IOI4 



HUMAN ANATOMY. 



NERVE-TERMINATIONS. 

 The terminations of the fibres composing the peripheral nerves — the axones of 

 certain motor neurones situated within the cerebro-spinal axis and the sympathetic 

 system and the dendrites of the neurones of the sensory gangha — supply the means 

 by which the various structures of the body are brought into intimate relation 

 with the nervous system. Some of these terminations transfer impulses resulting in 

 muscular contractions ; others convey impressions that produce various sensations 



(pain, pressure, muscle-sense. 

 Fig. 863, temperature). The nerve- 



terminations, therefore, may 

 be grouped according to func- 

 tion into motor and sensory 

 e?idhigs. 



Motor Nerve-Endings. 



The motor endings in- 

 clude (a) terminations of the 

 axones of neurones situated 

 within the motor nuclei of 

 the spinal cord and brain- 

 stem that pass to voluntary 

 muscle ; {b) terminations of 

 sympathetic neurones that 

 end in involuntary muscle and 

 (c) in cardiac muscle. 



Endings in Voluntary 

 Muscle. — On approaching 

 their peripheral destination 

 the medullated nerve-fibres 

 branch repeatedly, each fibre 

 in this manner coming into 

 relation with a number of mus- 

 cle-fibres. When the med- 

 ullated nerve- fibre reaches the 

 muscle-fibre which it supplies, its medullary sheath abruptly ends and the neurilemma 

 becomes inseparably fused with the sarcolemma, whilst the axis-cylinder passes beneath 

 this sheath to terminate in an end-platc. The latter appears as an oval area, from 

 .040— .060 mm. in its greatest diameter, which is applied 

 to the muscle-substance ; in profile it shows a slight 

 projection beyond the contour of the muscle-fibre, 

 although this is often wanting. Embedded within 

 a general nucleated sheet of granular protoplasm, the 

 solc-plate, lie the brush-like terminal arborizations of the 

 axis-cylinder formed of irregular varicosites and club- 

 shaped ends. From the details of the development of 

 the motor end plates, as described by Bardeen, it is 

 probable that the granular sole-plate and its nuclei are 

 differentiated from the sarcoplasm and the nuclei of the 

 muscle-fibre respectively. The much discussed relation 

 of the end-plate to the sarcolemma — whether outside or 

 beneath — seems to be decided in favor of a subsarco- 

 lemmal position, since the muscle-sheath appears sub- 

 sequently to the formation of the motor-ending, a fact 

 that explains the apparent piercing of the sarcolemma 

 by the axis-'Cylinder. Usually each muscle-fibre is pro- 

 vided with a single motor end-plate, which may lie at an 

 equal or unequal distance from the ends of the fibre. Exceptionally two end-plates 

 may be found on one muscle-fibre, in which case the endings lie near each other. 



Motor nerve-endings in voluntary muscle ; bundle of nerve-fibres is 

 seen separating; to supply the indixidual muscle-fibres. X 160. 



Fig. S64. 



Motor nerve-ending in voluntary 

 muscle ; a, axone terminating in end- 

 plate ; w, neurilemma ; j, sole-plate. 



X 400. 



