and testes

Responsible for 2 male sex characteristics

such as facial, underarm and pubic hair

Prompts the larynx and vocal cords toenlarge resulting in a lower voice

Promotes muscular strength



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9. Ovaries

Gonads found in females

Produce estrogen and progesterone

Stimulates growth of the vagina and uterus

Responsible for secondary sex

characteristics such as female body hair, fat

distribution and breast development Responsible for egg maturation

Regulates the uterine cycle

5 6 O e e doc e g a ds


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Bioethical focus: You decide

Hormone replacement therapy (HTR) is oftenused to counteract some of the problemsassociated with menopause or to prevent anincreased risk of osteoporosis

2002 a study found that HTR: May have risks that outweigh the benefits

Does not significantly increase the quality of life

Significantly increased the risk of breast cancer

May increase the risk of cardiovascular disease

Can prevent fractures as a result of osteoporosis

g


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10. Thymus gland

Lies beneath the sternum

This gland is largest and most active during

childhood

T lymphocytes mature here

Secretes hormones called thymosins that aid in

differentiation of lymphocytes

g


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11. Pineal gland

Located in the brain

Secretes melatonin

that regulates thesleep/wake cycle

(circadian rhythm)

May also regulate

sexual development

g


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Hormones from other tissues

Erythropoietin: secreted by the kidney to increase redblood cell production

Leptin:produced by fat cells and acts on thehypothalamus to give a feeling of being satiated

Prostaglandins: A groups of potent chemicals that are not carried in the

bloodstream but work locally on neighboring cells

Some cause smooth muscle contraction

Major impact on reproductive organs

Many other roles in the body

Aspirin and ibuprofen block the synthesis of these

g

15.7 Homeostasis

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Homeostasis

The nervous and endocrine systems are

important in maintaining homeostasis by:

The hypothalamus bridges regulatory

functions of both systems

The nervous system is able to respond to

changes in the external environment

15.7 Homeostasis

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How the nervous and endocrine

systems work with other body systems

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