《医学生理学 Medical Physiology》参考教材资料（PDF电子书籍）Neuroscience, Third Edition, 2004

Studying the Nervous Systems of Humans and Other Animals 19 Precentral Central sulcus Postcentral Frontal Parietal Cerebral Parieto- Occipital Lateral Frontal Parietal (Sylvian)fissure lobe Preoccipital Brainstem (B) Cingulate Central Diencephalon sulcus lobe Parieto- Cingulate gyrus Calcarine evel of section Level of section Corpus shown in(F) Anterior Internal Basal ganglia Cerebral cortex callosum teral callosum (gray matter) ventricle White Globus Third Anterior chiasm Amygdala Fornix

Studying the Nervous Systems of Humans and Other Animals 19 Precentral gyrus (A) (B) (E) (D) (F) (C) Postcentral gyrus Central sulcus Parieto￾occipital sulcus Preoccipital notch Lateral (Sylvian) fissure Cerebral hemisphere Cerebellum Brainstem Spinal cord Cerebellum Cingulate gyrus Parieto￾occipital sulcus Spinal cord Cingulate sulcus Diencephalon Corpus callosum Anterior commissure Brainstem Midbrain Pons Medulla Calcarine sulcus Central sulcus Corpus callosum Caudate Putamen Internal capsule White matter Optic chiasm Basal forebrain nuclei Anterior commissure Temporal lobe Cerebral cortex (gray matter) Amygdala Corpus Lateral callosum ventricle Fornix Third ventricle Hippocampus Mammillary body Lateral ventricle (temporal horn) Thalamus Caudate Putamen Globus pallidus Tail of caudate nucleus Basal ganglia Internal capsule Frontal lobe Temporal lobe Parietal lobe Occipital lobe Frontal lobe Temporal lobe Parietal lobe Occipital lobe Level of section shown in (E) Level of section shown in (F) Purves01 5/13/04 1:03 PM Page 19

20 Chapter One roughly halfway between the rostral and caudal poles of the hemispheres (Figure 1.12A). This prominent sulcus divides the frontal lobe at the rostral nd of the hemisphere from the more caudal parietal lobe. Prominent on either side of the central sulcus are the pre- and postcentral gyri. These gyri are also functionally significant in that the precentral gyrus contains the pri- mary motor cortex important for the control of movement, and the posten- tral gyrus contains the primary somatic sensory cortex which is important for the bodily senses(see below) The remaining subdivisions of the forebrain lie deeper in the cerebral hemispheres(Figure 1. 12B). The most prominent of these is the collection of deep structures involved in motor and cognitive processes collectively referred to as the basal ganglia. Other particularly important structures are the hippocampus and amygdala in the temporal lobes(these are vital sub- strates for memory and emotional behavior, respectively), and the olfactory bulbs(the central stations for processing chemosensory information arising from receptor neurons in the nasal cavity)on the anterior-inferior aspect of the frontal lobes. Finally, the thalamus lies in the diencephalon and is a crit ical relay for sensory information(although it has many other functions as well); the hypothalamus, which as the name implies lies below the thala- mus, is the central organizing structure for the regulation of the bodys many homeostatic functions(e.g, feeding, drinking, thermoregulation) This rudimentary description of some prominent anatomical landmarks provides a framework for understanding how neurons resident in a number of widely distributed and distinct brain structures communicate with one another to define neural systems dedicated to encoding, processing and relaying specific sorts of information about aspects of the organisms envi- ronment, and then initiating and coordinating appropriate behavioral Organizational Principles of Neural Systems These complex perceptual and motor capacities of the brain reflect the inte- grated function of various neural systems. The processing of somatic sensor nformation(arising from receptors in the skin, subcutaneous tissues, and the musculoskeletal system that respond to physical deformation at the body surface or displacement of muscles and joints) provides a convenient example. These widely distributed structures that participate in generating somatic sensations are referred to as the somatic sensory system(Figure 1. 13). The components in the peripheral nervous system include the recep tors distributed throughout the skin as well as in muscles and tendons, the related neurons in dorsal root ganglia, and neurons in some cranial ganglia The central nervous system components include neurons in the spinal cord, as well as the long tracts of their axons that originate in the spinal cord, travel through the brainstem, and ultimately terminate in distinct rela nuclei in the thalamus in the diencephalon. The still-higher targets of the thalamic neurons are the cortical areas around the postcentral gyrus that are collectively referred to as the somatic sensory cortex. Thus, the somatic sen- ory system includes specific populations of neurons in practically every subdivision of the nervous system. Two further principles of neural system organization are evident in the somatic sensory system: topographic organization and the prevalence of parallel pathways(see Figure 1. 13). As the name implies, topography refers to a mapping function--in this case a map of the body surface that can be discerned within the various structures that constitute the somatic sensor

