2 6 2015 Types of Neurons figure 6 4 Type Afferent Efferent Parts in PNS Body most of axon Most of axon Info Direction From receptor or stimulus To effector ex muscle gland neuron Relays between afferent and efferent Parts in CNS Small portion of axon 1 Small portion of axon 10 body dendrites All by definition 200K Interneurons n a CNS encompasses all of our interneurons For every one afferent neuron you have 10 efferent and 200K interneurons That mean we have more efferent than afferent neurons There are less sensory neurons than there are control neurons The cell body is in the middle of the axon That is why there are no dendrites Afferent Synapse Types Synapse connection between neurons Electrical o Via gap junctions o Fastest o Much faster than the chemical one o But the signal meanders back and forth before it gets there It can go either way Chemical o Slower o There is a space between neurons where neurotransmitters are released and bind to receptors on the other cell o Most common even though its send signals slower In theory it should be the electrical ones but the big gain with the chemical signals is that the communication can only travel in one direction so in the end communication with chemical is faster o Faster if we are talking about the overall process o One way o Composition Presynaptic and postsynaptic Most neurons are presynaptic and postsynaptic It depends on which synapse you are talking about Interstitial fluid between neurons o Terms Convergence pre post More presynaptic communication with one postsynaptic Figure 6 25 2 6 2015 Divergent pre post Less presynaptic than postsynaptic Membrane Potential know this charged components Electrical Charge separation across Plasma Membrane due to distribution of o Figure 4 11 o Ex most cells higher negative charge on the inside Inside of cell is slightly negative Electrochemical Gradient o Net gradient concentration gradient electrical gradient Directions could be Same ex sodium Opposite ex potassium o Concentration Sodium wants to move into the cell because the concentration is higher outside o Electrically sodium want to move inside the cell because the inside is negatively charge o Basically vector addition one will have a bigger influence than the other o Concentration potassium wants to move out of the cell because there is less potassium outside o Electric potassium wants to move into the cell because it is positively charged and the inside of the cell is negatively charged o One will dominate o Need to know sizes of gradients
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