Nervous system - Lecture Twenty Two : Neuroanatomy V - Structure and layout of the brain area; sensory and motor pathways

7 important questions on Nervous system - Lecture Twenty Two : Neuroanatomy V - Structure and layout of the brain area; sensory and motor pathways

Describe the external anatomy of the brain. Also explain its functions and its features

FUNCTIONS :
  • Frontal lobe : Motor control, language and personality
  • Parietal lobe : Somatosensory
  • Occipital lobe : Vision
  • Temporal lobe : Memory and hearing

FEATURES :
  • Transverse fissure : separates the cerebellum from the lobes
  • Lateral sulcus : separates the temporal lobe from the frontal lobe
  • Central sulcus : separates the frontal lobe from the parietal lobe
  • Parieto-occipital sulcus : separates the parietal lobe from the occipital lobe

What are the 3 types of white matter tracts in the brain ?

  1. Commissural tracts : Axons cross from side to side; in both directions.
  2. Projection tracts : Axons extend between cortex and other CNS areas outside the cerebrum.
  3. Association tracts : Axons on same side within cerebral cortex and communication between brain areas (either short or long distance)

What are the features of the Primary Motor Cortex ?

Location : Frontal lobe and the pre-central gyrus
  • Pre-motor cortex involves the planning of movement
  • Primary motor cortex is the execution of movements
  • The left cortex corresponds to the right side of the body , and vice versa
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Explain the Corticospinal tract pathway that occurs in the primary motor cortex 

  • Involves two neurons between the CNS and effector

UPPER MOTOR NEURON :
  • Cell body is located in the primary motor cortex
  • Axon extends from the cortex to the spinal cord on the opposite side
  • Synapses with the lower motor neuron in the ventral horn of the spinal cord

LOWER MOTOR NEURON :
  • Synapses with the upper motor neuron in the ventral horn of the spinal cord
  • Axon extends out of the spinal cord and into the body
  • Makes synapse on skeletal muscle fibres that controls precise movements of the hands/feet

What happens if the primary motor cortex is damaged ?

If someone had damaged their upper motor neuron in the primary motor cortex, the upper motor neurons die. This is because no signals going to the lower motor neuron.
This results in muscle weakness and paralysis in the region of the body corresponding to the location of damage, on the opposite side.

What are the features of the Primary Somatosensory cortex ?

Location : Parietal Lobe and the Post-Central gyrus
  • Its function is the primary somatosensory cortex
  • Specific regions of the somatosensory cortex receive sensory information from specific region of the body
  • The left cortex corresponds to the right side of the body, and vice versa

What happens if the primary somatosensory cortex is damaged ?

If there is damage to the post-central gyrus, that neuron in the somatosensory cortex will die.
If this happens there will be no neuron to receive the sensory information from the body. Meaning there will be no perception of touch in that area of the body on the opposite side.

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