Biology 2

 Nervous system regulates many body activities.  Endocrine system regulates life functions.

 The study of the endocrine system.  Changes effected by the endocrine system are more gradual than the changes made by the nervous system.

 Endocrine glands secrete chemicals directly into the bloodstream.  Exocrine glands release the chemicals they produce through a duct (Example: tear gland)

 Thyroid  Parathyroid  Adrenal  Pituitary  Thymus  Pancreas  Gonads  Pineal  Hypothalamus These glands send out chemical messengers to all parts of the body.

 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.

 Endocrine glands regulate themselves with a type of feedback mechanism.  2 types:  Negative feedback  Positive 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!

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

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

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

 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.

 When the thyroid gland produces too little thyroxin leading to a condition.  People with this condition tire easily and are often overweight.

 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.

 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.

 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.

 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

 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

 Corticosteroids  Also called corticoids  Influence the metabolism of carbohydrates, proteins, & fats.  Aldosterone  Helps control the balance of water and salts in the body.

 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

 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.

 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.

 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.

 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

 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.

 When a person has too low a level of sugar in the blood.  Caused when too much insulin is produced.

 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

 Made in the testes located in the scrotal sac.  Produces male secondary sex characteristics:  Facial hair  Broadening of the chest  Deep voice

 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.

 Located deep inside the brain.  Produces melatonin.  Helps regulate the onset of puberty and sexual maturity.