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.