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Fig. 6. Physiological characteristics of motor neurones innervating the accessory
flexor muscle. (A) Efferent activity simultaneously recorded from accessory
flexor nerve and N5B2 in the distal femur when the cricket was disturbed. When
two small units, two moderate-sized units, and one large unit fire in the
accessory flexor nerve (upper trace), only two moderate-sized units were
recorded from N5B2 (lower trace), suggesting that the two moderate-sized units
are common inhibitors. (B) Recording from the accessory flexor nerve efference
(upper trace) combined with an intracellular recording from a fibre in the
accessory flexor muscle (bottom trace) when the cricket is in the quiescent
state, showing that spikes of two CIs evoke inhibitory junctional potentials
(IJPs) in the muscle fibre. When the two CIs fired synchronously (asterisks),
summation of IJPs occurred. (C) Activity pattern of the motor neurones in a
ventilation phase. Initially two CIs and subsequently slow and intermediate
exciters are activated in expiration, resulting in hyperpolarization of the
slow muscle fibre. All units are declined in inspiration, resulting in resumed
activity of the muscle potential. Excitatory junctional potentials
corresponding to spikes of the intermediate exciter were not seen in this
recording but were detected in recordings from other muscle fibres, as noted
by Matheson and Field
(1995).
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