The process of respiration

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Trachea

Hospital Corpsman Revised Edition

The Neuron

THE PROCESS OF RESPIRATION
The rhythmical movements of breathing are controlled by the respiratory center in the brain. Nerves from the brain pass down through the neck to the chest wall and diaphragm. The nerve that controls the diaphragm is called the phrenic nerve; the nerve that controls the larynx is the vagus nerve; and the nerves that control the muscles between the ribs are the intercostal nerves.

The respiratory center is stimulated by chemical changes in the blood. When too much carbon dioxide accumulates in the blood stream, causing the blood to become acidic, the respiratory center signals the lungs to breathe faster to get rid of the carbon dioxide.

The respiratory center can also be stimulated or depressed by a signal from the brain. For example, changes in one's emotional state can alter respiration through laughter, crying, emotional shock, or panic.

The muscles of respiration normally act automatically, with normal respiration being 14 to 18 cycles per minute. The lungs, when filled to capacity, hold about 6,500 ml of air, but only 500 ml of air is exchanged with each normal respiration. This exchanged air is called tidal air. The amount of air left in the lungs after forceful exhalation is about 1,200 ml and is known as residual air.

THE NERVOUS SYSTEM

LEARNING OBJECTIVE: Identify the components and function of a neuron, recall the process of impulse transmission, and identify the components and functions of the central and peripheral nervous systems.

The activities of the widely diverse cells, tissues, and organs of the body must be monitored, regulated, and coordinated to effectively support human life. The interaction of the nervous and endocrine systems provides the needed control.

The nervous system is specifically adapted to the rapid transmission of impulses from one area of the body to another. On the other hand, the endocrine system, working at a far slower pace, maintains body metabolism at a fairly constant level.

In this section, you will study the neuron, the basic style="mso-spacerun: yes"> functional unit of the nervous system. Also, you will study the components and functions of the different divisions of the nervous system. The nervous system is divided into two major groups, the central nervous system (CNS) and the peripheral nervous system (PNS). Another division of the nervous system is the autonomic nervous system (ANS), which is further subdivided into the sympathetic and parasym- pathetic nervous systems.