Muscles

From WikiMD
Jump to navigation Jump to search

There are about 600 muscles in the human body. Muscles have a range of functions from pumping blood and supporting movement to lifting heavy weights or giving birth. Muscles work by either contracting or relaxing to cause movement. This movement may be voluntary (meaning the movement is made consciously) or done without our conscious awareness (involuntary).

Glucose from carbohydrates in our diet fuels our muscles normally although the body can adapt to using other fuels such as fat or even protein in extreme situations - see ketosis. To work properly, muscle tissue also needs particular minerals, electrolytes and other dietary substances such as calcium, magnesium, potassium and sodium.

A range of problems can affect muscles – these are collectively known as myopathy. Muscle disorders may cause weakness, pain or even paralysis.

Different types of muscle


The three main types of muscle include:

  • Skeletal muscle – the specialised tissue that is attached to bones and allows movement. Together, skeletal muscles and bones are called the musculoskeletal system (also known as the locomotor system). Generally speaking, skeletal muscle is grouped into opposing pairs such as the biceps and triceps on the front and back of the upper arm. Skeletal muscles are under our conscious control, which is why they are also known as voluntary muscles. Another term is striated muscles, since the tissue looks striped when viewed under a microscope.
  • Smooth muscle – located in various internal structures including the digestive tract, uterus and blood vessels such as arteries. Smooth muscle is arranged in layered sheets that contract in waves along the length of the structure. Another common term is involuntary muscle, since the motion of smooth muscle happens without our conscious awareness.
  • Cardiac muscle – the muscle specific to the heart. The heart contracts and relaxes without our conscious awareness.

Make-up of muscle


Skeletal, smooth and cardiac muscle have very different functions, but they share the same basic composition. A muscle is made up of thousands of elastic fibres bundled tightly together. Each bundle is wrapped in a thin transparent membrane called a perimysium.

The neuromuscular system


The brain, nerves and skeletal muscles work together to cause movement. This is collectively known as the neuromuscular system. A typical muscle is serviced by anywhere between 50 and 200 (or more) branches of specialised nerve cells called motor neurones. These plug directly into the skeletal muscle. The tip of each branch is called a presynaptic terminal. The point of contact between the presynaptic terminal and the muscle is called the neuromuscular junction.

To move a particular body part:

  • The brain sends a message to the motor neurones.
  • This triggers the release of the chemical acetylcholine from the presynaptic terminals.
  • The muscle responds to acetylcholine by contracting.

Shapes of skeletal muscle


Generally speaking, skeletal muscles come in four main shapes, including:

  • Spindle – wide through the middle and tapering at both ends, such as the biceps on the front of the upper arm.
  • Flat – like a sheet, such as the diaphragm that separates the chest from the abdominal cavity.
  • Triangular – wider at the bottom, tapered at the top, such as the deltoid muscles of the shoulder.
  • Circular – a ring-shape like a doughnut, such as the muscles that surround the mouth, the pupils and the anus. These are also known as sphincters.

Muscle disorders


Muscle disorders may cause weakness, pain, loss of movement and even paralysis. The range of problems that affect muscles are collectively known as myopathy. Common muscle problems include:


Wellness that matters!



Articles on Muscles


Topics related to Muscles

See other topics, articles and terms related to Muscles on WikiMD.

This article is a stub. YOU can help Wikimd by expanding it!



Health topics
A-Z health topics | Popular health topics

A |  B |  C |  D |  E |  F |  G |  H |  I |  J |  K |  L |  M | N |  O |  P |  Q |  R |  S |  T |  U |  V |  W |  X |  Y |  Z

Portals | Portal:Medicine

Medicines | Dentistry portal | Medications portal | Pharmacology portal | Psychiatry portal

Glossaries and dictionaries | Comprehensive dictionary of medicine

Glossary of medicine | Glossary of health topics | Anatomy | Diet | Pediatrics | Cardiology | Neurology | Pathology | Psychiatry | Obesity | Pharmacology | Rheumatology | Gynecology

W8MD Ad
Our sponsors:W8MD weight loss, sleep and medspa

WikiMD Resources for Muscles

Articles

Most recent articles

Most cited

Review articles

Articles on Muscles in N Eng J Med, Lancet, BMJ

Media Muscles

Powerpoint slides

Podcasts and MP3's

Videos

Evidence Based Medicine

Cochrane Collaboration

Clinical Trials

Ongoing Trials on Muscles

Trial results on Muscles

Clinical Trials on Muscles at Google

Books and news

Books on Muscles

Muscles in the news

Commentary Muscles

Blogs on Muscles

Patient Resources / Community

Patient resources

Discussion groups

Patient Handouts

Other resources

Social Media

Reddit
Quora.png
Pins
Instagram
YouTube videos
Flickr
Bing.png

W8MD Weight Loss, Sleep & MedSpa

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U |V | W | X | Y | Z

W8MD logo

Ad. Tired of being overweight?. W8MD's insurance weight loss can HELP*

Lose weight King of Prussia, PA | Lose weight NYC | Lose weight NJ | Lose weight Philadelphia | Advertise

Disclaimer: The entire contents of WIKIMD.ORG are for informational purposes only and do not render medical advice or professional services. If you have a medical emergency, you should CALL 911 immediately! Given the nature of the wiki, the information provided may not be accurate, misleading and or incorrect. Use the information on this wiki at your own risk! See full Disclaimer. * Individual results may vary for weight loss from our sponsors.

Our sponsors WikiMD is supported by W8MD weight loss, sleep and medical aesthetic centers.