Neurobiological Pathways and Circuits involved in Motor Control (ALS/MND) 2 Flashcards
Where does the upper motor neurons circuit run from and to?
From the cortex down to the brainstem
Which other neural circuit does Upper Motor Neurons Circuit neurons synapse with near the effector organs?
Local circuit neurons
Which functions are associated with the upper motor neurons circuit?
Involuntary movement initiation, control of complex movements
Which pathways are connected to the upper motor neurons circuit?
Corticospinal tract, corticobulbar tract, corticorubral tract, coticorectal tract and corticoreticular tracts
What does the corticospinal tract connect the upper motor neurons circuit to?
It connects it to the lower motor neurons (and so effector organs) via the SC
Where does the corticobulbar tract end up?
Cranial nerve
What is the corticobulbar tract responsible for?
Giving commands to the cranial nerve–> muscles in face, neck
Diseases associated with upper motor neurons circuit dysfunction?
Amyotrophic lateral sclerosis, primary lateral sclerosis, stroke
Function of cerebellar circuits?
Detects and corrects motor errors between intended and performed movements
Where do afferent pathways take information from and to?
From sensory organs to the brain
Diseases associated with cerebellar circuit dysfunction
Cerebellar ataxia, as well as some symptoms in parkinson’s and huntington’s
Where are basal ganglia circuits located?
Forebrain
What does the basal ganglia circutis consist of?
Striatum, globus pallidus, substantia nigra
Which parts of the brain are basal ganglia circuits connected to?
Cortex and thalamus
What type of effect (excitatory or inhibitory) can the striatum have on the substantia nigra and globus pallidus?
Inhibitory
What role, in relation to movement, does the direct pathway in the basal ganglia circuits have?
Facilitates movement
How does the cortex facilitate movement?
D1 receptor in striatum activated–> inhibits globus pallidus interna–> less inhibition of thalamus by GPi–> facilitates movement
How does the cortex inhibit movement?
Activates D2 receptor–> inhibits Globus Pallidus externa–> less inhibition of Nucleus subthalamicus by GPe–> more excitation of GPi by NS–> more inhibition of thalamus by GPi–> inhibition of movement
Direct pathway involving cortex that isn’t involving the GP?
Cortex activates D1 receptors in striatum–> inhibits Substantia nigra pars reticularis–> less inhibition of thalamus by SNPR–> movement facilitated
Diseases associated with dysfunction of basal ganglia circuit?
Parkinson’s and Huntington’s
How does the myotatic reflex mechanism work?
If the muscle is stretched, the depression in the muscle spindle is sensed. Info is taken to the SC where it is processed–> SC gives info to efferent neurons who take it to the muscle and the knee jerks
How does the baroreceptor reflex work?
Baroreceptors detect changes in blood pressure–> sends signals to the brain (increase in BP = more signals). The brain can then increase or decrease the blood pressure accordingly
What is done by baroreceptors as a result of decreased arterial BP?
Decreased baroreceptor nerve activity
Reult of decreased baroreceptor nerve activity?
Increased sympathetic activity and decreased parasympathetic activity–> increased heart rate, increased force of heart contraction and arteriolar vasoconstriction
