Structure of nerve cells
When we touch an object, see something or feel the wind on our skin, our body makes sure that this excitement is perceived by us. External stimuli must be somehow 'packed' and directed to the brain. For our brain is, so to speak, the control center for all processes: automatic, such as automatic. Perception (seeing, smelling, hearing, tasting), but also reacting and independent processes such as targeted movements of our body.
The task of transmitting stimuli is carried out by nerve cells (also known as neurons) occurring throughout our body. Our brain alone has about 1,000,000,000,000 (one trillion!) Nerve cells and can save, almost theoretically, almost infinitely much information by recombining the connections between the nerve cells.
But how exactly does such a nerve cell look like and how does it work?
Suppose we are touched by someone's hand. So-called dendrites take these body stimuli over a wide branch system and lead them to Zellkцrper (Soma) the nerve cell continues. On the Soma is the Axonhьgelthat touches the axon. In the axon hillock, the excitations picked up by the dendrites accumulate. However, the excitement is only forwarded if a certain electrical potential is exceeded. If every little electrical potential were passed on from outside, we would have to process so many sensory impressions that we would hardly be able to live. If the electrical stimuli exceed a certain threshold potential, transmission of the excitement via the axon occurs. To that Axon around are lipid-rich cells that electrically isolate the axon from the environment. These cells are also called Schwann cells referred to and consist of the fat-rich myelin.
In regular intervals, the Schwann cells of the Ranvier's Schnürring interrupted. The excitement flowing over the axon is passed from one ring to the other through the different tension on the un-isolated Ranvier rings. Invertebrates have neither Schwann cells nor Schnürrringe, so that the excitation line runs continuously with them. The process of 'leaping' stimulation conduction (saltatory excitation conduction) is the same in all vertebrates, and is clearly superior to continuous excitation in terms of speed.
At the end of the axon are the presynaptic end caps, At this point, the electrical stimulus is transformed into a chemical. Upon reaching the stimulus at the endknöpfe, this neurotransmitter shakes in the synaptic cleft out. The neurotransmitters dock to the receptors of the next dendrites (postsynaptic membrane) and thus provide an opening of the ion channels at the dendrite. This leads to a voltage change and thus to a forwarding of the electrical pulse. From the chemical reaction in the synaptic gap, accordingly, an electrical impulse has again become on the subsequent dendrites. The whole process is repeated now.
Survey of the components of the nerve cell
Soma (Greek = body): designates the body of the nerve cell
nucleus: is located in Soma
dendrit: extinctions emanating from soma; Excitations from other nerve cells are taken up via the dendrites and transmitted to the soma.
Axonhьgel (greek = axis): starting point of the axon; Postsynaptic signals accumulate at the axon hillock and then provide a transmission of the impulse to the axon
Axon: long nerve cell process, which transfers the electrical stimuli from the soma to the next nerve cell
myelin sheath: surround the axon and provide electrical isolation; the myelin sheath consists of the Schwann cells (glial cell), which are interrupted by the Ranvier Schnürrringen
Ranvier's Schnürringbetween two Schwann cells there is a Ranvier lace ring; The fact that these places are not isolated, the action potential can run faster. The stimulus jumps from a piercing ring to a piercing ring (Saltatoric excitation line)
Synaptic Endknöpfe: at the synaptic end-point the electrical stimulus is transformed into a chemical reaction; Neurotransmitters are released into the synaptic cleft, from there they bind to receptors of a postsynaptic neuron, thus transmitting the response to the next neuron