-Origin-Red nucleus of the midbrain

-Decussates in the Pons

-Joins corticospinal tract in the lateral column of the spinal cord

-Not used as much in humans (the function was taken over by corticospinal tract)

-It is an INDIRECT pathway

-Involved in involuntary adjustment of arm position in response to balance information; support of the body.

-Origin - vestibular nuclei in Medulla

-Medial:head and neck positioning

-Lateral:balance

-The fluid canals of the inner ear accompany head movement--this tact relays sensory information to the inner ear

-Origin - superior colliculus of Mid-brain

-Head and eye coordination

-Helps move head in response to new stimuli

-Receives direct input from retina, visual cortex, somatosensory cortex and auditory cortex--makes map and orientates head.

-Origin - Reticular formation of Brain Stem (runs the full length of the Brain Stem)

-Automatic adjustment to gravity (posture)

-Image of body in space (somatosensory, visual, proprioceptive units)

-Multiple connections with prefrontal cortex

-Involved in Higher Order Motor Planning

-Has connection to BA6

-Abstract thought, decision making, anticipating consequences of action

-Involved in Higher Order Motor Planning

-Has connection to BA6

-Selective inability to perform complex motor acts due to disruption in motor planning

-Can be acquired or developmental

-can be limb, speech/verbal or nonverbal types

-will probably be able to do things reflexively but not on command (speech apraxia is more consistent though)

-Automatic Control of posture and locomotion-

-indirect control (multiple synapses) from brainstem (origin)-

1. Vestibulospinal Tract

2.Tectospinal Tranct

3. Pontine Reticulospinal Tract

4. Medullary Reticulospinal Tract

-Termination - spinal interneurons controlling proximal and axial muscles

Corticospinal Tract

(Pyramidal Tract)

-Origin - motor cortex (BA4, BA6) and somatosensory cortex

-Passes through the inter capsule, then the mid-brain, then collects and forms tract at base of medulla

-Tract forms bulge called medullary pyramid

-Collects in lateral column of spinal cord and forms coticospinal tract

-Terminates in dorsolateral region of ventral horns

-It is a DIRECT tract

1. Corticspinal (longest in CNS)

2. Rubrospinal (smaller component of lateral pathways)

-For conscious voluntary movement-

-Direct control from cortex-

-Autoimmune Disorder characterized by weakness and fatigabilityof voluntary muscles

-Cause is less effective release of acetylcholine at neuromuscular junction so neurotransmission fails

-Muscle weakness fluctuates

-Treatment - acetylcholinesterase inhibitors (prolong the life of released acetylcholine)

-In PNS, relies of neurotransmitter acetlycholine

-Innervates glands, smooth muscle, heart, spinal cord and skeletal muscle

-Largest synapses in body

-Some toxins block neuromuscular transmission and this prevents muscle contraction

Amyotrophic Lateral Sclerosis

(Lou Gehrig's Disease)

-A motor neuron disease

-Initial Signs - muscle weakness and atrophy

-it takes 1 to 5 years for all voluntary movement to be lost

-Death is usually they result of respiratory failure

-Affects motor neurons only!

-Initial symptoms - Weakness/clumsiness that begins focally and then spreads to adjacent muscle groups

-Speech and swallowing eventually severally impaired

Starts in cortex

-Supplies input to the spinal cord

-Synapse to Lower Motor Neurons

-carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle

Lower Motor Neurons

(final common pathway)

-Located in brainstem motor nuclei or ventral horn of spinal cord

-Ventral horns, the larger the size, the more motor neurons they accommodate

-connects the brainstem and spinal cord to muscle fibers, bringing the nerve impulses from the upper motor neurons out to the muscles. A lower motor neuron's axon terminates on an effector muscle