Athena Vale
The human body has over 600 muscles, each with a specific function, from pumping blood around the body to helping you lift a heavy backpack. Muscles are made of thousands of small fibres woven together, and they help us do everything from holding our bodies still to running a marathon. There are three types of muscles: skeletal, smooth, and cardiac. Skeletal muscles are the only voluntary muscles, meaning we can control their movement consciously. Smooth and cardiac muscles are involuntary, working without our conscious input. Skeletal muscles are attached to bones and allow us to perform a wide range of movements. Smooth muscles line our organs and help with essential functions like moving waste through our intestines and helping our lungs expand when we breathe. Cardiac muscle makes up the heart and is responsible for its rhythmic contractions, pumping blood through our bodies.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | More than 600 |
| Muscle types | Skeletal, smooth, cardiac |
| Muscle functions | Movement, heartbeat, breathing, digestion, temperature regulation, vision, stability, posture, circulation, etc. |
| Muscle movements | Dorsiflexion, plantar flexion, abduction, adduction, supination, pronation, elbow extension, etc. |
| Muscle roles | Prime mover, agonist, antagonist, synergist, stabilizer |
| Muscle composition | Thousands of elastic fibres bundled together, wrapped in a thin membrane (perimysium) |
| Muscle contraction | Caused by the release of the chemical acetylcholine from the presynaptic terminals |
| Muscle control | Skeletal muscles are the only muscles that can be consciously controlled |
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What You'll Learn
Skeletal muscles allow for movement, like elbow extension or flexion
The human body has over 600 muscles, which help us do everything from moving our bodies to breathing and staying alive. Skeletal muscles, in particular, are responsible for allowing movement, including elbow extension or flexion.
Skeletal muscles are attached to bones and allow for movement. They come in four main shapes: spindle, flat, triangular, and circular. The spindle shape, like the biceps in the upper arm, is wider in the middle and tapered at both ends. Flat muscles, like the diaphragm, separate body cavities. Triangular muscles, like the deltoids in the shoulder, are wider at the bottom and tapered at the top. Circular muscles, like those surrounding the mouth, are ring-shaped.
Elbow extension and flexion are made possible by the triceps brachii, anconeus, biceps brachii, brachialis, and brachioradialis muscles. The triceps brachii and anconeus extend the elbow, while the other three flex it. The triceps brachii has four points of attachment: one insertion on the ulna and three origins (two on the humerus and one on the scapula). The anconeus acts as a synergist in elbow extension, assisting the prime mover, or agonist, in this action.
The prime mover is the muscle that provides the primary force for a movement. The agonist is responsible for driving the action and can be assisted by synergists, which are muscles that aid the prime mover. In the case of elbow flexion, the biceps brachii is the prime mover, while the brachialis and brachioradialis act as synergists.
Understanding the roles of different muscles in movements like elbow extension and flexion is essential for comprehending the musculoskeletal system, which includes both the skeleton and the muscles that enable movement.
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Smooth muscles are involuntary and control digestion
The human body has over 600 muscles, which help us do everything from breathing to moving our bodies. There are three main types of muscles: skeletal, smooth, and cardiac.
Skeletal muscles are voluntary muscles that are attached to bones and allow movement. They are under our conscious control, meaning we can decide to move them, such as waving our hand or walking.
Smooth muscles, on the other hand, are involuntary muscles that line the inside of some organs. They play a crucial role in controlling involuntary movements in the body, such as digestion and breathing. Smooth muscles are found in the walls of various internal organs, including the stomach, intestines, and blood vessels. They contract and relax rhythmically to move food through the digestive tract, a process known as peristalsis. This movement of food through the digestive system helps with digestion and nutrient collection. Smooth muscles in the blood vessel walls also adjust their diameter to regulate blood pressure without conscious effort.
The nervous system uses hormones, neurotransmitters, and other receptors to control smooth muscles spontaneously. For example, the use of bronchodilators to relax airway smooth muscle is a life-saving treatment for asthmatics. Additionally, medications like metoclopramide can stimulate and promote gastric emptying by increasing smooth muscle signaling.
Smooth muscles are essential for maintaining the body's basic functions, including digestion, nutrient collection, toxin removal, and electrolyte balance. Their ability to contract and relax involuntarily makes them vital for regulating various subsystems in the body.
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Cardiac muscle is the heart, which pumps blood
The human body contains three kinds of muscle tissue: skeletal, smooth, and cardiac. Cardiac muscle tissue, or myocardium, is a type of muscle tissue that forms the heart. It contracts and releases involuntarily and keeps the heart pumping blood around the body. The heart is a hardworking muscle that beats thousands of times a day to keep us alive. Cardiac muscle tissue gets its strength and flexibility from its interconnected cardiac muscle cells, or fibres.
