Neural Pathway

Question 1

Describe motor pathway (descending)

Answer 1

1. Primary sensory cortex relays information to primary motor cortex of posterior frontal lobe
2. Primary motor cortex sends action potentials down corticospinal tract, crossing to contralateral side in the brain stem and synapses with alpha motor neurones in the spinal cord
3. Impulses then pass to the peripheral neurones which innovate the muscles.
4. The cerebellum compares sensory feedback from body with messages regarding intended movement.
5. Then producing automatic responses feeding back to cerebral cortex
6. Planning of movement comes from basal ganglia which has connections to cerebral cortex and thalamus

Question 2

Describe somatosensory pathway (ascending)

Answer 2

1. Exteroceptive, interoceptive and proprioceptive stimuli are detected by sensory receptors in the skin, muscles and organs. By mechanoreceptors (sensation) and nociceptors (pain).
2. The sensory information is conveyed to CNS by afferent (primary) neurones.
3. Secondary neurones carry action potentials up the spinal cord in the dorsal column pathway, which crosses to contralateral side in medulla oblangata
4. Dorsal column ends by synapsing in the thalamus
5. The final part of this pathway goes from thalamus to primary somatosensory cortex at front of parietal lobe.
6. Sensory information also passes to cerebellum to help control co-ordination