Each region has a homunculus Fig. 10.10a S 2 Each region has a homunculus 10.10a.jpg

Initiates motor command Decision to move Fig. 10.01 S 4 Initiates motor command Coordinates secondary movements Corticospinal and corticobulbar tracts Balance and complex learned movements Pathways? Other inputs: Vestibular & Visual! 10.01.jpg Reflex Examples of motor disorders: Huntington’s Disease and Cerebellar Disorder

Jack Nicholson One Flew Over the Cuckoo’s Nest Frontal lobotomy

Extra-Pyramidal tracts Fig. 10.12 S 16 Pyramidal tract Descending Pathways Corticospinal tract Corticobulbar tract Fine motor control, esp. of extremeties Extra-Pyramidal tracts Reticulospinal tract Vestibulospinal tract Originate in brainstem, more involved with posture and equilibrium 10.12.jpg Diagram is not accurate: This is not a monosynaptic pathway! Descending axons synapse onto interneurons which then synapse onto motoneurons.

Who Cares? S 17 Video of Huntington’s Chorea Video of Cerebellar Dysfunction Locked-in Syndrome

Local control Muscle spindle What is their role? The stretch reflex… Spindle Afferent gamma motoneurons Muscle spindle Stretch receptor Intrafusal muscle fiber What is their role? The stretch reflex… Follow the reflex arc Be able to differentiate function of afferent fibers, alpha motor neurons, and gamma motor neurons 10.04.jpg Motor units of alpha motoneurons

Fig. 10.05ab S 7 10.05ab.jpg This doesn’t happen!

Fig. 10.05c S 8 10.05c.jpg Co-activation of alpha and gamma motoneurons insures that the stretch of muscle can be detected regardless of the initial length or state of contraction of that muscle.

Synergistic & Antagonistic Fig. 10.06 S 9 Proprioception pathway via dorsal column-medial lemniscus pathway One component of Stretch reflex is monosynaptic Most common example: patellar reflex = “knee jerk reflex” Synergistic & Antagonistic Muscles 10.06.jpg

Stretch Reflex S 10 Monosynpatic excitation of motoneurons of that muscle and synergistic muscles and polysynaptic inhibition of motoneurons to antagonistic muscles. Recall frog reflex lab and existence of spinal reflexes in single-pithed frogs. Also, example Christopher Reeve and patellar reflex. 10.06.jpg

Fig. 10.07 S 11 10.07.jpg

Golgi tendon organs involved in a reflex to oppose excessive muscle tension. Not monosynaptic. Not shown in text diagram: ascending axons in dorsal column-medial lemniscus tract. S 12 10.08.jpg

Other proprioceptors S 13 Joint angle detectors and cutaneous mechanoreceptors also contribute to sense of body position (proproiception.) Plus vision and vestibular inputs!

Something is incorrect on this figure from another textbook. Find it!