Lecture - Motor Systems Flashcards
Whats the classic faction of movement?
- Locomotion - walking, running
- Posture and Postural change - standing, balancing
- Sensory orientation - head turning, eye fixation
- Species specifc action patterns - ingestion, courtship, escape
- Acquired skills - speech, dressing, painting, driving
- Simple reflex - stretch reflex, knee jerk, mediated at the level of the spinal cord
Explain the knee jerk reflex?
Tapping the knee tendon stimulated tendon stretch receptors
Sensory neurone synapses surectly to motor neurone
Muscle contracts to cause limb extension
Where does it project through for the main motor output from the motor cortex?
The pyramidal tract to spinal cord then to peripheral motor neurones
Whats the run outside the pyramidal tract called?
Extrapyramidal system
Describe the tectospinal tract?
Coordinating head and eye movements as part of the optic reflexes
Explain the vestibulospinal tract?
Inflcunes postural muscles
Explain the reticulospinal tract?
Inhibition or facilitation of movement
Whats the primary motor cortex the source of?
Pyramidal tract neurones
Explain the supplementary motor cortex?
- conception and initiation of movement
- lesions cause deficits in voluntary movement or speech
Describe the premotor cortex?
- important in motor coordination
- lesions cause impairments in stability of stance, gait and hand coordination
What does the cerebellum control?
Controls neural ‘programs’ for the execution of skilled movements
Describe the basal ganglia?
- a group of subcortical forebrain nuclei
- modulate patterns of motor activity
Examples of neurological diseases of the motor system?
- paralysis
- apraxia
- decomposition of movement
- Parkinson’s disease
- huntingtons disease
Main
- duchennes muscular dystrophy
- myasthenia gravis
What happens when you damage the motor neurones?
• Viral (e.g. poliomyelinitis – leads to destruction of spinal motorneurones)
• Toxins and/or hereditary (e.g. amyotrophic lateral sclerosis – degeneration
of motoneurones in the brainstem and spinal cord)
• Injury
• Severing of spinal cord – permanent
• Bruising or compression of spinal cord – transient
What happens when you damage the primary motor cortex?
• Paralysis or partial paralysis of voluntary movement on one side of the
body (contralateral to damage)
• Extent of paralysis depends on extent of damage
• Often accompanied by spasticity and abnormal reflexes
Whats apraxia?
nability to carry out movements in response to commands
• no paralysis
• no loss of comprehension
• no loss of motivation
What could be the reason for apraxia?
May be du to disconnection of primary motor cortex from supplementary motor areas and premotor cortex
Symptoms of Parkinson’s disease?
- resting tremor in limbs
- muscle ridgidty
- akinesia
- stooped posture
- shuffling gait
- excessive sweating and salivation
Whats the neuropathology of Parkinson’s disease?
Nitro-striatal pathway degeneration
Leading to a depletion of striatal dopamine
Some degeneration of other dopamine pathways too
Treatment of Parkinson’s disease?
Prior to 1960s there were no effective treatments
- realisation of dopamines involvement left to use of drugs which increase brain dopamine
——— dopamine itself cannot cross from the blood to the brain
——— use precursor, LL-OPA, which enters the brain and is converted there into dopamine
———— can cause severe side effects
Surgical interventions and neuronal transplantations are under investigation as alternative therapies
Whats the huntingtons disease?
- progressive disease causing involuntary muscle jerks
- ultimately affects the whole body
- also intellectual deterioration, depression and occasionally psychotisim
- normally shows symptoms at 30 to 45 years
- genetically determined
Treatment for huntingtons disease?
- no effective treatments
- GABA replacement or dopamine antagonists provide some relief
- no means of halting the progression of the disease
What happens to the body during paralysis?
Damage to motor neurons or primarily motor cortex
- can be transient or permanent, depending on extent of damage
What happens to body during apraxia?
Damage to supplementary motor areas
Why is there decomposition of movement?
Due to damage to cerebellum
What occurs to the body to have Parkinson’s disease?
Degeneration of the nigrostriatal pathway
What occurs to the body for Huntingtons disease?
Degeneration of striatal output neurones