20 Chapter One roughly halfway between the rostral and caudal poles of the hemispheres (Figure 1.12A). This prominent sulcus divides the frontal lobe at the rostral end of the hemisphere from the more caudal parietal lobe. Prominent on either side of the central sulcus are the pre- and postcentral gyri. These gyri are also functionally significant in that the precentral gyrus contains the pri￾mary motor cortex important for the control of movement, and the postcen￾tral gyrus contains the primary somatic sensory cortex which is important for the bodily senses (see below). The remaining subdivisions of the forebrain lie deeper in the cerebral hemispheres (Figure 1.12B). The most prominent of these is the collection of deep structures involved in motor and cognitive processes collectively referred to as the basal ganglia. Other particularly important structures are the hippocampus and amygdala in the temporal lobes (these are vital sub￾strates for memory and emotional behavior, respectively), and the olfactory bulbs (the central stations for processing chemosensory information arising from receptor neurons in the nasal cavity) on the anterior–inferior aspect of the frontal lobes. Finally, the thalamus lies in the diencephalon and is a crit￾ical relay for sensory information (although it has many other functions as well); the hypothalamus, which as the name implies lies below the thala￾mus, is the central organizing structure for the regulation of the body’s many homeostatic functions (e.g., feeding, drinking, thermoregulation). This rudimentary description of some prominent anatomical landmarks provides a framework for understanding how neurons resident in a number of widely distributed and distinct brain structures communicate with one another to define neural systems dedicated to encoding, processing and relaying specific sorts of information about aspects of the organism’s envi￾ronment, and then initiating and coordinating appropriate behavioral responses. Organizational Principles of Neural Systems These complex perceptual and motor capacities of the brain reflect the inte￾grated function of various neural systems. The processing of somatic sensory information (arising from receptors in the skin, subcutaneous tissues, and the musculoskeletal system that respond to physical deformation at the body surface or displacement of muscles and joints) provides a convenient example. These widely distributed structures that participate in generating somatic sensations are referred to as the somatic sensory system (Figure 1.13). The components in the peripheral nervous system include the recep￾tors distributed throughout the skin as well as in muscles and tendons, the related neurons in dorsal root ganglia, and neurons in some cranial ganglia. The central nervous system components include neurons in the spinal cord, as well as the long tracts of their axons that originate in the spinal cord, travel through the brainstem, and ultimately terminate in distinct relay nuclei in the thalamus in the diencephalon. The still-higher targets of the thalamic neurons are the cortical areas around the postcentral gyrus that are collectively referred to as the somatic sensory cortex. Thus, the somatic sen￾sory system includes specific populations of neurons in practically every subdivision of the nervous system. Two further principles of neural system organization are evident in the somatic sensory system: topographic organization and the prevalence of parallel pathways (see Figure 1.13). As the name implies, topography refers to a mapping function—in this case a map of the body surface that can be discerned within the various structures that constitute the somatic sensory Purves01 5/13/04 1:03 PM Page 20

Studying the Nervous Systems of Humans and Other Animals 21 Cerebral cortex sylvius omatic sensory Cerebral cortex cortex Somatic sensory (A) Thalamus Spina Cervical Brainstem O Dorsal root nervous system Figure 1. 13 The anatomical and functional organi- zation of the somatic sensory system. Central ner- system. Thus, adjacent areas on the body surface are mapped to vous system components of the somatic sensory sys- adjacent regions in nuclei, in white matter tracts, and in the thal- m are found in the spinal cord, brainstem amic and cortical targets of the system. Beginning in the periph- information from the body surface is mapped onto ery, the cells in each dorsal root ganglion define a discrete der- dorsal root ganglia(DRG), schematically depicted matome(the area of the skin innervated by the processes of cells here as attachments to the spinal cord. The various from a single dorsal root). In the spinal cord, from caudal to ros- shades of purple indicate correspondence between tral, the dermatomes are represented in corresponding regions regions of the body and the drg that relay informa- of the spinal cord from sacral(back) to lumbar (legs)to thoracic tion from the body surface to the central nervous (chest)and cervical (arms and shoulders)(see Figures 1.13 and system Information from the head and neck is 1.11C). This so-called somatotopy is maintained in the somatic relayed to the CNS via the trigeminal ganglia. (B) sensory tracts in spinal cord and brainstem that convey infor- Somatosensory information travels from the peri- mation to the relevant forebrain structures of the somatic sen- pheral sensory receptors via parallel pathways for sory system(Figure 1.14) mechanical sensation and for the sensation of pain Parallel pathways refer to the segregation of nerve cell axons through the spinal cord and brainstem,ultimately that process the distinct stimulus attributes that comprise a par- ticular sensory, motor, or cognitive modality. For somatic sensa- which it is relayed to the somatic sensory cortex in tion,the stimulus attributes relayed via parallel pathways are the postcentral gyrus(indicated in blue in the image pain, temperature, touch, pressure, and proprioception( the sense of the whole brain; MRI courtesy of L E. White, J of joint or limb position). From the dorsal root ganglia, through Vovoydic, and S M. Williams)

