CHAPTER 46 The Mammalian Nervous System: Structure and Higher Functions

1. CHAPTER 46The Mammalian Nervous System: Structure and Higher Functions

2. Chapter 46: The Mammalian Nervous System: Structure and Higher Functions The Nervous System: Structure, Function, and Information Flow Functional Subsystems of the Nervous System

3. Chapter 46: The Mammalian Nervous System: Structure and Higher Functions Information Processing by Neuronal Circuits Understanding Higher Brain Functions in Cellular Terms

4. The Nervous System: Structure, Function, and Information Flow • Brain and spinal cord make up the central nervous system. • Cranial and spinal nerves make up the peripheral nervous system. • A nerve is a bundle of many axons carrying information to and from the central nervous system. Review Figure 46.1 4

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6. The Nervous System: Structure, Function, and Information Flow • The nervous system can be modeled conceptually in terms of direction of information flow and whether or not we are conscious of the information. Review Figure 46.2 6

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8. The Nervous System: Structure, Function, and Information Flow • The vertebrate nervous system develops from a hollow dorsal neural tube. • The brain forms from three swellings at its anterior end, which become the: • hindbrain, • midbrain, and • forebrain. Review Figure 46.3 8

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12. The Nervous System: Structure, Function, and Information Flow • The forebrain develops into the cerebral hemispheres and the underlying thalamus and hypothalamus. • The midbrain and hindbrain develop into the brain stem. • More primitive and autonomic functions are localized in the brain stem, and conscious experience depends on the cerebrum. 12

13. Functional Subsystems of the Nervous System • The nervous system is composed of many subsystems functioning simultaneously. • Some important ones are the spinal cord, reticular system, limbic system, and cerebrum. 13

14. Functional Subsystems of the Nervous System • The spinal cord communicates information between brain and body. • It processes and integrates much information, and can issue some commands to the body without brain input. Review Figure 46.4 14

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16. Functional Subsystems of the Nervous System • The reticular system of the brain stem is a complex network that directs incoming information to appropriate brain stem nuclei • They control autonomic functions, as well as transmitting the information to the forebrain resulting in conscious sensation. • The reticular system controls level of nervous system arousal. Review Figure 46.5 16

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18. Functional Subsystems of the Nervous System • The limbic system is an evolutionarily primitive part of the forebrain involved in: • emotions • physiological drives • instincts • memory. Review Figure 46.6 18

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20. Functional Subsystems of the Nervous System • The cerebral hemispheres are the dominant structures of the human brain. • Their surfaces consist of a layer of neurons called the cerebral cortex. 20

21. Functional Subsystems of the Nervous System • Most of the cerebral cortex is involved in higher-order information processing, and these areas are generally called association cortex. 21

22. Functional Subsystems of the Nervous System • The cerebral hemispheres can be divided into temporal, frontal, parietal, and occipital lobes. • Many motor functions are localized in the frontal lobe • Information from many receptors around the body projects to the parietal lobe • Visual information projects to the occipital lobe • Auditory information projects to the temporal lobe. Review Figures 46.7, 46.8, 46.9, 46.10 22

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28. Information Processing by Neuronal Circuits • The functions of the nervous system are beginning to be understood in terms of the properties of cells organized in neuronal circuits. 28

29. Information Processing by Neuronal Circuits • The autonomic nervous system consists of efferent pathways that control the body’s organs and organ systems. • Its sympathetic and parasympathetic divisions normally work in opposition. • They are characterized by their anatomy, neurotransmitters, and effects on target tissues. Review Figure 46.11 29

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32. Information Processing by Neuronal Circuits • Neuronal circuits in the occipital cortex integrate visual information. • Receptive field responses of retinal ganglion cells are communicated to the brain in optic nerves. • This information is projected to the visual cortex so as to create receptive fields for cortical cells. 32

33. Information Processing by Neuronal Circuits • A simple cell is stimulated by a bar of light with a specific orientation falling at a specific location on the retina. • A complex cell is maximally stimulated by such a stimulus moving across the retina. • The visual cortex seems to assemble a mental image of the visual world by analyzing edges of patterns of light. Review Figure 46.12 33

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35. Information Processing by Neuronal Circuits • Binocular vision results from circuits that communicate information from both eyes 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 Figure 46.13 35

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37. Understanding Higher Brain Functions in Cellular Terms • Humans have a daily cycle of sleep and waking. • Sleep can be divided into slow-wave and rapid-eye-movement sleep. • Human non-REM sleep is divided into four stages of increasing depth. Review Figure 46.14 37

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39. Understanding Higher Brain Functions in Cellular Terms • Some learning and memory processes have been localized to specific brain areas. • Repeated activations of identified circuits in brain regions have revealed long-lasting changes in synaptic properties referred to as long-term potentiation and long-term depression • These may be involved in learning and memory. Review Figure 46.15 39

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42. Understanding Higher Brain Functions in Cellular Terms • Complex memories can be elicited by stimulating small regions of association cortex. • Damage to the hippocampus can destroy the ability to form long-term memories. 42

43. Understanding Higher Brain Functions in Cellular Terms • Language abilities are localized mostly in the left cerebral hemisphere, a phenomenon known as lateralization. 43

44. Understanding Higher Brain Functions in Cellular Terms • When the corpus callosum is cut, communication between left and right cerebral hemispheres is eliminated. 44

45. Understanding Higher Brain Functions in Cellular Terms • 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 Figure 46.16 45

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