Chapter 14: Brain Control Of Movement Flashcards
What are the six steps of the corticospinal tract?
1) cortical spinal tract begins at spinal cord
2) pyramidal decussation
3) goes through the medullary pyramids in the medulla
4) goes through base of cerebral peduncle in the midbrain
5) goes through thalamus and internal capsule
6) reaches motor cortex
What are two effects of corticospinal lesions?
- difficulty moving distal limbs - may recover over time
- loss of ability to make independent finger movements - does not recover
Explain what each ventromedial pathway regulates
Vestibulospinal tract: balance
Tectospinal tract and tectbulbar tract: orienting reflexes
Pontine and medullary reticulospinal tracts: locomotion and posture
Explain the 2 steps of the vestibulospinal tract?
Starts in spinal cord
Reaches vestibular nucleus in medulla
Explain the tectospinal tract
Initiates in Spinal cord
Goes through medulla where it decussates
Terminates in superior colliculus
Explain the medullary reticulospinal tract
Spinal cord initiation
Terminates in medullary reticular formation
Explain the pontine reticulospinal tract
Initiates in spinal cord
Goes through medulla
Terminates in pontine reticular formation
Where do lateral pathways synapse
Synapse on motor neurons innervating distal pathways and flexors
Where do ventromedial pathways synapse
Synapse on motor neurons innervating axial muscles and extensors
What is the area for the primary motor cortex?
Area 4
Where does the corticospinal tract originate from?
Layer 5 Betz cells in area 4 of M1
In relation with voluntary movement, when does activity happen in M1 neurons?
Before and after
Explain direction vectors
Certain Cells fire most to leftward (example) direction vector points.
What does a higher firing rate entail (direction vectors)
Higher firing rate=more force
What can you say about direction vectors
Points in the preferred direction for the neuron, but it’s length depends on the firing rate over a range of direction
What is a population vector?
Vector sum
What does the primary motor area do? What area?
Initiation of complex voluntary movement
What do the supplementary motor And premotor areas do? What area?
Motor planning
Area 6
What are the 4 function of the prefrontal association cortex?
- executive function
- abstract thought
- decision making
- anticipating consequences of action
What does the P-T-O association cortex do?
- analysis of sensory inputs (vision, somatosensory, auditory)
- constructs representation of our sensory world
- proprioceptors - current position of our body in space
What does the basal ganglia do?
Selects and initiates willed movements
What are the 4 sections of the basal ganglia?
Striatum: caudate nucleus/putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra
Direct Pathway
EXCITATORY LOOP
Cortex excites striatum
striatum excites globus pallidus
globus pallidus inhibits thalamus
Thalamus excited cortex
Indirect Pathway
Suppresses unwanted movement
Cortex excites striatum
Striatum inhibits globus pallidus external
Globus pallidus external inhibits subthalamic nuclei
Subthalamic nuclei excites internal globus pallidus
Internal globus pallidus inhibits thalamus
Explain the body movement loop of the basal ganglia
Cortex transiently excited putamen (striatum)
The putamen transiently inhibits the globus pallidus
The globus pallidus inhibits the VL/VA thalamus
VL/VA is released from inhibition and excites the cortex
What leads to hypokinesis? Cite an example
An increase in GP output. Eg: Parkinson
What leads to hyperkinesis? Cite example
Over excitation of thalamus, Huntington’s, hemibalismus
Explain how the frontal/parietal cortex is linked with the cerebellum cortex
Frontal/parietal—>red nucleus—>inferior olive—>goes through inferior cerebellar peduncle—>cerebellar cortex
Or
Frontal/parietal cortex—>pontine nuclei—>goes through middle cerebellar peduncle—>cerebellar cortex
Which movement does the motor cortex dictate?
Intended movement
Which movement does the inferior cerebellar peduncle dictate?
Actual movement
Where does the cerebellar cortex receive inputs from?
Inferior olive, spinal cord, vestibular nuclei
Huntington’s Disease
Hyperkinesia
Loss of neurons in striatum and globus pallidus, not enough inhibition to thalamus, and thus over excitation
Parkinson’s Disease
Hypokinesia
Damage to dopamine cells in substantial Niagara
More inhibition of thalamus, feedback loop to cortex inhibited
Deep brain stimulation can be cure
Hemiballismus
Hyperkinesia
Due to stroke, subthalamic nuclei is damaged, inhibition of globus pallidus to cortex not enough, over excitation
Cells in Cerebellum
granule cells • tiny excitatory neurons • # of granule cells in cerebellum is almost = to the total # of neurons in the CNS! • Purkinje cells • largest neurons in the cerebellum • receives excitatory input from granule cells in the molecular layer • sends inhibitory axons to deep cerebellar nuclei
Cerebellum Function and Dysfunctions
Function: coordinate a detailed sequence of muscle contractions • Cerebellar lesions: • Ataxia: uncoordinated and inaccurate movements • Dyssynergia: decomposition of synergistic multi-joint movements • Dysmetria: overshoot or undershoot target • dyssynergia and dysmetria are characteristic of alcohol intoxication
Pontine nuclei
–Axons from layer V pyramidal
cells in the sensorimotor cortex
send massive projections to
pons
Corticopontocerebellar projection
– 20x larger than pyramidal tract –Lateral cerebellum projects back to motor cortex via VLc • Lesions suggest that the cerebellum is involved in the proper execution of planned, voluntary, multi-joint movement
Cerebellum and Learning
Site of motor learning
• Instructs the primary motor cortex (direction, timing, and
force of movement)
• Uses past experience to make predictions about outcome
• Skill mastery comes with practice
• Movements become smooth
