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Brains, Biology, and Behavior



Individuals' brains, biology, and behavior are influenced by the interplay between genes, environmental events, and intentional activities. Genes, which are inherited from parents, shape physical development. They also direct the development of brain structures involved in thinking, acting, and feeling. Genes can be turned on or off by environmental influences, a process called epigenesis. Environmental influences include everything from toxin exposure to family conflict to access to educational resources. The brain and nervous system are made up of neurons, cells that transmit messages throughout the brain and body. Both genes and the environment influence the development of connections between neurons. Different brain structures control and coordinate specific cognitive, motor, and emotional reactions. Modern brain imaging techniques have allowed psychologists to better understand the structure and function of the brain. The nervous system works alongside the endocrine system, which releases hormones to control behavior.

At A Glance

  • Genes, made up of DNA, are the basic units of heredity. Genes carry instructions for manufacturing proteins, which guide development and influence physical traits and behavior.
  • Genes that code for beneficial traits are likely to be passed on to future generations because they help an organism survive and reproduce.
  • Genes and the environment interact to shape physical and psychological traits. Genetic factors can influence environmental responses, and environmental factors can alter gene expression.
  • Neurons are made up of a cell body, dendrites that receive messages from other neurons, and an axon, which transmits messages.
  • Neurotransmitters are molecules used to transmit messages between neurons by making a neuron more or less likely to fire. Many drugs work by influencing or mimicking neurotransmitter activity.
  • The peripheral nervous system, made up of neurons outside the brain and spinal cord, transmits messages throughout the body. The somatic nervous system allows voluntary control of skeletal muscles, whereas the autonomic nervous system automatically controls internal organs and glands.
  • The central nervous system, made up of the brain and spinal cord, controls decision-making and behavior.
  • The cerebral cortex is responsible for sensory processing and complex brain functions, such as reasoning, language, planning, and self-regulation.
  • Each hemisphere of the brain is divided into four regions, referred to as the frontal, parietal, temporal, and occipital lobes.
  • The endocrine system releases hormones, which influence both neural activity and the release of other hormones.
  • Early studies of brain function involved exploring the effects of brain damage. Modern techniques make it possible to stimulate or inhibit specific brain regions, create detailed images of the brain, and observe brain activity.
  • Brain imaging techniques give psychologists a noninvasive way to observe brain structure and brain function.