Control of movement Flashcards
Define proprioception
This is the body’s ability to sense it’s own position, movement & spatial orientation, we receive sensory input from our environment through specialised receptors known as proprioceptors. Which are found in the muscles, joints & tendons. They contain muscles spindles, golgi tendon organs, vestibular systems & joint receptors.
Proprioceptors use the dorsal column and spinocerebellar pathway
Explain the importance of proprioception
Balance & coordination: needed to enable smooth movement and keeping balance as we walk/stay still
Motor control: it enables the brain to adjust itself during motor activities to allow smooth movement
Injury prevention: It helps the body respond to sudden changes in position allowing stance to be corrected to prevent injury
Rehab: After an injury, proprioception is a critical part of recovery. Exercises targeting proprioceptive abilities help re-train the nervous system to regain proper joint position sense
Sports performance: Athletes rely on proprioception to execute precise movements and adapt to quick changes in their environment
Describe the function of proprioception on normal movement
Feedback on postural control: Proprioception helps maintain posture and balance via proprioceptive receptors in your muscles, joints, and tendons send signals to your brain about the position of your body parts. The brain uses this feedback to adjust the muscles involved in maintaining your posture. This constant feedback loop allows for dynamic postural control in response to shifts in weight, uneven surfaces, or changes in activity, ensuring the body remains upright or balanced. This process occurs subconsciously
Motor learning: as you practice a skill the feedback loop helps the brain refine motor commands to perform the task smoothly and accurately, overtime the task becomes more automatic as the proprioceptive system tunes motor control
Accuracy and Precision: Proprioception enhances the accuracy and precision of movement by allowing the brain to compare actual limb positions to the intended ones. Proprioceptive input allows the brain to adjust the trajectory of your arm to ensure the hand moves accurately toward the target. This allows for complex actions such as catching a ball, adjusting your posture when lifting an object, or even performing a dance routine, without needing to focus on each individual muscle or joint.
Explain the consequences of impaired proprioception
- More likely to become injured or suffer frequent falls due to instability. Impairment leads to difficulty with balance leading people to sway as they stand (positive romberg test) or have difficulty standing for a long time, this may create difficulty with walking & standing. The body is unable to make quick adjustments leading to increased risk of injury
- Due to the lack of coordination an individual is likely to be clumsier when performing activities and suffer difficulty during fine motor tasks e.g., writing as the brain struggles to efficiently control the fingers
Name conditions that are associated with impaired proprioception
Neurological disorders: Conditions like multiple sclerosis, stroke, or Parkinson’s disease can lead to proprioceptive deficits due to damage in the nervous system.
Joint injuries: An injury to ligaments (e.g., ACL tears) or other soft tissues can affect proprioception, especially in the joints affected.
Diabetic neuropathy: Diabetes can damage the nerves, including proprioceptive receptors, leading to impaired sensation in the feet and lower legs.
Vestibular disorders: Problems with the inner ear, which is responsible for balance, can also disrupt proprioception, leading to dizziness and spatial disorientation.
Describe the vestibular system and its components
A sensory system located in the inner ear responsible for maintaining balance, motion, spatial awareness & coordination. It works with proprioceptors & visual systems to respond to changes in gravity & movement
consists of: semicircular canals, otolith organs, vestibular nerve, vestibular nuclei, scarpas ganglion & cerebellum
Describe the function and structure of semicircular canals
Consist of 3 fluid canals in the inner ear responsible for detecting rotational movements of the head. They correspond to 3 planes, vertical, horizontal & lateral. They are found at right angles to each other. The canals are filled with endolymph, at the base an ampulla is found which contains crista ampullaris which are hair receptors embedded in the culpa (gelatinous substance)
Horizontal canal: detects head rotation from side to side (shaking the head)
Anterior (superior) canal detects tilting of the head back & forth (nodding of head)
Posterior canal: detects tilting of the head sideways (ear to shoulder)
When the head rotates, the movement causes the endolymph fluid inside the canals to shift. This movement of fluid bends the hair cells within the crista ampullaris, triggering electrical signals that are sent to the brain via the vestibular nerve.
