Crossed Extensor Reflex
Crossed Extensor Reflex - Related Videos
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Cited by 13 •
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This article demonstrates how to conduct electrophysiological recordings of synaptic responses on the extensor muscle in the walking leg of a crayfish and how the nerve terminals are visualized to show the gross morphological differences of high- and low-output nerve terminals.
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Behavioral testing is the gold standard for determining outcomes following brain injury, and can identify the presence of developmental disabilities in infants and children. Neurodevelopmental reflexes are an early indicator of these abnormalities. A host of easily accomplished developmental reflex tests in the neonatal rodent were developed and described here.
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Reflex Activity
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A reflex activity is an automatic, involuntary response to specific stimuli. It is a part of our survival mechanism, designed to protect us from potential harm. For example, when a bright light suddenly shines into our eyes, we instinctively close them or look away. This is a simple reflex activity orchestrated by the nervous system without conscious thought or effort. A reflex exam is a diagnostic procedure performed by a healthcare professional to evaluate the functionality of a patient's...
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Urination, or micturition involves the coordination of the bladder's detrusor muscle and two sphincters to ensure controlled bladder emptying. The process begins with bladder filling, where the bladder wall stretches as urine accumulates. This stretching activates the urine storage reflex, mediated by the sacral spinal segments and the pontine storage center. Efferent sympathetic impulses stimulate the detrusor muscle to relax and the internal urethral sphincter to contract, facilitating urine...
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Early Reflexes During Infancy
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Early reflexes are automatic, involuntary responses to specific stimuli and provide information about neurological development during infancy. Some reflexes are present at birth or appear soon afterward. Known as primitive reflexes, they support early survival and adaptation.Primitive ReflexesPrimitive reflexes help newborns respond to their environment before voluntary motor control develops. The rooting reflex causes an infant to turn toward stimulation near the mouth, helping the infant...
FAQs
Spinal interneurons distribute incoming nociceptive signals into coordinated motor pathways rather than sending a single command to one muscle. Excitatory and inhibitory connections shape activity on both sides of the spinal cord, while commissural interneurons transmit the opposing pattern across the midline. This organization lets withdrawal and support develop as a linked response.
The stimulated limb needs a coordinated release from support so it can move away from the painful source. Exciting flexor muscles while inhibiting ipsilateral extensors creates opposing muscle activity that favors withdrawal instead of simultaneous resistance. This reciprocal organization makes the response efficient and helps prevent conflicting motor commands during a protective movement.
Commissural interneurons connect activity across the two sides of the spinal cord. They help produce contralateral extensor activation and flexor inhibition while the affected limb follows the opposite pattern. This cross-body coordination extends the reflex beyond local withdrawal, allowing the other limb to provide support and helping preserve balance during the response.
Its value extends beyond removing a limb from danger. By shifting the pattern of muscle activity between the two limbs, the reflex helps maintain support when one side withdraws. The same spinal coordination is relevant to posture and locomotion because it links sensory input with organized motor output that stabilizes the body during movement.
Begin with the painful stimulus and identify activation of nociceptors, then follow sensory-neuron input into the spinal cord. Next, trace interneuronal outputs to flexors and extensors on the stimulated side, including commissural pathways to the opposite side. Finally, relate the paired limb responses to withdrawal, support, and balance rather than viewing either limb in isolation.
The response provides a model for examining how the spinal cord integrates sensory information and organizes coordinated motor output. In biology, it illustrates polysynaptic circuit function, bilateral communication, and the relationship between reflexes and locomotion. In neurological assessment, studying the pattern can help relate observed limb responses to spinal coordination and protective function.