Cerebral Cortex and Limbic System PDF

Cerebral cortex and the limbic system HUMAN PHYSIOLOGY II COURSE CODE: 1601106 3 credit Units 01-03/12/2024 First Semester, 2024/2025 Session Dr Kasim Ibrahim, PhD Week 8 ...

Cerebral cortex and the limbic system HUMAN PHYSIOLOGY II COURSE CODE: 1601106 3 credit Units 01-03/12/2024 First Semester, 2024/2025 Session Dr Kasim Ibrahim, PhD Week 8  Week 8 At the end of this lecture, year 2 DDS students should be able to; describe the different lobes of the cerebral cortex and the concept of cerebral dominance describe the different areas in the frontal, parietal, temporal, and occipital lobes of the cortex explain the components of the limbic system and describe their functions 12/25/2024 2  Cerebral cortex Three Functional Principles of the Cerebrum 1. Each cerebral hemisphere receives sensory information from and sends motor commands to, the opposite side of the body 2. The two hemispheres have different functions, although their structures are alike 3. Correspondence between a specific function and a specific region of the cerebral cortex is not precise  Cerebral cortex Hemispheric Lateralization Functional differences between left and right hemispheres Each cerebral hemisphere performs certain functions that are not ordinarily performed by the opposite hemisphere The Left Hemisphere In most people, the left brain (dominant hemisphere) controls: Reading, writing, and math Decision-making, Speech, and language The Right Hemisphere Right cerebral hemisphere relates to: Senses (touch, smell, sight, taste, feel) Recognition (faces, voice inflections) Hemispheric Lateralization Left Cerebral Hemisphere Right Cerebral Hemisphere LEFT HAND RIGHT HAND Prefrontal Prefrontal cortex cortex Speech center Anterior commissure C C O O R R P P U U Writing S S Analysis by touch C C A A Auditory cortex Auditory cortex L L L L O O S S U U General interpretive center M M Spatial visualization (language and mathematical and analysis calculation) Visual cortex Visual cortex (right visual field) (left visual field)  Lobes of the cerebral hemispheres FRONTAL LOBE - forms the anterior part of the cerebral hemisphere - it ends posteriorly at the central sulcus and inferiorly at the lateral sulcus - Has the precentral gyrus which deals with voluntary motor functions, concentration, verbal communication, decision-making, planning, and personality  Lobes of the cerebral hemispheres PARIETAL LOBE - forms the superoposterior part of each hemisphere - terminates anteriorly at the central sulcus & laterally at the lateral sulcus and posteriorly at the parieto- occipital sulcus - has the postcentral gyrus – for general sensory functions such as evaluation of the shape & texture of objects being touched  Lobes of the cerebral hemispheres TEMPORAL LOBE - lies inferior to the lateral sulcus and is involved with hearing & smell OCCIPITAL LOBE - forms the posterior region of each hemisphere -important for processing incoming visual information -and storing visual memories INSULA - a small lobe deep to the lateral sulcus - is involved in memory and taste Lobes of the cerebral hemispheres  Functional areas of the cerebrum 3 categories exist: 1. Motor areas – control voluntary functions 2. Sensory areas - provide conscious awareness of sensation 3. Association areas – integrate and store information 25/12/2024 11  Motor areas Cortical areas that control motor functions Primary motor cortex (somatic motor area) - is located within the precentral gyrus Neurons here control voluntary skeletal muscle activity Their axons project contra-laterally to the brain stem and spinal cord The left primary motor cortex controls the right side voluntary muscles and vice versa Innervation of the primary motor cortex to various body parts can be diagrammed as a motor homunculus on the precentral gyrus 25/12/2024 12  MOTOR AREAS…… The motor speech area (Broca area) - located within the inferolateral portion of the left frontal lobe This region controls the muscular movements necessary for vocalisation 25/12/2024 13 3 categories of functional areas: 1) Motor areas 2) Sensory  SENSORY AREAS cortical areas within the parietal, temporal and occipital lobes involved in conscious awareness of sensation primary somatosensory cortex – found in the postcentral gyrus of the parietal lobes neurons receive general somatic sensations (sensory information) e.g. from touch, pressure, pain