Chapter 3 Notes

The Endocrine System The Endocrine system sends chemical messages called hormones to the brain. The Endocrine System consists of glands that secrete substances, called hormones, into the blood stream. These hormones stimulate growth and many kinds of reactions, such as changes in activity levels and moods.

The Hypothalamus This is in your brain and it directs the pituitary gland, which is the “master gland” The pituitary gland secretes a large number of hormones which carry messages through the blood stream These hormone messages carry information to the organs that regulate storing of nutrients, growth and reproduction.

The Thyroid Gland Produces the hormone thyroxine. Too little thyroxine makes people feel lazy and lethargic which is a condition called hypothyroidism. Too much thyroxine causes people to lose weight and become overactive. This is known as hyperthyroidism.

Adrenal Glands Become active when you are frightened or angry. They secrete adrenaline. This prepares your body to handle emergencies.

Heredity Debate Heredity is the transmission of genes from parent to child. Nature vs. Nurture asks the question “ Do people learn to be good athletes, or are they born that way?” and “Do people learn to do well in school, or are they born good at it?” In the past, one way to study genes and heredity was by studying twins. This is still used today to conduct research. Look on page 73.

Twin studies Identical twins develop from a single fertilized egg and share the same genes. Fraternal twins develop from two separate eggs and their genes are not more similar than those of brothers or sisters. Read the page 72 and 73 to learn more about several studies that have been conducted with twins