Chapter 16 Lecture: Sensory, Motor and Integrative Systems

somatic sensory pathway

contains thousands of sets of 3 orders of neurons- primary secondary and tertiary neurons

1st order/primary neurons

sensory neurons

conduct impulses from sensory receptors into spinal cord or brainstem

2nd order/secondary neurons

interneurons

conduct impulses from spinal cord or brainstem to thalamus

3rd order/tertiary neurons

interneurons

conduct impulses from thalamus to primary somatosensory area in parietal lobe

somatic direct motor pathways

lateral corticospinal pathway

anterior corticospinal pathway

upper motor neurons umn’s

neurons have cell bodies in motor areas of upper parts of cns

umn’s synapse

directly with lower motor neurons directly or synapse with local circuit neurons (interneurons) which in turn synapse with lower motor neurons

lower motor neurons lmn’s

neurons have cell bodies in lower parts of cns (brainstem and spinal cord)

from brainstem, axons of lmn’s extend through

cranial nerves to innervate skeletal muscles of face and head

from spinal cord, axons of lmn’s extend through spinal nerves

to innervate skeletal muscles of limbs and trunk