L15 Anatomy of the nervous system

• What are the functions of the nervous system?

  Control of vital functions and movement, reaction to external events for survival and cognitive/ emotional processes.
• What is the peripheral nervous system?


  The nerves outside the brain and spinal cord including the somatic nervous system and the autonomic nervous system.
• The somatic nervous system:

  • controls volunatry muscle movement
  • conveys info from sense organs to CNS and from CNS to muscles
  • ascending pathways (afferent) - bottom up
  • descending pathways (efferent) - top down from brain/ spinal cord to muscles
• SNS top-down connections:

  • motor cortex located anterior to the central sulcus elicits all voluntary movements
  • Two paths:
  • dorsolateral tract - controls movement in peripheral parts such as hands, fingers, and toes. Controls the contralateral part of the body.
  • Ventromedial tract - controls more proximal parts of the body e.g. neck, trunk. Controls bilateral movements like walking and controls both sides of the body
• SNS bottom up tracts:

  • dorsal column medial lemniscal pathway - carries info about touch, vibration, proprioception
  • spinal - thalamic tract - carries info about pain and temperature
• Autonomic nervous system:

  • Sympathetic NS = fight or flight. Prepares body for action during times of threat
  • Parasympathetic = active during times of relaxation and rest
• Homeostasis:

  • the centre of homeostasis regulation is the hypothalamus which organizes autonomic NS work and projects to higher brain areas
• Conventions for brain locations:

  • superior = above
  • anterior = in front of
  • posterior = behind
  • inferior = below
• Planes:

  • coronal = view from the front
  • Sagittal = view from the side
  • Horizontal = view from above
• Empty spaces inside the CNS:

  • central canal = a fluid-filled channel in the centre of the spinal cord
  • Ventricles = 4 fluid-filled cavities within the brain
  • Cerebrospinal fluid = a clear fluid within central canal and the ventricles
• White matter:

  • Interhemispheric connections e.g. corpus callosum
  • Cortico-subcortical pathways connect cortex to subcortical areas, motor areas in the brainstem and spinal cord (up-down)
  • Subcortical-cortical pathways: from brainstem, sensory areas in thalamus to the cortex (down-up)
  • Association pathways between different areas in the same hemispheres
• Nervous system development:

  during embryonic development of humans:

  • a neural tube undergoes cephalisation to form initially three, then five vesicles
  • phylogenesis = the sequence of events involved in the evolutionary development of a species
  • ontogenesis = the process of an individual organism growing
• Brainstem:

  • transmits info from and to the brain
  • Responsible for simple reflexible behaviour and physiological states
• What does the hindbrain consist of?

  The medulla = controls vital reflexes e.g. heart rate, coughing

  Pons = a major relay at which axonal projections cross sides, i.e. become contralateral

  Cerebellum = controls fine motor skills, coordination and balance
• What does the midbrain consist of?

  The midbrain is located at the top of the brainstem and contains structures that have secondary roles in vision, audition and movement.

  • superior colliculi = help guide eye movement and fixation of gaze
  • inferior colliculi = help sound localisation
  • substantia nigra = plays a role in reward, addiction, projects to the basal ganglia to integrate movements
• What does the forebrain consist of?

  Thalamus = relays and filters information from sensory organs and transmits it to the cortex

  Hypothalamus = regulates body temperature, hunger, thirst and sexual behaviour
• Key terms:

  • gyrus = a protuberance on a surface of the brain
  • sulcus = a fold that separates one gyrus from another
  • fissure = a long, deep sulcus
  • central sulcus = between frontal and parietal lobes
  • lateral fissure = between temporal cortex and frontal and parietal lobes
  • longitudinal fissure = between two hemispheres
• What is the primary cortex?

  An area of the cortex responsible for the first stage of sensory processing. Received inputs from lower structures and sends projections to higher level areas.
• What is the secondary cortex?

  An area of the cortex responsible for the second stage of sensory processing, analyses the meaning of the stimulus. Receives input from the primary cortex.
• What is the associative cortex?

  Used for advanced stages of sensory information processing, multi-sensory integration, or sensorimotor integration.
• What is the function of the frontal lobe?

  • important for movement and high cognition
  • the primary motor cortex
  • broca’s area
  • prefrontal cortex = planning, decision making, impulse control
• What is the function of the parietal lobe?

  • important for body sensations and spatial localisation
  • primary somatosensory cortex
• What is the function of the occipital lobe?

  Hosts the primary visual cortex
• What is the function of the temporal lobe?

  • auditory cortex
  • wernicke’s area = language comprehension and production
  • inferior temporal cortex = visual identification
• What is the role of basal ganglia?


  Participates in planning behaviour and emotional expression and direct intentional movements
• What does the limbic system consist of?

  hippocampus = creation of new memories, integration of new memories into stable knowledge

  amygdala = emotional behaviour and formation of emotional memories

  cingulate cortex = linking behavioural outcomes to motivation and learning