Musculoskeletal System: Form and Action at joints

• What are the muscle types?

  1. Skeletal Muscle
  2. Cardiac Muscle
  3. Smooth Muscle
• What is the skeletal muscle?

  They are composed of long multinucleate fibres organized into bundles (fascicles). They are responsible for voluntary movement and attached to bones by tendons.
• What is a Cardiac Muscle?

  It forms the walls of the heart and composed of branched striated cells with a single nucleus. It facilitates rapid communication and coordinates of contractions.
• What is Smooth muscle?

  It consist of elongated spindal - shaped cells with a single nucleus. It is found in walls of internal organs and blood vessels.

  It contracts involuntarily to regulate flow of substances and maintain organ function.
• How do skeletal muscle cause movement at synovial joints?

  • Attaches to bone (leveler)
  • Muscle structure (length, number of fibres,

  arrangement of fibres)

  Type of contraction (roles/action)

  • Where it crosses a joint (location)
• What are Anatomical levers?

  Bone = lever

  Joint = pivot or fulcrum

  Muscle Contraction = applied force/pull

  Weight of what is being pulled = load
• What are the three types of levers?

  First-class, second-class, third-class.
• What is first class lever?

  • stabilises joint function
  • fulcrum between force and load
• What is second class lever?

  • effective at overcoming heavy loads
  • load between fulcrum and force
• What is third class lever?

  • large range of movement
  • force between fulcrum and load
• Muscle form depends on the function of the:

  1. Length of muscle fibres
  2. Number of muscle fibres
  3. Arrangement of muscle fibres
• What is length of muscle fibres?

  Fibres can shorten 50% of the resting length, which the large range of motion is required = long muscle fibres.
• What is number of muscle fibres?

  It is the tension directly proportional to the cross section area, which has greater muscle fibres, greater CSA, greater tension.
• What are the two arrangements of muscle fibres?

  Parallel and Pennate.
• What is Parallel arrangement of muscle fibres?

  They are arranged vertically between muscle tendons and attachments. They are smaller CSA and greater shortening.
• What is Pennate arrangement of muscle fibres?

  Fibres are attached obliquely between tendons and attachments. Also greater CSA and lesser shortening.
• What are the types of muscle action?

  1. Concentric
  2. Eccentric
  3. Isometric
• What is concentric muscle action?

  The muscle is active and develops tension. The muscle shortens and the tension is greater than the load.

  There is a change in joint position.

  The angle decreases.
• What is Eccentric muscle action?

  The muscle is active and elongates and develops tension that is lesser than load. The muscle pulls in the opposite direction by muscle/gravity.

  There is a change in joint position.

  The angle increases.
• What is isometric muscle action?

  The muscle is active, but no change in length and develops tension, which doesn't overweigh the load.

  There is no change in joint position.

  No change to angle.
• What are the types of muscle roles?

  Agonist = creates movement

  Antagonist = opposes movement

  Stabiliser = holds joint still

  Neutraliser = stops unwanted movement
• What are the major muscles of the upper limb?

  • biceps brachii
  • triceps brachii
  • deltoid
  • illiopsoas
• What are the major muscles in lower limbs?

  • Gluteus Maximus
  • quadriceps maximus
  • hamstrings
  • tibialis anterior
  • triceps surae
• Biceps Brachii


  origin = scapula

  insertion = radial tuberosity

  movements:

  • shoulder for flexion
  • elbow - flexion
  • radioulnar joints - super nation
• Triceps Brachii


  origin = scapula and humerus

  insertion = olecranon process of ulna

  movement:

  • shoulder - extension
  • elbow - extension
• Deltoid 


  origin = scapula and clavicle

  insertion = deltoid tuberosity

  movements:

  • shoulder - flexion, abduction, extension
• Illiopsoas 


  origin = illiac fossa and lumbar vertebrae

  insertion = femur

  movement:

  • hip - flexion
• Gluteus Maximus


  origin = illium and sacrum

  insertion = femur

  movement:

  • hip - extenstion
• Quadriceps femoris 


  origin =

  • rectus femoris = illium
  • femur

  insertion = tubial tuberosity

  movements:

  • hip - flexion
  • knee - extension
• Hamstrings 


  origin = ischium

  insertion = tibia

  movement:

  • hip - extension
  • knee - extension and rotation
• Tibialis anterior


  origin = tibia

  insertion = tarsals

  movement:

  • ankles - dorsiflexion
• Triceps Surae


  origin =

  • condyles of femur
  • tibia and fibula

  insertion = calcaneus

  movements:

  • knee - flexion
  • ankles - plantarflexion