system. Thus, adjacent areas on the body surface are mapped to adjacent regions in nuclei, in white matter tracts, and in the thal￾amic and cortical targets of the system. Beginning in the periph￾ery, the cells in each dorsal root ganglion define a discrete der￾matome (the area of the skin innervated by the processes of cells from a single dorsal root). In the spinal cord, from caudal to ros￾tral, the dermatomes are represented in corresponding regions of the spinal cord from sacral (back) to lumbar (legs) to thoracic (chest) and cervical (arms and shoulders) (see Figures 1.13 and 1.11C). This so-called somatotopy is maintained in the somatic sensory tracts in spinal cord and brainstem that convey infor￾mation to the relevant forebrain structures of the somatic sen￾sory system (Figure 1.14). Parallel pathways refer to the segregation of nerve cell axons that process the distinct stimulus attributes that comprise a par￾ticular sensory, motor, or cognitive modality. For somatic sensa￾tion, the stimulus attributes relayed via parallel pathways are pain, temperature, touch, pressure, and proprioception (the sense of joint or limb position). From the dorsal root ganglia, through Studying the Nervous Systems of Humans and Other Animals 21 Central nervous system Peripheral nervous system Sensory receptors for body Sensory receptors for face Sensory receptor Thalamus Cerebral cortex Somatic sensory cortex (A) (B) Brainstem Spinal cord Thalamus Cerebral cortex Somatic sensory cortex Brainstem Spinal cord Dorsal root ganglia Dorsal root ganglia (DRG) Mechanical sensation Trigeminal ganglia Trigeminal ganglion Trigeminal ganglia Pain and temperature Mechanical sensation Pain and temperature Cervical Thoracic Lumbar Sacral Figure 1.13 The anatomical and functional organi￾zation of the somatic sensory system. Central ner￾vous system components of the somatic sensory sys￾tem are found in the spinal cord, brainstem, thalamus, and cerebral cortex. (A) Somatosensory information from the body surface is mapped onto dorsal root ganglia (DRG), schematically depicted here as attachments to the spinal cord. The various shades of purple indicate correspondence between regions of the body and the DRG that relay informa￾tion from the body surface to the central nervous system. Information from the head and neck is relayed to the CNS via the trigeminal ganglia. (B) Somatosensory information travels from the peri￾pheral sensory receptors via parallel pathways for mechanical sensation and for the sensation of pain and temperature. These parallel pathways relay through the spinal cord and brainstem, ultimately sending sensory information to the thalamus, from which it is relayed to the somatic sensory cortex in the postcentral gyrus (indicated in blue in the image of the whole brain; MRI courtesy of L. E. White, J. Vovoydic, and S. M. Williams). Purves01 5/13/04 1:03 PM Page 21

22 Chapter One the spinal cord and brainstem, and on to the somatic sensory cortex, these submodalities are kept largely segregated. Thus anatomically, biochemically, and physiologically distinct neurons transduce, encode, and relay pain, tem perature, and mechanical information. Although this information is subse- quently integrated to provide unitary perception of the relevant stimuli, neu- rons and circuits in the somatic sensory system are clearly specialized to process discrete aspects of somatic sensation This basic outline of the organization of the somatic system is representa- tive of the principles pertinent to understanding any neural system. It will in every case be pertinent to consider the anatomical distribution of neural cir- cuits dedicated to a particular function, how the function is represented or mapped"onto the neural elements within the system and how distinct stimulus attributes are segregated within subsets of neurons that comprise the system. Such details provide a framework for understanding how activ- y within the system provides a representation of relevant stimulus, the required motor response, and higher order cognitive correlates Somatic sensory Shoulder Neck Tr Arm Digits Feet Thumb Genitalia Nose Medial Figure 1.14 Somatotopic organization of sensory information. (Top)The locations of primary and secondary somatosensory cortical areas on the lateral surface of the sylvius brain(Bottom)Cortical representation of different regions of skin

