Do the Extraocular Muscles in the Carp Compensate for Eye Displacements Induced by Respiratory Movements?

The eyes in normally respiring carp are induced by elements of the respiratory pumping system to make small displacements in phase with the respiratory cycle. The ocular movements were studied by film analysis during the normal respiratory cycle and the cough. In the course of the movement, the optic axis remains nearly parallel to its starting position. This results in a smaller retinal image shift than would be produced by angular movements. Electromyography of the extraocular muscles showed that the external rectus and superior oblique muscles contribute to image stabilization during strong respiration, and the external rectus and the superior oblique muscles contribute during the cough

Anatomy of Respiratory Rhythmic Systems in Brain Stem and Cerebellum of the Carp

The afferent and efferent connections of two respiratory rhythmic loci in the dorsal mesencephalic tegmentum were studied by retrograde and anterograde transport of horseradish peroxidase. The injection areas were determined with extracellular activity recording using HRP filled glass micropipettes, and then followed by electrical stimulation and subsequent iontophoretic HRP delivery. One area in the nucleus of the posterior commissure was found to be optic related respiratory in nature and possessed afferents from optic tectum, pretectal nuclei, preoptic nucleus and the bulbar reticular formation. An extensive set of efferents is present to the torus longitudinalis, nucleus rotundus, corpus cerebelli and the various levels of the reticular formation. The second respiratory rhythmic area was localized in the vicinity of the oculomotor nuclei. This area receives afferent information from corpus cerebelli, vestibular nucleus and reticular formation, and has efferent connections to corpus cerebelli, preoptic nucleus and a major projection to the various parts of the reticular formation. Stimulation of both areas resulted in respiratory movements of the lower jaw and the opercula. Several injections in the corpus cerebelli resulted in retrograde labeling in the nucleus of the posterior commissure, which suggests the involvement of cerebellar circuits in optic related respiratory reflexes.

The role of mesencephalic neurons in the interactions between the medullary respiratory center and other systems in the carp, Cyprinus carpio L.

De sturing van de ademhaling bij de karper wordt verzorgd door het primaire ademregelsysteem gelegen in de medulla oblongata. Het ademhalingsritme ontstaat onder invloed van input van de ademritmegenerator op de motoriek en wordt gemoduleerd door input van de perifere terugmelding van het proprioceptieve systeem. In de normale situatie bij een intact dier hebben andere hersendelen een belangrijke invloed op dit primaire ademregelsysteem, terwijl dat op zijn beurt weer andere functies in de hersenen en andere systemen beinvloedt. Enkele van deze interacties zullen in dit proefschrift nader worden belicht. ... Zie: Samenvattin

Inhibitory commissural connections of neurones in the trigeminal motor nucleus of the rat

Physiological evidence is presented for the existence of commissural fibres that cross the midsagittal plane in the medulla of the rat at the level of the trigeminal motor nucleus (Mo5). These fibres, which have their origin in the Mo5, terminated in the contralateral Mo5. Small inhibitory postsynaptic potentials were recorded in jaw-closing motoneurones by electrical activation of the commissural fibres; jaw-opening and fusimotorneurones as well as the jaw-closing and jaw-opening reflex were not affected. Electromyographic recordings from jaw-closing and jaw-opening muscles in the unrestrained rat showed that masseter activity was inhibited by the commissural fibres. These trigeminal commissural connections might play a part in the co-ordination of bilateral activity of the jaw-closing musculature during unilateral chewing

Perception of forces exerted by jaw and thumb

By comparing the results of force matching between the jaw and the thumbs, whether subjects have any knowledge about the magnitude of exerted forces irrespective Of the motor system was studied. Subjects were asked to match isometric forces of their own choice exerted by flexion of one of the thumbs with the jaw, and the other way around. The results were compared with control experiments in which subjects matched forces exerted by flexion of one of the thumbs with the other thumb and vice versa. None of the subjects was able to match correctly in all experimental conditions. All subjects displayed inconsistent matching behaviour, showing a mixture of correct matching and mismatching. This holds both for absolute matches (in N), and for matches relative to the maximal forces. The results show that knowledge about the magnitude of exerted forces is different for the jaw and the thumbs. Sensations about isometric forces exerted by the jaw or the thumbs are different within each subject and from subject to subject.</p

Localization of motoneurons innervating the muscle of the hard palate in the rat: A horseradish peroxidase study

Using the horseradish peroxidase-technique, the myotopical arrangement of motoneurons innervating the transverse palatine muscle in the rat was studied. It appears that this muscle is innervated by axons from cells located in the ipsilateral intermediate subnucleus of the facial motor nucleus. By nerve transection and electrophysiological experiments it is shown that the transverse palatine muscle is innervated by the inferior as well as the superior buccolabial branch of the facial nerve

Brainstem influences on biceps reflex activity and muscle tone in the anaesthetized rat

This study analyzes the effect of electrical stimulation of the locus coeruleus (LC) and adjacent brainstem structures on the tonic reflex (TVR), the tonic stretch reflex (TSR) and on muscle tone (MT) in anaesthetized rat. Increases in TVR. TSR and MT of the m. biceps were evoked from regions rostrally and ventrally of LC, the caudal pontine reticular nucleus. the cuneiform nucleus and from the ventral paris of the colliculus inferior. Stimulation of the LC did not influence biceps EMG activity. The results indicate that the observed facilitation of muscle activity is due to stimulation of parts of the mesencephalic locomotor region. It is discussed that the recorded increase in TVR. TSR and MT possibly is due to an excitatory action on alpha-motoneurones on one hand and to an enhanced fusimotor drive on the other

Respiratory Neuron Activity in the Mesencephalon, Diencephalon and Cerebellum of the Carp

The functional properties, localization and connections of neurons with a respiratory-rhythmic firing pattern in the mesencephalon, diencephalon and cerebellum of the carp were studied. Some neurons acquire respiratory rhythm only as a side effect of respiration via sensory stimulation by movements or water current. In other neurons, however, the rhythm is the result of nervous input from the respiratory center. These were studied in more detail. Three categories were distinguished: 1. Plain respiratory neurons. None of the stimuli used could influence the firing pattern of these neurons. 2. Respiratory-optical neurons, which receive both respiratory and visual input. 3. Respiratory-movement-sensitive neurons, the firing pattern of which is sensitive to stimuli influencing the respiratory movements. The respiratory-optical neurons are argued to be components of a system correcting the visual image for respiration-induced displacements of the eyes. The movement sensitive neurons appear to process proprioceptive information at a level, where the demands on the cranial muscles of respiratory and other movements are integrated. The plain respiratory neurons, at least partly, can be regarded as interneurons between the respiratory center and the systems mentioned above.