The most purposeful functions of the microcirculation are the transport of nutrients to the tissues and removal of cell excreta . The small arterioles control blood flow to each tissue, and local conditions in the tissues, in turn, control the…
Vascular Distensibility A valuable characteristic of the vascular system is that all blood vessels are distensible. The distensible nature of the arteries allows them to accommodate the pulsatile output of the heart and to average out the pressure pulsations. This…
The function of the circulation is to serve the needs of the body tissues—to transport nutrients to the tissues, to transport waste products away, transport hormones from one part of the body to another and, in general, to maintain an…
Some of the most distressing types of heart malfunction occur because of abnormal rhythm of the heart. For example, sometimes the beat of the atria is not coordinated with the beat of the ventricles, so the atria no longer function…
From the discussion in Chapter 10 of impulse transmission through the heart, it is obvious that any change in the pattern of this transmission can cause abnormal electrical potentials around the heart and, consequently, alter the shapes of the waves…
When a cardiac impulse passes through the heart, electrical current also spreads from the heart into the adjacent tissues surrounding the heart. A small portion of the current spreads all the way to the surface of the body. If electrodes…
The human heart has a special system for rhythmic self-excitation and repetitive contraction approximately 100,000 times each day or 3 billion times in the average human lifetime. This impressive feat is performed by a system that does the following: (1)…
The heart, shown in Figure 9-1 , is actually two separate pumps, a right heart that pumps blood through the lungs and a left heart that pumps blood through the systemic circulation that provides blood flow to the other organs…
Contraction of Smooth Muscle Smooth muscle is composed of small fibers that are usually 1 to 5 micrometers in diameter and only 20 to 500 micrometers in length. In contrast, skeletal muscle fibers are as much as 30 times greater…
Neuromuscular Junction and Transmission of Impulses from Nerve Endings to Skeletal Muscle Fibers Skeletal muscle fibers are innervated by large myelinated nerve fibers that originate from large motoneurons in the anterior horns of the spinal cord. As discussed in Chapter…