Voluntary Movement Flashcards
what are the three types of movement
involuntary actions
semi automatic actions
voluntary actions
what are semi automatic actions
these are actions that are voluntary and we could adapt but we usually dont even think about them, like walking, chewing and breathing.
they are usually repeated movement sequences and appear stereotyped but could change them if we wanted to
what drives semi automatic actions
central pattern generators, which are collections of neurons specific to the action they initiate or maintain
what is the typical nerve cell structure
- cell body that houses the nucleus. from the cell body there are projections of the cell extension called dendrites that act as antennas to increae the surface area of the cell itself to allow it to receive input from various other cells to allow it to input the information
they are innervating other distinct circuits and will not be found in isolation
what does the output of CGPs do
innervate an effector organ which will allow the individual to repond in a particular way to their environment
what are central pattern generators
collections of neurons with a rhythmic output that will influence motor patterns of particular muscle groups
why is there reflex feedback in effector organs
this allows for the CGP ouput to be monitoried at all times to make sure it is relevant to the needs of that environment
describe sensory feedback sysems
this is where the environment can influence the CGP directly or indirectly through innervation of higher control neurons which in turn feedback to the CGP
what is the central feedback loop of the CGP
higher cortical regions can modifty the CGP using a voluntary response
what are the different feedback loops associated with CGPs
- reflex feedback
- central feedback loop
- sensory feedback system
what are voluntary actions
self initiated actions that are goal directed and learned. they can be adapted and improved with practice
where is the primary sensory cortex
posterior to the central sulcus
where is the motor cortex
anterior to the central cortex
describe the motor homunculus
areas in the homunculus that correspond to the face and hands are large because the motor units for these areas are small and highly packed to allow precision in movement.
limbs have a smaller area because the muscles are large and produce larger, less concise movements
what are the two descending pathways for voluntary movement
corticospinal and corticobulbar
describe the neuronal element of the descending motor pathways for voluntary movment
- only two
- upper neuron with cell bodies in motor cortex that has an axon that descends through the cortex to the brain stem to innervate muscle in the head and neck or to the spinal cord for the body
- lower neuron sends axon out to peripheral nerve to innervate the muscle for the actual contraction for movement
what are the three regions of white matter
dorsal funiculus
lateral funiculus
ventral funiculus
which funiculus are important when looking at descending motor pathways
the dorsolateral funiculus and the ventromedial funiculus
what is the motor innervation of trigeminal
muscle of mastication
what is the motor innervation of the facial nerve
muscle of facial expression
what is the motor control of the vagus nerve
soft palate
larynx
pharynx
what is the motor innervation of the hypoglossal
extrinsic muscles of the tongue
describe the corticobulbar pathway
this is the pathway for the recruitment of lower motor neurons comprising cranial nerves.
cortical portion is the location of the upper neuron and the bulbar is the relative position of the motor nuclei throughout the brainstem for each corresponding cranial nerve
where do cell bodies originate for the corticobulbar pathway
the motor cortex, and their axon goes down through the internal capsule through the basis pedunculi in the midbrain to give off branches that innervate the distinct motor neuron groups
where are the cell bodies for the trigeminal motor neuron bodies
trigeminal nucleus in the pons
what is the facial nerve cell body in the brainstem
the facial motor nucleus at the pontomedullary junction
where is the cell body of the vagus nerve
nucleus ambiguus in the medulla
where is the cell body of the hypoglossal nerve
nucleus ambiguus
how can we carry out simulataneous bilateral muscle contraction
the projections of lower motor neurons bifurcate to inneravate both sides of the neuroaxis to carry out the contraction on both sides
how does the spinocortical pathway differ from the corticobulbar pathway
axons project much further as they go own the spinal cord
the axons cross over to the other side of the spinal cord
what is the pyramidal dessucation
this is where majority of the axons in the spinocortical pathway will cross over to the other side of the neuroaxis at the level of the medulla
how many axons will remain on the same side of the neuroaxis at the pyramidal dessucation, and where do they cross over instead
15%, and they will only cross over once they reach the level of the motor neurons that they are due to innervate
which descending motor neurons in the spinocortical pathway are found in the lateral corticospinal tract
those that crossed at the pyramidal dessucation
which descending motor neurons in the spinocortical pathway are found in the anterior corticospinal tract
those that are confined to the same side of the neuroaxis until they cross over at their own level
which region of the spinal cord houses the lateral corticospinal tract
the dorsolateral funiculus
which region of the spinal cord houses the anterior corticospinal tract
the ventromedial funiculus
which pathways to motor neurons originate from the opposite side of the brain
the pathways to motor neurons controlling distal muscles originate from the opposite side of the brain.
