Nervous system

• The nervous system controls and coordinates functions throughout the body and responds to external and internal stimuli

  
• Functions of the nervous system

  • Detect changes within and around the body
  • Respond to external changes
  • Receive and interpret sensory information
  • Stimulate muscles and glands
• Central Nervous System (CNS)


  Consists of the brain and spinal cord, lying within the protection of the cranium and vertebral column, respectively

  
• Peripheral Nervous System (PNS)

  Consists of nerves joined to the brain and spinal cord (cranial and spinal nerves) and their ramifications within the body

  
• Neuron

  • Single cell body from which a variable number of branching processes emerge
  • Most of these processes are receptive in function and are known as dendrites
  • One of the processes attached to the cell body is called the axon (nerve fibre) and this carries information away from the cell body
  • The myelin sheath is produced by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system
• Ventral

  Oriented toward the ground
• Dorsal

  Oriented toward the sky
• Rostral

  Oriented toward the snout
• Caudal

  Oriented toward the tail
• Morphological subdivisions of the CNS

  • Cerebral hemisphere
  • Diencephalon
  • Cerebellum
  • Spinal cord
  • Medulla Oblongata
  • Pons
  • Midbrain

  
• Cerebral hemispheres

  • Largest part of the brain
  • Occupy the anterior and middle cranial fossae
  • A median longitudinal fissure incompletely separates the cerebrum into 2 halves; right and left

  
• Gyri


  Complicated irregular foldings (convolutions) of cerebral hemispheres
• Sulci

  • Intervening grooves between gyri
  • May be shallow or deep
  • Sometimes deep sulci are called fissures
• 70% of cerebrum is hidden in sulci
• Cingulate Gyrus

  • Running parallel with and curving around the corpus callosum
  • Part of the limbic system
• Insula

  • Within the depths of the lateral fissure
  • Variety of functions ranging from sensory processing to representing feelings and emotions
• Lobes of the cerebral hemispheres

  • Frontal
  • Parietal
  • Temporal
  • Occipital
  • Limbic

  
• Frontal Lobe


  Motor and pre-motor, Broca's speech area, frontal eye fields, Associational cortex for cognitive behaviours, goal directed behaviours, personality etc.
• Parietal Lobe


  Somatosensory (or touch) and certain aspects of visual / auditory / somatic association, Primary somatosensory cortical areas, Wernicke's area
• Temporal Lobe


  • Auditory and auditory association (Wernicke's area, shared with parietal lobe)
  • Primary auditory cortex
  • Higher order processing
  • Medial part of lobe: learning & memory
  • Inferior part: higher order processing
• Occipital Lobe


  • Vision and visual associations
  • Primary visual cortex
  • Rest of occipital lobe is involved in higher order processing of visual information

  
• Limbic Lobe


  • Emotional responses, drive-related behaviours and memory
  • Located in temporal lobe and both cerebral hemispheres

  
• Epithalamus

  • Most posterior part of the diencephalon
  • Consists of the Habenular nuclei, Habenular commissure, Striae medullaris thalami, Epiphysis (pineal gland), Posterior commissure
• Thalamus

  • Largest part of the diencephalon
  • Plays an important part in sensory, motor and cognitive functions
  • Has extensive reciprocal connections with the cerebral cortex
  • Consists of anterior, medial and lateral groups of nuclei

  
• Subthalamus

  • Small region lying deep to the ventricular wall
  • Contains the subthalamic nucleus, which is closely related functionally to the basal ganglia
• Hypothalamus

  • Forms the lower part of the walls and the floor of the third ventricle
  • Involved in the autonomic nervous system, the limbic system and the neuroendocrine system
  • Contains several nuclear groupings that include the mamillary bodies, pituitary gland and stalk

  
• Basal ganglia


  Also called corpus striatum, a number of complex subcortical nuclear masses that lie in inferior part of cerebral hemispheres in close relation with internal capsule

  
• Basal ganglia

  • Involved in control of movement behaviour (facilitate purposeful movement & stop unintentional movement)
  • Work like a stop/start valve
• Lesions in basal ganglia area cause basal ganglia disorders (loss of control of voluntary movements & posture, spasticity & involuntary movements: eg. Parkinson's)
• Basal ganglia


  • Involved in control of movement, posture and muscular tone
• White matter of cerebral hemisphere

  Myelinated axons that connect one part of the brain with the other/s

  
• Types of white matter fibres

  • Association (intrahemispheric)
  • Commissural (interhemispheric)
  • Projection
• Association (intrahemispheric) fibres


  • Connect cortical areas of the same hemisphere with each other
  • Divided into short (intralobar) and long (interlobar) association fibres
• Commissural (interhemispheric) fibres


  • Connect corresponding cortical regions of one cerebral hemisphere to the other

  
• Corpus callosum

  Main commissural fibre bundle, shaped like a fishing hook with parts: rostrum, genu, body, splenium
• Anterior commissure


  Runs transversely in front of the column of the fornix, near the IV foramen, interconnects the middle & inferior temporal gyri & olfactory regions of the 2 sides

  
• Projection fibres

  • Connect cerebral cortex with various subcortical structures such as thalamus, striatum, brainstem & spinal cord

  
• Projection fibre bundles

  • Corona radiata
  • Internal capsule
• Internal capsule

  Dense sheet of fibres deeper within the hemisphere, medial = thalamus & caudate nucleus, lateral = globulus pallidus & putamen

  
• Parts of the internal capsule

  • Anterior limb
  • Genu
  • Posterior limb
  • Retrolenticular
  • Sublenticular