Neuro 8 - Motor pathways Flashcards
What motor skill is cerebellum needed for?
Fine movement and motor learning
Where is the primary motor cortex (M1) located?
Pre central gyrus
What is in the post central gyrus?
Primary sensory cortex
The primary motor cortex is anterior to what sulcus?
Anterior to central sulcus
What is the function of the primary motor cortex?
Control fine, discrete, precise voluntary movement
It sends descending signals to execute movement
Describe the anterior corticospinal pathway
- (ALL RHS) Primary motor cortex to midbrain, to pons, past pyramids, to SC, where the motor neurone decussates at the anterior corticospinal tract
Describe the primary motor control pathway for voluntary movements
Primary motor cortex past midbrain to pons to medulla where decussation occurs at the pyramids. Then down the SC via lateral corticospinal tract, where it will synapse with a lower motor neurone.
Where is the premotor cortex located?
Frontal lobe, anterior to M1
What is the function of the pre-motor cortex?
Planning of movements, regulating externally cued movements (e.g. seeing an apple and reaching for it)
Where is the supplementary motor area located?
Frontal lobe, anterior to M1, medially
What is the function of the supplementary motor area?
Planning complex movements, regulates internally driven movements (e.g. speech). Active when thinking about a movement before executing the movement
What are association cortices?
Brain areas that are not strictly motor areas (activity doesn’t correlate with motor output)
Give examples of association cortices
- Posterior parietal cortex (ensure accurate movements towards objects in 3d space)
- Prefrontal cortex (selection of appropriate movements for particular action)
What is meant by corticobulbar?
Motor nucleus to hypoglossal nucleus
Upper motor neurone are ?
Corticospinal and corticobulbar
Pyramidal pathway?
Is the most common route (common lateral corticospinal pathway)
Extrapyramidal pathway is via?
Basal ganglia and cerebellum
In upper motor neuron lesions, there can be positive signs due to loss of inhibitory descending inputs. What are these signs
- Spasticity - increased muscle tone
- Hyper-reflexia - exaggerated reflexes
- Clonus - abnormal oscillatory muscle contraction
What are the negative signs of upper motor neuron lesions?
Loss of function
- Paresis (graded weakness of movements)
- Paralysis (plegia) - complete loss of muscle activity
What is apraxia?
Disorder of skilled movement (not paresis) but they’ve lost information how to perform skilled movements
Lesions in which lobes can cause apraxia
Inferior parietal lobe, frontal lobe (premotor cortex and supplementary motor area)
What are 2 common causes of apraxia
Stroke
Dementia
List some features of lower motor neuron lesions
- Weakness
- Hypotonia
- Hyporeflexia
- Muscle atrophy
- Fasciculations
- Fibrillations
Motor Neurone Disease (MND) is a disorder of the motor system. It is a spectrum of disorders. What else may it be referred to as
Amyotrophic Lateral Sclerosis (ALS)
What are some upper motor neuron signs of MND?
- Increased muscle tone (spasticity of limbs/tongue)
- Babinskis sign
- Brisk limbs and jaw reflexes
- Loss of dexterity
- Dysarthria
- Dysphagia
What are some Lower motor neuron signs of MND?
- Weakness
- Muscle wasting
- Tongue fasciculations/wasting
- Nasal speach
- Dysphagia
Where is the substantia nigra?
Basal ganglia
What features are present in the basal ganglia
- Caudate nucleus
- Lentiform nucleus (putamen + external globus pallidus)
- Subthalamic nucleus
- Substantia nigra
- Ventral pallidum, claustrum, nucleus accumbent, nucleus basalis of Meynert
What is the “striatum” in the basal ganglia
Lentiform + caudate
What are the 3 functions of the basal ganglia?
- Elaborating associated movements (e.g. swinging arms when walking, changing facial expression for emotion)
- Moderating and coordinating movement (suppressing unwanted movement
- Performing movements in sequence
What is the neuropathology of Parkinson’s?
Neurodegeneration of dopaminergic neurons originating in substantia nigra which project onto the striatum
5 motor signs of Parkinsons
- Bradykinesia
- Hypomimic face
- Akinesia
- Rigidity
- Tremor at rest
Explain how Huntingtons disease may arise
- Genetic neurodegenerative disorder - Chr4 Autosomal dominant
- CAG repeat
- Caused by degeneration of GABAergic neurones in striatum, caudate and then putamen
What are the motor signs of Huntingtons disease?
- Choreic movements
- Speech impairment
- Difficulty swallowing
- Unsteady gait
- Cognitive decline and dementia later on
What are the 3 layers of the cerebellum
- molecular layer
- piriform layer
- granular layer
In the cerebellum, all information goes to which cell?
Purkinje cell
How do inferior olive cells project to purkinje cells?
via climbing fibres
In the cerebellum, how are inputs to granule cells achieved?
Via mossy fibres, then onwards from granule cells via parallel fibres
In the cerebellum,, how does output from purkinje cells occur?
Via deep nuclei
What is the output of the cerebellum?
Purkinje cells
What are the 3 divisions of the cerebellum?
- Vestibulocerebellum
- Spinocerebellum
- Cerebrocerebellum
What does the vestibulocerebellum do?
- regulates gait, posture and eqm.
2. Coordinates head movements with eye movements
What does the spinocerebellum do?
- Coordinates speech
- Adjusts muscle tone
- Coordinates limb movements
What does the cerebrocerebellum do?
- Coordinates skilled movements
- Cognitive function, attention, lingual processing
- Emotional control
What is dysmetria?
Inappropriate force and distance judgement
What is dysdiadochokinesia?
Unable to perform rapidly alternating movements
What are the main signs of cerebellar dysfunction?
- Ataxia
- Dysmetria
- intention tremor
- Dysdiadochokinesia
- Scanning speech
