Building Muscle: What Is It?
Muscle is defined as any connective tissue or group of cells that are used for supporting the skeleton, organs and muscles. Muscles are responsible for many functions such as maintaining posture, moving objects, bending and extending bones and joints, breathing, heart pumping blood etc.
The term “muscle” is sometimes used interchangeably with “flesh”. However, there are differences between the two terms. A muscle consists of fibers which are made up of long chains of protein molecules called myofibrils. Myofibrils consist of three types of proteins; type I collagen (which makes up most myofibril), type IIA elastin and type IIB actin. Type IIA elastin is found in connective tissues like tendons and ligaments, while type IIB actin is found in bone and cartilage.
Types of Muscle Fibers
Type I Collagen Myofibrils – These are the main structural components of skeletal muscle fibers. They support the myofibers and provide strength and flexibility to them.
Type IIA Elastin Myofibrils – These are the secondary structural components of skeletal muscle fibers and they provide the muscle fibers with their flexibility.
Type IIB Actin Myofibrils – These are the smallest structural components of skeletal muscle fibers. They make up nearly 2% of skeletal muscle fibers’ composition. They determine the tensile strength of a muscle and how fast it can contract and extend.
How Muscles Work
Muscle cells (or fibers) are long and cylindrical and surrounded by a flexible membrane called the sarcolemma. Inside these cells, there are filaments made up of proteins. There are two types of filaments; thick filaments and thin filaments. There are three types of proteins in the thick filament; myosin, actin and another type of protein called troponin.
The thin filament is made of the only type IIB actin and two types of proteins called tropomyosin and ATPase. The thin filaments are arranged in a row between the thick filaments.
Muscles contract when an action potential (electrical signal) passes from one sarcomere to another. When this happens, the thin filaments move toward the center of the sarcomere, thus shortening the muscle (picture a Slinky toy being pulled slowly).
Muscles in the body are arranged in groups called muscle fibers. These muscle fibers are grouped together with connective tissue and blood vessels between them. These are called muscle cells and they give the body its movement.
Muscle cells can be classified as type I (red muscle) and type II (white muscle). Type I usually has a lot of mitochondria, myoglobin and blood vessels giving it a red color. Most of these muscles are in the limbs and maintain posture. Type II are white muscle cells and these are usually found in the abdomen. They contain few mitochondria with a lot of capillaries and these muscles allow for sudden bursts of activity (such as running away from a lion).
Muscle building occurs when skeletal muscles contract and their filaments overlap. The actin and myosin filaments in the muscle overlap, thus pulling the Z line and H zone closer together.
A single skeletal muscle is attached to either bone by tendons. These muscles contract and pull bones in one direction. The opposing muscles extend the limbs or move them in the opposite direction.
The two main types of muscles are skeletal and smooth. Skeletal muscles are attached directly to the skeleton by tendons and they allow for movement of the skeleton. The movements that skeletal muscles allow are called voluntary movements. Voluntary movements are controlled by the brain.
Smooth muscles have the ability to contract and relax without any conscious thought. These muscles allow for actions such as peristalsis (wave like motion that food goes through as it passes through your digestive tract), ejaculation, and opening and closing of the iris of the eye.
The three types of muscles in the human body are skeletal, smooth and cardiac. All muscles get their energy from the breakdown of ATP, however skeletal and smooth muscles have an additional way of getting ATP. This is known as a mitochondria and this creates a more efficient process for ATP breakdown.
Muscles allow the body to move, whether it’s a voluntary or involuntary movement, muscles are involved. They can be separated into three types: skeletal, smooth and cardiac (heart). This article goes into much more detail about muscles and how they work.
A typical myosin molecule has cross-bridges near the ends of its arms. When a myosin head binds to actin, it can pull itself toward the center of the F-actin strand (contracting the muscle). There are two main types of myosin heads: fast-twitch and slow-twitch.
Sources & references used in this article:
Beyond Bigger Leaner Stronger: The Advanced Guide to Building Muscle, Staying Lean, and Getting Strong by M Matthews – 2014 – books.google.com
Fit Is the New Skinny: The No-BS Truth About Building Muscle, Getting Lean, and Staying Healthy by D Randolph – 2015 – Simon and Schuster
EPIC WARRIOR MUSCLE WORKOUT GUIDE by M Matthews – 2012 – books.google.com
Investigating metformin for cancer prevention and treatment: the end of the beginning by T Calkins – imguruplr.com