what are distal muscles
hands
feet
lower half of the face
tongue
what is the command of the gag reflex
bilateral descending cortical demand
what happens if the lower motor neurons are damaged
we will not be able to initiate any movement at all because the final output to muscles are lost
describe bells palsy
they lose capacity to engage and contract muscles of facial expression
some think this could be due to inflammation
dissipates within two weeks with no long lasting effect
what is the purpose of additional descending motor projections
they serve to coordinate movement, help maintain posture and balance, and they help to integrate the actions of several muscles
where do additional descending motor projections arise from
various areas of the cerebrum and brainstem like the basal ganglia, cerebellum and brainstem
describe basal ganglia
these are comprised of several interconnected subcortical nuclei that link to the cerebral cortex via feedback loops
what does the basal ganglia do
influence and regulates output from the motor cortex
acts to initiate actions and switch from one action to another
what structure links the two hemispheres of the brain
corpus callosum
what can allow for the identification of the basal ganglia
the ventricles and associated bundles of white matter
where is the body of the caudate nucleus found
the lateral protrusion at the lateral aspect of the lateral ventricle
where is the putamen
the internal capsule of white matter, where there is a cluster of cells forming a grey matter
where is the globus pallidus
medial to the putamen
where is the thalamus
protrusion in the lateral aspect of the third ventricle
where is the substantia nigra
speckled grey matter posterior to the thalamus
what are the components of the basal ganglia
- body of caudate nucleus
- putamen
- globus pallidus
- thalamus
- substantia nigra
what makes up the corpus striatum
the caudate nucleus
putamen
globus pallidus
what makes up the sub thalamic nuclei
the thalamus
what are the three action selection centres formed from the basal ganglia
corpus striatum
subthalamic nuclei
substantia nigra
which region of the brain is affected by parkinsons disease
the substantia nigra
which region of the brain is affected by huntingtons disease
the corpus striatum
what causes parkinsons
dopamine deficiency in the substantia nigra
describe parkinsons disease
- hypokinetic disorder leading to reduced movements
- leads to a resting tremor due to paralysis agitans
- poverty of movement
- mask like face
- difficulty in initiating movements
what is the actual reason for the symptoms from parkinsons
deterioration of nerve cells in the substantia nigra
describe huntingtons disease
hyperkinetic disorder leading to excessive and uncontrolled movements
happens due to an imbalance in neurotransmitter (decreased GABA levels) in the striatum
describe the cerebellum
this region is important for coordinating movements and regulates actions of antagonistic muscle groups
it is important in maintaining balance and receives input from proprioceptors
acts to compare the actual performance with what is intended
where is the cerebellum
at the back of the brain behind the brainstem at the pons and fourth ventricle
occipital lobe found behind it
describe voluntary actions muscle usage
it is very rare for only one set of muscles to be involved in an action
action by one set of muscles are often accompanied by actions of other muscles
therefore they are coordinated to ensure posture and balance are maintained
what happens to maintain posture if we lean forward and stretch our calf muscles
the stretch reflexes that are mediated by muscle spindles will allow for contraction and this will return our posture back to normal
what maintains upright posture
series of small correcting actions that keep the head in position with the body’s centre of gravity
what initiates and refines motor output
initiated from activity from the motor cortex
refined from regions of the associated cortex and subcortical areas