This allows the brain to detect the direction and speed of head rotation, which is essential for coordinating balance and posture during rotational movements (e.g., turning your head).
Describe the structure & function of the otolith organs
These organs are made of the utricle & saccule, they detect head position in response to gravity & linear acceleration. Saccule and utricle contain macula which are hair cells embedded into the culpa, otoconia (calcium crystals) found in culpa which add mass, making it responsive to gravitational forces and head movements.
When the head moves in a linear direction (e.g., when moving in a car, or tilting the head up or down), the movement causes the otoconia to shift due to inertia. This shift bends the hair cells, leading to the generation of electrical signals.
The brain processes these signals to detect changes in head position (such as tilting the head or moving forward or backward) and acceleration.
Utricle: Primarily detects horizontal acceleration (e.g., forward/backward movement, or tilting the head left/right).
Saccule: Primarily detects vertical acceleration (e.g., moving up/down or tilting the head forward/backward).
Describe the structure and function of the vestibular nerve
Transmit signals from the semicircular canals & otolith organs. They join to form vestibular bundles which enter the brainstem via vestibular nuclei
The vestibular nerve transmits the information about head movements and position to the brain, where it is processed in areas like the brainstem and cerebellum.
This helps the brain coordinate the muscles and maintain proper posture and balance.
Describe the structure and function of the vestibular nuclei
Located in the brainstem and consists of a cluster of neurons that processes sensory information from vestibular nerve.
They integrate sensory information with visual and proprioceptive signals
The vestibular nuclei send signals to various areas of the brain and body, including the cerebellum (for motor coordination), the spinal cord (for balance control and posture), and the oculomotor nuclei (for eye movements).
Describe the structure and function of the scarpas ganglion
Also known as the vestibular ganglion, is a collection of nerve cells located in the inner auditory canal and has bipolar neurons,
These neurons receive signals from vestibular apparatus e.g., utricle and transmit them to the brain via the vestibular nerve
Its main function is to relay information related to head movement, balance etc to the brain. This information enables proper balance, eye coordination & posture
Describe the structure and function of the cerebellum on the vestibular system
The cerebellum is involved in the coordination of voluntary movements and balance. It receives input from the vestibular nuclei to help coordinate motor control and balance.
Structure:
The cerebellum is located at the back of the brain, below the cerebral hemispheres.
Function: It fine-tunes muscle activity to ensure smooth and controlled movements.
It helps adjust posture and balance based on feedback from the vestibular system, ensuring the body remains upright and stable during movement.
Describe the function of the otolith organs on acceleration
- Balance and Posture:
The otolith organs provide crucial information about the linear acceleration and orientation of the head in space, which helps the brain maintain balance and posture - Stabilizing Vision:
The otolith organs also contribute to the vestibulo-ocular reflex (VOR), which stabilizes the eyes during head movements, including when the head moves due to acceleration. This ensures that vision remains clear even when the head is moving. - Coordination of Movement:
The signals from the otolith organs work with input from other sensory systems (such as vision and proprioception) to coordinate smooth movements and adjustments in body posture during acceleration.
Describe the function of the otolith organs on linear acceleration
When the head accelerates (either in a straight line or when tilting), the otolith organs detect this motion due to the inertial movement of the otoliths within the gelatinous membrane. Here’s how it works:
Acceleration: When you move in a linear direction (e.g., when riding in a car or tilting your head), the otoliths in the utricle and saccule shift due to inertia. The gelatinous membrane moves, bending the hair cells embedded within it.
Hair Cell Stimulation: When the hair cells bend in response to this movement, they send electrical signals to the brain via the vestibular nerve.
