Muscles

• Smooth muscles move food in your stomach.
• Skeletal muscles move bones at joints to cause movements.
• Function of muscles is allows movements at joints.
• Slow twitch muscle fibres are specialised for long distance running and endurance events.
• The major functions of muscles are

  • Movement​
  • Support​
  • Stability​
  • Heat generation​
  • Energy storage ​
• A muscle is A band or bundle of fibrous tissue in a human or animal body with the ability to contract, producing movement. ​
• Muscle cells contain the proteins actin and myosin.​
• The three types of muscle are skeletal muscle, smooth muscle and cardiac muscle.
• Skeletal muscle structure

  • Each cell is known as a fibre​
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  • The cells are very long Muscle is literally muscle that is attached to your skeleton , covering it and giving your body shape.
• Voluntary – You control the movement​
• Involuntary – Movement occurs without your control
• Characteristics of skeletal muscle​

  • Rapid movement & contraction​
  • Makes bones and other voluntary structures move ​
  • Tires quickly​
• Smooth muscle structure​

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  • Non striated spindle shaped cells​​
  • A single elongated nucleus​​
  • They contain scattered actin and myosin fibres​​
  • Thin protein filaments are attached to dense bodies​
  • Dense bodies transmit contractions from cell to cell​
• Smooth muscle is associated with the organs of the body. It is involuntary muscle which is controlled by the autonomic nervous system​

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• Characteristics of smooth muscle​

  • Slow and rhythmic contraction​
  • Found in the lining of hollow organs and blood vessels​
  • It does not tire
• Cardiac muscle structure is

  • Cardiac muscle cells are extensively branched, forming connections with other cells​
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  • Cells interconnect at a structure called an intercalated disc ​
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  • Striated cells with a single nucleus​
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  • Cells possess many mitochondria​
• Cardiac muscle function​

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  Cardiac muscle is only found in the heart and produces highly coordinated cardiac muscle contractions.​

  Contractions are controlled by specialised cells called pacemakers. ​
• Characteristics of cardiac muscle​

  • Rapid, rhythmic contraction​
  • Pumps blood from the heart into the vessels of the circulatory system. ​
  • Never tires​
  • Although cardiac muscle cannot be consciously controlled, the pacemaker cells respond to signals from the autonomic nervous system to vary the heart rate. ​
• Steletal muscles are Attached to bones and around entry & exit sites of body ​
• Cardiac muscles are fount at the heart.
• Smooth muscles are located at Walls of major organs and passageways (arteries and stomach).
• • Muscles are only capable of contracting or pulling, they cannot push​​
  • As a result of this limitation muscles generally operate in pairs​​
  • A muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction​
  • This is described as antagonistic muscle action​
• Muscles work in antagonistic pairs this is a group of muscles working together eg: hamstring and quad.
• • A sarcomere is the basic contractile unit of muscle fibre. ​
• • Each sarcomere is composed of two main protein filaments—actin and myosin​
  • The most popular model that describes muscular contraction is called the sliding filament theory.​
• Thin filament of the muscle fibre is actin (aTIN for ThIN)
• The thick muscle fibre in muscle is called Myosin.
• How do muscles contract?

   Actin slides over the top of myosin, bringing the Z lines closer together, making the sarcomere contract.​
• Actin has specific binding sites which myosin attaches to. In the resting state these binding sites are blocked by the tropomyosin strand
• Smooth muscle is associated with the organs of the body, involuntary muscle which is controlled by autonomic nervous system.
• skeletal muscles- It is literally muscle that is attached to your skeleton. Covering it and giving your body it's shape. It is voluntary muscle controlled by the sensory nervous system.
• The bicep is a type of skeletal muscle.
• How do muscles contract?

  Actin slides over the top of myosin, bringing the Z lines closer together, making the sarcomere contract.
• For a contraction to occur

  1. Motor nerve stimulates an impulse or action potential to pass down the neuron to the neuromuscular junction

  2. Sarcoplasmic reticulum releases Ca2+ into the muscle cell

  3. Calcium binds with troponin allowing actin and myosin to form cross bridges

  4. Myosin heads move backwards, pulling the actin over the myosin (power stroke)

  5. ATP binds to myosin and converts to ADP+P, releasing energy allowing myosin to detach from the actin and "re-cock" ready to begin again

  6. Process continues until cells run out of energy, or there is no more calcium available
• Requirements for contraction

  • Nerve impulse
  • Calcium
  • ATP
• After contraction has finished:

  • Relaxation occurs when stimulation of the nerve stops.  ​
  • Calcium is then pumped back into the sarcoplasmic reticulum breaking the link between actin and myosin. ​
  • Actin and myosin return to their unbound state causing the muscle to relax. ​
  • Alternatively relaxation (failure) will also occur when ATP is no longer available.​
• Myosin heads bind to the actin to allow the muscles to contract.