Neuron axon, diagram

FIGURE 50-1 A schematic diagram of the olfactory epithelium. The initial events in odor perception occur in the olfactory epithelium of the nasal cavity. Odorants interact with specific odorant receptors on the lumenal cilia of olfactory sensory neurons. The signals generated by the initial binding events are transmitted along olfactory neuron axons to the olfactory bulb of the brain. 

Figure 303. Neuron. This diagram is drawn to scale for a neuron with a 1-cm axon (the axon is folded for diagrammatic purposes). Many PNS axons may be more than a meter in length. (From C. F. Stevens. The neuron. Sci. Am. 241, 54, 1979.)...

Figure 1. A. SimpMed diagram of the rodent hippocampal formation illustrating the major glutamatergic circuitry. The principal neuronal helds granule cells (GC) of the dentate gyrus and pyramidal cells of CAl and CA3 in Ammon s horn are shown. The main excitatory connections are also indicated the perforant path from entorhinal cortex to the granule cells, from there the mossy hbre (mf) axonal projections to CA3 and then the Schaffer collaterals (Sch) from CA3 to ipsilateral CAl and commissural (Comm) to contralateral CAl cells. Evoked responses in (B) were obtained by stimulating the afferent pathway from entorhinal cortex, the medial perforant path (Med), and recording the granule cell (GC) response in the hilus of the dentate gyrus.

Schematic diagram of a primary afferent neuron mediating pain, its synapse with a secondary afferent in the spinal cord, and the targets for local pain control. The primary afferent neuron cell body is not shown. At least three nociceptors are recognized acid, injury, and heat receptors. The nerve ending also bears opioid receptors, which can inhibit action potential generation. The axon bears sodium channels and potassium channels (not shown), which are essential for action potential propagation. Synaptic transmission involves release of substance P, a neuropeptide (NP) and glutamate and activation of their receptors on the secondary neuron. Alpha2 adrenoceptors and opioid receptors modulate the transmission process.

Pathways in the central nervous system. A shows two relay neurons and two types of inhibitory pathways, recurrent and feed-forward. The inhibitory neurons are shown in black. B shows the pathway responsible for presynaptic inhibition in which the axon of an inhibitory neuron synapses on the axon terminal of an excitatory fiber. C Diagram illustrating that dendrites may be both pre-and postsynaptic to each other, forming reciprocal synapses, two of which are shown between the same dendrite pair. In triads, an axon synapses on two dendrites, and one of these dendrites synapses on the second. In serial synapses, a dendrite may be postsynaptic to one dendrite and presynaptic to another, thus connecting a series of dendrites. Dendrites also interact through low-resistance electrotonic ("gap") junctions (two of which are shown). Except for one axon, all... 

Figure 7 Schematic diagram demonstrating the connection system between the nasal odor receptors and the (main) olfactory bulb. Sensory neurons expressing identical odorant receptors converge their axons to a limited number of defined glomeruli. AOB, accessory olfactory bulb NC, neocortex. Reproduced from K. Mori H. Nagao Y. Yoshihara, Science 1999, 286, 711-715, with permission from AAAS.

Fig. 2. Diagrams of the cerebellar circuit. Inhibitory neurons are indicated in black. A. Main circuit. B. Cortical interneurons and recurrent pathways. Abbreviations B = basket cell cf = climbing fiber G = Golgi cell GR = granule cell 10 = inferior olive mf = mossy fiber nc = nucleocortical axons no = nucleo-olivary axons pcc = recurrent Purkinje cell axon collaterals P cell = Purkinje cell PCN = precerebellar nuclei pf = parallel fiber pi = pinceau of basket cell axons S = stellate cell UBC = unipolar brush cell I = extracerebellar mossy fiber 2 = nucleo-cortical mossy fiber 3 = mossy fiber collateral of uni-polar brush cell.

