Chapter 2 Summary & Outline

• The nervous system is extensive—monitoring, regulating, and modulating the activities of all parts and organs of the body.

The Nervous System Is Composed of Cells

• At the microscopic level, neurons are the basic units of the nervous system. The typical neuron of most vertebrate species has four main parts: (1) the cell body, which contains the nucleus; (2) dendrites, which receive information; (3) an axon, which carries impulses from the neuron; and (4) axon terminals, which transmit the neuron’s impulses to other cells. Because of the variety of functions they serve, neurons are extremely varied in size, shape, and chemical activity. Review Figures 2.2 and 2.5, Web Activity 2.1
• The axon is generally tubular, branching at the end into many collaterals. Electrical signals, described in the next chapter, travel down the axon from the cell body to each axon terminal.
• Neurons make functional contacts with other neurons, or with muscles or glands, at specialized junctions called synapses. Synapses may be made onto dendritic spines, which exhibit neural plasticity, changing shape in response to experience. Review Figure 2.7
• At most synapses a chemical transmitter liberated by the presynaptic terminal diffuses across the synaptic cleft and binds to special receptor molecules in the postsynaptic membrane.
• Glial cells serve many functions, including the breakdown of transmitters, the production of myelin sheaths around axons, the exchange of nutrients and other materials with neurons, the direct regulation of the interconnections and activity of neurons, and the removal of cellular debris. Review Figure 2.6

Study questions: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17

The Nervous System Consists of Central and Peripheral Divisions

• At the gross anatomical level (i.e., to the naked eye), the nervous system of vertebrates is divided into peripheral and central nervous systems. Review Figure 2.8
• The peripheral nervous system includes the cranial nerves, spinal nerves, and autonomic nervous system. The autonomic nervous system consists of the sympathetic nervous system, which tends to ready the body for action; the parasympathetic nervous system, which tends to have an effect opposite to that of the sympathetic system; and the enteric nervous system, which innervates the gut. Review Figures 2.9 and 2.11, Web Activities 2.2, 2.3, and 2.4
• The central nervous system (CNS) consists of the brain and spinal cord. The main divisions of the brain are the forebrain (telencephalon and diencephalon), the midbrain (mesencephalon), and the hindbrain (metencephalon and myelencephalon). Web Activities 2.5, 2.6, 2.7, and 2.8

Study questions: 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38

The Brain Is Described by Both Structure and Function

• The human brain is dominated by the cerebral hemispheres, which include the cerebral cortex, an extensive sheet of folded tissue. The six-layered cerebral cortex is responsible for higher-order functions such as vision, language, and memory. Other neural systems include the basal ganglia, which regulate movement; the limbic system, which controls emotional behaviors; and the cerebellum, which aids motor control. Review Figure 2.15, Web Activities 2.9, 2.10, and 2.11
• The brain and spinal cord, surrounded and protected by the three meninges, float in cerebrospinal fluid (CSF), which surrounds and infiltrates the brain (via cerebral ventricles). Review Figure 2.10, Web Activity 2.12

Study questions: 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54

Specialized Support Systems Protect and Nourish the Brain

• The vascular system of the brain is an elaborate array of blood vessels that deliver nutrients and other substances to the brain. The walls of the blood vessels in the brain form the blood-brain barrier, restricting the flow of large, potentially harmful molecules into the brain. Review Figure 2.20

Study questions: 55 | 56 | 57 | 58 | 59 | 60

Newer Imaging Techniques Enable Us to Look into the Living Human Brain

• Modern imaging techniques make it possible to visualize the anatomy of the living human brain and regional metabolic differences. These techniques include computerized axial tomography (CT), positron emission tomography (PET), magnetic resonance imaging (MRI), functional MRI (fMRI), infrared optical imaging, and magnetoencephalography (MEG). Review Figure 2.21, Web Activity 2.13

Study questions: 61 | 62 | 63 | 64 | 65 | 66 | 67