Introduction to Psychology Chapter 3: The Biological Basis of Behavior

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

Nervous System

Peripheral Nervous System Somatic System: carries messages to and from sense organs and skeletal muscles Controls voluntary behavior

Peripheral Nervous System Somatic system: Afferent nerve fibers carry info from the body to the nervous system Efferent nerve fibers carry info from the nervous system to the body

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 times per second

Neurotransmitters Chemicals that alter activity in the neurons Travel from terminal buttons across synapse connect to special receptors sites dendrites/soma of 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 Hemisphere Detail oriented Speech and language Calculating Understands one word at a time, not the big picture

Right Hemisphere 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 lobes Roles 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

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

DNA, Chromosomes, and Genes Chromosomes: in the nucleus; threadlike structures that contain DNA DNA: contains genetic instructions Genes: unit of hereditary information; each has its own function and location

Nucleus (center of cell) contains chromosomes and genes Chromosomes are threadlike structures composed of DNA molecules Gene: a segment of DNA (spiraled double chain) containing the hereditary code Fig. 2.3

Polygenetic Inheritance Polygenetic Inheritance: when many genes interact to influence a characteristic Behavioral traits are caused by several genes (and the environment)

Genes Human Genome Project: Humans have 20,000-25,000 genes All humans: genes are 99.9% the same Humans and apes share 96-98% of their genes

Nature vs. Nurture Nature: the role of genes Nurture: the role of the environment and external conditions **Interactionist Perspective: Both nature and nurture shape development

Behavioral Genetics A field that looks at the influence of heredity and environment Twin studies: comparing identical and fraternal twins Adoption studies: are children more similar to the biological or adoptive parent?

Twin Studies Identical Twins share 100% of their genes Fraternal/non-twin siblings share 50% of their genes

Twin Studies We compare identical and fraternal twins If identical twins are more similar than fraternal twins, we can make the case for heredity

Adoption Studies If adopted children are more similar to biological parents, we can make the case for heredity More similar to adoptive parents: case for environment