1 Higher Center

• Central Nervous System


  • Brain - made up of nine paired structures
  • Cerebrum
  • Cerebellum
  • Brainstem
  • Midbrain
  • Pons
  • Medulla oblongata
  • Diencephalic structures
  • Thalamus
  • Epithalamus
  • Hypothalamus
  • Subthalamus

  Spinal Cord
• Peripheral Nervous System


  • Cranial Nerves
  • Spinal Nerves
• Central Nervous System (in physiology)


  • Higher Center
  • Lower Center
• Peripheral Nervous System (in physiology)


  • Somatic Nervous System
  • Autonomic Nervous System
• If the lesion is supratentorial

  Manifestations on the face and the body: contralateral
• If the lesion is on the brain stem


  • Manifestations: On the face: ipsilateral
  • On the body: contralateral
  • Motor: alternating hemiplegia or hemiparesis
  • Sensory: alternating hemisensory loss
  • Alternating: due to ipsilateral manifestation on the face and contralateral manifestation on the body
• Ventricles


  Where the CSF is formed

  Lateral ventricle - Inside the cerebrum, location of choroid plexus which primarily synthesizes CSF

  Interventricular foramen of Monro - Connects lateral ventricle to third ventricle

  Third Ventricle - Space between the thalami or diencephalon

  Cerebral aqueduct of Sylvius - Connects 3rd ventricle to 4th ventricle

  Fourth ventricle - Passes medially: Foramen of Magendie, Passes laterally: Foramen of Luschka
• Spinal Cord


  Cervical (7 segments, 8 spinal nerves) - innervates the upper extremity and diaphragm (C3-C5)

  Thoracic (12 spinal nerves) - innervates the trunk and abdomen, both the muscles and skin

  Lumbar (5 spinal nerves) - innervates the anterior aspect of the lower extremities

  Sacral (5 spinal nerves) - innervates the posterior aspect of lower extremities, sexual function, bowel, bladder control

  Coccygeal (1 spinal nerve)
• Functions of Spinal Cord


  Center for reflex actions

  Afferent pathway for both somatic sensory and autonomic nervous system

  Efferent pathway for both somatic motor and autonomic nervous system

  Center for micturition and defecation

  Exerts tonic influences on the muscles

  Involved in the execution of motor commands

  Provides communicating branches for autonomic nervous system
• Gray Matter of Spinal Cord


  Located in the middle, H-shaped or butterfly-shaped, has posterior horn and anterior horn, may have lateral horns that can only be seen in the thoracic region (called the intermediolateral column in other regions), divided into cytoarchitectural areas known as the 10 laminae of Rexed (Rexed laminae)
• Interneuron


  aka association neuron in neuroanatomy, present when there is no direct connection or communication with the anterior horn cells, a neuron between the sensory and the motor neuron, can be excitatory or inhibitory
• White Matter of Spinal Cord


  Surrounds the gray matter, consists of ascending and descending fiber pathways called tracts, divided into three divisions: posterior, lateral, and anterior
• Anterior white commissure


  Located between the central canal and anterior median fissure, contains decussating/crossing spinothalamic fibers (point of decussation at the level of spinal cord)
• Postero-intermediate sulcus


  Divides the posterior white matter into: Fasciculus gracilis - receives information/sensation from the lower extremities (T7-Coccygeal area), Fasciculus cuneatus - receives information/sensation from the upper extremities (C1-T6)
• Development of the nervous system


  Initially, there are two brain vesicles - prosencephalon and rhombencephalon

  As neural tube elongates, these two will be separated by the mesencephalon

  Prosencephalon develops into diencephalon and telencephalon

  Rhombencephalon develops into metencephalon and myelencephalon

  Telencephalon becomes the cerebrum or cerebral hemispheres

  Diencephalon becomes the four thalami - thalamus, epithalamus, subthalamus, and hypothalamus

  Mesencephalon becomes the midbrain

  Metencephalon becomes the pons and the cerebellum

  Myelencephalon becomes the medulla oblongata
• Features of the Midbrain

  Corpora quadrigemina - refers to both the superior and inferior colliculi, responsible for the special somatic sensations

  Cerebral peduncle - representative of the midbrain at the ventral aspect

  Rhomboid fossa - floor of the 4th ventricle, has two triangles

  Anteromedian/Ventromedian fissure - continuous to the spinal cord, divides the medulla oblongata into left and right

