Chapter Summary/Lecture Organizer

I. NEURAL BASES OF BEHAVIOR

A. What Is a Neuron? – The brain and the nervous system consists of as many as one trillion special cells called neurons that communicate information by sending and receiving signals to other neurons. Glial cells provide structural and support for the neurons. The main parts of the neuron are the dendrites, the soma, or cell body, and the axon (Figure 2.1). The dendrites are small branching structures attached to the soma that receive information from other neurons and transmit the information received to the soma (cell body). The soma determines whether to transmit information on to the axon. The axon is a part of the neuron that is specialized for carrying information away from the cell body toward other neurons or to muscles and glands. Axons may be covered with an insulating substance called myelin.

B. How Do Neurons Communicate? – When messages are received by the dendrites and cell body they are passed along the axon in the form of an electrical impulse, called an action potential. When no information is being conducted by the axon, it is said to be at its resting potential or to be polarized. The action potential either fires completely or not at all or is referred to as the all-or-none law. Information is transferred from one neuron to another at the synapse, the juncture between neurons via chemicals called neurotransmitters. When the action potential reaches the knoblike terminals at the end of the axon, neurotransmitters are released into the synapse.

Psychology at Work: How Neurotransmitters and Hormones Affect – The roles of neurotransmitters, endorphins, and hormones are explored. Neurotransmitters regulate glands and muscles, promote sleep, affect learning, memory, motivation, emotions, and psychological disorders, such as, Parkinson’s disease, schizophrenia, depression, and Alzheimer’s disease. Table 2.1 lists several neurotransmitters and their effects. Chemical substances act at the synapse by replacing, decreasing, or enhancing the amount of neurotransmitter. Endorphins are chemical messengers that produce effects similar to those of natural opiates by reducing pain and promoting pleasure. The chemical messengers in the endocrine system are called hormones. Working with the nervous system the endocrine system effects changes in behavior, as well as, maintaining the body's "status quo." In addition, the endocrine system secretes hormones that regulate the reproductive system. The major link between the endocrine and nervous systems is the hypothalamus and pituitary.

II. NERVOUS SYSTEM ORGANIZATION

A. Central Nervous System (CNS) – The nervous system is divided into the Central Nervous
System (CNS) and the Peripheral Nervous System (PNS). The CNS consists of the brain and the spinal cord and is encased in bone - the skull and spinal column. Recent research on the brain’s ability to reorganize, replenish brain cells, and respond to stem cell transplanting is highlighted. The concepts of neurogenesis and neuroplasty are introduced.The spinal cord is responsible for reflex actions that control all voluntary and reflex responses of the body below the neck. The workings of the “reflex arc” are highlighted.

B. Peripheral Nervous System (PNS) - The PNS includes all nerves going to and from the brain and spinal cord. Its two major subdivisions are the somatic and the autonomic nervous system. The somatic nervous system includes all nerves carrying afferent (incoming) sensory information and efferent (outgoing) motor information to and from the sense organs and skeletal muscles. The autonomic nervous system includes those nerves outside the brain and spinal cord that maintain homeostasis, normal functioning of the body’s glands, heart muscles, and the smooth muscles of the blood vessels and internal organs. The autonomic nervous system is