Nursing Entrance Exam

Equilibrium The semicircular ducts convey information about rotational movements of the head and the sensory receptors located in the ducts respond to these movements. These hair cells are active during a movement and are quiet when the body is still. For example, when you turn your head to the left, receptors stimulated in the semicircular ducts tell you the rapidness and direction of the movement. The saccule and the utricle express information about your position (with respect to gravity). Here is another example: if you were to stand with your head tilted to one side, the saccule and utricle receptors report the angle and whether your head tilts forward or backward. The saccule and the utricle are also activated by sudden acceleration. When your car accelerates from a stop, the saccular and utricular receptors give you the impression of increasing speed. 7.3 The Endocrine System – Tour of the System The endocrine system is an amazingly complex system with many important roles throughout the body. It works alongside the nervous system to coordinate functions of all of the different body systems. The endocrine system contains endocrine glands that release their products (known as hormones) directly into the bloodstream. Hormones are substances that rouse the body into activity.Hormones are often dependent upon one another in their action; that is, the secretion of one hormone will often excite another gland to also produce its hormone. The balance that the body strikes with these hormones is unique for each individual. A hormone released into the bloodstream is distributed throughout the body. Each hormone has target cells, which are specific cells that possess the receptors needed to bind and “read” the hormonal message when it arrives; however, all cells throughout the body are exposed to them whether or not they have the necessary receptors. At any moment, each individual cell can respond to only a few of the hormones present. The other hormones are ignored because the cell lacks the receptors to read the hormone’s messages. Endocrine communication is the activity of hormones in coordinating cellular activities in tissues located in distant areas of the body . 7.3.1 Functions The endocrine system secretes hormones into the bloodstream to regulate the body, helping to maintain homeostasis. 7.3.2 Components • Hypothalamus: This is the “master” endocrine gland, and it is located in the brain. The hypothalamus provides the highest level of endocrine control, and integrates the activities of

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