An axon often has to navigate great distance to reach its target cell (ie, another neuron or muscle fiber) and establish the synaptic connection. This process is axonal pathfinding. The axon does not navigate its natural pathway due to any single cue, but via combinations of signals. This redundancy makes axonal pathfinding extremely complex. Axonal [...]

The nervous system has three levels of organization: Level Overview Neuron At the most simple level is the neuron. A neuron is a large, complex cell designed to propagate and transmit chemical and electrical signals to other cells such as muscle fibers or fellow neurons. Local Circuit Within local circuits, interconnected nerve cells elaborate incoming [...]

Voltage is the tendency for electrically charged particles such as electrons or ions to move between two points. The principle of voltage is the foundation for action potentials. The action potential is a wave of depolarization of a neuron’s plasma membrane. This depolarization requires a resting membrane potential of about -70 millivolts, with the interior [...]

The Sodium/Potassium Pump puts Na+ outside the cell and K+ inside the cell. 3Na+ mols inside bind to receptor This stimualtes phosphorylation of receptor by ATP. This alters receptor shape, shape change dumps Na+ onto inside. Open receptors bind 2K+ ions outside. K+ binding triggers phosphate release. This restores original conformation. K+ released inside, NA+ [...]

All but one type of neuroglia (glial cells) are derived from same ectoderm that produces neurons. Most organs are from the mesoderm. There are six categories of neuroglia: Neurolemmocytes (Schwann cells) form myelin layers around axons in the PNS. Oligodendrocytes form myelin layers around axons in the CNS. Microglia are derived from mesoderm and remove [...]

Neurons cluster together to form ganglia. Usually, one ganglia is larger and more central than others. This ganglia is called the brain. In vertebrates, most cells of the nervous system are found in the brain and spinal cord. This is where most information processing, storage and retrieval occurs. Neurons vary considerably in size and shape, [...]