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 in the brain consists of short, nonmyelinated neurons and neuron cell bodies, organized into nuclei and distributed as cortical areas

  White matter primarily consists of myelinated axons with some nonmyelinated axons
• 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 perception, communication, memory, understanding, voluntary movements
  • Brodmann areas (BA): numbered areas for functional regions
  • 3 functional areas: motor, sensory, association
  • Each hemisphere handles sensory & motor functions of the opposite side of the body (contralateral)
  • Conscious behavior involves the entire cortex
  • Motor Areas:
  • Primary motor cortex, premotor cortex, Broca’s area & frontal eye field
• 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) in the occipital lobe
  • Visual association area surrounds PVC
  • Interprets visual images based on prior experience
• Visual Agnosia: the inability to recognize/understand things that you see
• Auditory areas:

  • 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
• Vestibular (equilibrium) cortex:

  • Located in the posterior part of the insula & adjacent parietal cortex
  • Awareness of balance, not visible at the surface but deep in the lateral sulcus
• Olfactory cortex:

  • Located in the medial aspects of temporal lobes (uncus)
  • Conscious awareness of different odors
• Gustatory cortex:

  • Located in the insula
  • Awareness of different tastes
• Visceral sensory area:

  • Located posterior to the gustatory cortex
  • Provides information related to visceral organs, such as stomach ache
• Anterior Association Area (Prefrontal Cortex):

  • Associated with intellect, complex learning, recall, personality, and working memory
  • Involves abstract ideas, judgment, reasoning, planning, and conscience
• Posterior Association area:

  • Parts of temporal, parietal & occipital lobes
  • Involved in recognition of patterns, faces, understanding written & spoken language (Wernicke’s area)
• Limbic Association area:

  • Provides emotional impact based on prior experience or learning
• Cerebral White Matter:

  • Commissural fibers connect corresponding areas between the 2 hemispheres, with the largest being the corpus callosum
  • Association fibers connect within a hemisphere, while projection fibers connect to or from the cortex and the rest of the nervous system
• Basal Nuclei:

  • Includes caudate nucleus, putamen, and globus pallidus
  • Influences muscle movements directed by the primary motor cortex
• Disorders associated with basal nuclei:

  • Huntington’s Disease: hereditary disorder leading to degeneration of the basal nuclei and cortex
  • Parkinson’s Disease: degeneration of dopamine-releasing neurons causing overactivity in the basal nuclei
• Diencephalon:

  • Includes thalamus, hypothalamus, and epithalamus
  • Thalamus acts as a gateway to the cerebral cortex for sensory information
• Hypothalamus:

  • Autonomic control center for bodily functions
  • Regulates emotional response, body temperature, food intake, water balance, sleep-awake cycles, and the endocrine system
• Epithalamus:

  • Forms the roof of the 3rd ventricle and includes the pineal gland that produces melatonin
  • Choroid plexus, a CSF-forming structure, is also part of the epithalamus