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Questions and Answers
What characterizes a spinal reflex?
What characterizes a spinal reflex?
- It is an involuntary response mediated through spinal pathways. (correct)
- It is the same as a conditioned reflex.
- It is a voluntary action requiring higher brain involvement.
- It always involves multiple sensory modalities.
Which type of muscle afferent reflex pathway is associated with proprioceptive feedback?
Which type of muscle afferent reflex pathway is associated with proprioceptive feedback?
- II pathway
- Ib pathway
- III pathway
- Ia pathway (correct)
What role do central pattern generators (CPGs) play in movement?
What role do central pattern generators (CPGs) play in movement?
- They solely control fine motor skills.
- They only function during voluntary movements.
- They generate rhythmic movements independent of sensory feedback. (correct)
- They completely replace the need for sensory input.
What is a key characteristic of muscle receptors involved in motor control?
What is a key characteristic of muscle receptors involved in motor control?
How are reflexes modulated in accordance with the task?
How are reflexes modulated in accordance with the task?
Which type of muscle afferent is primarily responsible for detecting muscle tension?
Which type of muscle afferent is primarily responsible for detecting muscle tension?
What has the perception of a 'reflex' traditionally been considered?
What has the perception of a 'reflex' traditionally been considered?
Which component is NOT typically associated with the spinal reflex arc?
Which component is NOT typically associated with the spinal reflex arc?
What is the current view on reflex responses in terms of adaptability?
What is the current view on reflex responses in terms of adaptability?
Which statement accurately describes proprioception?
Which statement accurately describes proprioception?
What are the types of proprioceptors involved in sensing body position?
What are the types of proprioceptors involved in sensing body position?
How do extrafusal muscle fibers differ from intrafusal muscle fibers?
How do extrafusal muscle fibers differ from intrafusal muscle fibers?
What determines the sensitivity of muscle spindles to changes in stretch?
What determines the sensitivity of muscle spindles to changes in stretch?
What role do visual systems play in proprioception?
What role do visual systems play in proprioception?
Which type of afferent fibers provide rapid responses to changes in muscle length?
Which type of afferent fibers provide rapid responses to changes in muscle length?
What is a critical aspect of reflex modulation?
What is a critical aspect of reflex modulation?
What is the primary biological function of the stretch reflex?
What is the primary biological function of the stretch reflex?
Which components are involved in detecting deviations from the desired muscle length?
Which components are involved in detecting deviations from the desired muscle length?
What role do gamma-motor neurons play in the stretch reflex?
What role do gamma-motor neurons play in the stretch reflex?
The gain of the myotatic reflex refers to what aspect of muscle response?
The gain of the myotatic reflex refers to what aspect of muscle response?
During neurological testing, which afferent input is predominantly used?
During neurological testing, which afferent input is predominantly used?
How is muscle tone maintained in muscles?
How is muscle tone maintained in muscles?
What role does the central pattern generator (CPG) primarily serve in the locomotion of animals?
What role does the central pattern generator (CPG) primarily serve in the locomotion of animals?
What is the significance of the γ-bias in the stretch reflex mechanism?
What is the significance of the γ-bias in the stretch reflex mechanism?
Which of the following statements is true regarding the activation of CPGs in humans?
Which of the following statements is true regarding the activation of CPGs in humans?
What functional role does the stretch reflex serve in muscle activity during contractions?
What functional role does the stretch reflex serve in muscle activity during contractions?
What happens when the dorsal roots are transected in spinal cord research?
What happens when the dorsal roots are transected in spinal cord research?
How does CPG activity adjust to different locomotion speeds in animals?
How does CPG activity adjust to different locomotion speeds in animals?
What type of drive activates central pattern generators in intact animals?
What type of drive activates central pattern generators in intact animals?
What additional functions are central pattern generators thought to control beyond locomotion?
What additional functions are central pattern generators thought to control beyond locomotion?
Why is the spinal cord circuitry essential for locomotion?
Why is the spinal cord circuitry essential for locomotion?
What is a significant feature of central pattern generators in relation to sensory input?
