Spinal cord reflexes

Spinal cord reflexes are involuntary, nearly instantaneous motor responses to sensory stimuli that occur through neural circuits localized within the spinal cord, often without direct cortical involvement [1]. These reflex arcs typically comprise a sensory receptor, an afferent neuron, one or more interneurons (in polysynaptic circuits), and an efferent motor neuron [1]. In clinical pathology, particularly following upper motor neuron lesions such as spinal cord injury or multiple sclerosis, these reflexes can become disinhibited, resulting in hyperreflexia and spasticity [2]. Pharmacological management of these conditions does not target the reflex itself as a single molecule but rather modulates the neurotransmitter systems—specifically GABAergic and adrenergic pathways—that regulate the excitability of the reflex arc [3]. Common therapeutic agents like baclofen and tizanidine function by reducing the transmission of excitatory signals to motor neurons, thereby alleviating muscle stiffness and spasms associated with overactive spinal circuits [3].

Other names

Spinal reflex arcMyotatic reflexWithdrawal reflexStretch reflexPolysynaptic reflex

Drugs modulate spinal cord reflexes by acting as agonists at inhibitory receptors (e.g., GABA-B receptors via Baclofen, Alpha-2 adrenergic receptors via Tizanidine) or as positive allosteric modulators (e.g., GABA-A receptors via Diazepam) to suppress the hyperexcitability of alpha motor neurons [3].