Cardiac muscle pumps blood around the body in order to supply the nutrients that are needed by the cells of the body. Smooth muscle in the walls of the blood vessels helps to maintain blood pressure. In the hollow organs of the digestive, urinary and reproductive tracts it helps to propel or squeeze substances for example, foodstuffs, urine, a baby respectively through the organs and along the tracts Marieb, Although we are not generally aware of it, our skeletal muscles are continually working and making minor adjustments to allow us to maintain an upright posture despite the constant force of gravity trying to pull us down.
Muscles and their associated tendons commonly cross joints and work together to stabilise them. This is particularly true of the knee and of the shoulder joint, which would be highly unstable were it not for the many muscles that hold it in place.
The body needs to be maintained at a constant temperature in order to function optimally - most of the heat required for this is produced by muscles, which generate heat as they contract.
The energy needed to produce muscle contraction is obtained from adenosine triphosphate ATP , which is manufactured in the muscle cells. The openings of digestive and urinary tracts are encircled by skeletal muscles. These muscles provide voluntary control over swallowing, urination and defecation Martini, The abdominal wall and the floor of the pelvic cavity consist of sheets of skeletal muscle that support the weight of the visceral organs and protect the internal tissues from injury.
We have seen that muscles have a number of essential functions and without them, human life cannot exist. The next three articles will examine in detail the structure and function of skeletal muscle, the largest of the three muscle types in the body.
Sign in or Register a new account to join the discussion. You are here: Nurse educators. Muscle physiology Part 1: overview of muscle physiology. NT Contributor.
Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. So all muscle cells contain a high-energy compound called creatine phosphate which is broken down to make more ATP quickly. Creatine phosphate can supply the energy needs of a working muscle at a very high rate, but only for about 8—10 seconds. Fortunately, muscles also have large stores of a carbohydrate, called glycogen, which can be used to make ATP from glucose.
But this takes about 12 chemical reactions so it supplies energy more slowly than from creatine phosphate. Oxygen is not needed — this is great, because it takes the heart and lungs some time to get increased oxygen supply to the muscles. A by-product of making ATP without using oxygen is lactic acid. You know when your muscles are building up lactic acid because it causes tiredness and soreness — the stitch. Within two minutes of exercise, the body starts to supply working muscles with oxygen.
When oxygen is present, aerobic respiration can take place to break down the glucose for ATP. This glucose can come from several places:. If the body temperature drops, negative feedback control raises the temperature back to normal. If the body temperature rises, negative feedback control lowers the temperature back to normal.
All of the methods to regulate body temperature mentioned so far are involuntary responses - we do not consciously decide to sweat or to shiver. In contrast, humans are also able to make voluntary responses, for example when we decide to take action to help regulate our body temperature.
Examples of voluntary responses when the environment is hot:.
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