Control of movement Flashcards
Outline the three types of sensory inputs and the information they encode to help with the control of movement/muscles.
There are visual and proprioceptive inputs which encode positional information, sensing where our body is, what we’re doing with it and where external stimuli are. There are also vestibular inputs, which encode balance information regarding the body.
Summarise the sensory receptors responsible for limb proprioception, the types of information that they encode, and the ascending pathways which transmit this information to higher centres of the brain.
There are three main areas of receptors relating to proprioception which are muscles/tendons, the skin and joints. Through the spinocerebellar pathway (unconscious), (muscles) muscle spindles will send information regarding changes in muscle length up to the brain, and golgi tendon organs will send information regarding changes in tension in muscles. Through the dorsal column pathway (conscious, fine touch), pacinian corpuscles and ruffini endings in the skin will send information regarding pressure and vibration, and tension and stretch in muscles. Also, through the dorsal column pathway, kinaesthetic receptors in the joints send information regarding changes in limb position.
Describe the role of proprioception in the control of normal movement.
Proprioception enables us to judge limb movements, positions, force, heaviness, stiffness, and viscosity. It combines with other senses to locate external objects relative to the body and contributes to body image.
Describe the vestibular apparatus and explain how they enable interpretation of the body’s position and movement.
The vestibular system is located in the middle and inner ear. Acting as accelerometers, the vestibular system detects changes in angular acceleration (semi-circular canals with ampullae at the base), and horizontal (utricle) and vertical (saccule) acceleration (otolith organs) of the head. Nerve fibres in the vestibular system will detect changes in membrane potential because of head movement, and action potentials will be sent through scarpa’s ganglion (where sensory nerve cell bodies lie), through the vestibular nerve, into the vestibular nuclei in the brainstem.
State the 4 main output targets of the vestibular nuclei.
Oculomotor complex - control of eye muscles
Cerebellum - integrates sensory (balance) information
Extensor LMNs - control tone of muscles to help with balance and posture
Cervical spinal cord - adjust head/neck movement
Briefly state two ways in which the basal ganglia can influence motor activity.
Components of the basal ganglia work together to control the scaling of movements (judge intensity of motor output) and action selection (facilitate or suppress relevant movements).
They also establish background patterns of movements, and control and adjust posture during voluntary movements.
Identify the structures of the brain that comprise the basal ganglia and explain their role in normal movement.
- Caudate nucleus - control spatial information
- Putamen - sequence repetitive movements and regulate movements
- Globus pallidus - initiate and smooth out movements
- Subthalamic nucleus - inhibition of movements
- Substantia nigra - promoting physical activity and contributes to scaling movements.
Describe the role of the visual system in the control of movement.
The visual system is known as being ‘the observer’ by controlling sight and processing. Visual information is integrated at the posterior parietal cortex, and has two streams to send information from the occipital lobe to relevant areas. The Dorsal visual stream sends information to sensory associative areas and the Ventral visual stream sends information to insula and temporal lobe memory areas to help with daily motor processing, and to develop motor programmes.
Predict the likely functional consequences of impaired visual system.
This is important because it will lead to a great loss of visual sense, which many people rely on, which leads to…
- Loss of a major proprioceptive sense
- Reliance on other proprioceptive modalities
- Much more severe difficulties if other senses impaired
Predict the likely functional consequences of impaired vestibular system.
Dizziness, vertigo – Deterioration of input to vestibular nuclei. False sensation of movement.
Balance disorders – Deterioration of input to vestibular nuclei. Postural and tonal feed to LMNs
Lack of coordination – Deterioration of input to cerebellum via vestibular nuclei.
‘Bouncing’ vision – Deterioration of input to oculomotor nuclei. Head / neck and eye coordination
Predict the likely functional consequences of impaired proprioception.
This will cause a loss of sense of knowing where your body is in relation to the environment. It can likely lead to heavily relying on the visual system to create movements, but anything outside of vision will be incredibly difficult. Movements that can be made need to be re-learned, are not meaningful and frontal areas of the brain in particular, have to work very hard to plan and complete a simple task.
Outline the CNS targets for proprioceptive information.
Somatosensory cortex and associative areas: e.g. early cognition
Primary motor cortex: e.g. initiation of motor control
Pre-motor cortex: e.g. develops patterns of movement
Basal ganglia: e.g. scaling and action selection
Cerebellum: e.g. refinement of motor control
Brain stem nuclei: e.g. refinement of motor control
Spinal cord: e.g. spinal reflex loops
Describe the functional consequences of losing all proprioceptive sensory neurons within the dorsal root ganglia.
Proprioceptive sensory neurons project axons both centrally to the spinal cord and peripherally to muscles and tendons, communicating peripheral information about the body to the CNS, so if they are damaged/no longer in use, there will be a reduced or no ability to sense stimuli and to send this information to the brain to be integrated/made sense of (feel no pain example).
Briefly describe the function effect of lesions in the basal ganglia.
It can lead to possibly having trouble starting, stopping, or sustaining movement, also, having trouble to suppress unwanted movements, facilitate wanted movements and to control intensity and patterns of movements.
Describe the general anatomy of the cerebellum, and explain its contribution to normal movement.
The cerebellum has 3 main functional divisions. They are the vestibulocerebellum (controlling balance, and has connections with the vestibular system and nuclei), the spinocerebellum (controlling posture/muscle tone, receives proprioceptive information and provides motor outputs in brain stem), and the corticocerebellum (controlling coordination and motor learning, and controls input and output from motor cortex).
The main role of the cerebellum is to compare actual movement with intended and predicted movement, and reduces errors in movement by outputting information to motor cortex and brainstem.