Fig. 4. Two examples (A and B) of corticostriatal neurons of the type which provide a projection to the pyramidal tract and a collateral to the striatum. These layer 5 neurons have several axon collaterals which arborize both locally in the area immediately around the parent cell and collaterals which extend to neighboring cortical areas. A The neuron depicted in (A) is diagrammed in a sagittal section of the brain showing its axon collateral in the striatum. The striatal axon issues only a few branches which make relatively focal arborizations. Adapted from Cowan and Wilson 1994.

Fig. 10. A) Diagram of a large aspiny striatal neuron that had been intracellularly filled to reveal its dendrites (black) and axon collateral that arborizes within the striatum (gray). From Wilson et al., 1990. B) Distribution of large aspiny striatal neurons labeled with choline acetyltransferase (ChAT) immunoreactivity in a coronal section of the striatum. The patch compartment was labeled in an adjacent section with calbindin immunoreactivity.

Fig. 13. A) Diagram showing an example of inputs to the globus pallidus (GP) from striatal spiny projection neurons. Typically there are two major sites of axonal arborization, one in the region immediately adjacent to the striatum and a second in the central region of the GP. B) Stylized drawing of two pallidal neurons showing how the dendrites of neurons are confined within the two regions of the GP that conform to the pattern of striatal inputs. C) The axonal projection of a globus pallidus neuron of the type with discoid dendrites, which provides collaterals to the striatum (CP), to the entopeduncular nucleus (EP), subthalamic nucleus (stn) and substantia nigra (SN). Adapted from Kita and Kitai 1994.

Figure 1.5 Diagram of neuron. The neuron carries messages to other neurons via an axon, which is often myelinated to increase the speed of the message. The end of the axon has terminals that release neurotransmitters. The neuron receives messages from its dendrites, which are spiny processes much shorter in length than the axon.

Fig. 1. Schematic diagram outlining the neurotrophic theory of cell death. Neurons extend axons in the presence of a low circulating level of neurotrophic factors. At a critical point in their development, usually corresponding to the period of target tissue innervation, the neuron becomes acutely dependent on the neurotrophic factor for its survival. At this stage those that make appropriate connections in the periphery obtain sufficient factor for their survival. Those not making correct connections do not obtain sufficient factor and die.

A neuron, or nerve cell, is an example of an excitable cell. These cells have cell bodies (or soma) containing the nucleus and elongated processes called axons and dendrites. These cells form a complex web with many connections. Figure 11 shows a schematic diagram of a connection between two such nerve cells. The presynaptic neuron is separated from the postsynaptic neuron by a small gap known as the synapse, typically 2-800 A wide. Presynaptic nerve endings contain small sacs or vesicles filled with one of several compounds called neurotransmitters. The postsynaptic neuron has receptor sites for specific neurotransmitters located on the cell membrane. When appropriately stimulated, and area of a presynaptic neuron membrane becomes depolarized (the transmembrane potential becomes more positive). The depolarized area propagates down the axon very rapidly. This wave-like movement of depolarization is called the action potential. When the depolarized areas reaches the nerve ending, the vesicles move to the cell wall, fuse with it, and dump their contents into the synaptic cleft—a process called exocytosis. (Exocytosis is accepted as the mechanism of neurotransmitter release in the peripheral nervous system, but it has not yet been demonstrated... 

Fig. 2.3 Olfactory pathways in the antennal lobe. Axons from pheromome sense cells terminate in the macroglomerulus whereas axons from other olfactory cells project to numerous ordinary glomeruli . Second-order cell bodies are located in the medial and lateral neuronal clusters of the antennal lobe. Axons from output neurons in these clusters form the tractus olfactorio globularis, which project to the calyces and lateral lobe of protocerebrum. The diagram is modified after Boeckh and Boeckh (1979) who found that second-order neurons in Antherea sp., responding to pheromones, were located exclusively in the medial clusters. However, in Manduca sexta, Matsumoto and Hildebrand, have revealed that output neurons with dendritic arborizations in the macroglomerulus are located in both clusters.

Fig. 1. Schematic diagram of a neuron. D dendrites or input processes of cell. C - cell body. A - axon or output process of cell. 

---