Definition of Skeletal Muscle
Skeletal muscle is a specialized contractile tissue found in animals that functions to move an organism's body. Skeletal muscle is composed of a series of bundles of muscle fibers surrounded by protective membranes. This arrangement allows skeletal muscle to rapidly contract and relax without subjecting the individual fibers to too much friction. Skeletal muscle tissue can be found throughout the animal kingdom in most multicellular life forms.
skeletal muscle structure
Skeletal muscle is made up of a series of muscle fibers made from muscle cells. These muscle cells are long and multinucleated. At the ends of each skeletal muscle, a tendon connects the muscle to the bone. This tendon connects directly to theepimysium, or outer covering of skeletal muscle collagen. Below the epimysium, muscle fibers are grouped into bundles calledfascicles. These fascicles are surrounded by another protective covering formed by collagen. Operimysium, as it is called, allows nerves and blood vessels to make their way through the muscle. These structures can be located in the image below.
Each fascicle is formed by tens to hundreds of grouped muscle fibers. Each muscle fiber is formed by a chain of multinucleated muscle cells. These fibers are then protected by another layer calledendomysiumhow they are grouped into fascicles. Each muscle cell has distinct regions when viewed under the microscope. These are known assarcomeres, and give the skeletal muscle a band orflutedappearance. Each sarcomere is a protein complex, which operates to contract the muscle.
Sarcomeres are made up ofactinemyosin, as well as various associated auxiliary proteins. The filaments seen between the dark bands are actin and myosin filaments. Actin, as seen in the image above, is made up of many actin units and takes the form of a twisted filament. Actin is accompanied by several proteins that help stabilize it and provide a pathway for muscle contraction. The two most important aretroponinetropomiosina. Tropomyosin surrounds the actin filament and prevents the myosin heads from attaching. Troponin locks tropomyosin in place until it receives the signal to contract. Myosin is a fiber composed of many intertwined tails of individual myosin units. The unit heads sit above the fiber and are attracted to the actin filament.
Skeletal muscle function
When you want to move your arm, your brain sends a nerve signal through your nerves. The simple act of lifting your arm requires a lot of muscles, so the signal is sent by many nerves to many muscles. Each skeletal muscle receives the nerve impulse inneuromuscular junctions. These are places where nerves can stimulate an impulse in a muscle cell. The impulse travels through channels in thesarcolema, the plasma membrane of skeletal muscle cells. At certain sites on the membrane, there are channels that lead into the cell. Thosetransverse tubulescarry the nerve impulse into the cell. The impulse releases calcium ions from a specialized endoplasmic reticulum, thesarcoplasmic reticulum. These calcium ions activate troponin to release from tropomyosin. Tropomyosin can then change position, allowing the myosin heads to attach to the actin filament.
Once the myosin heads are attached, available ATP will be used to contract the filament. This is done by each pair of myosin heads slowly crawling down the filament. ATP energy is used to move one head while the other is stuck. When many hundreds or thousands of heads are involved, this rapidly contracts the sarcomere to up to 70% of its original length. Because the nerve impulse reaches every muscle fiber and every muscle at the same time, the arm can be lifted in one fluid motion. As an additional measure of feedback, each skeletal muscle has special sensory cells that send feedback to the brain. These cells, calledmuscle spindles, have specialized proteins that can sense tension. When voltage is received by the cell, the cell initiates a nerve impulse and sends the signal through the neurons to the brain.
By piecing together this complicated structure of inputs and outputs, the brain can sense where the body is in space. Osomatic nervous systemcontrols these actions and allows us to move our body in a coordinated way. Skeletal muscle is controlled almost exclusively by the somatic nervous system, whereas cardiac and smooth muscle are controlled by the somatic nervous system.autonomic nervous system. This system can be easily demonstrated. Close your eyes and clap your hands several times. Did your hands meet? This is because your brain trains coordination from birth and recognizes the specific tensions in each muscle as you wave your hands. As you clap, these inputs are monitored and adjustments are made to ensure your hands remain in contact with each other. The same system is responsible for balance, coordination, and most physical movement.
