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Nervous Part C H. Biology II Adapted 2014-2015 Cerebral Cortex • Thin (2–4 mm) superficial layer of gray matter • 40% of the mass of the brain • Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding • Each hemisphere connects to contralateral side of the body • There is lateralization of cortical function in the hemispheres Cerebral Hemispheres • Surface markings – Central sulcus • Separates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe – Longitudinal fissure • Separates the two hemispheres – Transverse cerebral fissure • Separates the cerebrum and the cerebellum 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) Figure 12.6a Anterior Longitudinal fissure Frontal lobe Cerebral veins and arteries covered by arachnoid mater Parietal lobe Right cerebral hemisphere Occipital lobe Left cerebral hemisphere (c) Posterior Figure 12.6c Left cerebral hemisphere Brain stem Transverse cerebral fissure Cerebellum (d) Figure 12.6d Cerebral hemisphere Diencephalon (d) Birth Cerebellum Brain stem • Midbrain • Pons • Medulla oblongata Figure 12.3d Functional Areas of the Cerebral Cortex • The three types of functional areas are: – Motor areas—control voluntary movement – Sensory areas—conscious awareness of sensation – Association areas—integrate diverse information • Conscious behavior involves the entire 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 Figure 12.8a Posterior Motor Motor map in precentral gyrus Anterior Toes Jaw Tongue Swallowing Primary motor cortex (precentral gyrus) Figure 12.9 Posterior Sensory Anterior Sensory map in postcentral gyrus Genitals Primary somatosensory cortex (postcentral gyrus) Intraabdominal Figure 12.9 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 Figure 12.8a Premotor cortex Corpus callosum Cingulate gyrus Primary motor cortex Frontal eye field Prefrontal cortex Processes emotions related to personal and social interactions Orbitofrontal cortex Olfactory bulb Olfactory tract Fornix Temporal lobe (b) Parasagittal view, right hemisphere Uncus Primary olfactory cortex Central sulcus Primary somatosensory cortex Parietal lobe Somatosensory association cortex Parieto-occipital sulcus Occipital lobe Visual association area Primary visual cortex Calcarine sulcus Parahippocampal gyrus Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Figure 12.8b Brain Add in PPT • Do some clinical connections/disorders with brain components Broca’s Area • Anterior to the inferior region of the premotor area • Present in one hemisphere (usually the left) • A motor speech area that directs muscles of the tongue • Is active as one prepares to speak 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 Limbic Association Area • Part of the limbic system • Provides emotional impact that helps establish memories Ventricles of the Brain • Connected to one another and to the central canal of the spinal cord • Lined by ependymal cells • Contain cerebrospinal fluid – Two C-shaped lateral ventricles in the cerebral hemispheres – Third ventricle in the diencephalon – Fourth ventricle in the hindbrain, dorsal to the pons, develops from the lumen of the neural tube 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 Posterior horn Median aperture Lateral aperture view Figure 12.5 Regions and Organization of the CNS • Spinal cord – Central cavity surrounded by a gray matter core – External white matter composed of myelinated fiber tracts 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 Inner gray matter Figure 12.4 Reflex Arc Spinal Cord Trauma • Functional losses – Parasthesias • Sensory loss – Paralysis • Loss of motor function • Flaccid paralysis—severe damage to the ventral root or ventral horn cells – Impulses do not reach muscles; there is no voluntary or involuntary control of muscles – Muscles atrophy Spinal Cord Trauma • Spastic paralysis—damage to upper motor neurons of the primary motor cortex – Spinal neurons remain intact; muscles are stimulated by reflex activity – No voluntary control of muscles Spinal Cord Trauma • Transection – Cross sectioning of the spinal cord at any level – Results in total motor and sensory loss in regions inferior to the cut – Paraplegia—transection between T1 and L1 – Quadriplegia—transection in the cervical region Poliomyelitis • Destruction of the ventral horn motor neurons by the poliovirus • Muscles atrophy • Death may occur due to paralysis of respiratory muscles or cardiac arrest • Survivors often develop postpolio syndrome many years later, as neurons are lost Amyotrophic Lateral Sclerosis (ALS) • Also called Lou Gehrig’s disease • Involves progressive destruction of ventral horn motor neurons and fibers of the pyramidal tract • Symptoms—loss of the ability to speak, swallow, and breathe • Death typically occurs within five years • Linked to glutamate excitotoxicity, attack by the immune system, or both Multiple Sclerosis (MS) • An autoimmune disease that mainly affects young adults • Symptoms: visual disturbances, weakness, loss of muscular control, speech disturbances, and urinary incontinence • Myelin sheaths in the CNS become nonfunctional scleroses • Shunting and short-circuiting of nerve impulses occurs • Impulse conduction slows and eventually ceases Multiple Sclerosis: Treatment • Some immune system–modifying drugs, including interferons and Copazone: – Hold symptoms at bay – Reduce complications – Reduce disability Developmental Aspects of the CNS • CNS is established during the first month of development • Gender-specific areas appear in both brain and spinal cord, depending on presence or absence of fetal testosterone • Maternal exposure to radiation, drugs (e.g., alcohol and opiates), or infection can harm the developing CNS • Smoking decreases oxygen in the blood, which can lead to neuron death and fetal brain damage Developmental Aspects of the CNS • Age brings some cognitive declines, but these are not significant in healthy individuals until they reach their 80s • Shrinkage of brain accelerates in old age • Excessive use of alcohol causes signs of senility unrelated to the aging process