Introduction to Psychology

Brain and Behavior

Nervous System

CNS: Brain and Spinal Cord

Peripheral Nervous System: network of nerves that carries information to and from the nervous system

Peripheral Nervous System

Somatic System: carries messages to and from sense organs and skeletal muscles

Controls voluntary behavior

Peripheral Nervous System

Autonomic Nervous System: glands and organs; “automatic functions”

Heartbeat, digestion

Peripheral Nervous System

Sympathetic: fight or flight; prepares for action

Parasympathetic: quiets the body; lowers arousal

Neurons

Nerve cells in the brain

Carry messages; activate muscles and glands

100 billion neurons in the brain

The Neuron

Fig. 3.8

Parts of the Neuron

Dendrites: receives messages from other neurons

Soma: receives messages; sends nerve impulse down the axon

Parts of the Neuron

Axon: thin fiber leading to the terminal buttons; nerve impulses travel down the axon; carries messages

Myelin sheath: fatty layer covering the axon that helps nerve impulses move faster

Parts of the Neuron

Synapse: the microscopic space between the neurons over which messages pass

Neurotransmitters travel across the axon

Ions: electrically charged molecules found inside and outside the neuron, with + or - charges

Resting Potential

Electrical charge of an inactive neuron

-70 mv

Messages from other neurons raise or lower the resting potential

Threshold

If the charge raises to -50 mv, the neuron reaches its threshold

Threshold=trigger point for firing

Ready to fire

Neural Firing An action potential (nerve impulse)

sweeps down the axon

Ion channels open and sodium ions rush in

After the action potential....

Positive ions flow back out; the neuron becomes negatively charged again

Resting state is restored

After firing, the neuron dips below resting level and is less willing to fire

Firing...

Firing is an all or nothing event The neuron either fires, or doesn’t

fire

It take 1/1000 of a second for a neuron to fire; on average, they fire between 1-400 times per second

Neurotransmitters Chemicals that alter activity in the

neurons

Neurotransmitters travel from the terminal buttons across the synapse, and connect to special receptors sites on the dendrites and soma of the next neuron

Neurotransmitters

Neurotransmitters can excite or inhibit firing

Types of Neurotransmitters Dopamine: too little=Parkinson’s, too

much=schizophrenia Acetylcholine: activates muscles Serotonin: deficiency associated with

depression/anxiety Neuropeptides: influence memory,

pain, emotion, and mood Endorphins: released by the pituitary

glad; lessens pain

The Brain

Right and Left hemispheres

Lateralization

Divided by the corpus callosum

Left and Right Hemispheres

Left: Detail oriented Speech and

language Calculating Understands one

word at a time, not the big picture

Right: Non-verbal Face recognition Express/detect

emotion Understanding

speech context/nuances of language

The Brain’s Four Lobes

Fig. 3.7

Functions of Lobes of the Cortex

Frontal lobes

Occipital lobes

Temporal lobes

Involved in voluntary movement, thinking, personality, and intentionality or purpose

Function in vision

Active role in hearing, language processing, and memory

Parietal lobesRoles in registering spatial location, attention, and motor control

The Brain

Recent research:

Both heredity and environment shape the brain

The role of experience and brain plasticity

Dendritic Spreading

Fig. 3.11

Pruning

Changes to the dendrites and synapses Connections are formed and

terminated

Experience and the Brain Exposure to trauma:

PTSD: reduced size of the hippocampus

Depression: Parts of the brain atrophy over time

Addiction: Changes in neurotransmitters

Experience and the Brain Mice in deprived vs. enriched

environments: differences in brain weight, neural connections and activity

Children reared in deprived environments have depressed brain activity (i.e. Romanian orphans) Can be reversed; brain plasticity/resilience

The Brain in Adolescence

Adolescent emotions — Areas of the brain involved in emotional

regulation are still growing/changing

Poor self-control; seek rewards and pleasure

Risk taking

Lack of practical experiences; immature

judgment

Alcoholism

Alcohol doesn’t “kill” neurons, but damages the dendrites

Affects communication between neurons

Frontal lobe and limbic system Brain may atrophy