【Psychology and Life】Chapter 03 — Main Points

* All the following abstractions are excerpted from <Psychology and Life>, Richard J. Gerrig & Philip G. Zimbardo, 19th edition


Chapter 03 — The Biological and Evolutionary Bases of Behavior. 


— Heredity and Behavior

  • Species originate and change over time because of natural selection.

  • In the evolution of humans, bipedalism and encephalization were responsible for subsequent advances, including language and culture.

  • The basic unit of heredity is the gene. Genes determine the range of effects the environmental factors can have in influencing the expression of phenotypic traits.


— The Nervous System in Action

  • The neuron, the basic unit of the nervous system, receives, processes, and relays information to other cells, glands, and muscles.

  • Neurons relay information from the dendrites through the cell body (soma) to the axon to the terminal buttons.

  • Sensory neurons receive messages from specialized receptor cells and send them toward the CNS. Motor neurons direct messages from the CNS to muscles and glands. Interneurons relay information from sensory neurons to other interneurons or to motor neurons.

  • Once the summation of inputs to a neuron exceeds a specific threshold, an action potential is sent along the axon to the terminal buttons.

  • All-or-none action potentials are created when the opening of ion channels allows an exchange of ions across the cell membrane.

  • Neurotransmitters are released into the synaptic gap between neurons. Once they diffuse across the gap, they lodge in the receptor molecules of the postsynaptic membrane.

  • Whether these neurotransmitters excite or inhibit the membrane depends on the nature of the receptor molecule.


— Biology and Behavior

  • Neuroscientists use several methods to research the relation between brain and behavior: studying brain-damaged patients, producing lesions at specific brain sites, electrically stimulating the brain, recording brain activity, and imaging the brain with computerized devices.

  • The brain and the spinal cord make up the central nervous system (CNS).

  • The peripheral nervous system (PNS) is composed of all neurons connecting the CNS to the body. The PNS consists of the somatic nervous system, which regulates the body's skeletal muscles, and the autonomic nervous system (ANS), which regulates life-support processes.

  • The brain consists of three integrated layers: the brain stem, limbic system, and cerebrum.

  • The brain stem is responsible for breathing, digestion, and heart rate.

  • The limbic system is involved in long-term memory, aggression, eating, drinking, and sexual behavior.

  • The cerebrum controls higher mental functions.

  • Some functions are lateralized to one hemisphere of the brain. For example, most individuals have speech localized in the left hemisphere.

  • Although the two hemispheres of the brain work smoothly in concert, they typically embody different styles of processing: The left hemisphere is more analytic; the right hemisphere is more holistic.

  • The endocrine system produces and secretes hormones into the bloodstream.

  • Hormones help regulate growth, primary and secondary sexual characteristics, metabolism, digestion, and arousal.

  • New cell growth and life experiences reshape the brain after birth.


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