The Journal of physiology
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The Journal of physiology · Feb 1971
Primary afferent depolarization and flexion reflexes produced by radiant heat stimulation of the skin.
1. The reflex effects of pulses of intense radiant heat applied to the skin of the central plantar pad have been studied in unanaesthetized (decerebrate) spinal cats.2. Pad heat pulses produced flexion of the ipsilateral hind limb and increased ipsilateral flexor monosynaptic reflexes, due to post-synaptic excitation of flexor alpha motoneurones. ⋯ The motor and primary afferent effects of heat pulses always accompanied one another, beginning after the pad surface temperature had reached rather high levels (usually 48-55 degrees C).6. Negative DRPs increased excitability of cutaneous and group Ib afferents, and motoneurone activation produced by pad heat pulses was essentially unmodified when conduction in large myelinated afferents from the central plantar pad was blocked by cooling the posterior tibial nerve trunk.7. It is concluded that adequate noxious activation of cutaneous afferents of small diameter produces primary afferent depolarization in a variety of large diameter afferent fibres, as well as post-synaptic effects in alpha motoneurones.
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The Journal of physiology · Jan 1971
Metabolic, respiratory and vasomotor responses to heating the scrotum of the ram.
1. Oxygen consumption, respiratory frequency, and temperatures of the rectum, common carotid artery, external auditory meatus, and skin on the ears, near the distal end of the metacarpus and metatarsus, upper thigh and mid-side of the body, were measured in five rams before, during and after heating the scrotum. Effects on the woolly animal exposed to ambient temperatures of 17-19 degrees C, and on the shorn animal exposed to ambient temperatures of 5.6-24.5 degrees C, were determined.2. ⋯ The inhibition of panting in the shorn sheep at environmental temperatures below 20 degrees C remains unexplained.7. Body heating alone, by covering the shorn animal with a sheep skin coat in an environment of 19 degrees C, elicited well organized vasomotor changes in the ears and lower legs.8. As a result of the present study and previous work by others, it is clear that all thermoregulatory mechanisms, with the exception of vasomotor changes, may be influenced in a predictable manner by temperature changes of the scrotum.
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1. A detailed theory of cerebellar cortex is proposed whose consequence is that the cerebellum learns to perform motor skills. Two forms of input-output relation are described, both consistent with the cortical theory. ⋯ Each olivary cell is stimulated by one or more receptors, all of whose activities are usually reduced by the results of stimulating the corresponding Purkinje cell.7. It is shown that if (2') is satisfied, the circuit receptor --> olivary cell --> Purkinje cell --> effector may be regarded as a stabilizing reflex circuit which is activated by learned mossy fibre inputs. This type of reflex has been called a learned conditional reflex, and it is shown how such reflexes can solve problems of maintaining posture and balance.8. 5(a), and either (2) or (2') are essential to the theory: 5(b) and 5(c) are not absolutely essential, and parts of the theory could survive the disproof of either.
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The Journal of physiology · May 1969
The nature and location of certain phasic mechanoreceptors in the cat's foot.
1. The locations of the receptor endings of twenty-two phasic, primary afferent units which could be excited by small (less than 40 mum) point displacements of cats' large foot pads have been determined by dissection.2. Eleven of these units had endings located within or immediately below the skin on the plantar surface of the pad; eight had endings located deep within the pad and three had endings on the digits.3. ⋯ It was shown by dissection that the endings of four of the PC type units were Pacinian corpuscles and such corpuscles were seen within 1 mm of the apparent location of six other PC receptors. Pacinian corpuscles were found close to only two of the eleven superficial receptor locations.5. It is therefore concluded that of the two functionally distinct types of phasic receptors studied, the PC receptors are Pacinian corpuscles located deep in the pad or on the digits, whilst the RA receptors are located within or immediately below the skin and are not Pacinian corpuscles.
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The Journal of physiology · Jan 1969
Muscular, bronchomotor and cardiovascular reflexes elicited by mechanical stimulation of the respiratory tract.
1. The effects of mechanical stimulation in the nose, epipharynx, laryngopharynx and tracheobronchial tree, and of chemical irritation of the nasal mucosa, were studied on various somatic and autonomic functions in cats.2. Action potentials were recorded from the diaphragm and rectus abdominis muscles of spontaneously breathing cats, and from the phrenic and lumbar nerves of paralysed, artificially ventilated cats. ⋯ Nervous activity in cervical sympathetic efferent fibres was increased by the stimulations, especially those of the epipharyngeal and laryngopharyngeal regions.6. There was good correlation in time and magnitude between the changes in total lung resistance and in bronchoconstrictor fibre activity, and also between the changes in blood pressure and in efferent sympathetic discharge, although the mechanical changes lagged behind the nervous ones.7. In anaesthetized, spontaneously breathing cats stimulation of the respiratory tract evoked large variations in blood pressure accompanying the spasmodic respiratory efforts, probably by mechanical effects.