Physiology and biochemistry in modern medicine . n considering this integration of reflexes, as it is called, we must dis-tinguish between those that are allied and those that are antagonistic,and we must further distinguish between reflexes that are simultane- 821 822 THE CENTRAL NERVOUS SYSTEM ously competing for the same final common path and those which occupyit successively. INTEGRATION OF ALLIED REFLEXES Perhaps the simplest experiment to show this is performed by usingthe scratch reflex. The skin area from which this reflex can be elicitedis very widespread (see Fig. 217), the type of r
Physiology and biochemistry in modern medicine . n considering this integration of reflexes, as it is called, we must dis-tinguish between those that are allied and those that are antagonistic,and we must further distinguish between reflexes that are simultane- 821 822 THE CENTRAL NERVOUS SYSTEM ously competing for the same final common path and those which occupyit successively. INTEGRATION OF ALLIED REFLEXES Perhaps the simplest experiment to show this is performed by usingthe scratch reflex. The skin area from which this reflex can be elicitedis very widespread (see Fig. 217), the type of reflex produced from anygiven area being in general the same, although the local sign—thatis, the point at which the animal scratches—will vary according to thepoint stimulated. If then we take point A in the reflex scratch areaand apply to it a stimulus which is just inadequate to produce any reflexat all, and then, while this stimulus is still in progress, apply a similarsubliminal stimulus to point B a little removed from it, the two sub-. Fig. 216.—Diagram showing the reflex arcs involved in the scratch reflex. Ra and R(3 representthe afferent neurons connected with hairs on the skin of the hack and flank. The afferent im-pulses are transmitted by these fibers, and on entering the corresponding segments of the spinalcord terminate by synapses on cells of the internuncial neurons, whose arrows Pa and Pj3 traveldown in the lateral columns to terminate similarly around the cells of the motor neurons thatinnervate the muscles of the hind limb. Since afferent impulses coming from elsewhere, par-ticularly from the skin of the leg (R and L), also terminate on these neurons and may excitethem to a different type of action, the motor neuron is called the final common path (.).(From Sherrington.) liminal stimuli will become effective and produce a typical scratchingmovement. In other words, the subliminal stimulus of point A be-comes added on the final common path with the s
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