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Central Nervous System Anatomy & Physiology

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  • Divisions of the Nervous System

    Central nervous system (CNS): brain and spinal cord, integration and control center. Peripheral nervous system (PNS): nerves outside CNS, includes spinal and cranial nerves.

  • Primary Brain Vesicles in Embryonic Development

    Three primary vesicles form from neural tube: Prosencephalon (forebrain), Mesencephalon (midbrain), and Rhombencephalon (hindbrain). Posterior end becomes spinal cord.

  • Secondary Brain Vesicles

    Prosencephalon divides into Telencephalon (cerebral hemispheres) and Diencephalon (thalamus, hypothalamus, epithalamus, retina). Rhombencephalon divides into Metencephalon (pons, cerebellum) and Myelencephalon (medulla oblongata). Mesencephalon remains undivided.

  • Gray Matter vs White Matter in Brain

    Gray matter contains neuron cell bodies and is found in cortex and nuclei. White matter consists mostly of myelinated axons connecting different brain regions.

  • Ventricles of the Brain

    Four ventricles filled with cerebrospinal fluid (CSF): paired lateral ventricles, third ventricle in diencephalon, and fourth ventricle in hindbrain. Connected by interventricular foramen and cerebral aqueduct.

  • Functions of Ependymal Cells

    Ependymal cells line ventricles and secrete cerebrospinal fluid (CSF), aiding nutrient exchange and waste removal.

  • Cerebral Hemispheres

    Make up 83% of brain mass, divided into five lobes: frontal, parietal, temporal, occipital, and insula. Consist of cerebral cortex (gray matter), white matter, and basal nuclei.

  • Surface Markings of Cerebral Hemispheres

    Ridges called gyri, grooves called sulci, and deep grooves called fissures. Important fissures include longitudinal fissure (separates hemispheres) and transverse cerebral fissure (separates cerebrum and cerebellum).

  • Cerebral Cortex Functions

    Site of conscious mind including awareness, sensory perception, voluntary motor initiation, communication, memory, and understanding. Composed of six layers of interneurons.

  • Functional Areas of Cerebral Cortex

    Includes motor areas (voluntary movement), sensory areas (conscious sensation), and association areas (integrate information).

  • Primary Motor Cortex

    Located in precentral gyrus of frontal lobe; controls precise, skilled voluntary movements via pyramidal tracts.

  • Premotor Cortex

    Anterior to primary motor cortex; plans movements, controls learned motor skills, and coordinates sequential actions.

  • Broca's Area

    Located anterior to inferior premotor area, usually in left hemisphere; controls muscles for speech production and planning speech.

  • Primary Somatosensory Cortex

    Located in postcentral gyrus; receives sensory input from skin and proprioceptors for spatial discrimination.

  • Somatosensory Association Cortex

    Posterior to primary somatosensory cortex; integrates sensory input to understand object size, texture, and relationship.

  • Multimodal Association Areas

    Integrate diverse sensory, motor, and emotional information for purposeful action. Includes anterior association (prefrontal cortex), posterior association, and limbic association areas.

  • Limbic System

    Includes parts of cerebral hemispheres and diencephalon; involved in emotion, memory, and motivation. Key structures: amygdala, hippocampus, cingulate gyrus.

  • Reticular Formation and Reticular Activating System (RAS)

    Network of nuclei in brainstem involved in arousal and consciousness. RAS filters sensory input and maintains alertness.

  • Thalamus Functions

    80% of diencephalon; relays, sorts, and edits sensory and motor signals to cerebral cortex; involved in memory and emotion regulation.

  • Hypothalamus Functions

    Controls autonomic nervous system, emotional responses, body temperature, hunger, thirst, sleep-wake cycles, and endocrine system via pituitary gland.

  • Brain Stem Components

    Includes midbrain, pons, and medulla oblongata; controls automatic survival functions and contains nuclei for most cranial nerves.

  • Medulla Oblongata Functions

    Autonomic reflex center regulating cardiovascular, respiratory, vomiting, coughing, sneezing, and swallowing reflexes.

  • Cerebellum Functions

    Coordinates smooth, precise movements; receives input from cortex, brainstem, and sensory receptors; involved in motor learning and cognitive functions.

  • Protection of the Brain

    Protected by skull bones, meninges (dura mater, arachnoid mater, pia mater), cerebrospinal fluid, and blood-brain barrier.

  • Meninges Layers

    Dura mater: tough outer layer; arachnoid mater: middle layer with web-like extensions; pia mater: delicate inner layer clinging to brain.

  • Cerebrospinal Fluid (CSF) Functions

    Provides buoyancy, reduces brain weight, cushions CNS from trauma, and nourishes brain while removing waste.

  • Blood-Brain Barrier

    Selective barrier formed by capillary endothelium and astrocyte feet; protects brain by restricting passage of harmful substances.

  • Spinal Cord Gross Anatomy

    Extends from foramen magnum to L1-L2 vertebra; protected by vertebrae, meninges, and CSF; contains cervical and lumbosacral enlargements for limb innervation.

  • Spinal Cord Gray Matter

    Contains dorsal horns (sensory interneurons), ventral horns (somatic motor neurons), and lateral horns (sympathetic neurons in thoracic region).

  • Spinal Cord White Matter

    Contains ascending (sensory), descending (motor), and transverse (commissural) tracts; organized into dorsal, lateral, and ventral columns.

  • Spinal Cord Functions

    Conduit for sensory and motor signals; contains neural circuits for reflexes and central pattern generators.

  • Spinal Cord Trauma Effects

    Transection causes paralysis below injury: paraplegia (T1-L1), quadriplegia (cervical). Damage to ventral roots causes flaccid paralysis; damage to upper motor neurons causes spastic paralysis.