Muscle form + action at Joints Flashcards
What influences movement of muscles
*It’s attatchment to bone –> lever
*Muscle structure i.e length, no. of fibres and arrangement
*Types of contraction
*Location of the muscle to the joint
What is the lever?
Bones
What is the pivot point?
The joint
What is the load?
The weight
How does a lever aid in movement
The muscle pulls on the lever to lift the load
What are the different types of levers
Class 1
Class 2
Class 3
Class 1 lever
For balance and stability, fulcrum in between load and applied force eg. See saw
In the body, the load is the head, the fulcrum is the atlanto-occipital joint and the AP is the muscles contracting to pull the head up
Class 2 lever
For effectively lifting heavy loads, fulcrum at the end, load in the middle and AP at other end eg wheelbarrow
The leg where the pivot is the toes, the Load runs through the bone and applies down and the AP is the gastrocnemius contracting to lift up
Class 3 lever
For large range of motion + speed, the fulcrum at the end, applied force in the middle and the load at the end eg tongs/fishing rod
Dumbell in the hand, the pivot is the elbow and the AP is the bicep contracting to pull weight up. The fulcrum is closer to the AP
Points of muscle structure
*Length
*number of muscle fibres
*Arrangement
How much can fibres shorten?
upto 50% of resting muscle length
What kind of muscle fibre is required for a large ROM?
Long muscle fibres
How does number of muscle fibres influence movement?
The tension is proportional to the CSA. Therefore, if there are more muscles fibres in the CSA of a muscle = more tension i.e can life more heavier stuff
Two types of muscle fibre arrangement
Parallel and Pennate
Parallel muscle fibre arrangement
runs in straight lines besides each other and in between tendons
Less muscle fibres fit so less tension but better for ROM
Pennate muscle fibre arrangement
Runs obliquely, more muscle fibres can fit between tendons so more tension BUT can only contract half the shortest arrangement so not a lot of ROM
What are the types of muscle action?
*Concentric
*Eccentric
*Isometric
Concentric
The muscle is active, tension is developing and the tension is greater than the load so muscle shortens
Decreases angle between levers
Eccentric
The muscle is active, tension is developing but the tension is lesser than the load so muscle elongates
Angle increases between the levers
Could be the pull in opp. direction due to another muscle/Gravity
Isometric
The muscle is active, tension is developing
Tension = load
No change in muscle/ joint position
Muscle roles
*Agonost
*Antagonist
*Stabiliser
*Neutraliser
Agonist
*Moves concentrically to initiate a movement eg biceps brachii contracts to lift something
Antagonist
*Moves eccentrically to appose an agonist movement, controls the action of the agonist and makes sure its smooth Eg triceps brachii elongates to appose biceps brachii contracting
Stabiliser
*Holds joint in position i.e stable + still, isometric activity
Neutraliser
Eliminates an unwanted movement caused by another muscle eg. pronator muscles act as neutralisers in the arm to prevent supination when lifting a glass of water
The rule for muscle contraction with reference to the relative position of the muscle to the joint
Anterior - flexion
Posterior - extension
Lateral - abduction
Medial - Adduction
What do the muscles cause?
Movement towards itself
