Neuroscience course notes

Movement worksheet

Pyramidal Tracts
-Initiate voluntary motor movement (particularly skilled movement)
-Corticospinal Tract (CST): major neuronal pathway, in charge of voluntary motor functions.
-Voluntary movement of distal extremities (hands, fingers) via SPINAL NERVES
-Corticobulbar(brain stem) Tract (CBT)
-Voluntary movement of head and neck muscles

Upper Motor Neurons (UMNs)
-​ Initiate voluntary movement
-​ Origin of corticospinal tract
+-​ UMN cell bodies located in cortical motor areas:
-​ Supplementary motor area e
-​ primary motor cortex e
-​ premotor cortex e
-​ Primary motor cortex is organized vertically in primary motor cortex,
-​ Motor homunculus!

Lower Motor Neurons (LMNs)
-​ Start from the spinal cord/at the end of corticospinal tract
-​ Stimulate muscles to contract
-Receive input from UMNs or sensory neurons via reflex arcs
-The ONLY input to motor neurons to effect contraction
-Located: cell bodies in ventral horn of spinal cord
-Axons project into skeletal muscles or synapse on interneurons

Corticospinal Tract
-​ UMN cell bodies in motor cortices project axons that descend through brain
-​ 90% of axons decussate in medulla
- Axons synapse on LMN cell bodies in spinal cord
- The right and left side of the motor cortex control voluntary movement in the contralateral body.

Disorders
Amyotrophic Lateral Sclerosis(ALS):degeneration of corticospinal UMNs and LMNs.
-​ Symptoms: weakness/clumsiness and near total paralysis
-​ Decrease muscular mass(muscular atrophy)
-​ Voluntary eye movement, sensory systems & autonomic functions not affected
-​ Idiopathic: unknown cause in most cases

Neuromuscular junction (NMJ)
-​ LMNs release ACh. End plate potential(induces EPSPs like events) in the skeletal
muscle causing contraction in the muscles.