Skeletal muscle

Knowledge Base

The Skeletal System
What is Crohn's Disease? Because skeletal muscles move the insertion closer to the immobile origin, fixator muscles assist in movement by holding the origin stable. Another chemical that helps to keep muscles working is creatine phosphate. Skeletal muscle cells form when many smaller progenitor cells lump themselves together to form long, straight, multinucleated fibers. Skeletal muscles are under voluntary control, which means you consciously control what they do.

You can think of the human body as a biomechanical structure, made up of three systems:

Basic Concepts of Exercise Physiology

The skeletal system is comprised of all the bones in the body as well as their associated cartilage and joints. We will focus on the primary or major bones in the body associated with gross movements. Bones are divided into four basic types or classifications figure 2. Bone classification is based primarily on the shape of the bone.

Long bones are longer than they are wide and are primarily found in the appendages arms and legs. Long bones include the femur, tibia, fibula, radius, ulna, and humerus.

Long bones are slightly curved for strength and designed to absorb stress at several points. They consist of a long, thin part called the diaphysis , or shaft, and two bulbous-type ends called the epiphysis. Short bones are basically cube shaped and are about as wide as they are long. Examples are the bones found in the wrist and ankle.

Flat bones are thin and generally flat. They offer considerable protection and a great deal of surface area for muscles to attach. Examples of flat bones are the cranial bones, which protect the brain, and the scapula shoulder blade.

Irregular bones include many of the bones that do not fall into the other three categories. They have complex shapes and include bones like the vertebrae. A bone is made of many parts, with the proportions of each part depending on the size and shape of the bone. Generally, bones are composed of spongy and compact bone, periosteum and endosteum , and a medullary cavity figure 2.

The periosteum is a dense, white, fibrous sheath that covers the surface of the bone and is where muscles and tendons attach. The medullary cavity of the bone is a cavity in the center of the bone filled with yellow, fatty marrow. The endosteum is the layer of cells that line the medullary cavity. The rigid part of the bone is made of spongy and compact bone. The spongy bone is less dense and contains spaces so blood vessels and other nutrients can be supplied to the bone.

The compact part of the bone contains few spaces and provides protection and strength. They consist of a long, thin part called the diaphysis, or shaft, and two bulbous-type ends called the epiphysis. Generally, bones are composed of spongy and compact bone, periosteum and endosteum, and a medullary cavity figure 2. The process through which bone grows in the body is called ossification. Bones, in particular long bones, have cartilaginous growth plates located at either end called epiphyseal plates.

Initially, these plates are not completely hardened and are where growth occurs in the bone. These fragile growth plates can be damaged in growing children or teens and affect bone development. As a person matures, the epiphyseal plates harden, and growth stops between the ages of 21 and Children have large amounts of organic material in their bones, making their bones softer and more pliable.

As we age, we have larger proportions of inorganic material, which causes bones to become brittle and more fragile. The structures in bones are in a continuous state of being built up and broken down. When exercise is combined with adequate rest and nutrition, healthy bones become thicker and stronger.

Exercise helps build and promote healthy bone tissue and reduces the risk of bone disease such as osteoporosis. The smooth muscles are the other muscles in the body that are involuntary.

Smooth muscles are in many places. Muscles are made of many muscle cells. The cells contract together to make the muscle get shorter. The muscle cells know to do this together because many of them get information sent to them by nerves. The cells that get the message from nerves tell other cells that are near them. They tell the other cells by sending an electrical current. Muscle cells are filled with proteins called actin and myosin. These are the proteins that make the muscle contract get shorter.

When a nerve tells a muscle to contract, the muscle opens holes in its cell membrane. These holes are proteins that are called calcium channels. The calcium ions rush into the cell. Calcium also comes out of a special place in the cell called the sarcoplasmic reticulum. This calcium sticks to the specialized proteins actin and myosin. This triggers these proteins to contract the muscle.

The length of the exercise programs varied from 12 weeks to 12 months. Six studies involving participants tested the effect of exercise on ADL performance These positive effects were apparent with programs ranging in length from 12 wk Santana-Sosa et al.

Furthermore, the positive effects of a 3-mo intervention lasted 24 mo Teri et al. No adverse effects of exercise on ADL performance were noted. The study with the largest effect size implemented a walking and aerobic program of only 30 min four times a week Venturelli et al. Cochrane Database Syst Rev. A systematic review and meta-analysis of longitudinal studies". Longitudinal observational studies show an association between higher levels of physical activity and a reduced risk of cognitive decline and dementia.

A case can be made for a causal interpretation. Future research should use objective measures of physical activity, adjust for the full range of confounders and have adequate follow-up length. Ideally, randomised controlled trials will be conducted. On the whole the results do, however, lend support to the notion of a causal relationship between physical activity, cognitive decline and dementia, according to the established criteria for causal inference.

Role in Drug Addiction and Novel Treatments". There is accelerating evidence that physical exercise is a useful treatment for preventing and reducing drug addiction In some individuals, exercise has its own rewarding effects, and a behavioral economic interaction may occur, such that physical and social rewards of exercise can substitute for the rewarding effects of drug abuse. The value of this form of treatment for drug addiction in laboratory animals and humans is that exercise, if it can substitute for the rewarding effects of drugs, could be self-maintained over an extended period of time.

