study guide exam 3 Flashcards
aka ventral horn neurons innervates the skeletal muscles of the head and body
LMN
Functions: to commend for movement (reflexive or voluntary)
LMN
sensory neuron to lower motor neuron WITHOUT involvement of the upper motor neuron in cortex
reflexive movement
what are the neuronal types of reflexive movement
LMN, sensory, interneurons, brainstem UMNs
**NOT cortical UMNs
all the motor neurons innervating a single muscle are grouped together into a rod-shaped cluster
motor neuron pool
Proximal muscles –> medial LMNs with____ ____ control
body postural
distal muscles –> lateral LMNs w/ ___ ____ ___
skilled voluntary movement
the axon form a single alpha motor neuron branches within muscles to synapse on many extrafusal fibers
motor unit
generates small forces, most resistant to fatigue, low threshold for activation (tonically active and sustained effort)
slow motor unit
generates large force + easily fatigued
Fast Fatigable (FF) motor units
medium force + resistant to fatigue
Fast fatigue-resistant (FR) motor units
gradual increases in muscle tension (or force) results from the progressive recruitment of motor units in a fixed order (S –> FR–> FF)
size principle
maintain muscle length at a desired level ex. knee jerk reflex
muscle stretch reflex
maintain muscle tension (force) at a desired level ex. weight lifting
Golgi tendon reflex
Biological neural networks that produce rhythmic patterned outputs for locomotion without sensory feedback & without descending UMN
central pattern generators (CPGs)
encode movements in central personal space, purposeful/pre-programmed movements, population coding *purposeful movements instead of contractions
primary motor cortex
movements that are oriented toward extra personal space
premotor cortex
stabilizing head position (vestibulo-cervical reflex)
MEDIAL vestibular nucleus
stabilizing posture after existing unanticipated postural instability (vestibulo-spinal reflex)
lateral vestibular nucleus
stabilizing posture to anticipated postural instability
reticular formation
orienting head and eye movements (saccade)
superior colliculus
anterior medial white matter and terminate in medial cell groups in both sides (functions: govern posture and balance mechanism of axial muscles)
UMNs in brainstem
lateral white matter + terminate in lateral cell groups in contralateral side (functions: skilled voluntary movements of distal extremities)
UMNs in motor cortex
contains over 90% of the fibers present in the corticospinal tract and runs the length of the spinal cord. The primary responsibility of the lateral corticospinal tract is to control the voluntary movement of contralateral limbs
lateral corticospinal tact
Encode movements but not muscle contractions
Encode intentions for movements in central personal space
These movements are purposeful/preprogrammed movements
Population encoding
general functional organization of the primary motor cortex
subset of UMNs in premotor cortex fire in both planning and observations of the particular movements being performed by others
Mirror motor neurons
Medium spiny neurons in caudate and putamen receive inputs from which two brain regions?
Cerebral cortex + substantia nigra pars compacta
What are the main sources of output from the basal ganglia to upper motor neurons in motor cortex or superior colliculus?
Globus pallidus and substantia nigra pars reticulata
sequence of events that occur during the function of the basal ganglia circuit indirect (stop)
Striatum D2R MSNs -> GPe -> STN -> GPi -> Thalamus
sequence of events that occur during the function of the basal ganglia circuit direct (GO)
Striatum D1R MSNs -> GPi -> Thalamus
loss of ____ neurons in substantia nigra pars compacta causes Parkinson’s disease
dopamingeric
How does loss of dopaminergic inputs to striatum (caudate/putamen) cause hypokinetic symptoms in Parkinson’s disease?
Causes an increase of activity of the indirect pathway and diminishes the direct pathway
What are the effects of hypokinetic disorders on movement control pathways
Effects of hypokinetic disorders -> overactivity of indirect pathway, and underactivity of direct pathway —> more tonic inhibition of thalamus.