36: Lecture VERTEBRATE BRAIN
Summary. The vertebrate brain is the most complex organ in any organism, with 10 billion to 100 billion neurons in the human brain and over a hundred different neuronal cell types. Today we discuss the relationships of central and the peripheral nervous systems and focus on the brain. Although the various parts of the brain scale together in size, and brain size scales with body size for a large number of mammals, the brains of monkeys and apes, and of dolphins and porpoises are proportionately much larger for their body size than is the case in other mammals. Within the primates, brain size scales with body size, but after the human lineage split from chimps 6 million years ago our brain size has increased exponentially, with little increase in body size. We will examine how the cerebral cortex, the largest and evolutionarily newest part of the brain, is regionally specialized to perform different tasks of analyzing sensory information and producing appropriate motor behavior. To understand how we know this information about people requires an introduction to the methods used in modern neuroscience, including electrophysiological recording, studies of the effects of lesions, and studies of functional imaging.
Reading Assignment
Campbell, N. A. and Reece, J. B. (2008). 8th edition, Chapter 49 (pp. 1067-1079).
Objectives
1. To recognize the different parts of the vertebrate nervous system: the central nervous system (CNS): composed of Brain, Spinal cord, and the peripheral nervous system (PNS) made of nerves. 2. To understand the anatomy and the functions of the autonomic nervous system, both sympathetic and parasympathetic. 3. To be able to discuss the scaling of brain size and body size in mammals, especially primates. 4. To understand the concept of sensory maps and motor maps in the brain. Be able to discuss their organizational 5. principles. To be able trace the somatosensory system and its projection from periphery to cortex and see this as an ideal example of maps and parallel pathways. 6. To speculate how it is possible to have a map of a sensory system, e.g., the auditory world, without simply being a topographic projection of some peripheral sensory surface such as the skin or muscles. 7. To understand the importance of imaging techniques in neuroscience and the study of structure/function relationships in the brain. 8. Language and the brain: understand the kinds of evidence used to locate areas in the brain devoted to language and to understand how language is controlled by different structures in the brain.
Study Questions
1. Of what significance are the increased gyri and sulci in the cerebral cortex of humans compared to other apes, such as chimps. 2. One of the greatest advances in the study of brain function has come from imaging techniques that have allowed finer and finer resolution studies of activity patterns of brain areas engaged in specific behavioral and cognitive tasks. What are some of the imaging techniques used for studying brain function, and how do they work? 3. Trace the somatic senses of touch and pressure from the peripheral receptors on the skin, through the spinal cord, to the sensory cortex. What is meant by a sensory map in cortex? 4. Humans are bilaterally symmetrical creatures. Lesions, or stoke, affecting some areas of cortex will only have a deleterious effect on functions of one side of the body. However, lesions to some areas of the cortex on the left side of the brain will have a universal deleterious effect whereas a lesion to the same area on the right side will have little effect on the same function. Discuss an example of symmetrical cortical areas and an example of non-symmetrical areas and the behavioral functions they control.