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Biomedical subjects

H P Koepchen

Publications and source records attributed to H P Koepchen.

At least 19 recordsLinked to original sources
PubMed1996

Convergence of visceral and somatic afferents on single neurones in the reticular formation of the lower brain stem in dogs.

The reticular formation of the lower brain stem contains neuronal circuits for the generation of sympathetic tone, respiratory rhythm, muscle tone and the control of vigilance. In anesthetized dogs single neurone activities were recorded in the medial two-thirds of the reticular formation to investigate the organizing principles of this multifunctional system. The results from 110 recordings demonstrate that single neurones receive information from somatosensory afferents of skin, joints and muscles together with afferents from baro-, chemo- and lung inflation and deflation receptors. Whereas the composition of afferent spectra from somatosensory sources was different from neurone to neurone, baroreceptors had a more generalized activity-decreasing effect and chemoreceptors had a generalized activity-increasing influence, the former directing physiological systems to a trophotropic and the latter towards an ergotropic state. The functional significance of the results for the co-ordination of different physiological systems is discussed.

Afferent Pathways↗
PubMed1981

Neurophysiological background of central neural cardiovascular-respiratory coordination: basic remarks and experimental approach.

This paper is comprised of a review of past contributions and their theoretical consequences and a presentation of new results in studies of the origin of sympathetic rhythms and tone. Two basic mechanisms are involved: a primary intracentral coupling with the main cardiovascular-respiratory rhythm (MCRR) generator and a secondary reflex coupling. It was found that the activity and rhythms of certain sympathetic efferents, such as the cervical sympathetic, are closely related to the MCRR. Other efferents, such as the renal sympathetics, are loosely linked and follow drives from other circuits in the genesis of their rhythms and tone. New experimental evidence is given that rhythmic and tonic activity in sympathetic nerves originates from several sources. Hence central respiratory-autonomic systems interaction is not explained by simplistic concepts.

Animals↗
PubMed1977

Nucleus of the solitary tract and the J reflex.

Experiments were carried out on cats anaesthetized with chloralose-urethane with a view to defining certain central pathways for the J reflex elicited by the right atrial injection of phenyldiguanide. The resulting motor inhibition was manifested by reduction in the amplitude of the knee jerk. The dorsal surface of the medulla was exposed and free riding platinum quartz electrodes were introduced into the nucleus of solitary tract. Lesions were made in the NTS by passing current of know intensity through the electrodes. The J reflex was abolished by bilateral lesions in the NTS. It was concluded that the nucleus of solitary tractisan essential part of the central pathway of the J reflex.

Animals↗
PubMed1973

Mechanisms of central transmission of respiratory reflexes.

Several types of respiratory reflex actions can be discerned according to the reactions of typical respiratory neurons in the efferent part of the central rhythmogenic structure. Whereas respiration runs closely parallel with inspiratory neuron activity the behaviour of expiratory neurons cannot be derived from the resulting reflex changes of respiration. So expiratory apnoea can be combined with continuous activity or with inactivation of expiratory neurons. Extracellular records from a closed uniformly reacting population of expiratory neurons and from neighbouring reticular neurons allowed experimental differentiation between different types of central respiratory reflex actions. In experiments on anaesthetized dogs the responses to chemoreceptor and baroreceptor excitation and to pulmonary inflation were investigated. Chemoreceptor excitation leads to activation of inspiratory, expiratory, and reticular neurons, whereas the baroreceptor afferents act in the opposite direction. In contrast moderate lung inflation causes more specific effects: activation of expiratory neurons, inactivation of inspiratory neurons. But if a certain degree of lung inflations is exceeded a more general inhibition of both inspiratory and expiratory neurons takes place. These results only apply to the "typical" respiratory neurons. The principles used to distinguish between the different types of reflexes are proposed for a basis of classification also of other neural, chemical or pharmacological influences on breathing.

Animals↗