lecture 10 - muscle/joint action Flashcards
What are the parts of an ‘anatomical lever’?
Bones act as levers, joints as pivot/fulcrum, contracting muscles supply force, load.
What are the position of the components in a first class lever?
Pivot in middle, load and applied force on either side
What are the position of the components in a second class lever?
Pivot and applied force at either end, load in middle
What are the position of the components in a third class lever?
Pivot and load at either end, applied force in the middle
Plantar flex ion involves what class of lever?
Second class
What class of lever is involved with flexion of the elbow joint?
Third class
What are the three factors that affect muscle form/function?
Length, number and arrangement of fibres
How much can muscle fibres shorten?
Up to 50% of their resting length
If a muscle requires a large range of motion, will it be long or short?
Long, so the half-length is long
What is the tension/force of a muscle proportional to?
Cross sectional area of the muscle
The greater the concentration/number of fibres in a given area, the greater the….
tension the muscle can generate
What is the name for muscle fibres arranged vertically in line with tendons?
Parallel fibres
What is the name for muscle fibres arranged oblique to the tendons?
Pennate
Do pennate or parallel fibres have a greater cross sectional area?
Pennate
Why do pennate muscles generate greater force than parallel muscles?
The angle of the muscle fibres allows a greater number of fibres to fit in the same area than parallel muscles, allowing more force to be generated.
Why do muscles consisting of pennate fibres have a small range of motion?
Pennate fibres can only contract by half the length of their shortest fibre. The oblique arrangement leaves some very short fibres on the edges, which creates a small ROM.
What are the three types of pennate muscles?
Unipennate, bipennate, multipennate
What are the three types of muscle contraction?
Concentric, eccentric, isometric
What is concentric muscle action?
Muscle fibres are active, tension exceeds load so muscle shortens/contracts, moving the joint
What is eccentric muscle action?
Muscle fibres are active, developing tension. Load exceeds tension, so muscle lengthens. Usually, another muscle causes this lengthening. Changes joint position
What is isometric muscle action?
Muscle fibres are active, but the load is equal and opposite to the applied force, so there is no change in muscle length or joint position.
What are the four muscle roles at joints?
Agonist, antagonist, stabiliser, neutraliser
What are muscle agonists?
Muscles that act concentrically (shorten to cause the main movement at a joint)
What are muscle antagonists?
Muscles that act eccentrically, and are generally stretched as the result of the shortening of an opposite agonist muscle