I Neuroanatomy and Neurophysiology

• The nervous system is anatomically divided into 2 parts:

  • Central Nervous System (CNS): brain + spinal cord; integrating & command centre
  • Peripheral Nervous System (PNS): cranial & spinal nerves; communication between CNS & all parts of the body
• Sensory division: somatic & visceral fibers; from receptors to CNS
• Motor division: motor nerve fibers from CNS to effectors
• Somatic ns: voluntary; from CNS to skeletal muscle
• Autonomic ns: involuntary; from CNS to cardiac muscle, smooth muscle, glands

  • Sympathetic division: "fight or flight"
  • Parasympathetic division: conserve energy at rest
• The brain is divided into subdivisions:

  • Cerebral hemispheres
  • Diencephalon (thalamus, hypothalamus, epithalamus)
  • Brain stem (midbrain, pons, medulla)
  • Cerebellum
• Gray matter: short, nonmyelinated neurons and neuron cell bodies; some gray matter is organized into nuclei and distributed as cortical areas
• White matter: primarily myelinated axons; some nonmyelinated axons can be present as well
• Arrangement of Gray & White matter:

  • Spinal cord has central cavity surrounded by gray matter (butterfly shape) with white matter around the outside
  • Brain has a similar design with additional regions of gray matter; cerebral hemispheres & cerebellum have outer "bark" of gray matter
• Ventricles of Brain:

  • Paired lateral ventricles separated by narrow septum pellucidum
  • Each communicates with narrow 3rd ventricle in diencephalon via interventricular foramen
  • 3rd ventricle to 4th ventricle (dorsal to pons) via cerebral aqueduct
  • 4th ventricle continuous with central canal
  • 3 apertures connect ventricles to subarachnoid space (surrounds brain)
• The Cerebral Hemispheres:

  • Superior; ~83% of brain mass
  • Gyri separated by sulci; anatomical landmarks
  • Lobes: frontal, parietal, occipital, temporal, insular
  • Central sulcus: precentral/postcentral gyrus
  • Gyrus Think All, Sulcus Think Valley
• Cerebral cortex (gray matter):

  • Allows us to perceive, communicate, remember, understand, appreciate, initiate voluntary movements → conscious behavior
  • Brodmann areas (BA): numbered in early 1900s by Korbinian Brodmann according to differences in thickness & histology
  • 3 functional areas: motor, sensory & association
  • Each hemisphere handles sensory & motor functions of the opposite side of the body (contralateral)
• Motor Areas:

  • Primary motor cortex (BA 4): precentral gyrus of frontal lobe of each hemisphere; pyramidal cells allow control of skeletal muscles
  • Premotor cortex (BA 6): anterior to primary motor cortex; helps plan movements by selecting and sequencing basic motor movements into more complex tasks
• Broca's area:

  • In region of BA 44
  • Present in one hemisphere only – usually the left
  • Active when preparing to speak
• Frontal eye field:

  • Controls voluntary movements of the eyes
• Sensory Areas:

  • Primary somatosensory cortex (PSC): in postcentral gyrus of parietal lobe (BA 1-3); receives info from somatic sensory receptors & proprioceptors
  • Somatosensory association cortex: posterior to PSC (BA 5-7); integrates/analyzes somatic inputs
• Visual areas:

  • Primary visual cortex (PVC): posterior tip of the occipital lobe; contains map of visual space on retina
  • Visual association area: surrounds PVC; interprets visual image based on prior experience
• Visual Agnosia is the inability to recognize/understand things that you see
• Primary auditory cortex evaluates sound for pitch, rhythm, and loudness
• Auditory association area interprets sound based on memory, including speech, words, music, and recognition of loud, sudden noises
• Olfactory cortex in the medial aspects of temporal lobes allows conscious awareness of different odors
• Vestibular (equilibrium) cortex in the posterior part of insula & adjacent parietal cortex is responsible for awareness of balance
• Gustatory cortex in the insula is responsible for awareness of different tastes
• Visceral sensory area, located posterior to the gustatory cortex, processes information related to visceral organs
• Anterior Association Area (Prefrontal Cortex) is associated with intellect, complex learning, recall, personality, abstract ideas, judgment, reasoning, and planning
• Posterior Association area in parts of temporal, parietal & occipital lobes is involved in recognition of patterns, faces, understanding written & spoken language
• Limbic Association area provides emotional impact and awareness of danger based on prior experience or learning
• Cerebral White Matter facilitates communication between cerebral areas and with the rest of the nervous system
• Basal Nuclei, including caudate nucleus, putamen, and globus pallidus, influence muscle movements directed by the primary motor cortex
• Disorders associated with basal nuclei can result in too much movement (e.g., Huntington’s disease) or too little movement (Parkinson’s disease)
• The Diencephalon consists of the thalamus, hypothalamus, and epithalamus, with key roles in mediating sensation, motor activities, cortical arousal, learning, and memory
• Thalamus acts as a gateway to the cerebral cortex, sorting and editing sensory information
• Hypothalamus regulates autonomic functions, emotional responses, body temperature, food intake, water balance, sleep-awake cycles, and the endocrine system
• Epithalamus, the most dorsal part of the diencephalon, houses the pineal gland and choroid plexus