I’m always surprised at the misunderstandings the general public and fitness/nutrition professionals have about the roles of lean muscle, fat, and skin (thick skin) in our bodies. Especially disturbing is that most fitness and nutrition professionals who should know the differences among the three as they relate to the effects of exercise and diet, do not really understand their physiological connection and metabolic processes that act on each.
At a recent fitness convention, I attended a seminar where there were predominantly personal trainers. A questionnaire was passed out that asked: “What are the roles of muscle, fat and skin in our bodies?” To my shock, the answers were by and large incorrect. This made me wonder how much fitness people working in gyms really know about the composition and functions of the main components of our bodies.
We have a skeletal system with bones that have muscles attached to them, a vascular system that travels through our muscles and a layer of fat on the top of our muscles around the organs and marbled through the muscles, and then of course, skin. Let’s take a look at these vital components that allow us to physically move throughout the day.
Simply put, muscle is body tissue made up of cells that lengthen and shorten (contract), as the result of stimulus from nerve impulses to produce movement or force. There are approximately 640 muscles in the human body that make up half of our body weight. The three types of muscles in our bodies that perform different tasks, cardiac muscle, smooth muscle and skeletal muscle.
Cardiac muscle is what makes up your heart, which contracts regularly (on average 70 times per minute) to pump blood and oxygen through our body and keep us alive. The heart is the only place in our body that has this kind of muscle. It operates on its own, independently of our voluntary control, contracting to squeeze blood through the heart and relaxing on the offbeat to allow the heart to fill with blood again. This muscle requires stimulation from the autonomic nervous system, and does not require rest from performing its primary function. The heart’s main source of energy is glucose, although it can also use fatty acids for energy in the absence of glucose.
In the hollow organs of our bodies such as our stomach and intestines, smooth muscle lines their walls. Their job is to contract in order to perform necessary bodily functions like processing food, moving air through the lungs, expelling urine, and pushing a baby through the birth canal. Like the cardiac muscle, smooth muscle works involuntarily – automatically through the central nervous system. Like the cardiac muscle, smooth muscle needs to be stimulated by the autonomic nervous system.
What are Muscle Cells?
Our bodies are predominately made up of millions of muscle cells that make up our more than 640 individual muscles. Muscle cells are our body’s engine that allows us to function and survive. Without muscles cells, we would not be able to move or have any ability to exist. Our muscle cells are our “metabolic engine” (no different from a car’s engine) that controls every aspect of our active life.
Muscle cells are a series of layers of fibres within fibres constructed like a sturdy piece of rope. Thousands of parallel cylinders called sarcomeres are squished together to form muscle fibres. Larger muscles contain more bundles of muscle fibres, while small muscles contain fewer bundles. Our bicep muscles may contain 70,000 fibres, while our larger hamstring muscles may contain more than 140,000 muscle fibres.
Muscle fibres have their own blood vessels and connective tissue. Each also has its own nerve fibres to stimulate contraction, and its own artery and vein to keep it well fed with the oxygen and nutrients it needs to function.
Muscle fibres contain a cell membrane known as the Sarcolemma. The Sarcolemma has many functions including facilitating biochemical processes, and contains nerves that provide sensory information from the central nervous system (CNS) receptors to receive electrical stimuli impulses or commands.
The inside of the muscle fibres Sarcolemma is the Sarcoplasm, which contains the mitocondria (for energy production) multiple nuclei, glycogen (stored glucose) and fatty acids, for energy.
Each muscle cell contains hundreds or t Primarily energy supplied the cells ATP cycle, produced from stored glycogen thousands of thin and thick cylinder protein organelles called Myofibrils. Myofibrils are divided lengthwise into segments called Sarcomeres. The function of sarcomeres is the performance of muscle contractions.
Sarcomeres are separated by a Z-line between each of them at each end. There are two main types of myofibrils within the sarcomeres, Actin and Myocin. They
are composed of protein molecules. Myosin is a thick filament; Actin is a thin filament. These two myofibrils produce muscle contractions by working together by folding over top of each other, the sarcomeres Z-ends closer together. It is the sliding of the Myosin and Actin powdered by ATP (energy created in the mitocondria) that allows muscles to contract.
Surrounding the Myofibrils is a network of tubules called Sarcoplasm Reticulum where calcium is stored, which is a necessity for muscular contractions. Also in the Sarcoplasm is a red pigment called Myoglobin, which stores oxygen in the cell until it is required for muscular contraction activity.
To move a muscle, the brain sends a command through the motor neuron to the muscle to be used. The motor neuron activates a synapse receptor on the muscle cell. The receptor then releases a rush of sodium into the cell, which causes a chemical reaction. With this signal, Myocin and Actin (with energy from ATP) pull together over top of each other, shrinking the Sarcomere by contracting, thus performing work such as lifting a heavy object or working out at a gym.
Skeletal muscles are attached to our ligaments and bones, and have to be stimulated by nerve impulses to contract. These muscles literally cover our skeletons, form our muscular system, keep our posture, stabilize our joints, and give us our body shape. Skeletal muscles are our metabolic engine, which generates heat, expends calories and helps us to maintain a functional body temperature.
There are more than 640 skeletal muscles in all shapes and sizes that are attached to our bones directly or by other connective tissues called tendons. Skeletal musculature forms approximately 35 per cent to 50 per cent of our total body weight, making it the strongest part of our anatomy. Our muscular system forms our active motor system. The job of skeletal muscles is to perform the movements of our limbs and body parts we ask them to perform as we go about our day-to-day activities. In other words, skeletal muscles respond to voluntary control. You “tell” them what to do by sending messages from your brain to your muscle cells. Nerves (CNS) carry electrical signals from the brain through the spinal cord (central nervous system) to each muscle in order to direct and control their actions.
Skeletal muscles play a part in just about all body movements. Every time we walk, reach for something, turn your head, bend down or move in any way, there is a skeletal muscle contraction behind it.
Each muscle contains long, cylindrical muscle tissues made up of millions of muscle cells. Muscle cells contain a large number of proteins called myofibrils, which contract and act similar to a ratchet system when the muscle fibre is triggered by nerve stimulation, resulting in the performance of movement