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Chapter 22 Two physiological aspects of the electrically elicited blink reflex: motor unit potentials recruitment and levator palpebrae inhibitory components

Authors
Publisher
Elsevier Health Sciences
Identifiers
DOI: 10.1016/s1567-424x(09)70075-3
Disciplines
  • Biology
  • Medicine

Abstract

Publisher Summary This chapter focuses on the two aspects of the electrically elicited blink reflex (BR)—namely, motor unit potential recruitment and levator palpebrae inhibitory components. The chapter presents a pathological model to study the motor unit configuration of the electrically elicited BR, which allows for the activation of a single orbicularis oculi muscle (OOc) motor unit. R1 is made up of a very scarce number of motor unit action potentials (MUAPs) as an almost synchronized compound motor action potential, whereas R2 is a desynchronized response made up of the summation of the same MUAPs than the ones fired in a rhythmic repetitive manner. A basic mechanism of summation facilitation over the facial motoneurons, acting through multiple interneuronal paralleled chains, is proposed. Ultimate responses, however, must also relate to the excitability state of motoneurons and the strength of the afferent input. Some inhibitory reflex pauses are obtained from the steady activity of the levator palpebrae muscles as an integral part of the physiological BR. Different from the active OOc components, inhibitory I1 and I2, are always bilateral regardless of the stimulated side and have a longer duration than R1 and R2. The recovery cycles of I2 and R2 are different, which would support the involvement of different interneuronal systems on both these components. The inhibitory portion of the BR probably plays a meaningful role in this reflex and also in the different types of eye closing.

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