Voluntary Movement Flashcards
describe voluntary actions
self-initiated, purposeful, learned, improve with practice, adaptable
how are semi-automatic actions different from voluntary actions
they are still voluntary but you don’t have to think about them
what are semi-automatic actions and give examples
repeated movement sequences, adaptable e.g. walking, breathing and chewing
what are semi-automatic actions driven by?
CPGs (central pattern generators)
what do central pattern generators do?
influence whether muscle groups are going to contract or relax
what do the feedback circuits do?
they generate a complex circuit to help you refine the output from the central pattern generators
what type of feedback circuits are fedback to the CPGs?
reflex feedback, sensory feedback, central feedback (once it has gone through the higher control neurons)
how is movement refined?
from recruitment and influences from subcortical areas such as the thalamus and the basal ganglia
what is the circuit of reception to movement when passing through the cortexes?
receptor - spinal cord and brainstem - subcortical areas (thalamus and basal ganglia) - sensory cortex - association cortex - motor cortex - spinal cord and brainstem - muscles - movement
what does the anteriolateral funiculus contain?
secondary order pain receptors
describe the pathways that motor neurons take when innervating muscle groups in the head and neck
at the brain stem the sensory neurons activate lower motor neurons - lower motor neurons target motor nuclei for cranial nerves - these nuclei activate motor neurons which innervate muscle groups
what muscles does the trigeminal nerve supply?
muscles of mastication
what muscles does the facial nerve supply?
muscles of facial expression
what head and neckmuscles does the vagus nerve supply?
soft palate, pharynx, larynx
what muscles does the hypoglossal nerve supply?
extrinsic muscles of tongue
how can axons innervate both side of the body if they only project from one side of the brain
they bifurcate
describe the corticospinal pathway
upper motor neurons send axons down through the internal capsule of brain and brainstem - 85% of axons cross over beneath medulla to other side (contralateral part of spinal cord) this happens at the pyramidal decussation - these neurons are found in the dorsal lateral funiculus - the other 15% of nueorns are in the ventral medial funiculus
what is the difference between the corticospinal and corticobulbar pathways?
the corticobulbar pathway can innervate bilaterally but with the corticospinal pathway the axon has to cross to the other side of the spinal cord
what part of the brain is the motor nucleus of the trigeminal nerve found?
the pons
what part of the brain is the motor nucleus of the facial nerve found?
pons
what part of the brain is the motor nuclei of the vagus and hypoglossal nerves found?
medulla
where do the motor neurons for the distal muscles come from?
the opposite side of the brain
describe the descending motor pathway in terms of synapses
the upper motor neuron comes from the motor cortex and synapses with the lower motor neuron at the brainstem/spinal cord, the lower motor neuron then innervates the muscle and gives movement
what happens if there is damage (lesions) to descending pathways?
it impairs their normal functions causing paralysis - palsy
what pathway does paralysis to lower motor neurons affect?
final common pathway
what happens as a result of lower motor neuron paralysis?
nerve injury, viral infection (polio), no reflexes, no voluntary movement, muscle atrophy
what pathways does paralysis of the upper motor neurons affect?
corticospinal and corticobulbar pathways
what happens as a result of damage to upper motor neurons?
CNS injury (stroke), no voluntary movement, reflexes exaggerated, can’t kickstart descending pathway to recruit lower motor neurons
where are the lower motor neurons?
in the brainstem and spinal cord
where are the upper motor neurons?
in the motor cortex
what is Bell’s palsy?
temporary paralysis of the facial nerve
how is Bell’s palsy acquired?
could be inflammatory or viral
how is Bell’s palsy treated?
it normal dissipates within 2 weeks so there is no need to administer medicine
where do additional descending motor projections arise from?
various areas of the cerebrum and brainstem e.g. basal ganglia, cerebellum
what do additional descending motor projections do?
serve to co-ordinate movements, help maintain posture/balance, help integrate actions of several muscles
what is the basal ganglia made of?
several interconnected sub-cortical nuclei
what does the basal ganglia do?
influence/regulate output from the motor cortex, act to initiate actions and to switch from one action to another
what is the key component of the basal ganglia function?
you are able to move around without being interrupted
what does the grey matter of the brain contain?
nerve cells
what does the white matter of the brain contain?
bundles of axons
what does the corpus callosum do?
allows the two halves of the brain to communicate with each other
what fills the lateral ventricles?
cerebrospinal fluid
what does cerebrospinal fluid do?
help keep the brain tight and has mechanical protection function by bathing the brain in a fluid filled sack, provides immunological protections as well
what does the internal capsule do in the brain?
serves as a landmark to separate the thalamus and substantia nigra from the putamen and globus pallidus
what are the action selection centres of the basal ganglia?
corpus striatum, sub-thalamic nuclei and substantia nigra
what are the parts of the corpus striatum?
cuadate nucleus, putamen, globus pallidus
what does damage of the basal ganglia result in?
movement disorders
what is parkinson’s disease due to?
dopamine deficiency in substantia nigra
what is huntington’s disease due to?
cell death within corpus striatum
what is parkinson’s disease?
hypokinetic disorder decreasing movement
what are the physical consequences of parkinson’s?
resting tremor, poverty of movement, mask-like face, difficulty initiating movements
why are muscle movements affected in Parkinson’s
there is a deficit of innervation from corticospinal and corticobulbar pathways
what is huntington’s disease?
hyperkinetic disorder increasing movements
what are the physical consequences of huntington’s?
excessive controlled movements
why does everything become hyperexcitable in huntington’s?
there is an imbalance of neurotransmitters - decreased levels of GABA so everything becomes hyperexcitable
what are the two lobes of the cerebellum known as?
lateral hemispheres
what is the interconnecting portion of the cerebellum known as?
vermis
what does the cerebellum do?
co-ordinates movement, regulates actions of antagonistic muscle groups, maintains balance, compares actual performance with what is intended , controls extent of motor output
where does the principle sensory input of the cerebellum come from?
proprioreceptor afferent fibres
what does the cerebellum receive input from?
proprioreceptors, visual and auditory systems
what are cerebellar disorders characterised by?
loss of co-ordination
what are the cerebellar disorders?
unsteady gait, imprecise actions, inability to co-ordinate alternating contractions of antagonistic muscles, intention tremor
what are muscle contractions controlled by?
inputs from variety of receptors
what are stretch reflexes mediated by?
muscle spindles
