Motor Systems Flashcards

Question

What will you see in the brain of Parkinson's patients?

Answer 1

* Normally the substantia nigra is black because the dopaminergic neurones contain neuromelanin * Neuromelanin is a normal metabolic by-product in these neurones * In PD patients, you lose these dopaminergic neurones * They undergo degeneration and therefore you lose the substantia nigra * So in the brain you won't see will see less and less of the black NOTE: Takes about 60% loss of the dopaminergic neurones before you start to see symptoms.

Answer 2

Basal ganglia motor loops are important in modulating the activity of the motor cortex *(i.e. voluntary movement)* * Loss of the nigrostriatal pathway means that the motor cortex is no longer being modulated propely by the basal ganglia which leads to problems

Answer 3

* Bradykinesia * Slowness of (small) movements * e.g. Doing up buttons, handling a knife * Hypomimic face * Expressionless, mask-like * Absence of movements that normally animate the face * Akinesia * Difficulty in the initiation of movements because cannot initiate movements internally * *Essentially cannot voluntarily move their muscles* * Rigidity * Muscle tone increase, causing resistance to externally imposed joint movements * *Externally imposed as in when you move their limbs/joints* * *They can't initiate movements themselves anyway* * *Different from spasticity in that it is not velocity-dependent* * Tremor at rest * 4-7 Hz * Starts in one hand (“pill-rolling tremor”) - with time spreads to other parts of the body * *Pill rolling - looks like you are trying a roll a pill between your thumb and index finger*

Answer 4

Genetic neurodegenerative disorder * Autosomal dominant * You have a mutation on a gene on chromosome 4 * This results in several CAG trinucleotide repeats on the gene * *HTT gene codes for huntingtin protein* * *Mutated gene leads to mutant protein formation which leads to neuronal degeneration* * Degeneration of GABAergic neurons in the striatum: caudate then putamen * *Similar to PD, this means that the motor cortex is no longer being modulated propely by the basal ganglia which leads to problems*

Answer 5

* Choreic movements (Chorea) * Rapid jerky involuntary movements of the body * Hands and face affected first * Then legs and rest of body * Speech impairment * Difficulty swallowing * Unsteady gait * *i.e. Unsteady when walking* * Later stages, cognitive decline and dementia

Answer 6

* In the posterior cranial fossa * Has a fold of dura over it - tentorium cerebelli * Lies on the posterior aspect of the pons

Answer 7

3 layer structure - outer to inner: * Molecular Layer * *Not that many neurones there* * Piriform Layer * Purkinje cells *(type of neurone)* * Granular Layer * Granule cells *(another type of neurone)*

Answer 8

* Inferior olive projects to Purkinje cells via **climbing fibres** * *Inferior olive is a nucleus (collection of cell bodies) in the medulla oblongata* * *Also known as inferior olivary nucleus* * *Climbing fibres = axonal projections from inferior olive* * All other input to granule cells via mossy fibres and then onwards via parallel fibres * Mossy fibres from: * Cerebral cortex * Brainstem * Spinal cord * Parallel fibres arise from the axons of the granule cells which synapse with Purkinje cells * All output from Purkinje cells via deep nuclei * The Purkinje cells synpase with deep nuclei in the cerebellum * Fibres arising from these deep nuclei then project out of the cerebellum (efferent) SUMMARY: * Climbing fibres from the inferior olive synpase with Purkinje cells * Mossy fibres synpase with granule cells * Parallel fibres from the granule cells synapse with Purkinje cells * Purkinje cells synpase with deep nuclei * Cerebellar output originiates from deep nuclei

Answer 9

* Vestibulocerebellum * Spinocerebellum * Cerebrocerebellum NOTE: * These divisions are shown in the picture below in order (left to right) * The divisions only shown on one side but are present on both sides - cerebellum is symmetrical

Answer 10

Function: * Connected with the vestibular * Regulation of gait, posture and equilibrium *(i.e. balance)* * Coordination of head movements with eye movements Vestibulocerebellar syndrome: * Damage (tumour) causes syndrome similar to vestibular disease * It leads to gait ataxia and tendency to fall * Even when patient sitting and have their eyes open

Answer 11

Function: * Coordination of speech * Adjustment of muscle tone * Coordination of limb movements Spinocerebellar syndrome: * Damage (degeneration and atrophy associated with chronic alcoholism) affects mainly legs * Causes abnormal gait and stance (wide-based)

Answer 12

Function: * Coordination of skilled movements * *Skilled movements are the ones that are developed through training and practice - so they are _learned_ movements* * Cognitive function, attention, processing of language * Emotional control Cerebrocerebellar (or lateral cerebellar) syndrome: * Damage affects mainly: * Arms or skilled coordinated movements * Leads to tremor * Speech

Answer 13

REMEMBER: Deficits apparent only upon movement * Ataxia * General impairments in movement coordination and accuracy * Disturbances of posture or gait: * wide-based, staggering (“drunken”) gait * Dysmetria * Inappropriate force and distance for target-directed movements * e.g. Knocking over a cup rather than grabbing it * Intention tremor * Increasingly oscillatory trajectory of a limb in a target-directed movement (nose-finger tracking) * *The amplitude of an intention tremor increases as an extremity (limb) approaches the endpoint of deliberate and visually guided movement* * Dysdiadochokinesia * Inability to perform rapidly alternating movements, * e.g. Rapidly pronating *(palm down)* and supinating *(palm up)* hands and forearms * Scanning speech * Staccato, due to impaired coordination of speech muscles * *Scanning speech is when the normal "melody" or speech pattern is disrupted - you get abnormally long pauses between words or individual syllables of words*