Efferent pathways

Fig. 2.20 Efferent pathways into bulb showing (a) cholinergic (ACh) fibres projecting to MOB from basal forebrain nuclei. AON = ant. olfactory nucleus, OT = olfactory tract, DB = diagonal band nuc. (from Davis et al., 1978). (b) Nor-Adrenalin input to AOB, via MFB pathway from brain stem centres (nuclei A1-2, A6) (from Keveme, 1971).

Enhancing the positive effects of serotonin and norepinephrine in the afferent and efferent pathways of the micturition reflex... 

The efferent pathways of the ANS consist of two neurons that transmit impulses from the CNS to the effector tissue. The preganglionic neuron originates in the CNS with its cell body in the lateral horn of the gray matter of the spinal cord or in the brainstem. The axon of this neuron travels to an autonomic ganglion located outside the CNS, where it synapses with a postganglionic neuron. This neuron innervates the effector tissue. 

Figure 9.1 The autonomic nervous system and its effector organs. The efferent pathways of this system consist of two neurons that transmit impulses from the CNS to the effector tissue, preganglionic neuron (solid line), and postganglionic neuron (dashed line). As illustrated, most tissues receive nervous input from both divisions of the ANS the sympathetic and the parasympathetic.

Mieda, M., Williams, S. C., Sinton, C. M. et al. (2004a). Orexin neurons function in an efferent pathway of a food-entrainable circadian oscillator in eliciting food-anticipatory activity and wakefulness. J. Neurosci. 24, 10493-501. 

Efferent pathway a neural pathway leading from the central nervous system to the periphery. 

FIGURE 12.1 The afferent and efferent pathways of the parasympathetic mechanism for enhancing the defecation reflex. 

Many of these effects can still be observed after pretreatment with kainic acid in the neostriatum (113). This treatment degenerates the neostriatal efferent pathways and by consequence also the neostriatal efferent part(s) of the nigrostriatal loop. Apparently postsynaptic dopamine receptors, if located on these striatonigral neurons play only a minor role in the regulation of dopamine synthesis and turnover in dopaminergic neurons and the major role has to be attributed to dopaminergic autoreceptors. 

Surmeier DJ, Kitai ST (1994) Dopaminergic regulation of striatal efferent pathways. Cur Opin Neurobiol 4 915-919. 

Arbuthnott GW, Mitchell MJ, Tulloch IF, Wright AK (1976) Efferent pathways from lateral hypothalamic neurones [proceedings]. J Physiol (Lond) 253 131P-132P. 

Figure 13.12. Afferent and efferent pathways of the hippocampus. Reprinted with permission of MRC Centre for Synaptic Plasticity, University of Bristol, 2005.

Afferent and efferent pathways of regulation of energy intake and expenditure. [Reproduced with permission from M, Rosenbaum, R. L. Leibel, and J. Hirsch. Obesity. N. Engl. J. of Med. 337 396 (1997).]... 

During the last 150 years the morphology of the cerebellum attracted numerous histologists. Its relatively simple structure, with its three-layered cortex and clearly defined afferent and efferent connections made it one of the favourite sites in the brain to test out new hypotheses on the connectivity, the development and chemical interaction in nervous tissue. We have attempted to review present knowledge about the external and internal morphology of the cerebellum and to relate the classical topography of the cerebellum to the more recently discovered chemical specificity of its neurons and afferent and efferent pathways. Not all what is new in the histochemistry of the cerebellum is relevant to a better understanding of its chemoarchitecture. This review, therefore, does not pretend to be complete. It is focussed on afferent and intrinsic connections of the cerebellum. The efferent connections of the cerebellum to the brain stem and the spinal cord have not been systematically covered. 

Before investigating two more detailed examples of potential misuse, it is necessary first to describe something of the structure of the human nervous system. This is divided into the central nervous system (brain and spinal cord) and the peripheral nervous system.46 Information from peripheral sense organs is received via afferent pathways and processed within the central nervous system. Output from the central nervous system is sent via efferent pathways to the somatic nervous system (muscles) and to the autonomic nervous system (heart, gut, glands, etc.). 

A direct link between the immune (thymus) and endocrine system via the brain has been proposed (Rebar, 1983 Hall and Goldstein, 1983). Such a link is supported by the observations that (1) efferent pathways between the central nervous system (CNS) and the immune system exist, (2) hypophysec-tomy alters immune responsiveness (i.e., prolongs skin graft and lowers antibody production), (3) thymic hormones such as thymosin aj and thymosin p4 are found in discrete areas of the brain, and (4) administration of thymic hormones alters endocrine hormone levels (Comsa et al., 1975 Rebar et al., 1980, 1981a,b Hall and Goldstein, 1983 Palaszynski et al., 1983 Healy et al., 1983). 

Major efferent pathways of the amygdala relevant to anxiety include ... 

Experiments of Dawes (22) on cats showed that the Veratrum apnea following intravenous injection is due to reflexes from special receptors in the lungs. Experiments of Heymans and de Vleeschhouwer (24) on dogs show that bradycardia by veratridine may be induced by three mechanisms, namely, reflexly by stimulation of the carotid body chemoceptors by a direct stimulation of the cardio-inhibitory vagal center and reflexly by stimulation of receptors located in the thorax, the afferent and efferent pathways being located in the vagi-aortic nerves. Hyperpnea may be induced by veratridine by stimulation of the carotid body chemoceptors. 

The central auditory system consists of the cochlear nuclei groups of brainstem nuclei including the superior olivary complex (SOC), nuclei of the lateral lemniscus (LL), and inferior colliculus (1C) and the auditory thalamocortical system consisting of the medial geniculate in the thalamus and multiple areas of the cerebral cortex. Figure 5.4 schematically indicates the nuclear levels and pathways. Efferent pathways are not shown. Page constraints prevent us from providing uniform detail for all levels of the auditory system. 

Nervous cells (neurons) can be connected by means of synapses which serve as switching units. An adequate stimulation of the neuron produces a nervous impulse through a shift in the ions which will be cancelled out metabolo-energeiically after approximately 1 ms the neuron again becomes receptive to stimuli. The peripheral nervous system consists of nerve pathways in the peripheral area sensitive nerves transmit stimuli from the environment and the body to the central nervous system (centripetal, afferent pathways). Motoric nerves transmit the commands of the central nervous system to the muscles (centrifugal, efferent pathways). 

Heidenhain had found that his vagally denervated pouch secreted a little juice when he put water or easily digestible food in the stomach through a fistula, and he surmised that secretion was the result of a reflex carried in the sympathetic nerves accompanying blood vessels to the pouch. Pavlov and Schumowa-Simanovskaya said that secretion still followed sham feeding in a dog whose splanchnic nerves had been cut therefore the efferent pathway is in the vagus nerve alone." ... 

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