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What are the sensory receptors in the skin that provide tactile sensory information to the central nervous system?
Mechanoreceptors
What is proprioception?
The sensation and perception of limb, trunk, and head position and movement.
Which of the following are characteristics influenced by tactile sensory information? (Select all that apply)
Where are mechanoreceptors located?
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What role do muscle spindles play in proprioception?
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Proprioceptors are found only in the muscles.
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What information does the Golgi tendon organ provide?
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Which sensory system is associated with vision?
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What was the main finding of Lee and Aronson's 'moving room' experiment with infants?
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Which sensory system do we tend to trust the most according to the research?
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In the 'moving room' experiment, the floor was also moving along with the walls.
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What happens to an infant’s posture when the walls of the 'moving room' move?
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The _______ is responsible for allowing the eye to focus at various distances.
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Match the following terms with their definitions:
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Which type of photoreceptor is responsible for detecting low light levels?
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The _______ of the eye adjusts to changes in illumination.
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What types of cells are activated when light hits the discs in the outer segment of the rods and cones?
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What do the discs of rods hold?
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The optic nerve sends information to the brain where different signals are processed as a complete image.
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What happens to the image when light waves pass through the cornea?
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What part of the visual field is detected by the inner halves of each eye?
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What is the significance of binocular vision in motor control?
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Monocular vision provides more accurate distance estimates than binocular vision.
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What is the role of central vision when reaching to grasp an object?
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The visual field extends approximately ______ degrees horizontally and ______ degrees vertically.
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What do GTOs detect?
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Which neurons do GTOs synapse with in the spinal cord?
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All joints contain the same types of receptors.
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What type of vision provides information needed to grasp an object?
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Which of the following are types of joint receptors? (Select all that apply)
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What effect does deafferentation have on monkeys' ability to grasp food?
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Peripheral vision is not important for guiding reaching and grasping movements.
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What is optical flow?
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What feedback do proprioceptors provide to influence movement accuracy? (Select all that apply)
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How does proprioception affect the timing of motor commands?
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What happens when central vision is blocked during a prehension task?
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The ____ stream is responsible for the fine analysis of the visual scene.
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What role does proprioception play in postural control? (Select all that apply)
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Vision is the predominant sensory system used when performing motor skills.
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What is perception-action coupling?
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What can cause movement coordination issues, according to research?
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Which visual channel processes high-speed movement information?
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What are the two characteristics influenced by proprioceptive feedback in coordination control?
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What effect does peripheral vision have during locomotion?
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What activates rods and cones when light hits them?
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Rods hold rhodopsin while cones hold photopsin.
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What determines the size of the image on the retina?
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What does the optic nerve do?
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What is the function of the optic chiasm?
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The visual field refers to the image or scene being viewed; it extends approximately _____ degrees horizontally.
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Binocular vision is important for:
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Monocular vision enhances movement efficiency as the distance of the object increases.
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What distinguishes central vision from peripheral vision?
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Without peripheral vision, participants increased their time to contact an object by approximately _____ percent.
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Study Notes
Sensory Components of Motor Control
- Touch, proprioception, and vision significantly contribute to skill motor control and are included in somatic and visual sensory systems.
- Tactile sensory receptors in the skin provide essential sensory information to the central nervous system (CNS) for motor control.
Touch and Motor Control
- Touch is used during motor skills to manipulate objects, people, or interact with the environment through tactile sensory receptors.
- Mechanoreceptors in the skin activate when touched, sending information about pain, temperature, and movement to the CNS.
- The highest concentration of mechanoreceptors is found in the fingertips, enhancing fine motor control.
Role of Tactile Sensory Information
- Tactile sensory feedback influences key movement characteristics:
- Accuracy: Decreases without tactile information, affecting skills like typing and pointing.
- Consistency: Reduced when tactile feedback is unavailable; studies show decreased performance in typing tasks.
- Timing: Influenced particularly in rhythmic movements, e.g., optimal timing in juggling with tactile cues.
- Force adjustments: Essential for regulating grip force when using objects like cups.
- Movement distance estimation improves with tactile feedback during specific movements.
Proprioception
- Proprioception allows sensation and perception of body and limb position, transmitting information on direction, location, velocity, and muscle activation to the CNS.
- Plays a vital role in both closed-loop (feedback-based) and open-loop (feedforward) models of movement control.
Neural Basis of Proprioception
- Proprioceptors located in muscles, tendons, ligaments, and joints are responsible for detecting body position and movement.
- Key types of proprioceptors include:
- Muscle spindles: Detect changes in muscle length.
- Golgi tendon organs: Sense muscle tension or force but are poor at detecting length changes.
- Joint receptors: Measure changes in force and rotation in joints, particularly at extreme joint positions.
Muscle Spindles
- Embedded within skeletal muscles, particularly numerous in finer muscle groups (e.g., hands, eyes, neck).
- Detect changes in muscle length, stretching speed, and provide critical feedback for joint angle and movement execution.
- Involved in reflex actions and voluntary movement control through nerve impulses relayed to the spinal cord and CNS, enhancing motor planning and execution.
