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 class of lever is this?
Second class
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
What are muscle stabilisers?
Muscles that hold a joint still (isometric action)
What are muscle neutralisers?
Muscles that eliminate unwanted muscle movement, using extension and flexion.
Generally, what kind of movement will a muscle lying anterior to a joint produce?
Flexion
Generally, what kind of movement will a muscle lying posterior to a joint produce?
Extension
Generally, what kind of movement will a muscle lying medial to a joint produce?
Adduction
Generally, what kind of movement will a muscle lying lateral to a joint produce?
Abduction
What joint is the exception to the concentric muscle rules?
The knee joint
What kind of movement will a knee muscle lying anterior to the joint produce?
Extension
What kind of movement will a knee muscle lying posterior to the joint produce?
Flexion
How many heads does the bicep brachii have?
Two
Where is the superior attachment of the biceps brachii?
Scapula
Where does the inferior end of the biceps brachii attach?
The radius - the radial tuberosity
What movement is generated by the biceps brachii at the shoulder and why?
Flexion, muscle anterior to joint
What movement is generated at the elbow by the biceps brachii and why?
Flexion, muscle anterior to joint
How many heads does the triceps brachii muscle have?
Three
What are the three heads of the triceps brachii?
Long, short, medial
Where does the long head of the triceps brachii attach?
The scapula
What heads of the triceps brachii attach to the humerus?
Short and medial
Where does the inferior end of the triceps brachii attach?
The olecranon of the ulna
What movement is generated by the triceps brachii at the shoulder, and why?
Extension, muscle posterior to joint
What movement is generated by the triceps brachii at the elbow, and why?
Extension, muscle posterior to joint
What is the shape of the deltoid muscle?
Triangular