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Have you ever been working out and suddenly your muscle curls into a ball and is no longer of use to you? This experience is called a muscle cramp, also known as a charley horse. These cramps occur “when muscles involuntary contract and cannot relax” (Muscle Cramp: A Common Pain). You can go through a whole range of muscle cramps from ones that are very weak to extremely strong and painful. These cramps can occur anywhere in the body and to any type of person. However, the young, elderly, the obese, and athletes tend to be more vulnerable to muscle cramps occurring.
The first reason muscle cramps occur is due to straining or overuse of the muscle. This is used as a protection mechanism in order to prevent the muscle from becoming more damaged.
The second reason muscle cramps occur is caused by dehydration. Dehydration is dangerous to the body for many different reasons. Specifically focusing on cramping, when the body is dehydrated, there is much more of an issue transporting the necessary minerals and electrolytes in order to keep the body supplied. Due to this slow reception of the necessary ingredients to keep the muscle working, the muscle can cramp up.
This leads us to our third reason, a lack of minerals and electrolytes being supplied to the body. When the muscle does not receive enough electrolytes or minerals (such as potassium) it looses its ability to function and cramping ensues.
There are other ways that muscle cramps can occur, such as damage to the spinal cord, or damage to the brain; however, these are much less likely options.
Anatomy of the muscle
Skeletal muscle is where most muscle cramping occurs and it is where we shall focus our attention. Skeletal muscle is made up of small muscle fibers that are surrounded by endomysium. These muscle fibers come in bunches, which are wrapped together by perimysium. These groupings are called muscle fascicles. Combining many groups of muscle fascicles into one bundle forms skeletal muscle (Korthuis).
Skeletal muscle receives all of its necessary nutrients from the arteries, arterioles, and capillaries that flow through it. It also removes all of the waste and byproducts by transporting it out of the muscle cells or releasing the waste into the veins to be transported elsewhere.
The Neuromuscular system
The neuromuscular system is the connection between the muscles and the brain. This connection begins to evolve with different sensory receptors and nerves that are attached to the muscles. There are also thermoreceptors and nocioceptors that gather information about the muscles and the environment that they are in. Two other receptors of important are the golgi tendon organs and the muscle spindle. The golgi tendon organ is sensitive to stretch which the muscle spindle will be responsive to stretch. The information that is sent to the brain by the dorsal medial lemniscal pathway and the anterolateral pathway about the muscles is used to let the brain know that a muscle cramp is occurring. A few ways that the brain can react to try to relieve the cramp and the pain that comes with it, is to deliver more blood and send commands to bring more minerals to the muscles. Finally, the brain can send commands down descending pathways to the rest of your body to move other limbs in order to perform a movement that involves reaching, grabbing your toe, and then stretching your leg if that is where the cramp is occurring. For more information on the dorsal column medial lemniscal pathway you can refer to this link for a short
. Overall, it is through these pathways that the afferent and efferent nerves that are attached to the muscle communicate with the brain consciously and subconsciously in order to understand what is happening when a muscle cramps and to then counteract the effects.
Overall, muscle cramps occur because the muscle is put in a position where it needs to protect itself from injury and it communicates this through cramping. Whether this occurs through lack of minerals, blood supply, or other problems does not matter. The same response will occur, muscle cramping. Muscle cramping can occur based on these issues stated, or in rare cases can be symptoms of a larger and more serious disease. The nerves sense a cramp occurring and sends the information to your brain through ascending pathways. Then, the brain responds by processing the information, sending commands down descending pathways, and resupplying the muscle with whatever it needs to remove the cramp.
Glossary of Terms
Endomysium-Connective tissue that covers the muscle fibers that make up the muscle
Cramp-Involuntary, sustained muscle contraction
Perimysium-Connective tissue the encompasses the bundles of muscle fibers
Neuron-any conducting cell in nervous system
Anterolateral Pathway-descending pathway associated with pain
Dorsal Column Medial Lemniscal Pathway-descending pathway dealing with conscious and sensory movement
True or False: A muscle cramp is a result of overuse of the muscle.
A muscle cramp is a result of:
lack of nutrients
all of the above
True or False: The muscle fiber contains bundles of muscle fascicles.
The brain communicates with the muscle by:
The dorsal column medial lemniscal pathway:
Transports harmful waste from the body
Sends information to the muscles from the brain
Sends information from the brain to the muscles
Tell sensory nerves exact what they are sensing
True or false: Endomysium and perimysium essentially serve the same role.
Are muscle cramps:
Voluntary muscle contractions
Involuntary muscle contractions
True or false: Effector neurons are the primary neurons the communicate with the muscle and ascending and descending pathways.
Can a muscle cramp be permanent?
Can muscle cramps occur in the form of serious diseases?
Answer key: T,1,F,4,2,T,2,T,YES,YES
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Katzberg HD, Khan AH, So YT (2010). "Assessment: Symptomatic treatment for muscle cramps (an evidence-based review): Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology".
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The Nervous System & Skeletal Muscle
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