Cardiac muscle is the only muscle in the body that is not under our conscious control. It contracts and relaxes involuntarily to pump blood through the cardiovascular system. The heart contains specialised types of cardiac tissue containing "pacemaker" cells. These contract and expand in response to electrical impulses from the nervous system. Pacemaker cells generate electrical impulses, or action potentials, that tell cardiac muscle cells to contract and relax. The pacemaker cells control heart rate and determine how fast the heart pumps blood.
The individual cardiac muscle cell (cardiomyocyte) is a tubular structure composed of chains of myofibrils, which are rod-like units within the cell. The myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of the muscle cells. Sarcomeres are composed of long proteins that organise into thick and thin filaments, called myofilaments. Thin myofilaments contain the protein actin, and thick myofilaments contain the protein myosin. The myofilaments slide past each other as the muscle contracts and relaxes. This process activates from the release of calcium from the sarcoplasmic reticulum (SR) when delivering an action potential to the muscle, in a process called excitation-contraction coupling. The sliding of actin and myosin past each other produces the formation of "cross-bridges", which causes contraction of the heart and generation of force.
Regular aerobic exercise can help strengthen the cardiac muscle tissue and keep the heart and lungs healthy. Aerobic activities involve moving the large skeletal muscles, which causes a person to breathe faster and their heartbeat to quicken. Regularly engaging in these types of activities can train the heart to become more efficient. Cardio workouts are named for their cardiac muscle benefits. They can help lower blood pressure, reduce heart rate, and make the heart pump more effectively.
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Muscles control breathing
The human body has over 600 muscles, which help us do everything from breathing to running marathons. The diaphragm, a dome-shaped muscle that separates the chest cavity from the abdomen, is the most important muscle for breathing. It contracts to increase the length and diameter of the chest cavity, expanding the lungs and allowing us to inhale. The diaphragm is attached to the base of the sternum, the lower parts of the rib cage, and the spine.
The intercostal muscles and neck muscles help move the rib cage and assist in breathing. The rib cage muscles, including the intercostals, parasternals, scalene, and neck muscles, mostly act on the upper part of the rib cage and are involved in both inhalation and exhalation. The abdominal muscles are the most important muscles for exhalation, contracting and raising abdominal pressure to push air out of the lungs.
During exercise, the expiratory muscles play a more active role in breathing, working in coordination with the inspiratory rib cage muscles. This mechanism prevents rib cage distortion, unloads the diaphragm so it can act as a flow generator, and decreases the volume of the abdomen.
The accessory inspiratory muscles include the sternocleidomastoid, the scalenus anterior, medius, and posterior, the pectoralis major and minor, and the serratus anterior. The accessory expiratory muscles include the abdominal muscles: rectus abdominis, external oblique, internal oblique, and transversus abdominis. These accessory muscles are recruited during exercise due to the increased metabolic need and during dysfunction in the respiratory system.
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Muscles help with vision
The human body has over 600 muscles, which help with various functions, from pumping blood to supporting movement. While muscles are often associated with body movement, they also play a crucial role in vision.
There are two types of eye muscles: extrinsic and intrinsic. The extrinsic muscles, also known as extraocular muscles, control eye movement and position. These muscles enable the eyes to move in all directions and ensure proper eye alignment. There are six extraocular muscles and one muscle that controls the movement of the upper eyelid.
On the other hand, the intrinsic muscles control near focusing and the amount of light entering the eye. These muscles work together with the extrinsic muscles to maintain clear vision and proper eye function.
Various conditions and disorders can affect the eye muscles, impacting vision. Strabismus, for example, is a condition where the eyes are not properly aligned, resulting in double vision and potential issues with peripheral vision and depth perception. Eye strain, or Computer Vision Syndrome, is another common issue caused by prolonged focus and computer use, leading to eye fatigue and headaches.
Vision therapy and specific eye exercises can help improve eye alignment, focusing, and eye strain issues. Exercises such as pencil push-ups and near-and-far focusing techniques can help train the eyes to focus effectively. Overall, muscles play a vital role in maintaining healthy vision and ensuring the eyes function properly.
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Frequently asked questions
Skeletal muscles are attached to the bones and allow you to perform a wide range of movements and functions. They are the only muscles that are under voluntary control. Skeletal muscles also help with maintaining body temperature, storing nutrients, and stabilizing joints.
Cardiac muscles make up the middle layers of the heart and are responsible for the rhythmic contractions of the heart. They are under involuntary control.
Smooth muscles are involuntary muscles that line the inside of some organs. They play an important role in many body systems, including the female and male reproductive systems, the urinary system, the respiratory system, and the digestive system.
Intercostal muscles are located around the ribs and help facilitate inhaling and exhaling.
