Motor and sensory systems

corticospinal tract

only tract that runs thru pyramids

corticospinal tract

involves several parallel pathways and recurrent feedback loops involved w/ motor control

corticospinal tract

originates in precentral gyrus, projects down via axons thru cerebral white matter and brainstem to reach SC

pyramidal decussation

where corticospinal tract crosses in medulla

contralat

corticospinal tract lesion above decussation

ipsilat

corticospinal tract lesion below decussation

ant horn

corticospinal tract synapses in ___ of each SC gray matter seg

cerebellum and basal ganglia

functions as feedback systems designed to refine movement

cerebellum and basal ganglia

helps modulate output of corticospinal tract and other descending motor systems

basal ganglia

receives motor input from motor cortex only

cerebellum

receives motor input from motor cortex, brainstem, and SC (receives info from LMNs but not directly)

thalamus

cerebellum and basal ganglia both project motor info back to motor cortex via

ataxia

lesion in cerebellum causing coordination and balance issues

basal ganglia

Parkinson’s disease affects the ___ causing hypokinetic movements

motor cortex, pons, cerebellum, thalamus, motor cortex

motor feedback A

motor cortex, basal ganglia, thalamus, motor cortex

motor feedback B

proprioception, vibration, fine touch

Post (dorsal) column pathway sends what sensory info

pain, temp, crude touch

Anterolat pathways send what sensory info

post (dorsal) column pathway

dorsal root → ipsilat white matter dorsal column → dorsal column nuclei (gracilis and cuneatus nuclei) in medulla → secondary sensory neuron (crosses) → thalamus → primary sensory cortex (postcentral)

anterolat pathway

dorsal root → synapses immediately in SC gray matter → axons cross then ascend anterolat white matter (spinothalamic tract) → thalamus → primary sensory cortex

spinothalamic tract

anterolateral white matter tract

thalamus

gray matter structure; major relay station for motor and sensory (except smell); processes info then sends to cortex

brainstem

deficits here can affect motor, sensory, and autonomic functions

midbrain, pons, medulla

brainstem contains

monosynaptic stretch reflex

provides rapid local feedback for motor control

muscle spindle

receptor for rate and amount of m stretch

monosynaptic stretch reflex

M spindle → afferent fibers → dorsal root (w/ ganglion) → SC gray matter → ventral root → LMN (motor/efferent)

reticular formation

w/in brainstem; extends from medullar to midbrain

motor and autonomic functions

caudal portion (medulla and lower pons) of reticular formation involves

consciousness (awake/alert) lvls

rostral portion (midbrain and upper pons) of reticular formation involves