The Endocrine System

The Endocrine System

What is the Endocrine System?

• Glands in the body that secrete hormones

• Hormones stimulate growth and affect moods and emotions – they are like neurotransmitters because they have specific receptor sites

• Major glands: pituitary gland, thyroid, adrenal glands, testes and ovaries

The Pituitary GlandThe Pituitary Gland

Located just below the hypothalamus, it is the “master gland”Regulates growth of bones, muscles, and other glandsSecretes hormones necessary for pregnancy and motherhood

The Thyroid Gland

• Produces thyroxin – controls metabolism

• Too little thyroxin can make people overweight, too much can make people underweight

• Located in the neck

The Adrenal GlandsThe Adrenal Glands

Located above the kidneys, produce adrenalineAdrenaline causes the body to become excited during stressful situationsCan intensify emotions such as fear and anxiety

Testes and Ovaries• Produce sex hormones• Testosterone – helps in the growth

of muscle and bone, is directly involved in male sexual development and characteristics (beard growth, chest hair)

• Estrogen – responsible for female sex characteristics and development

• Progesterone – stimulates growth of reproductive organs and prepares body for pregnancy

• Males and females produce all of these hormones, but at different levels and for different reasons

Genes and HeredityGenes and Heredity

Heredity

• The transmission of characteristics from parents to their children

• These characteristics, along with hormones, play a major role in a person’s development

• Children can inherit physical traits (eye color, height, skin color)

• Some psychological traits (shyness, leadership ability, aggression) are influenced by heredity, but the environment also plays a major role in their development

Genes and ChromosomesGenes and ChromosomesGenes – the basic building blocks of heredity – genes are found in chromosomesGenes are organized in pairs – we get one gene from our mother and one from our fatherChromosomes – small, thread-like structures made up of DNAThere are 23 pairs of chromosomes in normal cells (46 chromosomes total – 23 from your mother and 23 from your father)If a child does not have 46 chromosomes, he may have physical or behavioral disordersMost common disorder is an extra chromosome on the 21st pair of chromosomes – causes Down syndrome

Nature Vs Nurture

• Nature – what people inherit biologically from their parents

• Nurture – the environmental factors people are exposed to in their life (family, education, living conditions, culture)

• Some people believe personality is based in their biology while others argue that the person’s environment determines how his personality will develop

• Most modern psychologists believe both nature and nurture influence a person’s development, but they still disagree on the extent to which each has on personality and behavior

Studying Heredity through KinshipStudying Heredity through Kinship

Identical Twins share 100% of their genesChildren share 50% of their genes with each parent and, on average, their siblingsA child shares 25% of his genes with aunts and unclesFirst cousins share 12.5 % of their genesPsychologists use this information to determine how much a trait is influenced by geneticsIf a trait is determined by genes, then people who share more genes should be more likely to show the trait

Twin Studies• Differences among identical

twins must develop from environmental factors since they share 100% of their genetic material

• Identical twins are more likely than fraternal twins to have the same personality traits and share the same psychological disorders (schizophrenia, autism)

• HOWEVER identical twins are usually raised in the same environment and treated similarly, so it’s hard to determine how much of their identity is determined by nature and how much by nurture

Adoptee StudiesAdoptee Studies

Psychologists can study nature vs. nurture by examining children who were separated from their natural familiesPsychologists look for similarities that an adoptee has with his biological family and similarities with his adopted family to determine the effects of nature and nurture

Twins Raised Apart

• In 1979 a group of psychologists studies sets of twins who were raised apart from one another

• They found that many psychological traits like shyness, aggression, intelligence, and leadership, are determined by HEREDITY