Biology The Endocrine System

!

!

The Endocrine SystemThe endocrine system is a collection of glands in your body that produce hormones. The hormones regulate metabolism,

growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things.

Main Glands: !pituitary gland thyroid gland

parathyroid glands adrenal glands

pancreas ovaries (in females) testicles (in males)

HormonesHormones are powerful chemicals that help keep our bodies working normally. They stimulate, regulate, and control the function of various tissues and organs.

Made by specialized groups of cells within structures called glands, hormones are

involved in almost every biological process including sexual reproduction, growth,

metabolism, and immune function.

Unlike the fast-acting chemicals of your nervous system (neurotransmitters), the hormones of your endocrine

system work slowly in your body.

How much of our behavior is hormonal?

Take for example PMS (premenstrual syndrome): emotional and physical symptoms that women experience sometime during the

10 days before their menstrual cycle (period) begins. Women might experience mood swings, depression, crying spells, anger, irritability, anxiety, social withdrawal, or lack of concentration.

…And this is due to chemical changes within the body!

!PMS can also cause a lack of

serotonin in the brain, triggering depression.

Things that cause hormonal changes:

Weight gain Stress

Puberty in Teenage Years Aging

Menstrual Cycle (women) Certain diseases

Things that result from hormonal changes:

Changes in mood Tiredness/fatigue

Unexplained weight loss or gain Anxiety, irritability, depression

Acne

Thyroid

Pituitary

Ovaries

Testes

AdrenalHypothalamus

Hormone: Cortisol

It’s released by your hypothalamus gland in high stress situations. The cortisol in your body causes you to get a quick boost of energy!

(This is good in danger situations) but if you’re stressed all the time, your body will eventually run out of cortisol. This leaves you feeling

exhausted and apathetic.

Hormone: Oxytocin

This hormone is nicknamed “the love hormone” because whenever you touch someone (even when you hug a friend!), it is released into your body generating feelings of pleasure. High levels can increase sex drive, increase trust between

people, and lower stress.

Not having enough oxytocin released as a child leads to

lower social skills in the future. Oxytocin level is closely linked to social functioning, and some

people inherit a gene that makes their oxytocin levels

naturally higher.

Hormones of the Thyroid

The are called Thyroxine (T4) and triiodothyronine (T3). They regulate your metabolism, which is how fast you grow and burn energy. (Those with

a “high metabolism” are usually skinnier because their bodies burn fat faster). If your thyroid hormone levels are too high (hyperthyroidism), you burn energy too fast - leaving you feeling tired and sluggish. If your thyroid levels are too low (hypothyroidism), you burn energy slowly and will gain

weight. Factors such as chronic stress, nutritional deficiencies, and inflammation can cause imbalances in these hormones.

Hormone: Estrogen

Women have more estrogen then men do, because the ovaries produce it in great quantities. The amount of estrogen in a woman’s body changes throughout the month, or throughout the different

phases of her menstrual cycle. At times, it causes irritability, migraines, depression, and PMS.

As teenagers, men have low levels of estrogen

and high levels of testosterone. As they

age, the level of estrogen increases, which can

cause changes in mood and personality.

Hormone: Testosterone

Men have more testosterone then women do, because the testicles produce it in great quantities. Men produce about 20

times more testosterone each day than women. In both, it increases sexual desire, muscle strength, bone density, and metabolism. If you don’t have enough in your body, it can leave you sluggish,

depressed, unfocused, and disinterested.

Nature vs.

Nurture

back to…

Nature vs. Nurture DebateNature:

!Because we inherit

genes from our parents, we are born with a certain set of

characteristics. We clearly inherit

physical traits, but we also inherit

personality traits and preferences.

Nurture: !

The environment around us impacts the way our personalities

and preferences develop. “Nurture” and “environment” refer to the home and city we live in, and how we are raised by our parents, teachers, and friends.

?

Nature vs. Nurture DebateAn argument for

Nature: !

“Studies show that we inherit some

genes that are related to certain personality

traits.”

An argument for Nurture:

!“Often Identical twins

grow up to have very different

personalities and preferences.”

?

EpigeneticsThis is a new branch of genetics that is shedding light

on the “nature vs. nurture” debate. “Epi” means “around” or “on top of” so epigenetics refers to modifications that occur on top of your genes. Environmental factors actually cause your cells and genetic code to change

over your lifetime. Your genetic code itself is always the same, but genes can be “turned on” or “turned off.”

For example, your diet can cause “epigenetic changes” to your DNA. It is possible to pass these changes on

to your offspring’s DNA.

Epigenetics

The DNA of twins begins the same, but over the course of their lives, different health choices and environmental stimuli

cause the DNA code to change.

EpigeneticsQ: What does this mean for the nature vs. nurture debate?

!A: That we are not defined by our genes. Our lifestyle choices can actually impact our genetic codes, causing certain genetic traits to

express themselves more or less strongly.

But, this does not mean that our genes don’t impact who we are.

The nature vs. nurture debate rages on as psychologists try to understand which plays a larger part in our development. They also try to discover which plays a larger part in specific behaviors - like

gender expression.

Nature vs. NurtureFor example, is there a biological reason why girls like dolls and

the color pink? Is there a biological reason why boys like toy cars and the color blue? Or is this something that children are

nurtured to like by their parents and other societal factors?