Neurons, geniculate ganglion

Koga T, Bradley RM. Biophysical properties and responses to neurotransmitters of petrosal and geniculate ganglion neurons innervating the tongue. J Neurophysiol 2000 84 1404-1413. 

The electrical pulse activity of geniculate ganglion neurons has been studied (8, In both the cat and the dog by recording discharges when the tongue was stimulated with various chemical solutions. In both the cat and the dog these chemosensory neurons have been divided Into a number of functional neural groups (9, ... 

Figure 6. Spontaneous and evoked spike activity recorded from taste neurons of the geniculate ganglion of the cat. The classification of the three different sensory neurons is indicated by Groups I, II, and III.

Figure 1. Diagram of the three cranial nerves and associated sensory ganglia that innervate taste buds. As illustrated, electrical recordings were taken from single neurons in the ganglia. Geniculate ganglion in facial nerve petrosal in glossopharyngeal nodose in vagus.

The fungiform papillae taste systems consist of taste bud receptors distributed on the fungiform papillae which are located on the anterior surface of the tongue and the peripheral sensory neurons in the geniculate ganglion of the facial nerve. These neurons collect sensory information relevant to the chemical nature of food substances in the mouth. This chemosensory information is encoded into a series of pulses and transmitted to the central nervous system over nerve fibers that stretch from the tongue to the central nervous system (Figure 3). These pulse trains can be measured electrically with microelectrodes in the... 

By flavor chemistry is meant the chemistry of the total complement of sensory responses elicited by a food or a food component. In human sensory research, the sensory responses are psychophysical sensations, whereas in neurophysiological studies the responses are measured from neurons. The flavor chemistry of the geniculate ganglion fungiform papillae taste systems would then consist of a description of the neural responses to foods and to the types of compounds present in food. The neural responses of both the dog and the cat have been examined with respect to the excitability of many of the compounds found in vertebrate tissues. The cat has been tested with more compounds than the dog, but the results will also apply in large part to the dog, since the two species are so similar with respect to the majority of the compounds considered. 

Neurotrophin 4/5 is not as well characterized as other members of the neurotrophin family. Much of what is known is derived from analysis of NT4/5 and TrkB knockout mice. Elucidating the actions of NT4/5 is complicated by virtue of the fact that both NT4/5 and BDNF exert their effects via the TrkB receptor. It appears that NT4/5 functions largely overlap with those of other neurotrophin family members, particularly BDNF. NT4/5 knockout mice are essentially normal, in contrast to BDNF knockout mice, which do not live long. NT4/5 is likely to have unique actions on a subpopulation of neurons in the nodose and geniculate ganglia, which are not supported by BDNF. Like BDNF, NT4/5 acts on sensory neurons and retinal ganglion cells, supporting their survival. 

Clinical evidence, lesion, and stimulation studies all point toward the participation of vitally important neural sites in the control of saccades, including the cerebellum, superior colliculus (SC), thalamus, cortex, and other nuclei in the brain stem, and that saccades are driven by two parallel neural networks [Enderle, 1994, 2002]. From each eye, the axons of retinal ganglion cells exit and join other neurons to form the optic nerve. The optic nerves from each eye then join at the optic chiasm, where fibers from the nasal half of each retina cross to the opposite side. Axons in the optic tract synapse in the lateral geniculate nucleus (a thalamic relay), and continue to the visual cortex. This portion of the saccade neural network is concerned with the recognition of visual stimuli. Axons in the optic tract also synapse in the SC. This second portion of the saccade neural network is concerned with the location of visual targets and is primarily responsible for goal-directed saccades. 

Ganglion cells are foe cell bodies of neurons. The axons of the ganglion cells form the optic nerve, which synapses in the lateral geniculate body of the mitl-brain. 

The retina contains photoreceptors which are connected to the ganglion cells via neuronal circuits. The ganglion cells axons form the optical nerve. Besides the optical nerve, the visual pathway encloses the optic chiasm and the LGN (Lateral Geniculate Nucleus). The main processing unit for visual perception is the terminal of the optical path The visual cortex, which contains visual stimuli responsive cells performing the final formation of mental representations of the perceived scene (see Fig. 1). It shall be noted that the fibres of the inner (nasal) and outer (temporal) part of the retina of each eye are separated in the optic chiasm and conducted to the same terminal in the visual cortex. Thus, the left hemisphere processes the right visual field of both eyes, whereas the right hemisphere processes the left visual... 

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