Signal Processing: The brain processes these signals to interpret the direction and intensity of the acceleration, allowing you to perceive the motion and adjust your body accordingly.
Describe the effects of the damage to the vestibular system
- false sensation of movements causing dizziness & vertigo
- impaired balance
- lack of coordination due to lack of input to cerebellum
- bouncy vision due to reduction in head, neck & eye coordination
Describe the role of the visual system
role in normal movement and coordination by providing essential information about our environment and helping the body adjust to changes in position, direction, and spatial orientation. It works in tandem with other sensory systems, such as the vestibular system and proprioception, to ensure smooth, coordinated, and accurate movements.
Visual Input for Spatial Awareness: The visual system provides continuous input about the position of the body in space relative to objects around us. This information is essential for guiding movement and maintaining spatial orientation. Key components of the visual system involved in this process include:
Eyes: Capture visual stimuli from the environment and convert them into neural signals.
Retina: The layer at the back of the eye, where light is converted into electrical signals by photoreceptors (rods and cones). These signals are transmitted via the optic nerve to the brain.
Brain: The visual cortex in the occipital lobe of the brain processes the incoming visual information and integrates it with other sensory inputs (such as proprioception and vestibular input).
Guidance of Movement: Visual input helps to guide voluntary movements, such as walking, reaching for objects, and maintaining balance. Visual cues help us target specific actions and adjust our movements accordingly: e.g., Eye-Hand Coordination, Visual information is critical for tasks that require coordination between the hands and eyes, The brain uses visual input to adjust the position of the hands and arms in space, ensuring accurate and efficient movements.
Describe the dorsal stream on the visual system
Dorsal stream processes an object or person’s location and helps guide to correct response, it ensure we can accurately move towards or reach for the object/person
Involved in spatial awareness, motion detection & coordination
Information travels from the occipital lobe to the parietal lobe, enables us to plan motor actions
Describe the ventral stream on the visual system
Both streams work together, The ventral stream identifies an object, colour, shape etc, Takes info from occipital to temporal lobe, associated with recognizing faces and visual memory.
Describe the effects damage to visual system
- loss of a major proprioceptive sense
- rely heavily on other proprioceptive sensors
- More difficult if other sensors are also impaired e.g., vestibular system
Describe the structure of basal ganglia
BG needed for normal movement because it coordinates movement & regulates muscle tone
The key structures of the basal ganglia include the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra, all of which interact through complex circuits that allow the brain to plan, initiate, and coordinate movements
Describe the function of the caudate nucleus
CN is the largest structure in the basal ganglia, a long & curvy shape. It is involved in motor processing as well as emotional & cognitive functions. It initiates movement and aids in motor learning
Describe the function of the putamen
Regulates movement & muscle tone, works with CN to process movement information, involved in automatic habits e.g., walking
Describe the function of the Globus Pallidus
GP is divided into internal & external GP (GPi & GPe)
GPi is needed for inhibition of movement by sending inhibitory signals to the thalamus to prevent unwanted movement
GPe regulates movement by influencing activity of subthalamic nucleus
Describe the function of the Subthalamic Nucleus
A small almond-shaped structure is found below the thalamus. It regulates basal ganglia activity, helps facilitate voluntary movement activities
Describe the function of the Substantia Nigra:
Part of the brainstem, consists of 2 parts:
1. Pars compacta (SNc)
2. Pars reticula (SNr)
SNc is needed to produce necessary dopamine for movement control
SNr sends inhibitory signals to the thalamus to regulate movement and prevent excessive or unwanted motor activity e.g., tremors
Describe the direct and indirect pathway in the basal ganglia
Direct pathway facilitates muscle movement as dopamine promotes voluntary movement.
