Reflexes

Reflexes:
• rapid and predictable involuntary motor response of muscles to a stimulus
• beneficial

Components of a reflex arc:
• Receptor – site of stimulus
• Sensory neuron – afferent transmission
• Integration centre – in CNS; monosynaptic or polysynaptic
• Motor neuron – efferent transmission
• Effector – gland or muscle fibre responsive to efferent impulse

Stretch/myotatic reflex:
• Due to stretching of muscle spindles  contraction of stimulated muscle and inhibition of antagonist; the muscle “fights back” when stretched
• Help maintain posture, equilibrium an balance

Deep tendon reflex:
• Due to stimulus of Golgi tendon organs
• Polysynaptic
• Cause relaxation of stimulated muscle and contraction of antagonist

Flexor/withdrawal reflex:
Due to painful stimuli  quick contraction of flexor muscles  withdrawal of limb from stimulus causing injury (has a protective function)
Polysynaptic (signal passes many synapses)

Extensor reflex:
• crossed; contraction of extensor muscles in limb opposite to the one that was withdrawn as result of flexor reflex (to help keep balance)

Superficial reflexes:
• eg plantar response; abdominal reflex
• due to cutaneous stimulation
• use corticospinal pathways

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