what are the four major neural movement centers?
- lower motor neurons
- upper motor neurons
- cerebellum
- basal ganglia
where are lower motor neurons located? what are their function?
they are located in the brainstem, which send axons to muscles of the head
and in the spinal cord, which send axons to muscles and the rest of the body.
what is the 1:1 ratio?
individual muscle fibers are only innervated by a single motor neuron.
how are muscles activated?
- sensory info enters spinal cord via dorsal root.
- motor info exits spinal cord via ventral root.
- muscles receive neural input from motor neurons in the spinal cord.
- motor neurons release acetylcholine.
where are upper motor neurons located?
- brainstem
- cerebral cortex
- motor cortices
what are the four descending projections of upper motor neurons in the brainstem? what are their function?
- tectospinal tract: controls neck musculature and generates head + eye movement.
- rubrospinal tract: controls arm musculature.
- reticulospinal tract: temporal and spatial coordination of movment + cardiovascular and respiratory.
- vestibulospinal tract: balance/posture + controls axial and antigravity muscles + eye fixation during movement.
what are the three regions of motor cortices that upper motor neurons are located? what are their functions?
- primary motor cortex
- supplementary motor area: planning movements.
- premotor cortex: planning and control of limb movements.
what is the function of the primary motor cortex?
- controls voluntary movement of contralateral side of body.
- topographic organization.
what is the primary motor cortex monkey experiment?
- joystick starts in the center
- monkey is trained to move the joystick in 1 of 8 different directions.
- on each trial the monkey moves the joystick in one direction.
- in this example the monkey moves the joystick to the left.
what are the three functional components of the cerebellum? what are their functions?
- vermis + anterior lobe: motor coordination and limb control.
- posterior lobe: initiation, planning, and timing.
- flocculonodular lobe: vestibular control.
what are the three layers of the cerebellar cortex?
- molecular layer
- purkinje cell layer
- granular layer
what is special about purkinje cells?
- GABAergic
- recieve more synaptic inputs than any other nueron.
what is special about granule cells?
- glutamtergic
- very few dendrites
Being one of the external inputs to the cerebellar cortex, what are climbing fibers?
- come from inferior olive
- glutamatergic
- synapse on purkinje cell dendrites.
Being the other external input to the cerebellar cortex, what are mossy fibers?
- come from pontine nuclei
- glutamatergic
- contact granule cells
what is the primary output from the cerebellar cortex?
purkinje cells which project to deep cerebellar nuclei to the thalamus to the cerebral cortex.
what is the order of the anatomical loop?
- cerebral cortex
- pontine nucleus
- cerebellum
- deep cerebellar nuclei
- thalamus
- back to cerebral cortex
what are some things that could be affected following damage to the cerebellum?
- behavioral traits
- balance
- guided movements
- range and force of motion
- inability to rapidly stop limbs
what is the basal ganglia?
a group of interconnected subcortical brain structures.
how does the basal ganglia differ in primates vs rodents?
- primates: caudate and putamen are combined.
- rodents: caudate and putamen are combined into one structure (striatum).
what are the two projections from the cortex to the striatum?
- pyramidal tract: upper motor neurons that project to brainstem and spinal cord.
- Intertelencephalic (IT) neurons: motor cortex neurons that DO NOT project to brainstem and spinal cord.
where do direct pathway neurons of the basal ganglia send axons to?
- GPI
- SNR
where do indirect pathway neurons of the basal ganglia send axons to?
- GPE
- to STN
- then to GPI and SNR
where do GPI and SNR send axons to?
thalamus then back to cerebral cortex
