Psychological Science, 3e: W. W. Norton StudySpace

What Is the Genetic Basis of Psychological Science?

• Heredity Involves Passing Along Genes through Reproduction: The Human Genome Project has mapped the genes that make up humans'23 chromosomal pairs. Genes' variations are either dominant or recessive. The genome represents the genotype, and the observable characteristics are the phenotype. Many characteristics are polygenic.
• Genotypic Variation Is Created by Sexual Reproduction: Because half of each chromosome comes from each parent and the two halves are joined randomly, there is enormous potential variation in the resulting zygote's genome. Mutations also give rise to variations.
• Genes Affect Behavior: Behavioral geneticists can quantify the similarity and variation in a population's shared characteristics. Twin studies, research on adoptees, and other investigations of hereditary and genetic influence provide insight into heritability.
• Social and Environmental Contexts Influence Genetic Expression: Gene expression is a complex interaction between genetic makeup and environmental context.
• Genetic Expression Can Be Modified: Genetic manipulation has been achieved in mammals such as mice, but has proved difficult in humans. However, animal studies using the technique of "knocking out" genes to determine their effects on behaviors and on disease are a valuable tool for understanding genetic influences.

How Does the Nervous System Operate?

• Neurons Are Specialized for Communication: Neurons are the basic building blocks of the nervous system. They receive and send chemical messages. All neurons have the same basic structure, but neurons vary by function and by location in the nervous system.
• Action Potentials Cause Neural Communication: Changes in a neuron's electrical charge are the basis of an action potential, or neural firing. Firing is the means of communication within networks of neurons.
• Neurotransmitters Bind to Receptors across the Synapse: Neurons do not touch; they release chemicals (neurotransmitters) into the synapse, a small gap between the neurons. Neurotransmitters bind with the receptors of postsynaptic neurons, thus changing the charge in those neurons. Neurotransmitters 'effects are halted by reuptake of the neurotransmitters into the presynaptic neurons, enzyme deactivation, or autoreception.
• Neurotransmitters Influence Mind and Behavior: Neurotransmitters have been identified that influence aspects of the mind and of behavior in humans, including emotions, motor skills, sleep, learning and memory, pain control, and pain perception. Drugs and toxins mimic neurotransmitters' actions or reduce neurotransmitters' availability.

What Are the Basic Brain Structures and Their Functions?

• The Brainstem Houses the Basic Programs of Survival: The top of the spinal cord forms the brainstem, which is involved in basic functions such as breathing and walking as well as general arousal.
• The Cerebellum Is Essential for Movement: The cerebellum ("little brain"), the bulging structure connected to the back of the brainstem, controls balance and is essential for movement.
• Subcortical Structures Control Emotions and Basic Drives: The subcortical structures play a key part in psychological functions because they control vital functions (the hypothalamus), sensory relay (the thalamus), memories (the hippocampus), emotions (the amygdala), and the planning and producing of movement (the basal ganglia).
• The Cerebral Cortex Underlies Complex Mental Activity: The lobes of the cortex play specific roles in controlling vision (occipital), touch (parietal), hearing and speech comprehension (temporal), and planning and movement (frontal).

How Are Neural Messages Integrated into Communication Systems?

• The Peripheral Nervous System Includes the Somatic and Autonomic Systems: The body's internal environment is regulated by the autonomic system, which is divided into the alarm response (sympathetic) and the return-to-normal response (parasympathetic). The somatic system relays sensory information.
• The Endocrine System Communicates through Hormones: Both endocrine glands and organs produce and release chemical substances, which travel to body tissues through the bloodstream and influence a variety of processes, including sexual behavior.
• Actions of the Nervous System and Endocrine System Are Coordinated: Most of the central control of the endocrine system occurs through the actions of both the hypothalamus and the pituitary gland; the latter controls the release of hormones from the rest of the endocrine glands.

How Does the Brain Change?

• The Interplay of Genes and the Environment Wires the Brain: Chemical signals influence cells' growth and function. Environmental experiences, especially during critical periods, are necessary for cells to develop properly and for them to make more detailed connections.
• Culture Affects the Brain: Daily social interactions, which vary among cultures (and subcultures and individuals), are reflected in each brain's unique organization.
• The Brain Rewires Itself throughout Life: Although plasticity decreases with age, the brain retains the ability to rewire itself throughout life. This ability is learning's biological basis.
• Females' and Males' Brains Are Similar and Different: Although males' and females' brains are predominantly similar, males' brains are larger than females' (on average), and females' verbal abilities are organized more bilaterally (more equally in both hemispheres). There are sex differences in the rate of development for some areas of the brain.
• The Brain Can Recover from Injury: The brain can reorganize its functions in response to brain damage, although this capacity decreases with age. Anomalies in sensation and in perception, such as synesthesia, are attributed to cross-wiring connections in the brain.

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