Golgi Tendon Organs (GTO)
- Located at the junction of muscles and tendons, sense muscle tension.
- Prevent excessive muscle tension by inhibiting force generation through a reflex mechanism, protecting against injury.
Joint Receptors
- Receptors in the joint capsule and ligaments (Ruffini endings, Pacinian corpuscles) respond to changes in force, rotation, and angular movement at joints.
- Variability exists in receptor types among different joints, influencing proprioceptive feedback during movement.### Mechanoreceptors and Proprioception
- Joint receptors serve as mechanoreceptors, responding to force and rotation in joints as well as changes in movement angle, particularly at extreme limits.
- They play a key role in proprioception, which is essential for motor control.
Limitations of Proprioception
- Some limb movements can occur without proprioceptive feedback, but limitations exist.
- Bimanual coordination can remain synchronous despite a lack of proprioception, as shown in studies involving sensory neuropathy patients.
Movement Accuracy
- Proprioception significantly affects movement accuracy:
- Monkeys exhibited clumsiness and difficulty grasping food post-deafferentation.
- Altered posture in animals led to decreased pointing accuracy.
- Joint capsule replacement severely disrupted distance movements while maintaining some position accuracy.
- Proprioceptors provide crucial feedback on limb displacement, velocity, and force, which are essential for spatial position corrections and distance accuracy.
Timing of Motor Commands
- Proprioceptive feedback influences when motor commands are initiated.
- In a study, both normal and deafferented participants initiated finger extension first in response to an auditory signal.
- When acting at their own pace, normal participants used proprioceptive info to control the timing of their actions more effectively, unlike deafferented individuals.
Coordination Control
- Proprioception is vital for coordinating body and limb segments:
- It aids postural control, working alongside other sensory systems to maintain balance.
- Details from the "moving walls" study revealed that infants corrected posture based solely on visual cues during sensory conflicts.
- Proprioceptive feedback ensures effective spatial-temporal coupling during bimanual tasks and multi-joint actions.
Vision and Motor Control
- Vision holds a predominant role in the execution of motor skills, often overriding proprioceptive input.
- Anecdotal experiences highlight reliance on vision, such as typing or learning to dance, where visual feedback seems critical for performance.
- The "moving room" experiment illustrates how individuals prioritize visual cues over proprioceptive signals when they conflict, leading to unnecessary adjustments.
Research Insights
- Vision’s role in motor control will be explored through neurophysiology, experimental methods, and its influence on coordinated movement tasks.
- The “moving room” experiment demonstrates the tendency to rely on visual feedback over proprioceptive input, showing the high priority given to vision in maintaining balance.### Vision and Motor Control
- Experimental evidence highlights the priority given to vision in postural control, as seen in "moving room" studies.
- Conflicting information between proprioceptors and visual inputs leads to an over-reliance on vision, causing unnecessary postural corrections.
- Research indicates that vision is often the most trusted sensory system for performing motor skills.
Neurophysiology of Vision
- Vision results from sensory receptors in the eyes transmitting light wavelengths to the visual cortex via the optic nerve.
- The eye functions like a high-quality camera, focusing on objects and adjusting to varying illumination automatically.
- Key components include:
- Cornea: Clear, blood vessel-free surface allowing light entry.
- Pupil: Regulates light intake, diameter changes controlled by iris muscles.
- Iris: Colored part of the eye surrounding the pupil.
Anatomy of the Eye
- Lens: Transparent structure behind the iris, allowing focus at different distances, altered by ciliary muscles.
- Sclera: Firm outer layer maintaining eye shape; attachment site for eye movement muscles.
- Aqueous and Vitreous Humor: Fluids maintaining intraocular pressure and eye shape; essential for image clarity.
Neural Components of Vision
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Retina: Lines the back of the eye; contains neurons and photoreceptor cells (rods and cones) for light detection.
- Fovea Centralis: Area for sharp central vision, crucial for visual acuity.
- Optic Disk: Convergence point for retinal neuron axons transmitting signals to the optic nerve.
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Photoreceptors:
- Rods: Function in low-light conditions; important for night vision.
- Cones: Responsible for color vision and central vision; three types detect blue, green, and red light.
Visual Processing
- Light passing through the lens is refracted, creating an upside-down image on the retina.
- Image size and distance are dictated by the angle of light waves; significant for tasks requiring object interception.
- The optic nerve transmits visual information to the brain, where images are processed and perceived as coherent.
Visual Fields and Depth Perception
- The nasal part of the visual field is detected by the inner halves of each eye, while the temporal part is seen by the outer halves.
- At the optic chiasm, nasal fibers cross to the opposite hemisphere for processing, crucial for depth perception.
- Binocular vision through both eyes allows for three-dimensional image perception, enhancing spatial awareness.
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Description
This quiz covers the sensory components essential for motor control, focusing on touch and the sensory receptors involved. Students will describe how tactile sensory information is processed by the central nervous system. Perfect for 1st semester students in the AY 2324 program.
