which of the following is true regarding nuclear bag fibres of motorunit ?: (A) responds to length only, (B) responds to both length and velocity changes, (C) responds to contraction of muscle fibres, (D) responds to reflex relaxation
Answer is B. Two types of intrafusal fibres -- nuclear bag fibre * primary (la) afferent -- supplies annulospiral ending in the centre -- provide information on muscle length and velocity (phasic response) fast stretch reflex -- nuclear chain fibre * primary (la) and secondary (II) afferent -- supplies flower spray ending -- monitor the length of the muscle (tonic response) --slow stretch reflex ref : guyton and hall