Control of movement Flashcards
What are the three different kinds of motor neurons?
Somatic
Visceral
Special neurosecretory
What are somatic motor neurons?
Supply voluntary (striated) muscles
What are visceral motor neurons?
Autonomic neurons which supply involuntary (smooth) muscles
Describe upper motor neurons
Above the point where the cerebral cortex and anterior horn synapse
Describe lower motor neurons
Peripheral nerve neurons beyond where the cerebral cortex and anterior horn synapse
What are some signs of defects related to upper motor neurons?
Spastic paralysis
No muscle atrophy
Hyper-reflexivity
Presence of babinski reflex in adults
What are some signs of defects related to lower motor neurons?
Flaccid paralysis
Atrophy of muscles
Hyporeflexivity
Babinski not present
What are three types of reflexes?
Spinal reflexes (e.g. patella tendon reflex) Brain stem reflexes (e.g. vomiting reflex) Cortical reflexes (e.g. pupillary reflex)
What are monosynaptic reflexes?
One synapse only
E.g. stretch reflex
Explain the NS response during the stress reflex.
Tap on the patella tendon detected
Excessive stretch detected
Impulse sent to spinal cord via sensory neuron
Synapse directly with motor neuron
Impulse sent to muscle via motor neuron
Muscle fibres contract - counteracting the original stimulus
What are polysynaptic reflexes?
Two or more synapses involves
E.g. withdrawal (flexion) reflex
Explain the NS response to stepping on a pin
Sensation sent to spinal cord via sensory neuron
Synapses with motor neurons (more than one) [front and back leg muscles]
Allows us to withdraw leg and keep balance
Describe what would occur when there is damage to cranial nerves.
Optic nerve damage
Damage to 3, 4 or 6 - double vision
Shingles in 5 - spots and pain on face
Virus infection in 7 - Bell’s palsy
Streptomycin damage to 8 - loss of hearing and balance
Motor neuron disease in 9, 10, 11 - inability to swallow
What would occur if disease affects the spinal cord
Grey matter damage White matter damage Tertiary syphilis Polio ALS: amytrophic lateral sclerosis
Describe cortical control of movement
Primary motor cortex receives information from other cortical areas.
Sends commands to the brainstem and spinal column
Basal ganglia and cerebellum provide adjustments ot these commands.
What are the areas involved in cortical control of movement?
Association areas of cortex and basal ganglia (strategy)
Motor cortex and cerebellum (tactics)
Brain stem and spinal cord (execution)
What are the three main cortical areas?
Primary motor cortex (homunculus, phantom limb)
Supplementary motor cortex
Premotor cortex
What is the basal ganglia?
Part of the forebrain (developed before birth)
Comprises the caudate nucleus, putamen, globus pallidus, subthalamus nuclei, substantia nigra
What is the basal ganglia responsible for?
Amplitude and direction of movement
Modulates activity initiated in cortical areas
Generation of movement influenced by memories (automatic movements)
Important for species-specific movements
Two pathways that act on the thalamus
What are the four common disorders of movement?
Lower motor neuron disorders
Upper motor neuron disorders
Basal ganglia disorders
Cerebellar disorders
What are some examples of lower motor neuron disorders?
Muscles de-enervated (weakened) Paralysis Atrophy or death of muscles Reflexes reduced or lost Diabetes, lead poisoning, progressive muscular atrophy, spinal muscular atrophy, ALS
What are some examples of upper motor neuron disorders?
Paralysis and spasticity
Loss of voluntary control of muscles (not de-enervation)
LMNS intact but inability to control
Minor muscle wastage
After initial trauma, reflexes reappear and are exaggerated.
Primary lateral sclerosis, pseudobulbar palsy, ALS.
Describe primary lateral sclerosis.
Onset usually occurs spontaneously after 50 and progresses gradually.
Begins in the legs, but may start in the tongue or hands.
What are some symptoms of primary lateral sclerosis?
Difficulty with balance, weakness and stiffness in the legs Clumsiness and spasticity in the hands, feet, legs
Foot dragging
Speech and swallowing problems
Breathing may become compromised in later stages
Describe basal ganglia disorders
Damage caused by many things
Two common symptoms are decrease ability to move voluntarily and increase involuntary movements.
What are some examples of basal ganglia disorders?
Parkinson’s disease
Huntington’s disease
Cerebral palsy
What are some symptoms of cerebellar disorders?
Problems in controlling, rate, timing and force of movements Decreased balance and posture Poor coordination and balance Ataxia (loss of control) Intention tremor Progressive supranuclear palsy
