Pyramidal cell

The pyramidal cells are a type of particularly large neurons. They get their name after the shape of its cell body, which appears dreizipfelig sectional image and thus resembles a pyramid or a cone. This cell shape occurs only in the cerebral cortex ( cerebral cortex ) and in the almond kernels of mammals, where it accounts for approximately 85 % of the nerve cells, the remaining 15 % are called stellate cells.

Morphology

Pyramidal cells are densely throughout the cortex to close as columns, mainly in the third and fifth cortical layer. Your fine dendrites are characterized by a rope ladder -shaped ( John Carew Eccles describes them " cartridges like a belt " ) arranged excitatory contacts with stellate cells, while the cell bodies sit predominantly inhibitory synapses. The axon branches Tapered in different directions, making tens of thousands of excitatory synapses on several, sometimes distant cells.

As a morphological feature of the pyramidal cell 's ability to be seen next to the large cell body to form very long connecting cables, which can be up to two meters long in the pyramidal tract. This longest axons of the body also have the largest cell bodies among the pyramidal cells, the Betz giant cells in the motor cortex.

Detailed information ( afferent )

Each pyramidal cell receives two different types of afferent excitation, specific and non-specific. The specific afferents lead, for example, the information from the sense organs from the thalamus to the cortex, they end at the cell body. The nonspecific excitations and inhibitions of pyramidal cells originate from the non-specific activation system ( ARAS ) of the reticular formation and travel from the thalamus via the basal ganglia to the cortex. Here they are only switched on stellate cells, which act in turn with a special rope-ladder- shaped synaptic connection on the dendrites of pyramidal cells. This nonspecific excitations from the reticular part of the thalamus are rhythmic and act synchronously over the whole cortex to the degree of alertness and attention activating or inhibitory, and if they are slower than 6 Hz, the cerebral cortex is put to sleep. In sleep the pyramidal cells respond to stimuli barely, only very strong " Weckreize " they bring to the excitement.

The electrical voltage fluctuations, which can be registered from the scalp with EEG, are the expression of this synchronous nonspecific excitations.

Networking

For the specific excitations of pyramidal cells is considered as in many places of the nervous system, the convergence - divergence principle, which states that each cell is excited by many others and even sends to many other neurons impulses. Thus every part of the cortex is connected across the bar with a mirror image of the other half of the brain, but the pyramidal cells also form far verfächerte compounds in the same page, links to the cerebellum, brain stem, etc.

The growth of these innumerable, incalculable compounds and the formation of synaptic contacts between pyramidal cells is particularly strong in the first months and years instead, it is the growth of neural networks, which are seen as carriers of memory function since the description by Donald O. Hebb.

• Cell type
• Telencephalon
• Nervous tissue