Skeletal muscle location
Skeletal muscle, as the name implies, is any muscle that connects and controls the movements of the skeleton. Altogether, there are somewhere between 600 and 900 muscles in the human body, but an exact number is difficult. Many muscles are obscurely small or sometimes grouped with similar muscles. Skeletal muscle is found between bones and uses tendons to connect the epimysium to theperiosteum, or outer covering, of bone.
Skeletal muscle is adapted and shaped in many different ways, giving rise to complex movements. Skeletons are not always internal as in humans. Even animals withexoskeletons, like crabs and mussels, have skeletal muscle. Although muscle can be adapted differently depending on the animal, skeletal muscle is defined by its striations and connections to the skeleton. Everything from the flapping of a bird's wings to the crawling of a beetle is performed by skeletal muscle.
Quiz
1. A very bad doctor is trying to test a patient who is unconscious from a head injury. . The doctor tells the patient to raise his arm. The patient is unable to do so and the physician records the response. Why was this an unnecessary test at this point in the patient's recovery?
A.Unconscious patients are notoriously bad listeners.
B.To control the somatic nervous system, a conscious patient is needed
C.No test is a waste of time!
Answer to question #1
Bis correct. The somatic, or voluntary, nervous system is aptly named. To control it, the mind must be in some form of consciousness. Someone who is unconscious has no control of their skeletal muscle. So asking them to use skeletal muscle is a waste of time.
2. Clams have an interesting adaptation to help them survive. The adductor muscle, which holds the shell closed, is made up of two smaller muscles. One of the muscles is a skeletal muscle while the other is a smooth muscle. Why would this be beneficial to a mollusk?
A.Double the muscle, double the power!
B.Skeletal muscle can act quickly, while smooth muscle can maintain a contraction
C.Smooth muscle is used to open the shell and skeletal muscle to close it.
Answer to question #2
Bis correct. Skeletal muscle and smooth muscle are specialized for different purposes. Skeletal muscle can contract and relax quickly with a lot of energy. Smooth muscle can maintain a contraction for a long period of time. Thus, the mollusk can quickly close its shell if it feels danger using skeletal muscle. If danger persists or the mollusk is out of water, the smooth muscle can keep the shell closed for days before needing to relax.
3. Stretching before and after a workout is often recommended by trainers. Why is this?
A.Stretching helps lengthen muscle fibers
B.Stretching helps keep tendons elastic
C.Both mentioned above!
Answer to question #3
Cis correct. Stretching is an important aspect of training. When you contract your skeletal muscles during exercise, you are putting a lot of pressure on them. The pressure and tension in the muscles can be enormous. Stretching helps combat this by stretching the sarcomeres back to length, releasing tension in the tendons and allowing fluids to circulate to the tissues.
References
- Brusca, R.C., & Brusca, G.J. (2003).Invertebrates.Sunderland, MA: Sinauer Associates, Inc.
FAQs
Skeletal Muscle: Definition, Function, Structure, Location | biology dictionary? ›
Skeletal muscles comprise 30 to 40% of your total body mass. They're the muscles that connect to your bones and allow you to perform a wide range of movements and functions. Skeletal muscles are voluntary, meaning you control how and when they work.
Where is skeletal muscle structure function and location? ›Skeletal muscle is found throughout the body, attached to bones via tendons. It is also present in the tongue, diaphragm, eye socket, and upper esophagus.
What is skeletal muscle definition structure and function? ›Structure and Function
Skeletal muscle is one of the three significant muscle tissues in the human body. Each skeletal muscle consists of thousands of muscle fibers wrapped together by connective tissue sheaths. The individual bundles of muscle fibers in a skeletal muscle are known as fasciculi.
skeletal muscle, also called voluntary muscle, in vertebrates, most common of the three types of muscle in the body. Skeletal muscles are attached to bones by tendons, and they produce all the movements of body parts in relation to each other.
