16 - Sensorimotor System 2 Flashcards
Is motor control always controlled by the cortex?
no the brainstem is involved
What are some examples of movement NOT controlled via cortex?
brainstem motor control of ocular muscles, speech and respiration
Is motor control via primary motor cortex top down or bottom up processing?
top down
What type of neurons are upper motor neurons?
What structure can upper motor neurons project through to project indirectly to spinal cord?
-pyramidal neurons -> pyramidal tract
-brainstem
Why is the homunculus an oversimplified concept of motor control/somatosensation?
because there is lots of overlap in the representations of each organ
What are the two descending tracts of the motor cortex?
What are the two routes in each tract called?
dorsolateral tract
ventromedial tract
each tract has direct and indirect route
Does the dorsolateral or ventromedial tract project to the distal muscles?
dorsolateral distal muscles
ventromedial proximal muscles
Which motor control tract projects to the contralateral side of the spinal cord? What contralateral muscles does this tract innervate?
dorsolateral projects to contralateral side of spinal cord to innervate the facial muscle
In what ways can the ventromedial tract project to the spinal cord?
either to the ipsilateral side or it projects to both sides
Which tract projects thru the red nucleus?
Where is the red nucleus located?
dorsolateral
brainstem
What nuclei can the ventromedial tract project to?
tectum, vestibular nuclei, reticular formation, cranial nerve nuclei
What are basal ganglia?
What are some nuclei included in basal ganglia?
-group of nuclei lying deep within cerebral hemispheres
-striatum, globus pallidus, substantia nigra, subthalamic nucleus
What sort of input does the basal ganglia receive from the cortex?
How does the basal ganglia return the signal back to cortex? via which structure?
-excitatory
-inhibitory signals (mainly) via thalamus
How does the basal ganglia nuclei cause increased excitation to the lower motor neurons?
-which nuclei are involved
-
striatum is transiently excited and globus pallidus is transiently inhibited -> disinhibition of thalamus and increase excitation of lower MN
How does the basal ganglia react to inhibitory and excitatory signals from motor cortex?
inhibitory -> reduced excitation*
excitatory input -> increased excitation
Do basal ganglia and cerebellum have direct projections to lower/upper motor neurons?
no always indirect:
both via thalamus?
Where are almost half of the CNS neurons located?
cerebellum
Does the cerebellum project to the upper MN?
yes to almost all upper MN
Where does the cerebellum receive information from?
cortex, spinal cord and vestibular system
Why does the cerebellum receive information from the vestibular system?
because the vestibular system inputs information about rotational and acceleratory HEAD MOVEMENT
What sort of information does the cerebellum receive from spinal cord inputs?
True or false: the cerebellum receives inputs from motor cortex?
-info about proprioception
-motor cortex and somatosensory and visual
What is the general theory of the role of the cerebellum in motor control
cerebellum computes motor error and adjusts motor commands accordingly based on inputs its given
What is the futuristic medical benefit of the connection between primary motor cortex to lower motor neurons?
What are some difficulties with this?
-exoskeleton allows tetraplegic patient to walk using direct projection of primary motor cortex to lower MN
-decoding is difficult and movement is carried out without the benefit of ascending sensory feedback systems + reflexes
