Chapter Summary

• The brain and spinal cord make up the central nervous system (CNS); the cranial and spinal nerves make up the peripheral nervous system (PNS).

• The nervous system can be modeled conceptually in terms of the direction of information flow and whether we are conscious of the information. The afferent component of the PNS carries information from sensory cell receptors to the CNS, and the efferent component of the PNS carries information from the CNS to the target tissues and organs that are being controlled. Review Figure 46.1

• The vertebrate nervous system develops from a hollow dorsal neural tube. The brain forms from three swellings at the anterior end of the neural tube, which become the hindbrain, the midbrain, and the forebrain. The developing forebrain consists of the telencephalon and the diencephalon. The telencephalon develops into the cerebrum (cerebral hemispheres). The underlying diencephalon develops into the thalamus and hypothalamus. The midbrain and hindbrain develop into the brainstem and the cerebellum. Review Figure 46.2

• The spinal cord communicates information between the brain and the rest of the body.

• The reticular-activating system is a complex network that directs incoming information to appropriate brainstem nuclei that control autonomic functions, and transmits information to the forebrain that results in conscious sensation. The reticular-activating system controls the level of arousal of the nervous system, including sleep and wakefulness.

• The limbic system is a complex set of phylogenetically old forebrain structures involved in emotions, mood, physiological drives (such as hunger and thirst), instincts, and memory. Review Figure 46.3

• The cerebral hemispheres are the dominant structures of the human brain. Their surfaces are layers of neurons called the cerebral cortex. The cerebral hemispheres can be divided into the temporal, frontal, parietal, occipital, and insular lobes. Many motor functions are localized in parts of the frontal lobe. Information from many sensory receptors projects to a region of the parietal lobe. Visual information projects to the occipital lobe, and auditory information projects to a region of the temporal lobe. The insular cortex integrates much information about the physiological state of the body, but it is also activated by psychological and emotional conditions and may be responsible for the sense of self. Review Figures 46.4, 46.5, Activity 46.1

• The autonomic nervous system (ANS) controls the physiological function of organs and organ systems. Its sympathetic and parasympathetic divisions are characterized by their anatomy, neurotransmitters, and effects on target tissues. Review Figure 46.8

• The neural network of vision involves patterns of light falling on receptive fields in the retina. Receptive fields have a center and a surround, which have opposing effects on ganglion cell firing. Review Figure 46.10, Activity 46.2, Animation 46.1

• Information from retinal ganglion cells is communicated via the optic nerve to the thalamus and then to the visual cortex. The visual cortex seems to assemble an image of the visual world by analyzing edges of patterns of light.

• Binocular vision is possible because information from both eyes is communicated to binocular cells in the visual cortex. These cells interpret distance by measuring the disparity between where the same stimulus falls on the two retinas. Review Focus: Key Figure 46.10

• Humans have a daily cycle of sleep and waking. Sleep can be divided into rapid eye movement (REM) sleep and non-REM sleep. Deep non-REM sleep is known as slow-wave sleep because of its characteristic EEG patterns. Review Figure 46.11

• Language abilities are localized mostly in the left cerebral hemisphere, a phenomenon known as lateralization. Different areas of the left hemisphere—including Broca’s area, Wernicke’s area, and the angular gyrus—are responsible for different aspects of language. Review Figures 46.12, 46.13, Activity 46.3

• Some learning and memory processes can be localized to specific brain areas. Long-lasting changes in synaptic properties referred to as long-term potentiation (LTP) and long-term depression (LDP) may be involved in learning and memory.

• Complex memories can be elicited by stimulating small regions of association cortex. Damage to the hippocampus can destroy the ability to form long-term declarative memory.

• A sense of the physiological state of the body may be created in the insular cortex from visceral afferent information. Evolution of this integrative function in humans and other higher primates could be the basis for conscious experience.