What is a significant feature of central pattern generators in relation to sensory input?
What is the primary function of the muscle spindle system?
What is the primary function of the muscle spindle system?
In a flexion reflex pathway, which action occurs in response to nociceptive stimuli?
In a flexion reflex pathway, which action occurs in response to nociceptive stimuli?
What role do Renshaw cells play in motoneurone regulation?
What role do Renshaw cells play in motoneurone regulation?
What is the effect of excitatory input to a Renshaw cell on motoneuronal response?
What is the effect of excitatory input to a Renshaw cell on motoneuronal response?
Which sensory receptors are primarily involved in triggering the flexion reflex?
Which sensory receptors are primarily involved in triggering the flexion reflex?
What happens to the flexion reflex when descending pathways are damaged?
What happens to the flexion reflex when descending pathways are damaged?
Which of the following best describes the role of supraspinal inputs on Renshaw cells?
Which of the following best describes the role of supraspinal inputs on Renshaw cells?
Study Notes
Spinal Control of Movement and Locomotion
- Spinal reflex: an involuntary response activated by sensory receptors through spinal pathways, now understood as highly modifiable based on context and task.
- Reflex modulation indicates reflex responses depend on the specific task being performed rather than being hard-wired.
Proprioception and Muscle Receptors
- Proprioception: the sense of body position, movement, and effort, derived from various specialized mechanoreceptors called proprioceptors.
- Key proprioceptors include:
- Muscle spindles: sense changes in muscle length and movement velocity.
- Golgi tendon organs: monitor muscle tension.
- Joint receptors: contribute to proprioceptive feedback.
- Integration of proprioceptive information occurs alongside signals from vestibular, cutaneous, and visual systems to accurately determine body position.
Muscle Spindles and the Stretch Reflex
- Muscle spindles consist of intrafusal muscle fibers responsible for sensory input, maintaining sensitivity to stretch regardless of muscle length.
- Stretch reflex serves as a feedback control mechanism to adjust muscle length based on detected deviations, activating α-motor neurons for appropriate muscle contraction.
- Muscle tone, or steady muscle tension, is maintained by group II muscle spindle afferents.
Spinal Reflexes and CNS Integration
- The central nervous system utilizes spinal cord organization to minimize processing demands on higher brain centers, integrating gamma drive to influence muscle activity during slow contractions.
- Reflex gain is determined by excitability of α-motor neurons and sensitivity of muscle spindles controlled by γ-motor neuron activity.
- Ib inhibitory interneurons receive various synaptic inputs, modulating the reflexive response.
Protective Reflexes
- Flexion reflex pathways activate due to cutaneous nociceptors, triggering polysynaptic pathways that excite ipsilateral flexors while inhibiting extensors.
- Descending pathways can suppress reflex actions; damage can lead to reflex activation by other stimuli.
Recurrent Inhibition and Renshaw Cells
- Renshaw cells, identified in the 1940s, inhibit motoneurons via feedback loops, regulating motoneuron firing in response to higher-level inputs from the brain.
- Inhibition of Renshaw cells increases motoneuron responsiveness, while excitation decreases it, demonstrating a gain control mechanism.
Rhythmic Movements and Central Pattern Generators (CPGs)
- Rhythmic movements (e.g., locomotion, breathing) are managed by central pattern generators situated in the spinal cord.
- CPGs can generate oscillating motor patterns independent of sensory input, influenced by supraspinal and peripheral feedback.
- Speed of locomotion in animals can adjust based on treadmill speed, illustrating the role of stretch reflexes in spinal motor programs.
- CPGs enable coordinated movements even after spinal cord injuries, prompting locomotion in cats and rats.
- In intact animals, CPGs are activated by tonic descending drive from the brain, generating foundational rhythmic patterns for movement and respiration.
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Description
This quiz focuses on spinal control of movement and locomotion, including reflexes managed by muscle and cutaneous afferents. Drawing from key chapters in renowned neuroscience texts, students will deepen their understanding of spinal reflex mechanisms.
