Neurons have physiology {neuron, physiology}.
signals: initiation
Neurotransmitter reception reduces membrane voltage. Membrane voltage reduction spreads. At axon hillock, membrane voltage can reach threshold voltage, causing depolarization spike, which initiates depolarization-spike traveling wave down axon.
Perhaps, only one dendrite-and-cell-body membrane potential distribution can cause initiation. Only one distribution can reach threshold potential. One distribution has much higher probability than others, because it can happen in the most ways. Dendrite and cell body changes can change distribution. Perhaps, neuron groups also detect only one input distribution.
signals: firing rate
Neuron input to neuron-firing rate ratio is linear or S-shaped.
conduction rate
Non-myelinated-axon conduction rate is between 0.5 and 2 meters per second, 1 millimeter per millisecond. Myelinated-fiber conduction rate is between 2 and 120 meters per second, 10 millimeters per millisecond, and is faster because signals jump from one Ranvier node to the next {saltatory conduction, myelin}.
Conduction rate in axons varies irregularly.
Faster impulse conduction became necessary as animals became larger.
conduction rate: synapse
Conduction rate across synapse is one micrometer per millisecond. Irregular synapse sizes and neurotransmitter-packet release times vary conduction rate.
Post-synaptic decay takes up to ten milliseconds.
conduction rate: synchronization
Information-flow rates along axons, synapses, and receptors change typically do not synchronize with rates on other axons, synapses, and receptors.
neuron growth
Neurons grow, differentiate, migrate, and extend axons and dendrites, at different rates. Extracellular substances, cell-membrane molecules, and cell and axon spatial arrangements affect growing axons. Cell-membrane-molecule and extracellular-substance gradients change over time. Target neurons grow and mature in coordination with axon growth.
neuron growth: direction
Adhesion-glycoprotein neurotrophins guide growing nerve processes to appropriate target neurons.
neuron growth: process
First, several axons travel over relatively short distance. After axons stop extending, they produce multiple branches, which form many connections. Branch retraction and synapse reduction then reduce connections. First nerve impulses, which are possibly synchronous, refine axon connections [Thompson, 1940] [Wolpert, 1977].
nutrition
Nerve cells need glucose and oxygen, because they have no substitute biochemical pathways.
plasticity
Neuron number, spatial arrangements, diameters, composition, lengths, types, controllers, molecules, membranes, axons, dendrites, cell bodies, receptors, channels, synapses, threshold voltages, and packet number can change. Receptor number, type, effectiveness, and position can change.
plasticity: repair
After brain damage, nearby axons invade damaged region to make new circuits, and axons try to contact nearby dendrites.
Biological Sciences>Zoology>Organ>Nerve>Neuron>Physiology
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Date Modified: 2022.0224