What is the location of skeletal muscle quizlet? ›Skeletal muscle covers the bony skeleton, striated and is a voluntary movement and controls the body's movement. Cardiac muscle is located in the heart and are striated and involuntary. Smooth muscle is located in the walls of visceral organs (e.g. urinary bladder, stomach and respiratory passages and is not striated.
What is structure of skeletal muscle? ›Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium.
What is the structure of the skeletal muscle tissue? ›Skeletal muscles contain connective tissue, blood vessels, and nerves. There are three layers of connective tissue: epimysium, perimysium, and endomysium. Skeletal muscle fibers are organized into groups called fascicles. Blood vessels and nerves enter the connective tissue and branch in the cell.
What is the definition of skeletal muscle quizlet? ›Skeletal muscle. Muscle attached to bones and causes body movement.
What is the function of skeletal muscle quizlet? ›Skeletal muscles are responsible for all locomotion and manipulation. tension in skeletal muscles maintains body posture against the effects of gravitational forces. the skeletal muscles in the abdominal wall support the weight of the visceral organs and protect internal tissues from injury.
What is the structural and functional unit of skeletal muscle quizlet? ›The structural and functional unit (smallest contractile unit) of skeletal muscle is the SARCOMERE,which is bounded by Z lines.
What is the function of the skeletal muscle cells? ›
Skeletal muscle cells are responsible for practically all movements that are under voluntary control. These cells can be very large (2–3 cm long and 100 μm in diameter in an adult human) and are often referred to as muscle fibers because of their highly elongated shape.
What is the location and function of smooth muscle? ›Smooth muscle is present throughout the body, where it serves a variety of functions. It is in the stomach and intestines, where it helps with digestion and nutrient collection. It exists throughout the urinary system, where it functions to help rid the body of toxins and works in electrolyte balance.
What is the location and function of the cardiac muscle? ›Cardiac muscle is highly organized and contains many types of cell, including fibroblasts, smooth muscle cells, and cardiomyocytes. Cardiac muscle only exists in the heart. It contains cardiac muscle cells, which perform highly coordinated actions that keep the heart pumping and blood circulating throughout the body.
What is the location of skeletal muscle contraction? ›Skeletal muscle contraction begins first at the neuromuscular junction, which is the synapse between a motoneuron and a muscle fiber. Propagation of action potentials to the motoneuron and subsequent depolarization results in the opening of voltage-gated calcium (Ca2+) channels of the presynaptic membrane.
What is the location and function of the cardiac muscle tissue? ›Cardiac muscle tissue is one of the three types of muscle tissue in your body. The other two types are skeletal muscle tissue and smooth muscle tissue. Cardiac muscle tissue is only found in your heart, where it performs coordinated contractions that allow your heart to pump blood through your circulatory system.
What is the major function of muscle? ›Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction.
What is the location of cardiac muscle? ›Cardiac muscle makes up the thick middle layer of the heart and is surrounded by a thin outer layer called the epicardium or visceral pericardium and an inner endocardium.
What is the location of smooth muscle? ›Smooth muscle is found throughout the body where it serves a variety of functions. It is in the stomach and intestines where it helps with digestion and nutrient collection. It is found throughout the urinary system where it functions to help rid the body of toxins and works in electrolyte balance.
What are the 4 main functions of muscles? ›Four functions of muscle contraction are movement, posture, joint stability, and heat production. Three types of muscle are skeletal, smooth, and cardiac.
What are the functions of the skeletal system responses? ›The major functions of the skeletal system are body support, facilitation of movement, protection of internal organs, storage of minerals and fat, and blood cell formation.
What are the characteristics of a skeletal muscle? ›
Skeletal muscle cells are long, cylindrical, and striated. They are multi-nucleated meaning that they have more than one nucleus. This is because they are formed from the fusion of embryonic myoblasts. Each nucleus regulates the metabolic requirements of the sarcoplasm around it.
What is one functional unit of a skeletal muscle _____? ›The sarcomere, the region from one Z-line to the next Z-line, is the functional unit of a skeletal muscle fiber.
What is the functional and structural unit? ›Cells are called the structural and functional unit of life because all the living organisms are made up of cells and also all the functions taking place inside the body of organisms are performed by cells. Cells provide specific conditions, for the occurrence of the metabolic reactions.