Signals from the cortex are sent to the putamen & C nucleus the GP becomes excited which causes less inhibition of the thalamus, allowing more excitatory signals to be sent from the thalamus to the motor cortex, therefore promoting movement
Indirect pathway: This pathway causes inhibition of signals. It suppresses unnecessary movement. The GP is inhibited which then inhibits the subthalamic nucleus (STN)
STN releases excitatory signal to the GP, inhibiting relay of signal to thalamus causing reduced motor output
Describe the role of dopamine in the basal ganglia
Dopamine is released from the substantia nigra and modulates both direct/indirect pathways
Dopamine excites the direct pathway which promotes voluntary movement
Dopamine inhibits indirect pathway to reduce inhibition of motor cortex which enables smooth movement
lack of dopamine causes lack of activity in direct pathway and excessive inhibition of indirect pathway, creating symptoms such as rigidty, tremors & impaired movement as seen in parkinsons patients
Describe and explain parkinsons disease
A neurodegenerative disorder that occurs in the brain where dopamine neurons are degraded, creating an imbalance between direct & indirect pathways, results in impaired mobility, memory & tremors
Describe the involvement of the basal ganglia in normal movement
- movement initiation: helps initiate and process motor movement by receiving signals from the cortex and regulating signals relayed from the thalamus to motor cortex
- muscle tone: ensure muscles remain ‘ready’, prevents too much tension/stretch or too relaxed, keeps balance
- Motor learning: aids in developing automatic habits, help consolidate learned skills, allowing us to perform tasks much smoother over time the more we practice them
4/5. help with coordination of movement and control involuntary movements e.g., tremors/tics
Describe the function and structure of the cerebellum
It is found at the back of the brain, involved in involuntary movements, e.g., balance, posture & coordination. It also contributes to motor learning & eye movement.
It integrates sensory feedback into its motor commands allowing us to respond smoothly to our environment.
Consists of: the cortex, the DCN & cerebellar peduncles
Describe the function of the cortex
It is the outer layer of the cerebellum, highly folded to give large SA, where motor processing occurs, has 3 layers:
1. The molecular layer has few neurons, many synapses & dendrites of Purkinje fibers
2. The Purkinje cell layer is where P cells are found, inhibitory structures that project into the cerebellum
3. Granule cell layer has granule cells that send axons to the molecular layer, they form excitatory synapses with Purkinje cells
Describe the function of the deep nuclei & cerebellar peduncles
A peduncle is a bundle of nerve fibers which are connects the brainstem to cerebellum
3 types:
1. superior peduncle: carries output from cerebellum to the midbrain/thalamus
2. Inferior peduncle: carries sensory info from SC to the cerebellum
3. middle peduncle: transmits input from the pons to the cerebellum
The DCN is composed of 4 nuclei: Dentate nucleus (the largest and most lateral), Emboliform nucleus., Globose nucleus & Fastigial nucleus. These receive input from purkinje fibers and send signals to thalamus/brainstem & motor cortex
Describe the cerebellar lobes
There are 4 lobes
1. Anterior lobe: regulates muscle tone, coordination of limb movements & balance, receives info from SC
2. Posterior lobe: involved in fine motor movements, needed for smooth movement, plans & executes voluntary movements
3. Flocculonodular lobe: Found at base, involved in balance & eye movement, stabilizes head & neck & posture control
4. Vermis lobe: central part of cerebellum, helps maintain balance & posture through control of trunk & limbs
Describe the role of the cerebellum
- Coordination & movement: The cerebellum adjusts motor commands based on sensory input allowing smooth movement
- Motor learning: helps learn new motor skills, forms muscle memory, adapts based on feedback
- Posture & balance: regulates muscle tone & coordinate muscle groups to prevent falls
- Eye movement: enables tracking of moving objects & gaze stability
Describe the effects of lesions on the cerebellum
- Ataxia: leads to a lack of coordination leading to difficulty with tasks needing precision
- Tremor: tremors may occur during voluntary movement
- Dysmetria: lack of ability to judge distances, undershooting/overshooting
- Impaired balance: difficulty maintaining posture & balance e.g., when standing or walking, leading to increased risk of falls
