Neocortex Cell Types

Axons that decussate between the pyramids of the medulla oblongata belong to the ________ tracts.

Structure of Neurons There are 4 parts of a neuron that enables it to communicate with other neurons. Dendrites, the cell body, axons, and terminal buttons. 1. Dendrites are short, branchlike extensions and detect signals from neighboring neurons. 2.

The three main tissues that support and protect the CNS are commonly known as the meninges. They protect by preventing direct circulation of blood through the cells of the brain and spinal cord. These layers have elasticity within the tissues coating the CNS. In order the layers are the dura mater, the arachnoid layer, and pia mater. The last two layers have cerebrospinal fluid within which acts as a shock absorber to the brain. The cerebrospinal fluid transports hormones, white blood cells and nutrients to the cells of the

Stratum Granulosum is another shallow layer; it is made up 3 to 5 layers of flat packed grainy cells called kertaohylain cells which act similar to a water filter, to absorb any foreign bodies. This eases water loss and keeps up hydration in the skin.

Glial cells are the most numerous cells in the brain, outnumbering neurons nearly 3:1, although smaller and some lacking axonal and dendritic projections. Once thought to play a subpar role to neurons, glial cells are now recognized as responsible for much greater functions. There are many types of glial cells, including: oligodendrocytes, microglia, and astrocytes. Oligodendrocytes form the myelin sheath in the CNS, by wrapping themselves around the axons of neurons. Their PNS counterpart, Schwann cells, are also considered glial cells. This sheath insulates the axon and increases the speed of transmission, analogous to the coating on electrical wires. Microglia are considered to be “immune system-like”; removing viruses, fungi, and other wastes that are present. Astrocytes, however, are considered to be the most prominent. Their functions span throughout the brain, including, but not limited to: the synchronization of axonal transmission via G-protein-coupled receptors, blood flow regulation via the dilation of blood vessels, and the performance of reactive gliosis in conjunction with microglia. Both astrocytes and oligodendrocytes develop from neuroepithelial cells. Other types of glial cells include Radial glia, which direct immature neuron migration during development.

Then outer nuclear layer changes occur: photoreceptor cell death, death of interneurons, phagocytosis of dead neurons.

7. Myelin Sheath whitish fatty segmented sheath around most long axons. It protects the axon, electrically insulates fibers from one another , and increases the speed of nerve impulse transmition.

The three layers covering the brain are the Dura Mater, Arachnoid Mater and the Pia

3.The long tube-like structure that carries the neural message to other cells on the neuron is the axon.

That layer of cells forms a barrier between the capillaries and the cells and fluid of the brain.

The excitatory (glutamatergic) inputs to the hippocampal formation originate from the neurons in the different layers of the entorhinal cortex\cite {1}\cite{2}\cite{3}\cite{4}\cite{5}. The axons, projecting from the superficial second layer of entorhinal cortex to dentate gyrus and CA3, constitute for the perforant pathway and are strictly unidirectional and excitatory \cite{2}. Whilst layer II neurons of entorhinal cortex innervate the neurons found in dentate gyrus and the CA3 neurons, neurons from layer III of entorhinal cortex send their axons to subiculum and CA1. The granule cells, synonymously called principal cells, are located in the granule cell layer of dentate gyrus. Here, the granule cells send their axons, the mossy fibers, through

-Granular layer- 2 to 4 layers thick, the cells begin to die and flatten. It is the middle layer of

the epidermis, 5-6 layers of cork are seen. Cortex is 12-16 layered. In the middle

Neurons are highly polarized cells with specific morphology linked to their func-tional role. The long, single axon, multiple short dendrites and the tiny neurites that

It is about one fourth of a millimeter thick. It has nerve cell bodies. These bodies are separated by dendrites and axons. The layer at the back has the rods and cones. The middle layer is between the retinal ganglion cells and the rods and cones. The middle layer has three different nerve cells: bipolar cells, horizontal cells, and amacrine cells. Bipolar cells receive information from the rods and cones. Many of these go directly to the retinal ganglion cells in the front. Horizontal cells link rods and cones to bipolar cells. Amacrine cells connect bipolar cells and retinal ganglion cells. The front layer has the retinal ganglion cells. Each eye has about 125 million rods and cones. However, it only has one million retinal ganglion cells (Hubel,