The nervous system pdf

Neurons and Nervous Systems 1! Some humans enjoy stimulating their fear response through risk-taking behaviors. How does the aforementioned relate to how a small brain tumor so dramatically affect personality and behavior? Nervous Systems Consist of Neurons and Glia The nervous system is composed of the central nervous system CNS and peripheral nervous system PNS , which together form the network that transmits impulses among the body, coordinating both voluntary and involuntary actions.

The nervous system has two types of cells: 1. Thus, neurons are excitable. A nerve is distinct from a neuron. A nerve is a bundle of axons that is composed of the axons of manny different neurons nerve cells whereas a neuron is a single nerve cell. Neurons and Nervous Systems 2! Until recently, it was believed that animals, including humans, were born with all of their neurons.

However, recently neurogenesis the growth and development of nervous tissue has been discovered to occur due to new experiences and as the result of exercise. It is an expanding area of research. Glia support, nourish, and insulate neurons. What if your arms seemed to wander unless you kept an eye on them. This is the exact situation that Christina found herself in after waking up one morning. I feel weird—disembodied. This integral part of her nervous system had suddenly deteriorated.

Because the sense of body positioning is determined by three things: vision, balance organs, and proprioception, which she had lost, Christina learned to control her body with her eyes, but she found that she could do nothing without using her eyes. In fact her body would collapse into a heap the minute she closed her eyes. Gradually over time Christina learned to walk again and to function with the usual business of life, but only with great care in maintaining attention to the particular movement and never at the same level as before.

She found that there was no in between, or gradual change with movement. Strict focus had to be maintained for even the simplest tasks. The nervous system coordinates voluntary and involuntary actions in the body by sending and receiving information. The nervous system is comprised of an enormous number of cells over billion , primarily of two types: neurons the signaling units and glial cells the supporting units.

However, nervous system function is mostly a story of the neuron. The neuron is the functional unit of the nervous system and is designed to transmit information between cells. Interestingly, neurons with a particular function are found in a predictable location. This regularity in structure has permitted neurobiologists to categorically organize the nervous system based on location and function see figure below.

Thus, the nervous system can first be divided into two major parts: the central nervous system CNS and the peripheral nervous system PNS.