Work to date in [laboratory animals and humans] regarding exercise as a treatment for drug addiction supports this hypothesis. However, a RTC study was recently reported by Rawson et al. Animal and human research on physical exercise as a treatment for stimulant addiction indicates that this is one of the most promising treatments on the horizon.

Similar to environmental enrichment, studies have found that exercise reduces self-administration and relapse to drugs of abuse Cosgrove et al. There is also some evidence that these preclinical findings translate to human populations, as exercise reduces withdrawal symptoms and relapse in abstinent smokers Daniel et al. In humans, the role of dopamine signaling in incentive-sensitization processes has recently been highlighted by the observation of a dopamine dysregulation syndrome in some patients taking dopaminergic drugs.

This syndrome is characterized by a medication-induced increase in or compulsive engagement in non-drug rewards such as gambling, shopping, or sex Evans et al.

Am J Drug Alcohol Abuse. The limited research conducted suggests that exercise may be an effective adjunctive treatment for SUDs. In contrast to the scarce intervention trials to date, a relative abundance of literature on the theoretical and practical reasons supporting the investigation of this topic has been published. From human to animal studies". As briefly reviewed above, a large number of human and rodent studies clearly show that there are sex differences in drug addiction and exercise.

The sex differences are also found in the effectiveness of exercise on drug addiction prevention and treatment, as well as underlying neurobiological mechanisms. The postulate that exercise serves as an ideal intervention for drug addiction has been widely recognized and used in human and animal rehabilitation. In particular, more studies on the neurobiological mechanism of exercise and its roles in preventing and treating drug addiction are needed.

Exercise is moderately more effective than a control intervention for reducing symptoms of depression, but analysis of methodologically robust trials only shows a smaller effect in favour of exercise. When compared to psychological or pharmacological therapies, exercise appears to be no more effective, though this conclusion is based on a few small trials.

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Molecular Aspects of Medicine. Retrieved 27 May Clinical Nutrition Edinburgh, Scotland. During the first 2. It may seem difficult for one to reconcile that acute provision of CaHMB, in the absence of exogenous nutrition i. EAA's and following an overnight fast, is still able to elicit a robust, perhaps near maximal stimulation of MPS, i. A Journal of Cerebral Circulation.

Medicine and science in sports and exercise. Sports Medicine, Training and Rehabilitation. The Journal of sports medicine and physical fitness. Journal of Applied Physiology. American journal of physical medicine. European journal of applied physiology and occupational physiology. Medicine in Science and Sports and Exercise. Exercise and Sports Sciences Reviews. From a molecular perspective, elevated systemic levels of circulating growth factors such as vascular endothelial growth factor and insulin-like growth factor 1 IGF-1 in blood elicited by increased exercise have been shown to mediate, in part, enhancements in neurogenesis Trejo et al.

Importantly, physical exercise can improve growth factor signalling directly or indirectly by reducing pro-inflammatory signalling [33].

Exercise-induced increases in brain monoamines norepinephrine and serotonin may also contribute to increased expression of hippocampal BDNF []. In addition, other growth factors—insulin-like growth factor-1 IGF-1 and vascular endothelial growth factor—have been shown to play an important role in BDNF-induced effects on neuroplasticity [33,,,], as well as exerting neuroprotective effects of their own [33,,], thereby contributing to the beneficial effects of exercise on brain health.

Abundant research in the last decade has shown that exercise is one of the strongest promoters of neurogenesis in the brain of adult rodents 97, and humans 1,61 , and this has introduced the possibility that proliferating neurons could contribute to the cognitive enhancement observed with exercise.

Although the action of exercise on brain angiogenesis has been known for many years 10 , it is not until recently that neurovascular adaptations in the hippocampus have been associated with cognitive function Exercise-related improvements in brain function and structure may be conferred by the concurrent adaptations in vascular function and structure. Aerobic exercise increases the peripheral levels of growth factors e. Consistent with this, exercise-related enlargement of hippocampus was accompanied by increases in cerebral blood volume and capillary densities Pereira et al.

Enhanced cerebral perfusion may not only facilitate the delivery of energy substrates, but also lower the risk of vascular-related brain damages, including WMH and silent infarct Tseng et al. The Cochrane Database of Systematic Reviews. British Journal of Sports Medicine. Am J Prev Med. Pan American Health Organization. Retrieved 10 January Cross-sectional and longitudinal evidence from a European-wide study".

Public health interventions for increasing physical activity in children, adolescents and adults: Medicine and science in sports and exercise: Centers for Disease Control and Prevention. Archived from the original on 18 December Retrieved 8 December Stockholm on a Shoestring. Dancing In The Park". Retrieved 20 September Archived from the original on 29 July Retrieved 8 April Proceedings of the Nutrition Society.

The Journal of Experimental Biology. Comparative Biochemistry and Physiology Part A: Comparative Biochemistry and Physiology A. Journal of Comparative Physiology B. The Journal of Physiology. The effects of specialised exercise training on performance". Journal of Experimental Biology. Find more about Exercise at Wikipedia's sister projects. Sprinting Strength training Bodyweight exercise Weight training. Exercise equipment Exercise physiology Outline of exercise Physical fitness Neurobiological effects of physical exercise.

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This page was last edited on 12 September , at By using this site, you agree to the Terms of Use and Privacy Policy. Skeletal muscle morphology and exercise performance adaptations.

Muscle strength and power. Mitochondrial density and oxidative function. Ability in activities of daily living. Systolic blood pressure resting.

Muscles - Skeletal, smooth and cardiac