The Brain and How it Affects Behavior

Neurotransmitters and Hormones

A Brief Tour of the Brain

• Localization of Function– The idea that different parts of the brain perform

separate, but overlapping functions

Brain Stem

• Made of the Medulla ,Pons, and Reticular Activating System (RAS)– Medula: responsible for unconscious processes

like breathing and heart rate– Pons: involved in sleeping, waking, dreaming– RAS: dense network of neurons, screens incoming

information, arouses brain when it needs to be alert to something

Cerebellum

• Sits on top of the brain stem• Two lobes• Means “lesser brain”• Helps with balance and coordination• Helps remember simple skills and reflexes

Thalamus

• Deep in interior brain

• “Traffic officer of the brain”– Guides information to the right part of the brain for

processing…• You see a beautiful beach scene…the thalamus directs

the sight to the visual-processing part of the brain

– Except for smell…it has it’s own processing area by the “emotional” part of the brain

Hypothalamus

• “Under” thalamus• Involved in drives associated with survival– Hunger– Thirst– Emotion– Sex

• Also regulates body temperature and natural rhythms

• Controls the Autonomic Nervous System (glands, blood vessels, internal organs)

Pituitary Gland

• Cherry-sized

• Controlled by the Hypothalamus

• Master Gland– Sends hormones out to other glands

The Limbic System

• Loosely connected structures involved in emotional reactions and motivated behavior

• “Pleasure Center” and rat experiment (pg 141)– Amygdala

• Takes in sensory info, evaluates, and determines its emotional importance, helps decide…fight or flight?

• Mediates anxiety/ depression

– Hippocampus• “seahorse” – for its shape• Takes in senses, compares them to what you’ve learned about them• Helps form new spatial memories and memories about facts and

events

Cerebrum

• Largest brain structure• In charge of sensory, motor, and cognitive processing• Has two hemispheres connected by band of fibers

called the corpus callosum • Has 4 lobes:

– Occipital: visual– Parietal: pain, touch, pressure, temperature– Temporal: memory, perception, emotion, hearing, language– Frontal: short-term memory, planning, thinking, speech, etc.

NeurotransmittersMessengers of the Brain

Neurons

• Building block cells of nervous system• Cells that transmit messages throughout the

body• They communicate through electrical and

chemical signals• Neurons stop being produces shortly after

birth and are “pruned” throughout life

Neuron Structure

What is a neurotransmitter?

• A chemical substance that is sent from one neuron to another causing changes in the activity of the receiving neuron

• Can be – Excitatory (fires up an action)– Inhibitory (slows down an action)

• Thousands of neurotransmitter messages are being fired at a time…the receiving neuron must average out the messages and decide what to do.

• www.youtube.com/watch?v=haNoq8UbSyc

Where are neurotransmitters?

• Brain

• Spinal cord

• Peripheral nerves

• Some glands

Well-known neurotransmitters• Serotonin

– Sleep, appetite, sensory perception, temperature regulation, pain suppression, mood

• Dopamine– Voluntary movement (you choose to do), learning, memory, emotion

• Acetylcholine– Muscle action, cognitive functioning, memory, emotion

• Norepinephrine– Heart rate, stress reactions, learning, memory, dreaming, waking,

emotion• GABA

– The major inhibitory neurotransmitter in the brain• Glutamate

– Excitatory neurotransmitter….critical for long-term memory

Neurotransmitter Function Drugs that AffectNeurotransmitters

NeurotransmitterDeficiencies Result In

Norepinephrine Arousal, energy, drive

Cocaine, speed, caffeine, tobacco

Lack of drive, depression, lack of energy

GABA Staying calm, relaxation, focus

Valium, alcohol, marijuana, tobacco

Free-floating anxiety, fearfulness, insecurity, can't relax or sleep, unexplained panic

Endorphins Psychological / physical pain relief, pleasure, reward, good / loving feelings toward others

Heroin, marijuana, alcohol, sugar, tobacco

Overly sensitive, feelings of incompleteness, anhedonia (inability to experience pleasure normally), world lacks color, inability to love

Serotonin Emotional stability, pain tolerance, self-confidence

Sugar, marijuana, ecstasy, tobacco

Depression, obsession, worry, low self-esteem, sleep problCES, hunger, irritability

Neurotransmitter study/drugs

Endorphins• Like natural opiates (they reduce pain and promote pleasure)

• Play a role in appetite, sexual activity, blood pressure, mood, learning, and memory.

• Most kinds alter the effects of neurotransmitters…prolonging or limiting what they do.

• Endorphins shoot up in times of stress– Evolutionary advantage when you don’t feel pain during stress and then are able to act

quickly

• Some have suggested that endorphins come when comforted by mother…child attached to parent because addicted to “love”/ good feelings from endorphins?

Hormones

• Released directly into blood stream from glands in body

• Can do things like regulate digestion, increase growth, promote aggression, mess with emotion!....ladies…?

Adrenal Hormones

• Come from adrenal glands…above kidneys• Involved in emotion and stress

– Fire up when emotional event occurs (good or bad)• Cortisol – increases blood-sugar/energy• Epinephrine(adrenaline) and norepinephrine

• These hormones activate the sympathetic nervous system which increases arousal and prepares you for action– Slows metabolism…pulls resources from stomach and intestines

to be used elsewhere…why you lose appetite when very stressed or happy or emotional

Melatonin

• Produced deep within the brain• Helps regulate biological rhythms – Urine volume, blood pressure, menstruation, stomach

contractions, alertness, daydreaming, etc.

• Circadian Rhythms (more later)– Follow the rotation of the earth….like the sleep-wake

cycle• Melatonin rises and falls in your body according to

light and dark conditions

Sex Hormones

• Secreted by the gonads (ovaries or testes)

• Androgens: masculinizing hormones (like testosterone)– mostly in testes, but in ovaries and adrenal glands as well

• Estrogens: feminizing hormones

• Some research about Estrogen aiding in learning and memory, but no research about “emotional” women or “angry” men.