Similar observations were made in the dog in spite of the fact that the greater stimulation of the vasomotor center during the anoxic and hypoglycemic period created conditions for improved brain circulation 492. Changes in the ionic balance which lower the blood pressure lead to a diminution of these reflexes. Tucker, who read the manuscript in part or entire and greatly aided him by their criticism; to Dr. The discharge of motor impulses in a nerve twig to an external intercostal muscle in three successive inspirations of varying depth: A, moderate; B, deep; C, shallow. Apparently the modification by posture fixation of a joint, etc.
Diagnosis will be aided by such vn viii Physiological Foundations of Neurology and Psychiatry knowledge, and therapeutic procedures will be based on it. Pain and the Pupil, 271. Moreover the principles developed in the studies on the motor cortex are applied in order to arrive at a rational therapy of motor lesions of the central nervous system. In the invertebrate retina limulus each nerve fiber responds only to the excitation of a single retinal cell, and the discharge rate increases with increases in the intensity of illumination. These areas are markedly extended in pain 1156 Fig. The phenomenon of multiple representation in the motor cortex has been put on a firm anatomical basis by Glees's work.
Some are excited by muscle tension no matter whether it results from passive stretch or active contraction; others react only to passive tension and cease firing on contraction of the muscle. If a muscle is acutely denervated, it fails to show action potentials when adjacent muscles are in a state of activity. This large, handsome, and well-printed volume presents us with another excellent text book in a field not overly rich with good texts. Obviously the experimental work discussed in this section neither supports nor contradicts the clinical findings concerning the therapeutic values of these procedures. Further questions applicable to the neuron in general are discussed in Chapter 11, in which a survey of the action of neurohumors is given.
The latter are the propagated action potentials which may also be recorded from the phrenic nerve and the diaphragm. At the first stage Fig. Another group of stretch receptors which influence circulation and, to a lesser degree, respiration are located in the carotid sinus and the arch of the aorta. This is well illustrated by Pitts and Bronk's investigations 1018 on the sympathetic system. Extensive material, however, is available on the influence of deafferentation on voluntary movements in man and animals. Frequency analysis has confirmed these findings. Ten minutes after the restoration of circulation the low-resistance area is the same as in the control a.
As in many other neurophysiological questions, the hierarchical structure of the nervous system in general and the motor system in particular must be taken into account. Apparently the same neurons react first to voluntary activation and electrical stimulation. The Brain Stem in Anoxic and Hypoglycemic Convulsions, 157. The Interaction of Willed Movements with Spinal Reflexes, 98. The quantitative relation between 84 Physiology and Pathology of Movements antagonistic complexes depends in both instances on the degree of activity of the agonists. They are activated progressively with increasing inflation of the lungs.
Proprioception and Cortically Induced Movements, 70. If the magnesium depletion is carried out far enough, spontaneous convulsions ensue 571. The interaction of various synergists, which is apparently based on the activation of the functional complexes previously described in our Analysis of Voluntary Movements 91 experiments on stimulation of the motor cortex, suffers in patients with a deafferented extremity. Some aspects of autonomic physiology are treated in Chapters 11 and 12, although care has been taken in these as in all other parts of this book to choose functional considerations and not anatomical 6 Physiological Foundations of Neurology and Psychiatry boundaries as the basis for discussion. Repetition is therefore unavoidable, though kept to a minimum by the use of cross references.
Contributions to the Physiology and Pathology of Movements Chapter 3. The effect of proprioceptive excitation and inhibition is not restricted to the muscles of the same limb. Although the excitation of proprioceptive receptors remains to a large extent below the level of consciousness and expresses itself in the coordination and reinforcement of cortically or reflexly induced The Unit Analysis of Nervous Activity 25 movements, their impulses reach the sensorimotor cortex 416. The very limited use of anthropoid apes has been confined almost exclusively to explorations of the motor cortex and to behavioral studies. The Oxygen Consumption of the Convulsive Neuron, 161. In epileptics and psychopathic patients, however, slow, large potentials may appear under these conditions 623. Barron and Matthews 76 have studied the relation between the slow electrotonic potentials and the fast spikes in the motor root after different degrees of reflex stimulation.
Apparently impulses originating in the stretched muscle shunt those coming from the motor cortex into those neurons which innervate the stretched muscle. The Newer Work on Sympathin, 236. Apparently synaptic transmission and excitation of nerve and muscle involve a loss of potassium. The similarity between the voluntary discharge and that induced by slowly rising currents applied to motor nerves in the human being suggests that both processes are initiated in a similar manner, i. But inhibition of the sympathetic discharge can also be accomplished by appropriate stimulation of the sympathetic centers.
Recordings from the whole 28 Factors Regulating Neuronal Activity nerve show recruitment and decruitment respectively under these conditions 875, 876. Thus extension of the elbow induces in anesthetized animals not only a stretch reflex in the elbow flexors biceps and brachioradialis but also in the extensors carpi, which have previously been shown to be a part of the biceps complex. The synchronizing effect is probably due to action potentials of some discharging neurons which influence adjacent neurons. Multiple Representation in Threshold Responses The electromyographic method is adequate to decide the question whether the concept of multiple representation of movements established for suprathreshold stimulation is applicable for threshold conditions of stimulation. The Brain Stem and Cortical Homeostasis, 404. The greatest recorded frequency is similar in different units, but increases only slightly as the tension is increased. A disturbance in the quantitative interplay of these muscles accounts for the fact that the foot may be dorsiflexed upon supination or pronation.