Chapter 2 neurons and glia

Nervous systems vary in structure and complexity. There are several types of glia that serve different functions. In a cnidarians, nerve cells form a decentralized nerve net.

Glial cells of the b peripheral nervous system include Schwann cells, which form the myelin sheath, and satellite cells, which provide nutrients and structural support to neurons.

Glia are non-neuronal cells in the nervous system that support neuronal development and signaling.

structure of a prototypical neuron

Satellite glia provide nutrients and structural support for neurons in the PNS. The nervous system is made up of neurons, specialized cells that can receive and transmit chemical or electrical signals, and glia, cells that provide support functions for the neurons by playing an information processing role that is complementary to neurons.

Glia can be compared to the workers at the electric company who make sure wires go to the right places, maintain the wires, and take down wires that are broken.

Neuron cytosol

Along the axon there are periodic gaps in the myelin sheath. In animals exhibiting bilateral symmetry such as c planarians, neurons cluster into an anterior brain that processes information. These neurons are not found in vertebrates but are found in insects where they stimulate muscles or glands. Sequencing of human genome Genetic basis of many diseases of the nervous system Role of genetic engineering and gene targeting 12 The Prototypical Neuron— cont. Mollusks such as squid and e octopi, which must hunt to survive, have complex brains containing millions of neurons. When glia do not function properly, the result can be disastrous—most brain tumors are caused by mutations in glia. This insulation is important as the axon from a human motor neuron can be as long as a meter—from the base of the spine to the toes. Although glia have been compared to workers, recent evidence suggests that also usurp some of the signaling functions of neurons. For mammals, new neurons also play an important role in learning: about new neurons develop in the hippocampus a brain structure involved in learning and memory each day. The axon Axon hillock beginning Axon proper middle Axon terminal end Differences between axon and soma ER does not extend into axon. This number compares to 75 million in the mouse and million in the octopus.

This is distinctive from the PNS where a single Schwann cell provides myelin for only one axon as the entire Schwann cell surrounds the axon. Dendrites can have small protrusions called dendritic spines, which further increase surface area for possible synaptic connections.

neurons and glial cells difference

A pseudounipolar cell has a single process that extends from the soma, like a unipolar cell, but this process later branches into two distinct structures, like a bipolar cell. A neuron can be compared to an electrical wire—it transmits a signal from one place to another.

action potential

But neurons are also highly specialized—different types of neurons have different sizes and shapes that relate to their functional roles.

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Neurons and Glial Cells