  Anterolateral sulcus - lateral to the ventromedian fissure, also known as pyramido-olivary sulcus because it divides the division of medulla oblongata into pyramid and olive

  Posterolateral sulcus - seen when viewed ventrally

  Basilar sulcus - where the basilar arteries will rest for the Circle of Willis
• General Locations of the Cranial Nerves


  Upper midbrain - III

  Lower Midbrain - IV

  Midpons - V

  Lower pons - VI, VII, VIII

  Upper Medulla Oblongata - IX, X, XII

  Lower Medulla Oblongata - XI, XII
• Cranial Nerves located in the Lower Medulla Oblongata


  CN XI Accessory Spinal Nerve

  CN XII Glossopharyngeal Nerve
• Brain stem lesion manifestation = ipsilateral on the face; contralateral on the body EXCEPT: Destroyed LEFT INFERIOR COLLICULUS (ORIGIN of CN IV) manifestation= RIGHT, Destroyed CN IV NERVE (right) manifestation= LEFT
• Other Contents of the Medulla Oblongata


  BARORECEPTOR REFLEX- involves CN IX & CN X

  CHEMORECEPTOR REFLEX- also associated w/ CN IX & X

  CARDIAC CENTER

  RESPIRATORY CENTER (dorsal respiratory cells)- responsible for spontaneous respiration (inspiration)

  ALMOST ALL CENTERS

  SWALLOWING, VOMITING, COUGH, GUSTATORY reflexes, etc involving CN IX & X
• Uncal herniation - uncus in the cerebrum descends towards the foramen magnum, compressing the medulla oblongata= DEATH (compressed cardiac, respi centers)
• Medial geniculate body of the thalamus is connected to the inferior colliculus

  AUDITION/ HEARING
• Lateral geniculate body is connected to the superior colliculus

  VISION
• Pons


  CORNEAL/ CONJUNCTIVAL BLINK REFLEX= CN V & CN VII

  AUDITORY REFLEX= CN VIII & CN IX

  Pneumotaxic Center in the upper Pons= inhibits inspiration/ Dorsal Root Ganglion

  Apneustic Center in the lower Pons= inhibits the inhibitor for the next inspiration
• Tumor in the Pneumotaxic center will cause continuous inspiration until maximum lung expansion (no inhibition)
• Cerebellum


  Feed-forward mechanism= anticipation of mistakes

  Motor memories

  Anatomically divided transversely into: Anterior lobe (paleocerebellum), Posterior lobe (neocerebellum), Flocculonodular lobe (archicerebellum)

  Anatomically divided sagittally into: Vermis, Paravermal portion/ Intermediate cerebellum/ Spinocerebellum/ Paleocerebellum, Lateral cerebellum/ Cerebrocerebellum/ Neocerebellum/Corticocerebellum
• Corneal/conjunctival blink reflex


  CN V & CN VII
• Auditory reflex


  CN VIII & CN IX
• Pneumotaxic center


  In the upper pons, inhibits inspiration
• Apneustic center


  In the lower pons, inhibits the inhibitor for the next inspiration
• Tumor in the pneumotaxic center


  Causes continuous inspiration until maximum lung expansion (no inhibition)
• Cerebellum


  • Feed-forward mechanism: anticipation of mistakes
  • Motor memories
• Anatomical divisions of the cerebellum (transverse)

  • Anterior lobe (paleocerebellum)
  • Posterior lobe (neocerebellum)
  • Flocculonodular lobe (archicerebellum)
• Anatomical divisions of the cerebellum (sagittal)

  • Vermis
  • Paravermal portion/Intermediate cerebellum/Spinocerebellum/Paleocerebellum
  • Lateral cerebellum/Cerebrocerebellum/Neocerebellum/Corticocerebellum
  • Archicerebellum (Flocculonodular lobe)
• Pupillary light reflex


  CN II (sensory) & CN III (motor)
• Lesion on the upper midbrain (CN III)


  Instead of pupil constriction (miosis), pupil dilation (midriasis) will occur
• Hypothalamus


  Highest center, regulates all bodily activities except voluntary motor activities
• Pineal gland


  In the epithalamus, responsible for the biologic rhythm/sleep-wake cycle; produces melatonin if there is light
• No light


  Melatonin will bind to its receptor to inhibit the reticular activating system = sleep
• Subthalamus


  Part of motor activities (basal nuclei - subcortical motor areas)