What is the basic structural and functional unit of a skeletal muscle fiber? ›Myofibrils are the basic functional unit of skeletal muscle and are composed of syncytia of multinucleated cells that vary considerably in their biochemical and physiological properties.
What are the functions of skeletal muscle Wikipedia? ›The functions of skeletal muscle include producing movement, maintaining body posture, controlling body temperature, and stabilizing joints. Skeletal muscle is also an endocrine organ.
What is the structure of skeletal and smooth muscle? ›Muscle tissues differ in structure. Skeletal muscle fibres are packed into regular parallel bundles. Smooth muscle has bundles of thin and thick filaments. Cardiac muscle bundles are branched but connected.
What is an example of a skeletal muscle? ›An example of skeletal muscles include any that are attached to your bones, or skeletal system. This allows you to move. Examples would be your biceps on the tops of your arms, triceps on the bottoms of your arms, calves on the back of your lower legs, and pectoral muscles in your chest.
Is skeletal muscle striated? ›The body possesses two types of striated muscle, cardiac and skeletal.
What is the structure of the cardiac muscle? ›Cardiac muscle cells form a highly branched cellular network in the heart. They are connected end to end by intercalated disks and are organized into layers of myocardial tissue that are wrapped around the chambers of the heart.
What is the structure of the smooth muscle? ›smooth muscle, also called involuntary muscle, muscle that shows no cross stripes under microscopic magnification. It consists of narrow spindle-shaped cells with a single, centrally located nucleus. Smooth muscle tissue, unlike striated muscle, contracts slowly and automatically.
What five functions does the skeleton perform? ›
The skeletal system works as a support structure for your body. It gives the body its shape, allows movement, makes blood cells, provides protection for organs and stores minerals.
What are the three functions of muscles? ›The muscular system consists of various types of muscle that each play a crucial role in the function of the body. Muscles allow a person to move, speak, and chew.
Where is sarcolemma located? ›The sarcolemma is the plasma membrane of the muscle cell and is surrounded by basement membrane and endomysial connective tissue. The sarcolemma is an excitable membrane and shares many properties with the neuronal cell membrane.
What is the location of cardiac muscle quizlet? ›Cardiac muscle is found only in the walls of the heart. When cardiac muscle contracts, the heart beats and pumps blood. Cardiac muscle contains a great many mitochondria, which produce ATP for energy. This helps the heart resist fatigue.
What is the location and function of skeletal connective tissue? ›Skeletal connective tissue is a type of connective tissue which is composed of solid matrix and cells. It consists of bone, cartilage, tendons and ligaments. The main function of it is to provide support and protect the soft part of the body.
Where are the functions of the skeletal system? ›The major functions of the skeletal system are body support, facilitation of movement, protection of internal organs, storage of minerals and fat, and blood cell formation.
What is connective tissue location? ›Connective tissue is found in between other tissues everywhere in the body, including the nervous system. The three meninges, membranes that envelop the brain and spinal cord, are composed of connective tissue.
What are the 5 functions of the skeletal structure? ›- Supporting your body and helping you move. Your bones literally hold up your body and keep it from collapsing to the ground. ...
- Protecting your internal organs. ...
- Producing your blood cells. ...
- Storing and releasing fat. ...
- Storing and releasing minerals.
- supports the body.
- facilitates movement.
- protects internal organs.
- produces blood cells.
- stores and releases minerals and fat.
Protection – The vital function of the skeletal system is to protect the internal organs.
What is the main function of the muscular system? ›
The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction.
What are the types of skeletal muscles? ›- Skeletal muscle – the specialised tissue that is attached to bones and allows movement. ...
- Smooth muscle – located in various internal structures including the digestive tract, uterus and blood vessels such as arteries. ...
- Cardiac muscle – the muscle specific to the heart.
Cardiac muscle makes up the thick middle layer of the heart and is surrounded by a thin outer layer called the epicardium or visceral pericardium and an inner endocardium.