22 Chapter One the spinal cord and brainstem, and on to the somatic sensory cortex, these submodalities are kept largely segregated. Thus anatomically, biochemically, and physiologically distinct neurons transduce, encode, and relay pain, tem￾perature, and mechanical information. Although this information is subse￾quently integrated to provide unitary perception of the relevant stimuli, neu￾rons and circuits in the somatic sensory system are clearly specialized to process discrete aspects of somatic sensation. This basic outline of the organization of the somatic system is representa￾tive of the principles pertinent to understanding any neural system. It will in every case be pertinent to consider the anatomical distribution of neural cir￾cuits dedicated to a particular function, how the function is represented or “mapped” onto the neural elements within the system, and how distinct stimulus attributes are segregated within subsets of neurons that comprise the system. Such details provide a framework for understanding how activ￾ity within the system provides a representation of relevant stimulus, the required motor response, and higher order cognitive correlates. Somatic sensory cortex Shoulder Neck Head Neck Arm Hand Digits Thumb Eyes Nose Face Lips Jaw Tongue Throat Toes Genitalia Feet Leg Trunk Lateral Medial Figure 1.14 Somatotopic organization of sensory information. (Top) The locations of primary and secondary somatosensory cortical areas on the lateral surface of the brain. (Bottom) Cortical representation of different regions of skin. Purves01 5/13/04 1:03 PM Page 22

Studying the Nervous Systems of Humans and Other Animals 23 Functional Analysis of Neural Systems A wide range of physiological methods is now available to evaluate the elec- trical(and metabolic) activity of the neuronal circuits that make up a neural ystem. Two approaches, however, have been particularly useful in defining how neural systems represent information. The most widely used method is single-cell, or single-unit electrophysiological recording with microelec- trodes(see above; this method often records from several nearby cells in addition to the one selected, providing further useful information). The use of microelectrodes to record action potential activity provides a cell-by-cell sis of the organization topographic maps(Figure 1.15), and can give pecific insight into the type of stimulus to which the neuron is" tuned"(i.e the stimulus that elicits a maximal change in action potential activity from the baseline state). Single-unit analysis is often used to define a neuron receptive field-the region in sensory space(e.g, the body surface, or a spe- cialized structure such as the retina)within which a specific stimulus elicits the greatest action potential response. This approach to understanding neural systems was introduced by Stephen Kuffler and Vernon Mountcastle in the early 1950s and has now been used by several generations of neuro- cientists to evaluate the relationship between stimuli and neuronal re sponses in both sensory and motor systems. Electrical recording techniques cortex Activity of cortical neuron Touch in the center Recepti ⅢH Touch in the surround of r Touch outside of receptive field has no effect Period of stimulation Central Postcentral neuron, showing the firing pattern in response to a specific peripheral siia dal Figure 1.15 Single-unit electrophysiological recording from cortical pyran )Typical experimental set-up. (B)Defining neuronal receptive fields

Functional Analysis of Neural Systems A wide range of physiological methods is now available to evaluate the elec￾trical (and metabolic) activity of the neuronal circuits that make up a neural system. Two approaches, however, have been particularly useful in defining how neural systems represent information. The most widely used method is single-cell, or single-unit electrophysiological recording with microelec￾trodes (see above; this method often records from several nearby cells in addition to the one selected, providing further useful information). The use of microelectrodes to record action potential activity provides a cell-by-cell analysis of the organization topographic maps (Figure 1.15), and can give specific insight into the type of stimulus to which the neuron is “tuned” (i.e., the stimulus that elicits a maximal change in action potential activity from the baseline state). Single-unit analysis is often used to define a neuron’s receptive field—the region in sensory space (e.g., the body surface, or a spe￾cialized structure such as the retina) within which a specific stimulus elicits the greatest action potential response. This approach to understanding neural systems was introduced by Stephen Kuffler and Vernon Mountcastle in the early 1950s and has now been used by several generations of neuro￾scientists to evaluate the relationship between stimuli and neuronal re￾sponses in both sensory and motor systems. Electrical recording techniques Studying the Nervous Systems of Humans and Other Animals 23 (A) (B) Somatic sensory cortex Receptive field (surround) Activity of cortical neuron Period of stimulation Central sulcus Postcentral gyrus Record Receptive field (center) Touch in the surround of receptive field decreases cell firing Touch outside of receptive field has no effect Touch in the center of receptive field increases cell firing Figure 1.15 Single-unit electrophysiological recording from cortical pyramidal neuron, showing the firing pattern in response to a specific peripheral stimulus. (A) Typical experimental set-up. (B) Defining neuronal receptive fields. Purves01 5/13/04 1:03 PM Page 23