EFFECTOR MECHANISMS 



391 



plain fibres and responsible for quick tonic contractions (Ostrect, Pecten, 



etc.). 



The anterior and posterior adductor muscles are supplied by nerves from 

 the cerebral and visceral ganglia respectively; the byssal retractor by the 



J-I00//V d 



llltf IUhnlfilillUiiili -r l U^t-A-tilt - 



T***^ limner 



SM 



40^ftr-j)H+^ 



5 sec 



Fig. 9.14a. Electrical and Mechanical activity of 

 Pecten Adductor Muscle 

 M, myograms; SM, STR, potentials in smooth and striated parts of muscle, respec- 

 tively; a, striated muscle potentials recorded during swimming movements of the intact 

 animal; b, smooth and striated muscle responses to tactile stimulation of the visceral 

 ganglion ; c, records from two experiments showing responses of the striated muscle to 

 electrical stimulation of the visceral ganglion; d, electrical activity in the smooth muscle 

 during a sequence of swimming movements. 



\50pV 



J WO/jV 



jy^/M|f^^ 



sec 



10 



20 



30 



40 50 60 70 80 Sec 



Fig. 9.14b. Recordings from Posterior Adductor Muscle of Mytilus 

 Upper tracing, myogram; below, muscle potentials. Spontaneous activity of intact 

 animal in water; a, small and large contractions; b, muscle potentials recorded during 

 contraction. (From Lowy (81, 82).) 



pedal ganglion. Anterior retractor muscles of the mantle receive their 

 nerve supply from the cerebral ganglion. According to Pumphrey (106), 

 the anterior adductor and mantle retractor muscles of Mya receive two 

 kinds of excitatory nerve fibres. During reflex stimulation activity in one 



