Questions and Answers
What is the function of the flexor reflex?
In both UE and LE, it causes movement of the flexor muscles to move a limb away from a harmful stimulus. In the LEs, it is also used for locomotion.
The flexor reflex is initiated by which type of receptors?
Cutaneous
Where are cutaneous receptors located?
In the skin; they respond to touch, pressure, pain, and temperature.
The flexor reflex arc is:
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What is the flexor reflex receptor organ?
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The afferent neuron of the flexor reflex arc is in what group?
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In the flexor reflex arc, the interneuron is:
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What type of neuron is the effector (efferent) neuron in the flexor reflex arc?
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List the five components of the flexor reflex arc.
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Describe the mechanism of the Flexor Reflex Afferents (FRA).
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Interneurons are also known as what?
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What is the purpose of FRA collaterals that synapse on various interneurons in the spinal cord?
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Describe the purpose of various interneurons for reciprocal innervation in the flexor reflex.
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Interneurons for the reflex arc and reciprocal innervation synapse with cell bodies of motor neurons in which part of the spinal cord?
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What is the function of alpha motor neurons?
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What motor response do alpha motor neurons cause in the flexor reflex?
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When does flexor withdrawal in the LE occur?
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Describe reciprocal innervation in the flexor withdrawal of the LE.
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Every movement has reciprocal innervation.
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What is the crossed extension (extensor) reflex in the LE?
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Describe reciprocal innervation in the crossed extension reflex of the LE.
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What type of interneuron is required for the movement of the contralateral leg in the crossed extension reflex?
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What is locomotion?
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How does locomotion relate to the flexor reflex?
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What two principles are involved with locomotion (and flexor reflex)?
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How are intersegmental interneurons involved with locomotion?
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How does the cerebrum influence spinal reflexes during locomotion?
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Role of reciprocal innervation for locomotion?
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Flexor withdrawal in UE - typical chain of neural events?
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Reciprocal innervation of UE in flexor reflex?
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What happens during flexor reflex in the UE when there is a stronger stimulus?
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Describe associated reaction (UE).
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Describe crossed extension (UE).
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Describe the effects of the associated reaction and crossed extension during flexor withdrawal of the UE.
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Describe the mechanisms of Associated Reactions.
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Describe the mechanisms of Crossed Extension during flexor reflex of UE.
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Describe how the ipsilateral leg is flexed via reciprocal innervation.
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Describe how the contralateral leg is flexed via reciprocal innervation.
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Which of the following are proprioceptive reflexes? (Select all that apply): a) Flexor reflex, b) Stretch reflex, c) GTO reflex.
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What are the structures responsible for initiating the stretch reflex and the GTO reflex?
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Study Notes
Function of the Flexor Reflex
- Facilitates movement of flexor muscles to withdraw a limb from harmful stimuli.
- In lower extremities (LE), assists in locomotion.
Receptor Types
- Initiated by cutaneous receptors found in the skin.
- Respond to touch, pressure, pain, and temperature.
Structure of the Reflex Arc
- Flexor reflex arc is multi-synaptic.
- Includes cutaneous receptors as the receptor organ.
- Afferent neurons classified as Group II (touch, pressure) or Group III (pain, temperature).
- Interneurons are excitatory, while afferent fibers synapse on them.
Neuron Types
- Alpha motor neurons act as effector (efferent) neurons, synapsing on flexor muscles to generate movement.
- The flexor reflex arc consists of three neurons: afferents, interneurons, and motor neurons.
Mechanism of Flexor Reflex Afferents (FRA)
- FRA fibers are stimulated by cutaneous sensations.
- Action potentials travel to the spinal cord, synapsing on excitatory interneurons, which in turn synapse on alpha motor neurons.
- Axon collaterals extend to higher centers and additional interneurons for reflexive movement coordination.
Function of Interneurons
- Interneurons facilitate reciprocal innervation during the reflex: excitatory for flexors and inhibitory for extensors.
- Located in the ventral horn of the spinal cord for motor neuron synapses.
Response Types
- Alpha motor neurons produce flexor withdrawal (movement away from stimuli) in both upper extremities (UE) and lower extremities.
- In the LE, this is notably activated when stepping on sharp objects.
Crossed Extension Reflex
- Occurs in the contralateral leg during LE flexor withdrawal to maintain balance by extending the opposite limb.
- Involves reciprocal innervation: ipsilateral leg flexors activated while extensors inhibited; contralateral leg extensors activated while flexors inhibited.
Locomotion and Reflex Coordination
- Involves flexor withdrawal and crossed extension reflexes for coordinated movement during walking or running.
- Intersegmental interneurons ensure smooth coordination between upper and lower body movements.
Cerebrum's Influence on Reflexes
- Changes gait patterns based on terrain through descending tracts affecting spinal reflex responses.
Reciprocal Innervation Role
- Ensures efficient and coordinated movement patterns during activities like running, facilitating flexor activation and extensor inhibition.
Specifics of Upper Extremity Flexor Reflex
- Strong stimuli can lead to associated reactions affecting the contralateral limb and crossed extension affecting the lower limbs.
- Flexor muscles (e.g., brachialis and biceps) are excited, while extensor muscles (e.g., triceps) are inhibited during reflex actions.
Mechanisms of Associated Reactions and Crossed Extension
- Associated reactions involve bilateral flexor withdrawal due to excitatory and inhibitory commissural interneurons.
- Crossed extension involves shifting weight and activating or inhibiting motor neurons in an intersegmentally coordinated manner across the body.
Proprioceptive Reflexes
- Stretch reflex and Golgi tendon organ (GTO) reflex are considered proprioceptive reflexes, while the flexor reflex is classified as a cutaneous reflex.
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Description
Explore the function and structure of the flexor reflex in this quiz. Learn about the role of cutaneous receptors, neuron types, and the multi-synaptic nature of the reflex arc. Test your knowledge of how flexor muscles respond to harmful stimuli and assist in locomotion.