Dominic Stone
The human body is made up of more than 600 muscles, which help us move, breathe, swallow, and stay alive. There are three types of muscle tissue in the body: skeletal, smooth, and cardiac. Skeletal muscles are voluntary muscles that can be consciously controlled, such as the muscles in the neck, arms, and legs. They attach to bones and respond to nerve signals from the brain that lead to muscle contraction. These muscles can convert chemical energy into mechanical energy to cause voluntary muscle contraction and movement.
| Characteristics | Values |
|---|---|
| Type | Skeletal muscles |
| Controlled by | Somatic nervous system |
| Consists of | Multiple bundles of cells and muscle fibres |
| Appearance | Striated |
| Location | Attached to bones by tendons |
| Function | Contraction and relaxation |
| Examples | Muscles of the neck, arms, legs, back, and trunk |
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What You'll Learn
- Skeletal muscles are voluntary muscles that attach to bones
- Voluntary muscles are controlled by the somatic nervous system
- Cardiac muscle is striated but is not under voluntary control
- Smooth muscles are involuntary and found in internal organs
- Voluntary movements are actions consciously controlled by the individual
Skeletal muscles are voluntary muscles that attach to bones
Skeletal muscles are the most common type of muscle in the human body, accounting for 30-40% of body weight. They are attached to bones by tendons and are found all over the body, including in the tongue, diaphragm, eye socket, and upper oesophagus. They are also present in the neck, arms, back, trunk, and legs.
Skeletal muscles are voluntary muscles, meaning that they are under conscious control. They are composed of flexible muscle fibres that contract to allow for movement. Each muscle can contain thousands of fibres, and these fibres can be red or white. They are also striated, or striped, and are often referred to as striated muscles.
The somatic nervous system sends signals to the skeletal muscles to make them function. These muscles receive neural inputs, allowing for conscious control. Skeletal muscles serve many purposes, including producing movement, sustaining body posture and position, maintaining body temperature, storing nutrients, and stabilising joints.
Skeletal muscles are involved in various bodily functions, such as breathing, speaking, swallowing, and digesting food. They also play a role in metabolism and blood sugar level regulation. Weakness or inability to control voluntary skeletal muscles can signal a health issue, such as a neuromuscular disorder or electrolyte imbalance.
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Voluntary muscles are controlled by the somatic nervous system
Voluntary muscles, such as the muscles in the neck, arms, and legs, are under the control of the somatic nervous system. This system is a subdivision of the peripheral nervous system, which includes all of the nervous system except the brain and spinal cord. The somatic nervous system is responsible for all the functions that can be consciously influenced, such as moving the arms, legs, and other body parts.
The somatic nervous system consists of both afferent (sensory) and efferent (motor) nerves. The afferent nerves send information to the brain and spinal cord, while the efferent nerves send signals from the brain. The motor neurons in the efferent nerves are responsible for voluntary movements, such as walking or lifting an object. The somatic nervous system also includes the cranial nerves, which are 12 pairs of nerves that use Roman numerals to differentiate them. Eleven of these pairs have connections that are part of the somatic nervous system.
The cranial nerves connect to different parts of the body below the head, such as the neck, and send signals to and from the brain. The spinal nerves, on the other hand, branch out to form the nerves that spread throughout the body. These nerves are also responsible for carrying sensory information from the body to the spinal cord and sending muscle commands from the spinal cord to the skeletal muscles.
The somatic nervous system is also responsible for a specific type of involuntary muscle response known as reflexes, controlled by a neural pathway called the reflex arc. The reflex arc involves using interneurons to perform rapid reflexive actions, such as quickly contracting a muscle to avoid an injury.
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Cardiac muscle is striated but is not under voluntary control
There are three major categories of muscles in the human body: skeletal, cardiac, and smooth muscle. Skeletal muscles are the most common type of muscle in the human body. They are attached to bones by tendons and are under voluntary control. They make up between 30% and 40% of the human body's total mass. Examples of skeletal muscles include shoulder, hamstring, and abdominal muscles.
Cardiac muscle, also called the myocardium, is responsible for the contractility of the heart and, therefore, the pumping action. It is composed of striated muscle fibres containing actin and myosin filaments that power contraction. However, unlike skeletal muscle, cardiac muscle is under involuntary control. The body's autonomic nervous system (ANS) and its own pacemaker cells control the cardiac muscle, causing it to contract automatically and rhythmically.
