Central Nervous System Overview

Central Nervous System Overview

• The central nervous system (CNS) is composed of the brain and spinal cord
• The CNS is the control center of the body, responsible for receiving, interpreting, and responding to information from the body and the environment.

Brain Regions

• Cerebral Hemispheres (Cerebrum):

  • Two layers: cortex (outer layer) and medulla (inner layer)
  • Paired (left and right), superior parts of the brain
  • Make up more than half of the brain mass
  • Surface is made of ridges (gyri) and grooves (sulci)
  • Contains gray matter (neuron cell bodies), primarily in the cortex
  • Contains white matter (myelinated fibers) inside the gray matter, in structures like the corpus callosum which connects the hemispheres
  • Lobes include frontal, parietal, temporal, and occipital, named after the bones they sit under
  • Specialized areas within the hemispheres control functions like speech, language, memory, sensory perception, and voluntary movement

• Diencephalon:

  • Sits on top of the brain stem
  • Enclosed by the cerebral hemispheres
  • Made up of the thalamus and hypothalamus
  • Thalamus: a relay station that transfers sensory impulses to the correct part of the cortex for localization and interpretation
  • Hypothalamus: an important autonomic nervous system center that regulates body temperature, water balance, and metabolism and is part of the limbic system (emotions)

• Brain Stem:

  • Attaches to the spinal cord
  • Parts of the brain stem include the midbrain, pons, and medulla oblongata
  • Midbrain: mostly composed of tracts of nerve fibers and reflex centers for vision and hearing
  • Pons: a bulging center part of the brain stem; primarily composed of fiber tracts, and includes nuclei involved in breathing control
  • Medulla Oblongata: the lowest part of the brain stem, important fiber tracts and vital control centers including heart rate, blood pressure, breathing, swallowing, and vomiting
  • Reticular Formation: a diffuse mass of gray matter along the brain stem, involved in motor control of visceral organs, and plays a role in awake/sleep cycles and consciousness

• Cerebellum:

  • Two hemispheres with convoluted surfaces
  • Coordinates skeletal muscle movement
  • Fibres connect to inner ear, eye, and muscle proprioceptors.

Specialized Areas of the Cerebrum

• Primary motor area: sends impulses to skeletal muscles in the frontal lobe
• Somatic sensory area: receives impulses from the body's sensory receptors in the parietal lobe
• Broca's area: in the frontal lobe, involved in the ability to speak (motor)
• Somatosensory association area: involved in recognizing sensory information (identifying what we are touching, feeling, etc)
• Gustatory area: handles taste in parietal lobe
• Auditory area: is in the temporal lobe; responsible for interpreting sound
• Olfactory area: handles the sense of smell, in frontal lobe
• Visual area: in occipital lobe, involved in vision input
• Speech and language interpretation areas: are important areas for complex language processes

Basal Nuclei (Ganglia)

• Internal islands or centers of gray matter that help to control skeletal muscle movements (motor centers)
  • Structures include Striatum, Caudate, Putamen, and Globus pallidus

Cranial Nerves

• Cranial nerves are nerves that originate in the brain and emerge from the brainstem
• A list of cranial nerves and their names are shown in one of the images