Central Nervous System CNS CNS brain and spinal
Central Nervous System (CNS) • CNS brain and spinal cord • Cephalization • Development of rostral (anterior) portion of CNS • Neural groove fuses to form neural tube • Neural tube gives rise to brain & spinal cord Copyright © 2010 Pearson Education, Inc.
Neural crest 3 Neural fold cells migrate to form the neural crest, which will form much of the PNS and many other structures. Copyright © 2010 Pearson Education, Inc. Figure 12. 1, step 3
Head Surface ectoderm Tail Neural tube 4 The neural groove becomes the neural tube, which will form CNS structures. Copyright © 2010 Pearson Education, Inc. Figure 12. 1, step 4
Effect of Space Restriction on Brain Development • Midbrain and cervical flexure cause forebrain to move toward the brain stem • Cerebral hemi surfaces crease and fold into convolutions • Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) Copyright © 2010 Pearson Education, Inc.
Lissencephaly • Lissencephaly -malformed brain lack the characteristic convolutions of normal cerebral cortex. Caused by abnormalities in neuronal migration, a sequence of events in early brain development in which nerve cells travel to their final destinations to populate and an abnormal four-layered cortex (Normally form six layers of the cerebral cortex). Copyright © 2010 Pearson Education, Inc.
Lissencephaly • This process occurs between 12 and 16 weeks gestation. When the brain first forms, neurons are generated in a region of the brain known as the ventricular zone. From there, they travel by crawling outward along other cells, known as radial glia, to reach the cortical surface. The traveling neurons need instructions on when to start, continue, and stop moving, and these processes are controlled by a complicated molecular machinery. Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc.
Cerebral hemisphere Diencephalon (d) Birth Copyright © 2010 Pearson Education, Inc. Cerebellum Brain stem • Midbrain • Pons • Medulla oblongata Figure 12. 3 d
• Spinal cord • Central cavity surrounded by a gray matter core - external white matter composed of myelinated fiber tracts • Brain • Similar pattern with additional areas of gray matter • Nuclei in cerebellum and cerebrum • Cortex of cerebellum and cerebrum Copyright © 2010 Pearson Education, Inc.
Cortex of gray matter Inner gray matter Central cavity Migratory pattern of neurons Cerebrum Cerebellum Region of cerebellum Outer white matter Gray matter Central cavity Inner gray matter Outer white matter Brain stem Gray matter Central cavity Outer white matter Spinal cord Copyright © 2010 Pearson Education, Inc. Inner gray matter Figure 12. 4
Ventricles of the Brain • Lined by ependymal cells • Contain cerebrospinal fluid (CSF) • Two C-shaped lateral ventricles in cerebral hemispheres • Third in diencephalon • Fourth in hindbrain, dorsal to pons, develops from lumen of the neural tube Copyright © 2010 Pearson Education, Inc.
Lateral ventricle Septum pellucidum Anterior horn Inferior horn Lateral aperture Interventricular foramen Third ventricle Inferior horn Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view (b) Left lateral Copyright © 2010 Pearson Education, Inc. Posterior horn Median aperture Lateral aperture view Figure 12. 5
Precentral gyrus Frontal lobe Central sulcus Postcentral gyrus Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral sulcus Occipital lobe Temporal lobe Transverse cerebral fissure Cerebellum Pons Medulla oblongata Spinal cord Fissure (a deep sulcus) Gyrus Cortex (gray matter) Sulcus White matter (a) Copyright © 2010 Pearson Education, Inc. Figure 12. 6 a
Frontal lobe Central sulcus Gyri of insula Temporal lobe (pulled down) (b) Copyright © 2010 Pearson Education, Inc. Figure 12. 6 b
Anterior Longitudinal fissure Frontal lobe Cerebral veins and arteries covered by arachnoid mater Parietal lobe Right cerebral hemisphere Occipital lobe Left cerebral hemisphere (c) Copyright © 2010 Pearson Education, Inc. Posterior Figure 12. 6 c
Left cerebral hemisphere Brain stem Transverse cerebral fissure Cerebellum (d) Copyright © 2010 Pearson Education, Inc. Figure 12. 6 d
Cerebral Cortex • Thin (2– 4 mm) superficial layer of gray matter • 40% of mass of brain • Conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding • Hemisphere connects to contralateral side of body • There is lateralization of cortical function in hemispheres Copyright © 2010 Pearson Education, Inc.
Functional Areas of the Cerebral Cortex • Three types of functional areas (not discrete location): • Motor —control voluntary movement • Sensory —conscious awareness of sensation • Association—integrate diverse information • Conscious behavior involves the entire cortex Copyright © 2010 Pearson Education, Inc.
Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca’s area (outlined by dashes) Prefrontal cortex Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Sensory areas and related association areas Primary somatosensory cortex Somatic Somatosensory sensation association cortex Gustatory cortex (in insula) Taste Wernicke’s area (outlined by dashes) Primary visual cortex Visual association area Auditory association area Primary auditory cortex Vision Hearing Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Copyright © 2010 Pearson Education, Inc. Figure 12. 8 a
Primary Motor Cortex • Large pyramidal cells of precentral gyri • Long axons pyramidal (corticospinal) tracts • Allows conscious control of precise, skilled, voluntary movements • Motor homunculi: upside-down caricatures representing the motor innervation of body regions Copyright © 2010 Pearson Education, Inc.
Posterior Motor map in precentral gyrus Anterior Toes Jaw Tongue Swallowing Copyright © 2010 Pearson Education, Inc. Primary motor cortex (precentral gyrus) Figure 12. 9
Premotor Cortex • Anterior to precentral gyrus • Controls learned, repetitious, or patterned motor skills • Coordinates simultaneous or sequential actions • Planning movement that depend on sensory feedback Copyright © 2010 Pearson Education, Inc.
Broca’s Area • Present in one hemisphere (usually the left) • Motor speech area that direct tongue muscles • Is active as one prepares to speak Copyright © 2010 Pearson Education, Inc.
Frontal Eye Field • Controls voluntary eye movements Copyright © 2010 Pearson Education, Inc.
Sensory Areas • Primary somatosensory cortex • Somatosensory association cortex • Visual areas • Auditory areas Copyright © 2010 Pearson Education, Inc. • Olfactory cortex • Gustatory cortex • Visceral sensory area • Vestibular cortex
Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca’s area (outlined by dashes) Prefrontal cortex Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Sensory areas and related association areas Primary somatosensory cortex Somatic Somatosensory sensation association cortex Gustatory cortex (in insula) Taste Wernicke’s area (outlined by dashes) Primary visual cortex Visual association area Auditory association area Primary auditory cortex Vision Hearing Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Copyright © 2010 Pearson Education, Inc. Figure 12. 8 a
Primary Somatosensory Cortex • In postcentral gyri • Receives sensory information from skin, skeletal muscles, and joints • Capable of spatial discrimination: identification of body region being stimulated Copyright © 2010 Pearson Education, Inc.
Posterior Sensory Anterior Sensory map in postcentral gyrus Genitals Primary somatosensory cortex (postcentral gyrus) Copyright © 2010 Pearson Education, Inc. Intraabdominal Figure 12. 9
Somatosensory Association Cortex • Integrates sensory input from primary somatosensory cortex • Determines size, texture, and relationship of parts of objects being felt Copyright © 2010 Pearson Education, Inc.
Visual Areas • Primary visual (striate) cortex of occipital lobe • Receives visual information from the retinas • Visual association area • Uses past visual experiences to interpret visual stimuli (e. g. , color, form, and movement) • Complex processing involves entire posterior half of hemispheres Copyright © 2010 Pearson Education, Inc.
• Visual association area • Surrounds the primary visual cortex • Uses past visual experiences to interpret visual stimuli (e. g. , color, form, and movement) • Complex processing involves entire posterior half of hemispheres Copyright © 2010 Pearson Education, Inc.
Auditory Areas • Primary auditory cortex of temporal lobes • Interprets info from inner ear as pitch, loudness, and location • Auditory association area • Stores memories of sounds and permits perception of sounds Copyright © 2010 Pearson Education, Inc.
OIfactory Cortex • Medial aspect of temporal lobes • Part of primitive rhinencephalon, along with olfactory bulbs and tracts • (Remainder of rhinencephalon in humans is part of the limbic system) • Region of conscious awareness of odors Copyright © 2010 Pearson Education, Inc.
Gustatory Cortex • In insula • Involved in perception of taste Copyright © 2010 Pearson Education, Inc.
Visceral Sensory Area • Posterior to gustatory cortex • Conscious perception of visceral sensations, e. g. , upset stomach or full bladder Copyright © 2010 Pearson Education, Inc.
Vestibular Cortex • Responsible for conscious awareness of balance (position of the head in space) Copyright © 2010 Pearson Education, Inc.
Anterior Association Area (Prefrontal Cortex) • Most complicated cortical region • Involved with intellect, cognition, recall, and personality • Contains working memory needed for judgment, reasoning, persistence, and conscience • Development depends on feedback from social environment Copyright © 2010 Pearson Education, Inc.
Limbic Association Area • Part of limbic system • Provides emotional impact that helps establish memories Copyright © 2010 Pearson Education, Inc.
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