Nervous System Organization PDF

OVERVIEW AND ORGANIZATION OF THE NERVOUS SYSTEM BIO336 Audrey Forbes-Cardinali, D.C. Mercyhurst University  REVIEW: THE NERVOUS SYSTEM The nervous system is structurally subdivided into the central nervous system and peripheral nervous system. Central nervous...

OVERVIEW AND ORGANIZATION OF THE NERVOUS SYSTEM BIO336 Audrey Forbes-Cardinali, D.C. Mercyhurst University  REVIEW: THE NERVOUS SYSTEM The nervous system is structurally subdivided into the central nervous system and peripheral nervous system. Central nervous system (CNS) Brain Spinal cord Peripheral nervous system Cranial nerves ang ganglia Spinal nerves and ganglia Autonomic nerves and ganglia Enteric nervous system  CNS DEVELOPMENT Develops from infolding of the ectoderm which give rise to a neural tube  CNS DEVELOPMENT The tube develops folds and outpouchings that become different parts of the CNS, while the space within the tube becomes the ventricles and central canal and will be filled with cerebrospinal fluid (CSF) The brain may be subdivided based on embryological origins: 1. Forebrain – Prosencephalon 2. Midbrain – Mesencephalon 3. Hindbrain – Rhombencephalon CLINICAL CASE STUDIES FIGURE 2.2 Embryological Development of the Central Nervous System ORIENTATION OF THE CNS  OVERVIEW OF CNS HISTOLOGY Nervous tissue is composed of two main cell types: Neurons and Glial cells Neurons are the parenchymal cells, while glial cells are the stromal cells Typical Neurons possess a cell soma, dendrites, axon, axon collaterals, axon terminals The axon is covered by segments of myelin known as internodes, while the bare areas between the myelin are the Nodes of Ranvier.  OV E RV I E W OF CNS H I S TO L O G Y  STRUCTURAL CLASSIFICATION OF NEURONS  REVIEW OF NEURONAL FUNCTION Communication between neurons occurs at the … These can occur between _____________ or ________________ or __________________ Neurotransmitters are released at the presynaptic terminal, which diffuse across the synaptic cleft to bind with receptors on the postsynaptic terminal. Opening of channels on the postsynaptic membrane allow ions to diffuse in or out, creating an electrical change of the postsynaptic cell known as excitatory postsynaptic potentials (EPSP) or inhibitory postsynaptic potentials (IPSP). Summation of potentials may result in the formation of an action potential  OVERVIEW OF NERVOUS TISSUE Myelinated axons appear pale compared to cell soma, dendrites or axon terminals White matter vs. Grey matter Pattern of organization of white and grey matter is different in various parts of CNS Brain: Grey matter is found on the periphery and clustered deep within the brain Spinal cord: White matter is found in the periphery and grey matter is found deep within OVERVIEW OF NERVOUS TISSUE  TERMINOLOGY FOR WHITE MATTER Terms for white matter in the CNS include: Tracts, bundles, lemniscus, fascicle and Commissure* The terms afferent and efferent may also be used in reference to structure in the CNS and PNS. Afferent Efferent  OVERVIEW OF SPINAL CORD STRUCTURE 33 pairs of spinal nerves Cervical and lumbar enlargements Cervical plexus, brachial plexus, lumbar plexus, and sacral plexus Conus medullaris is the termination of the cord Cauda equina is the bundle of nerves below the conus medullaris  OV E RV I E W O F S P I N A L C O R D S T RU C T U R E Each spinal nerve is formed by Dorsal root (sensory) Dorsal root ganglion Ventral root (motor) Branches from the spinal nerve are typically mixed and are called rami (sing. Ramus) OVERVIEW OF BRAIN STRUCTURE OVERVIEW OF BRAIN STRUCTURE What are suci and gyri?  OVERVIEW OF BRAIN STRUCTURE Comprised of 2 hemispheres separated by longitudinal fissure (AKA interhemispheric fissure or sagittal fissure) 4 lobes on each hemisphere that are externally visible: Frontal, parietal, temporal and occipital lobes. Lateral fissure (AKA Sylvian fissure) separates the frontal and temporal lobes Central sulcus of Rolando separates the frontal and parietal lobes Parietooccipital sulcus separates the parietal lobe from the occipital lobe on a midsagittal cut  OVERVIEW OF BRAIN STRUCTURE Precentral gyrus Superior frontal gyrus Superior frontal sulcus Middle frontal gyrus Inferior frontal sulcus Inferior frontal gyrus  OVERVIEW OF BRAIN STRUCTURE Superior temporal gyrus Superior temporal sulcus Middle temporal gyrus Inferior temporal sulcus Inferior temporal gyrus  OVERVIEW OF BRAIN STRUCTURE Postcentral gyrus Superior parietal lobule Intraparietal sulcus Inferior parietal lobule Supramarginal gyrus Angular gyrus  OVERVIEW OF BRAIN STRUCTURE Corpus callosum Rostrum Genus Body Splenium Cingulate gyrus Cingulate sulcus Paracentral lobule Precuneus Cuneus Calcarine Fissure Lingula  OVERVIEW OF BRAIN STRUCTURE Orbital frontal gyri Olfactory sulcus Gyrus rectus Inferior temporal gyrus Occipitotemporal sulcus Occipitotemporal (fusiform) gyrus Collateral sulcus, Rhinal sulcus Parahippocampal gyrus.  OVERVIEW OF BRAIN STRUCTURE  PRIMARY CORTICES Primary motor cortex Primary sensory cortex Primary visual cortex Primary auditory cortex  ASSOCIATION AREAS OF THE NEOCORTEX Unimodal association cortices are located next to primary cortex Heteromodal association cortices are more distant and integrate information from multiple modalities. Wernicke’s area - in dominant hemisphere (usually left) Responsible for language comprehension. Deficit is known as global aphasia, sensory aphasia or receptive aphasia Broca’s area – adjacent to the primary motor cortex Controls movement of the pharynx, face, lips and tongue. Deficit is known as motor aphasia, expressive aphasia,  ASSOCIATION AREAS OF THE NEOCORTEX Terms  OTHER CORTICAL AREAS Brodmann’s cytoarchetectoninc areas (1909) OTHER CORTICAL AREAS  OTHER CORTICAL AREAS Beginning in 1920’s, further studies and medical procedures helped solidify our understanding of these regions from a functional perspective. Wilder Penfield – Motor and sensory homunculi, distribution of topography as it relates to function of anatomical region not size, function of parietal and occipital lobes with regards to memories, dreams and language.  HISTOLOGY OF THE NEOCORTEX Neocortex is organized into layers numbered I-VI from outer surface inward. Layer I- Primarily dendrite and some axons from deeper layers Layer II and III – Neurons that project to other cortical areas Layer IV – Neurons that receive thalamic inputs Layer V – Neurons that project to subcortical areas (but not the thalamus) Layer VI – Neurons project to the thalamus HISTOLOGY OF THE NEOCORTEX  OVERVIEW OF THE BRAINSTEM Cranial Nerves I-XII Midbrain Interpeduncular fossa Cerebral peduncles (Crus cerebri) Pons Middle cerebellar peduncle Pontomedullary junction Medulla oblongata Pyramids Olives  OVERVIEW OF THE BRAINSTEM Pineal gland Superior colliculus Brachium of superior colliculus Lateral geniculate body Inferior colliculus Brachium of inferior colliculus Medial geniculate body Superior cerebellar peduncle  OVERVIEW OF THE BRAINSTEM Middle cerebellar peduncle Inferior cerebellar peduncle Cuneate tubercle Gracile tubercle Facial tubercle