Question

UNIT Section Date REVIEW Check Your Understanding Critical Thinking and Application Questions 1 Neurons are amitotic, which means that after a certain stage, they do not divide further. Most tumor cells are characterized by a rapid rate of mitosis. Considering this, of which cell types (neurons or neuroglia) must brain tumors be composed? Why? 2 You are examining a neuronal process and you find that it generates action potentials. Is this an axon or a dendrite? How can you tell? You are examining another neuron, and find that it has two processes, both of which generate action potentials. What is the structural class of this neuron? How did you come to this conclusion? 3 4 A traumatic brain injury may result in a large number of damaged or dying neurons. In such a case, which neurogli cell would you expect to be present in large numbers? Explain. Introduction to the Nervous SystemI UNIT 10

Answer 1

1. Brain consist of neurons and other non-neuronal cells such as glial cells. Neurons communicate with themselves and other cells of the body by sending and receiving electrical signals. Neuroglia are non-conducting cells that insulate and providing support to the neurons.

Neurons are cells that do not divide after certain time as they are non-mitotic. As they are not-capable of cell division, they cannot form tumors. Tumors are formed by abnormal cell division. Glial cell, conversely, can divide in adulthood. Hence, they undergo mitosis. Hence, glial cells can form tumors when mutated. Around 80% of brain tumors are caused by glial cells.

2. Neurons are composed of the dendrite, the soma and the axon. Action potentials are created at the axonic terminals. Dendrites receive electrical signals from axons. The action potential is generated by axon and received by the dendrite.

Axons are specialized for the conduction of action potential away from the cell bod. They conduct action potentials toward the axon terminus. Action potential are caused by depolarization of the plasma membrane due to influx of sodium ions. Dendrites receive these signals from the axon and transmit them to the soma or cell body. These electrical impulses will travel via soma to axon hillock. If they increase over the threshold value, an action potential is created at the axon.

As HOMEWORKLIB’s rule, only one question needs to be answered.