CNS

• Central nervous system (CNS)


  • Consists of the brain and spinal cord
• CNS


  • Covered with the meninges (dura mater, arachnoid membrane, pia mater)
  • Space under the arachnoid membrane is filled with cerebrospinal fluid, in which the brain floats
• Cerebrospinal fluid production


  1. Produced in the choroid plexus of the third ventricle

  2. Through the cerebral aqueduct into the fourth ventricle

  3. Then into the subarachnoid space

  4. Finally back into the blood supply
• Development of the nervous system begins around the eighteenth day after conception
• Brain


  • Divided into three major regions: Forebrain, Midbrain and Hindbrain
  • Forebrain is the farthest forward, Midbrain is next, Hindbrain is farthest from the forebrain
• Hindbrain


  • Evolutionarily the oldest and most primitive part of the brain
  • First part of the brain to develop prenatally
• Forebrain


  • Most recent evolutionary addition to the brain
  • Last of the three portions of the brain to develop prenatally
• Forebrain


  • Comprises the cerebral cortex, basal ganglia, limbic system, thalamus, and hypothalamus
• Diencephalon


  • Thalamus and hypothalamus
• Telencephalon


  • Rest of the forebrain
• Cerebral cortex


  • Outer layer of the cerebral hemispheres
  • Plays a vital role in thinking and other mental processes
• Corpus callosum


  • Dense aggregate of neural fibres that connects the two cerebral hemispheres, allowing transmission of information back and forth
• Cerebral hemispheres and cortex


  • Divided into four lobes: frontal, parietal, temporal, occipital
• Frontal lobe


  • Associated with motor processing and higher thought processes (abstract reasoning, problem solving, planning, judgment)
  • Involved in producing speech
  • Prefrontal cortex involved in complex motor control and tasks requiring integration of information over time
• Parietal lobe


  • Associated with somato-sensory processing (touch, pain, temperature, limb position)
  • Involved in consciousness and paying attention
• Temporal lobe


  • Associated with auditory processing and comprehending language
  • Involved in retention of visual memories and matching new things seen to visual memory
• Occipital lobe


  • Associated with visual processing
  • Contains numerous visual areas specialised to analyse specific aspects of a scene (color, motion, location, form)
• Basal ganglia


  • Collections of neurons crucial to motor function
  • Dysfunction can result in motor deficits (tremors, involuntary movements, changes in posture/muscle tone, slowness of movement)
  • Observed in Parkinson's and Huntington's diseases
• Limbic system


  • Important to emotion, motivation, memory, and learning
  • Allows suppression of instinctive responses and flexible adaptation of behaviors
  • Comprises the septum, amygdala, and hippocampus
• Amygdala


  • Plays an important role in emotion, especially anger and aggression
  • Stimulation can result in fear
  • Damage can result in maladaptive lack of fear, visual agnosia, and hypersexuality
  • Limited activation observed in autism
• Hippocampus


  • Essential for flexible learning, seeing relations among learned items, and spatial memory
  • Keeps track of what is where
  • Damage prevents formation of new memories
• Thalamus


  • Relays incoming sensory information to the appropriate cortical region
  • Helps control sleep and waking
  • Abnormalities observed in schizophrenia
• Hypothalamus


  • Regulates behavior related to species survival (fighting, feeding, fleeing, mating)
  • Regulates emotions and reactions to stress
  • Interacts with the limbic system
  • Involved in sleep regulation and endocrine system functioning
• Midbrain


  • Surrounds the cerebral aqueduct and consists of the tectum and tegmentum
• Tectum


  • Located in the dorsal portion of the midbrain, contains the superior and inferior colliculi
• Hypothalamus


  Small structure at the base of the forebrain, beneath the thalamus, that plays an important role in regulating emotions, reactions to stress, sleep, and the endocrine system
• Hypothalamus


  Interacts with the limbic system
• Dysfunction and neural loss within the hypothalamus are noted in cases of narcolepsy
• Midbrain


  Surrounds the cerebral aqueduct and consists of the tectum and tegmentum
• Tectum


  • Located in the dorsal portion of the midbrain, contains the Superior and Inferior Colliculi which are involved in the visual and auditory systems
• Reticular activating system (RAS)


  • Network of neurons essential to the regulation of consciousness, sleep, wakefulness, arousal, attention, and vital functions like heartbeat and breathing
• The RAS extends into the hindbrain
• The RAS and the thalamus are essential to our having any conscious awareness of or control over our existence
• Brainstem


  Connects the forebrain to the spinal cord, comprises the hypothalamus, thalamus, midbrain, and hindbrain
• Periaqueductal gray (PAG)


  Region in the brainstem that seems to be essential for certain kinds of adaptive behaviors
• Hindbrain


  Comprises the medulla oblongata, pons, and cerebellum
• Pons


  • Serves as a relay station, contains neural fibers that pass signals from one part of the brain to another, and a portion of the RAS
• Cerebellum


  • Controls bodily coordination, balance, muscle tone, and some aspects of procedural memory
• Medulla oblongata


  • Controls heart activity, breathing, swallowing, and digestion, and is where nerves from the right and left sides of the body cross over
• Spinal cord


  Long, conical structure that distributes motor fibers to effector organs and collects somatosensory information to pass to the brain