CNS: Anatomy and Physiology Dr. Milind Kothari Professor of Neurology Assoc Dean Student Affairs

Two Anatomical Divisions – Central nervous system (CNS) Brain Spinal cord – Peripheral nervous system (PNS) All the neural tissue outside CNS Afferent division (sensory input) Efferent division (motor output) – Somatic nervous system – Autonomic nervous system General Organization of the nervous system

Brain & spinal cord

Why is this so hard? Multiple anatomies Embryological Lobes Vascular anatomy Neurochemical anatomy 3 dimensional Structures with multiple names Sometimes left is right and sometimes left is left

Principal CNS regions Telencephalon Diencephalon Brainstem Midbrain Pons Medulla Spinal cord Cerebellum

31 spinal levels: 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal The bones of the skull & vertebrae dictate the name of the underlying CNS Principal CNS regions

Frontal Parietal Temporal Occipital Principal CNS regions

These named structures provide critical reference points for learning region-specific function as well as localizing a diagnosis… …they also permit a significant expansion of the cortical surface area. The paired cerebral cortices are covered by named sulci and gyri. Telencephalon

Midbrain Pons Medulla Brainstem

Diencephalon, Brainstem & Cerebellum

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CNS Structures Lobes Cortex Ventricles Subcortical structures Brainstem Spinal Cord

Central Nervous System – CNS: brain and spinal cord – Necessary for the maintenance of homeostasis – Contains neurons – Contains synapses – Responsible for everything we perceive, do, feel, and think

Histology of neural tissue Two types of neural cells in the nervous system:  Neurons - For processing, transfer, and storage of information  Neuroglia – For support, regulation & protection of neurons

Glial Cells – 90% of CNS composed of glia – Five types of glial cells Astrocyte—numerous functions Ependymal cells—line cavities Microglia—phagocytes Oligodendrocytes—form myelin Schwann cells (located in PNS)—form myelin

Glial Cells

Astrocytes – Development of neural connections – Possibly modulate synaptic activity – Remove neurotransmitter from synaptic cleft – Communicate to neurons through chemical messengers – Protect neurons against toxic substances and oxidative stress

Microglia – Protect CNS from foreign matter through phagocytosis Bacteria Dead or injured cells – Protect CNS from oxidative stress

CNS: Physical Support

Cerebrospinal Fluid (CSF) – Extracellular fluid of the CNS – Secreted by ependymal cells of the choroid plexus Circulates to subarachnoid space and ventricles Reabsorbed by arachnoid villi – Functions Cushions brain Maintains stable interstitial fluid environment

Cerebral Spinal Fluid

CSF Production – Total volume of CSF = 125–150 mL – Choroid plexus produces 400–500 mL/day – Recycled three times a day

Blood Supply to the CNS – CNS comprises 2% of body weight (3–4 pounds) Receives 15% of blood supply – High metabolic rate Brain uses 20% of oxygen consumed by body at rest Brain uses 50% of glucose consumed by body at rest – Depends on blood flow for energy

CNS: Gray and White Matter

White Matter in Brain – Projection fibers Cerebral cortex with lower levels of brain or spinal cord – Association fibers Connect two areas of cerebral cortex on same side of brain – Commissural fibers Connect same cortical regions on two sides of brain – Corpus callosum Primary location of commissural fibers

CNS: Gray and White Matter

Brain

Midbrain Spinal cord Pons Medulla oblongata Forebrain Cerebrum Thalamus Hypothalamus Pituitary gland Brainstem Diencephalon Cerebellum Corpus callosum (c)Midsagittal section Brain: Midsagittal View

Premotor cortex (coordinates voluntary movements) Primary somatosensory cortex (somesthetic sensations and proprioception) Sensory association areas (integration of sensory information) Primary motor cortex (voluntary movement) Central sulcus Prefrontal association areas (idea and plan for voluntary movement, thoughts, personality) Broca’s area (speech formation) Limbic association cortex (emotions, learning, and memory) Olfactory cortex (smell) Visual association areas (higher vision processing) Wernicke’s area (language comprehension) Auditory association areas Primary auditory cortex (hearing) Primary visual cortex (vision) Functional Areas of Cerebrum

Topographical Organization: Motor

Topographical Organization: Sensory

Imaging CT MRI

Advantages of CT cost availability decreased scan time decreased sensitivity to patient motion better visualization of acute blood better visualization of bony abnormalities

Computerized Tomography Brain window Bone window

Advantages of MRI no ionizing radiation ( peds & pregnant ) direct coronal, sagittal and transverse images excellent contrast resolution no interference from bony structures

Axial view

Coronal View

Sagittal view

Questions?