سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 5961)

(1) Muscle tissue is specialized for contraction. When muscle cells contract, they shorten and bring about some type of movement. There are three types of muscle tissue: skeletal, smooth, and cardiac. The movements each can produce have very different purposes. Skeletal muscle (2) Skeletal muscle may also be called striated muscle or voluntary muscle. Each one describes particular aspect of this tissue, as you will see. The skeletal muscles cells are cylindrical have several nuclei each, and appear striated or striped. The striations are the result of the precise arrangement of the contracting proteins within the cells, skeletal muscle tissue makes up the muscle that are attached to bones. These muscles are supplied with motor nerves, and this move the skeleton. They also produce a significant amount of heat, which is important to help maintain the body’s constant temperature. Each muscle cell has its own motor nerve ending. The nerve impulses that can then travel to the muscles are essential to cause contraction. Although we do not have to consciously, plan all our movements. The nerve impulses for them originate in the cerebration. The “thinking” part of the brain. Let us return to the three names for this tissue “skeletal” describes its location, “striated” describes its appearance, and “voluntary” describes how it functions. Smooth Muscle (3) Smooth muscle may also be called involuntary muscle or visceral muscle. The cells of smooth muscle have tapered ends, a single nucleus. and no striations. Although nerve impulses do bring about contractions, this is not something most of us can control, once the name involuntary. The rerun visceral refers to internal organs, many of which contain smooth muscle. The function of smooth muscle are actually functions of the organs in which muscle is found in the smooth and infections, smooth muscle contracts in waves called peristalsis to propel food through the digestive tract. In the walls of arteries and values, smooth muscle constricts or dilates the velars to maintain normal blood pressure. The inks of the eye have two types of smooth muscle. There to constrict or dilates the pupil which regulates the amount of light that strikes the retime. Other functions of smooth muscle are mentioned in later chapters. This is an important time that you will come across again and again in our study of the injured body. (4) The cells of the heart, cardiac muscle, are branched have one muscles each, and have faint serration. The cell membranes at the ends of these cells are somewhat folded and fit into matching folds of the membranes of the next cells. (Interlock the fingers of both hands to get an idea of what these adjacent members look like.) These interlocking folds are called intercalated discs, and permit the electrical impulses of muscle confection to pass swiftly from cell to cell. This enables the heart to beat in a very perceive wave of contractions from the upper chambers to the lower chambers. Cardiac muscle (4) cardiac muscle as a whom is called the myocardium, and forms the walls of the four chambers of the heart. Its function. Therefore, is the function of the heart, to bump blood. The contractions of the myocardium create blood pressure and keep blood circulating throughout the body, so that the blood can carry out its many functions. Cardiac muscle cells have the ability to contract by themselves. Thus, the heart maintains its own beat. The rule of nerve impasses is to increase or decrease the heart rate, depending upon whatever is needed by the body in the particular situation. Nerve Tissue (5) Nerve tissue consists of nerve cells called neurons and some specialized cells found only in the nervous system. The nervous system has two divisions: the central nervous system (CNS) and the peripheral nervous system (PNS). The brain and spinal cord are the organs of the CNS. They are made of nervous and specialized cells called neuroglia. the PNS consistencies of all the nerves that energy from the CNS and supply the rest of the body. there nerves are made of neurons and specialized cells called Schwann cells. the Schwann cells form myelin sheaths to electrically instate nervous. Nervous are capable of generating and transmuting electrochemical impulses. There are carry different kinds of nervous. but they all have the same basic structure. The cell body contains the muscles and is essential for the continuing life of the nervous. An axon is a process (the name “process” here means “something that sticks cell.” a cellular extension) that carries impulses away from the cell body. Its neuron has only one axon. Dendrites into processes that carry impulses forward the cell body, a neuron may have several dendrites. A nerve impulse travels along the cell membrane of a nervous and is electrical. But where nervous need there is a small space called synapse. Which an electrical imputes cannot cross. At a synapse, between the axon of the neuron and the dendrite of cell body of the next neuron, impales transmission depends upon chemicals called neurotransmitters