Form and Action at joints Flashcards
How does the skeletal muscle cause movement at synovial joints
Attaches to bone
Muscle structure
Type of contraction
Where it crosses a joint
Level arrangement…
determines function
Example of first class lever
See saw, scissors
The anatomical levers are
Bone
Joint
Muscle contraction
Weight of what is being moved/load
Second lever class function
-Effective at overcoming heavy loads
-Load between fulcrum and force
The classes of levers
First second third
First lever class function
-Stabilises joint positon
- Fulcrum between force and load
Example of second class lever
Wheelbarrow, bottle opener
Third lever class function
-Large range of movement, speed
-Force between fulcrum and load
Example of third class lever
tweezers, fishing rod
Muscle form determines function depending on
- Length of muscle fibres
- Number of muscle fibres
- Arrangement of muscle fibres
Length of muscle fibres explain
-Fibres can shorten up to 50% of resting length
-If large ROM required - long muscle fibres
Fibres can shorten up to what percentage of resting length
50%
If a larger ROM is required,
the longer the muscle fibres will be
Number of muscle fibres explain
- Tension is directly proportional to the cross sectional area
- Greater number of fibres = greater cross sectional area and greater tension
Two types of muscle arrangement
Parallel and pennate
Explain the parallel muscle arrangement
- Fibres are arranged vertically between muscle tendons/attachments
- Smaller cross sectional area, greater shortening
Explain pennate muscle arrangement
- Fibres are arrange obliquely between muscle tendons/attachments
-Greater cross sectional area, lesser shortening
Concentric
-Muscle is active, develops tension
-Tension is greater than load
-Muscle shortens
-Change in joint position
Muscles can contract in three ways which are
Concentric
Eccentric
Isometric
Eccentric
- Muscle is active, develops tension
-Tension is lesser than load
-Muscle elongates, pull in opposite direction by another muscle/gravity
-Change in joint position
Agonist
creates movement
Isometric
-Muscle is active, develops tension
-Tension does not outweigh load
-No change in length of muscle
-No change in joint position
Types of muscle roles at a joint
Agonist
Antagonist
Stabiliser
Neutraliser
Antagonist
opposes/controls movement
Stabiliser
holds joint still
neutraliser
stops unwanted movement
Agonists acts…
concentrically to create a movement at a joint
Antagonist acts…
eccentrically to oppose and control the movement
Stabilisers holds..
a joint still and prevents the movement of a joint
When holding a heavy book, what happens with the biceps brachii
The role of the biceps brachii is the stabiliser, in action it is isometric. There is no change in the length of the biceps brachii and no movement at elbow joint
Neutralisers eliminates…
an unwanted movement caused by another muscle
Concentric actions of muscles
Anterior - flexion
Lateral - abduction
Medial - adduction
Posterior - extension
What influences the movements a muscle produces at a joint
Its structure, location and type of contraction
Muscle action and role changes…
depending on the movement
