The Central Nervous System

Gray Matter and White Matter

• Gray matter: contains neuron somas, existing in clusters called nuclei or along the outer surface of the cerebral cortex.

• White matter: contains myelinated nerve axons, facilitating signal transmission between brain regions.

Senses: Body to Brain

• Sensory fibers provide information from receptors in skin, tissues, and viscera.

• Receptors for pain, touch, vibration, temperature, and pressure.

• Proprioceptors in joints and tissues help determine body position.

• Signals travel through nerves to the spinal cord, forming tracts that ascend to the brain.

• The dorsal column carries fibers for fine touch, vibration, and proprioception.

• Some Fibers travel along the spinothalamic tract.

• Axons sensing fine touch and vibration ascend ipsilaterally in the dorsal column, decussating in the brainstem.

• The right brain processes information from the left side of the body, and vice versa.

• Axons sensing pain and temperature decussate in the spinal cord before traveling to the thalamus.

• The thalamus sends information on to the somatosensory cortex in the parietal lobe