and temperature receptors sensory homunculus may be traced on the postcentral gyrus surface 25/12/2024 15  SENSORY AREAS…… The primary visual cortex - located in the occipital lobe, it receives and processes visual information The primary auditory cortex - located in the temporal lobes and they receive and process auditory information The primary gustatory cortex - is located in the insula, and it processes taste information The primary olfactory cortex - located in the temporal lobes and it provides a conscious awareness of smells 25/12/2024 16 Functional Areas of the Cerebral Cortex  ASSOCIATION AREAS Adjacent and connected to the primary motor and sensory cortical regions either process or interpret incoming data or co- ordinate a motor response Association areas integrate new sensory inputs with memory of past experiences 25/12/2024 18  ASSOCIATION AREAS…. The premotor cortex (somatic motor association) area - located in the frontal lobes - lies immediately anterior to the precentral gyrus - process motor information - responsible for co-ordinated and learned skilled motor activities 25/12/2024 19 Association Areas of the Cerebral Cortex  ASSOCIATION AREAS…. The somatosensory association area - located in the parietal lobe - lies immediately posterior to the postcentral gyrus - interprets sensory information - responsible for integrating and interpreting sensations to determine the texture, temperature, pressure and shape of objects - allows us to identify objects while our eyes are closed auditory association area is located within the temporal lobe visual association area is located in the occipital lobe 25/12/2024 21  Integrative Centers Are located in lobes and cortical areas of both cerebral hemispheres Receive information from association areas Direct complex motor or analytical activities 1) General Interpretive Area Also called Wernicke’s area Present in only one hemisphere (left) Receives information from all sensory association areas involved in recognizing, understanding, and comprehending spoken or written language Works together with Broca’s area for fluent communication Coordinates access to complex visual and auditory memories 2) Gnostic area composed of regions of the parietal, temporal, occipital lobes integrates all sensory, auditory and visual information being processed by the association areas within the lobes provides comprehensive understanding of the current activities  Motor and Sensory Regions of the Cerebral Cortex Frontal eye field Speech center Prefrontal General cortex interpretive area The left hemisphere generally contains the general interpretive area and the speech center. The prefrontal cortex of each hemisphere is involved with conscious intellectual functions. 3) Other Integrative Areas Speech center Is associated with general interpretive area Coordinates all vocalization functions Prefrontal cortex of frontal lobe Integrates information from sensory association areas Performs abstract intellectual activities (e.g., predicting consequences of actions)  The limbic (motivational) system i Structures of the limbic: Amygdaloid body Hippocampus Fornix Functions of the limbic: Establishes emotional states & behavioural drives Links conscious functions of the cerebral cortex with autonomic functions of the brain stem Facilitates memory storage and retrieval Figure 14-11a The Limbic System Corpus Pineal callosum Fornix gland Components of the Limbic System in the Cerebrum The region of the cerebral hemisphere shown in green is known as the limbic lobe. Cingulate gyrus (superior portion of Components of the limbic lobe) Limbic System in Parahippocampal the Diencephalon gyrus (inferior portion of limbic lobe) Anterior group of thalamic nuclei Hippocampus Hypothalamus Mamillary body Temporal lobe of cerebrum A diagrammatic sagittal section through the cerebrum, showing the cortical areas associated with the limbic system. The parahippocampal gyrus is shown as though transparent to make deeper limbic components visible. Figure 14-11b The Limbic System Cingulate gyrus Corpus callosum Anterior nucleus Fornix of thalamus Hypothalamic Mamillary nuclei body Olfactory Hypothalamus tract Parahippocampal gyrus Amygdaloid body Hippocampus (with dentate gyrus) A three-dimensional reconstruction of the limbic system, showing the relationships among the major components. Table 14-7 The Limbic System Further reading