Autorhythmic cardiac cells do not contract but set the pace of contraction for other cardiac muscle cells, which the ANS can modulate. Contractile cardiac cells, or cardiomyocytes, constitute the majority of the heart muscle and can contract. These cells are striated, branched, and contain many mitochondria. The cardiac muscle must contract with enough force to pump blood and supply the metabolic demands of the entire body.
Smooth muscles, on the other hand, are found inside organs like the blood vessels, stomach, and intestines. They help move substances through the organs and control the internal diameter of blood vessels. Like cardiac muscle, smooth muscles are under involuntary control.
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Smooth muscles are involuntary and found in internal organs
Smooth muscles are involuntary muscles that are found in the internal organs of the body. They are an integral part of the human body and are required for life. Smooth muscles are found in almost every organ system, including the cardiovascular system, the gastrointestinal system, and the urinary system. They help regulate blood pressure and flow, open and close airways, and play a role in digestion and nutrient collection.
Smooth muscles differ from skeletal muscles in that they are non-striated and cannot be controlled voluntarily. They consist of thick and thin filaments that are not arranged into sarcomeres, giving them a homogeneous appearance under a microscope. Smooth muscle cytoplasm contains a large amount of actin and myosin, which are the main proteins involved in muscle contraction.
Smooth muscle can be further categorized into two types: single-unit and multi-unit. Single-unit smooth muscle consists of multiple cells connected through connexins, allowing for synchronous contraction. Multi-unit smooth muscle, on the other hand, has finer control, with each cell receiving its synaptic input. This type of smooth muscle is found in the airways of the lungs, large arteries, and ciliary muscles of the eye.
Smooth muscles play a vital role in maintaining the body's subsystems. For example, in the cardiovascular system, smooth muscles help maintain blood pressure and flow, ensuring that the body receives adequate oxygenation during exercise or increased physical activity. In the gastrointestinal system, they aid in digestion and the movement of substances through the organs.
In summary, smooth muscles are involuntary muscles found in the internal organs, where they serve essential functions such as digestion, nutrient collection, and regulation of bodily functions like blood pressure and oxygenation. Their unique structure and ability to contract involuntarily make them crucial for maintaining the body's homeostasis and overall health.
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Voluntary movements are actions consciously controlled by the individual
The human body has more than 600 muscles that help us move, breathe, swallow, and stay alive. These muscles use a combination of voluntary and involuntary movements to work with nearly all our body's systems and functions. Voluntary movements are actions that we consciously control and choose to perform, using our nervous system to direct our muscles to move our bodies. For example, flicking your thumb to scroll through an article on your phone and sprinting around a track are both voluntary movements.
Voluntary movements are controlled by skeletal muscles, which are attached to the bones by tendons. These muscles make up 30% to 40% of human body weight in a healthy person. They respond to nerve signals from the brain that lead to muscle contraction. Skeletal muscles can convert chemical energy into mechanical energy to cause voluntary muscle contraction and movement. Their composition involves bundled units of fascicles, made up of muscle fibers or muscle cells. Each muscle fiber is divided into myofibrils that contain thick (myosin) and thin (actin) myofilaments.
In contrast, involuntary movements happen automatically without conscious thought. These movements are controlled by smooth and cardiac muscles, which are found in the internal walls of the intestines, stomach, uterus, and blood vessels. Smooth muscles do not have striations in their cells and have a single, centrally located nucleus. Cardiac muscles, on the other hand, are striated like skeletal muscles but are controlled by both the autonomic nervous system and their own pacemaker cells, causing them to contract automatically and rhythmically.
Disorders such as amyotrophic lateral sclerosis (ALS) and Charcot-Marie-Tooth disease can affect the nerves that control voluntary movements, leading to muscle weakness and atrophy. Maintaining muscle health is important to ensure the proper functioning of both voluntary and involuntary movements.
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Frequently asked questions
Skeletal muscles are the type of muscles that are under voluntary control.
Skeletal muscles are attached to bones and respond to nerve signals from the brain that lead to muscle contraction.
Muscles in your neck, arms, and legs are skeletal muscles.
Involuntary muscles are controlled by the autonomic nervous system. These include smooth muscles and cardiac muscles.
The muscles in your heart and blood vessels, and in your digestive system are involuntary muscles.
