Sensorimotor Neuroanatomy

Nervous System

  • CNS: All neurons & glia contained to brain & spinal cord

  • PNS: all neurons & glia outside of brain & spinal cord

  • Neurons:

    • nerve cells

    • receives, processes, & outputs info

    • basic functional unit

  • Sensory Neurons, Motor Neurons, & Interneurons

  • Glia

    • support cells, outnumber neurons

  • Sensory neurons

    • deliver info to CNS from endings on surface of body & within tendons & muscles. Info about body relative to environment. Afferent

  • Motor neurons

    • neurons connected to muscle cells to cause muscle contractions. Voluntary movement activity. Efferent

  • Interneurons

    • Perform processing functions (memory, planning, emotion, etc.) Connect neurons to other neurons. Account for majority of neurons in nervous system

  • Glia cells: insulate, support, & nourish neighboring neurons

    • produce Myelin, which insulates axons of many neurons to speed up transmission of impulses (Multiple sclerosis is the degradation of myelin which slows down transmission)

Motor Cortex

  • Decides direction, magnitude, & speed of movement

  • Premotor cortex

    • helps plan movements

  • Supplementary motor cortex

    • assists in complex movements    

  • Primary motor cortex

    • when you’re ready to actually start a movement

  • Homunculus

    • representation of the relative size of the motor cortex allocated to each body part

Rest of brain

Lateralization

  • Left hemisphere

    • right side of body

    • specification of muscle force & timing

  • Right hemisphere

    • left side of body

    • tactile discrimination

    • spacial discrimination

  • Corpus Callosum

    • “bridge” for communication between hemispheres

  • Basal Ganglia

    • initiates internally generated movement

    • role in planning complex movement

    • no direct connection to spinal cord; indirectly influences movement

  • Cerebellum

    • directly behind brainstem

    • adjusts output & controls posture indirectly

    • when damaged motor coordination is lost

Spinal Cord

  • Nerves exit spinal cord at specific levels to connect to peripheral muscles

    • ex: cervical spine connects to neck & delt muscles

  • Dorsal roots carry info toward spinal cord (afferent)

  • Ventral roots carry info away from spinal cord (efferent)

  • Spinal nerves are generaly mixed: contain afferent & efferent neurons