Biology 2. Nervous system regulates many body activities. Endocrine system regulates life functions.

THE ENDOCRINE SYSTEM

Biology 2

“Under Control”

Nervous system regulates many body activities.

Endocrine system regulates life functions.

Endocrinology

The study of the endocrine system. Changes effected by the endocrine

system are more gradual than the changes made by the nervous system.

Endocrine vs. Exocrine

Endocrine glands secrete chemicals directly into the bloodstream.

Exocrine glands release the chemicals they produce through a duct (Example: tear gland)

Endocrine Glands

Thyroid Parathyroid Adrenal Pituitary Thymus Pancreas Gonads Pineal Hypothalamus

These glands send out chemical messengers to all parts of the body.

Chemical messages

Chemical messangers = hormones Hormones travel through the blood;

therefore, travel much more slowly than nerve impulses, but their effects are much longer.

Hormones influence the action of target cells.

Target cells contain receptors for specific hormones.

Target cells are often located at a distance in the body from the endocrine glands that produce the hormones.

Feedback mechanisms

Endocrine glands regulate themselves with a type of feedback mechanism.

2 types: Negative feedback Positive feedback

Negative feedback

If the end product stops the first stem, then it is negative feedback.

The end product stops the production of a particular hormone.

MOST ENDOCRINE GLANDS USE NEGATIVE FEEDBACK!

Positive feedback

If the end product is needed in order for the first step to begin, then it’s positive feedback.

Thyroid

A two-lobed gland located in the neck. It produces the hormone thyroxin.

Thyroxin

Helps regulate the body’s growth and metabolism (the rate at which the body oxidizes its food).

Hyperthyroidism

When the thyroid gland produces too much thyroxin leading to a condition.

People with this condition usually have high blood pressure and an overactive metabolism.

Hypothyroidism

When the thyroid gland produces too little thyroxin leading to a condition.

People with this condition tire easily and are often overweight.

Cretinism

When a baby has an underactive thyroid gland.

This condition stunts the growth and can cause mental retardation.

This condition can be corrected if diagnosed early.

Iodine deficiency

Causes problems with the thyroid gland. The thyroid needs iodine to produce

thyroxin and without it abnormal growth of thyroid tissue can occur producing an enlarged thyroid called a goiter.

Goiters are rare today largely due to the addition of iodine to table salt.

Parathyroid Glands

There are 4 located in the back of the thyroid gland.

Parathyroid glands secrete the parathyroid hormone called parathormone. Parathormone helps control the levels of

calcium in the blood. It is very important in the formation of bones

and controlling proper functioning of nerves and muscles.

Adrenal Gland

Located at the top of each kidney. Each adrenal gland has an inner layer

(medulla) and an outer layer (cortex). Medulla - Produces the hormones

adrenaline and noradrenaline. Cortex – Produces the hormones

corticosteroids & aldosterone

Medulla produces Adrenaline and Noradrenaline

Adrenaline helps the body respond to stressful situations. Increases the level of blood sugar Increases the heart rate and blood pressure Enlarges blood vessels Increases the flow of blood to muscles that are

attached to skeleton. Noradrenaline

Produces the same effects on the body as adrenaline

Cortex produces Corticosteroids & Aldosterone

Corticosteroids Also called corticoids Influence the metabolism of carbohydrates,

proteins, & fats.

Aldosterone Helps control the balance of water and salts in

the body.

Pituitary Gland

Also called the “Master Gland” because it controls the actions of many other endocrine glands.

Small structure located at the base of the brain.

Divided into 2 lobes: Anterior (Front) Lobe Posterior (Rear) Lobe

Anterior Lobe

Secretes 3 major hormones: GH (Growth Hormone) – stimulates growth of

bones in body. LH (Luteinizing Hormone) – Causes secretions

of sex hormones by the testes & ovaries. FSH (Follicle Stimulating Hormone) –

Influences the maturing of eggs and the production of sperm.

Posterior Lobe

Secretes 2 major hormones: Oxytocin – Begins uterine contractions in a

woman when her child is about to be born & controls the production of milk after the child is born.

Vasopressin - Regulates water absorption by the kidneys.

Thymus Gland

Located in the chest below Thyroid gland. It is large in small children, but becomes

smaller in adults. Produces the hormone Thymosin.

Helps children develop their immune systems.

Pancreas

Found in the abdomen near the stomach. Produces digestive enzymes. Contains area of cells called Islets of

Langerhans. Produce hormones that enter the bloodstream

directly: Insulin & Glucagon Insulin – Decreases blood sugar level Glucagon – Increases blood sugar level

Diabetes mellitus

When a person lacks the correct amount of insulin.

Condition where there is a high level of sugar in the blood, and the cells of the body are being denied the sugar they need to produce energy.

Hypoglycemia

When a person has too low a level of sugar in the blood.

Caused when too much insulin is produced.

Gonads

Responsible for producing gametes & hormones.

2 types of gametes: Sperm (produced by testes in males) Eggs (produced by ovaries in females)

Also produces hormones. 3 types: Testosterone - Male Estrogens Progesterone

Female

Testosterone

Made in the testes located in the scrotal sac.

Produces male secondary sex characteristics: Facial hair Broadening of the chest Deep voice

Estrogens & Progesterone

Both are made in the ovaries located in the female’s internal pelvic region.

Estrogen Regulate the development of the female

secondary sex characteristics. Progesterone

Helps control the female’s monthly reproduction cycle.

Pineal Gland

Located deep inside the brain. Produces melatonin.

Helps regulate the onset of puberty and sexual maturity.