. Psychology and the school. nglia; (2) a muchmore complex type in which the impulses pass throughthe cerebral cortex. Sensori-motor arcs of the first level. — Let us ex-amine the simple type first. This may most readilybe done by a reference to the structure and functionof the spinal cord. A cross-section of the spinal cordis represented in Fig, 8. The outer portion is whitematter; the inner butterfly-shaped portion is gray mat-ter. It will be noted from Fig. 4 that at various in-tervals nerves run into the spinal cord. The nerves,as we have seen, are composed of fibers. Some of thefibers are
. Psychology and the school. nglia; (2) a muchmore complex type in which the impulses pass throughthe cerebral cortex. Sensori-motor arcs of the first level. — Let us ex-amine the simple type first. This may most readilybe done by a reference to the structure and functionof the spinal cord. A cross-section of the spinal cordis represented in Fig, 8. The outer portion is whitematter; the inner butterfly-shaped portion is gray mat-ter. It will be noted from Fig. 4 that at various in-tervals nerves run into the spinal cord. The nerves,as we have seen, are composed of fibers. Some of thefibers are connected with the sensitive portions of the THE NERVOUS SYSTEM 27 skin; others are connected with the muscles. Thefibers connected with sensitive parts of the body areknown as sensory fibers; those connected with themuscles are known as motor fibers. Both sensory andmotor fibers from the same general region of the bodyare bundled together and pass to the spinal cord inthe form of nerves. All of the sensory fibers pass to. Fig. 8. Cross section of spinal cord. The nervous impulse is rep-resented by the arrows as passing from a sensory surface of theskin across the gray matter of the cord to the muscles at the right. the back of the spinal cord and enter the gray matterthere on either the right or the left of the cord. Themotor fibers enter the front of the gray matter of thecord either to the right or the left. Neurones constituting the gray matter between thefront and the back of the cord serve to bring the motorand the sensory neurones together by means of synap-tic connections with each. Hence numerous completesensori-motor paths are made, beginning in some sen-sitive portion of the skin, and continuing by a sensory 28 PSYCHOLOGY AND THE SCHOOL fiber to the gray matter at the back of the cord, thencethrough the gray matter of the cord to the motor fiberat the front part of the cord, and thence to some mus-cle. Sometimes the connection is made between sen-sory and motor ne
Size: 1909px × 1309px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyo, bookyear1921
