Week 2 - muscle actions etc Flashcards
7 functions of muscles
- Produce movement
- maintain postures + positions
- stabilise joints
- support + protect viscera (organs)
- alter/control pressures in internal spaces eg. chest cavity
- maintenance of temp
- control entrances + exits to the body eg. swallowing
How do muscles do their job
By developing tension (pulling force at either or both ends of a linear object)
Describe a concentric contraction
When muscle tension force is greater than external load +/- gravity
- muscle shortens + joint movement is produced
Describe an eccentric contraction
When muscle tension force is less than external load but greater than gravity
- muscle lengthens + joint movement produced
Describe an isometric contraction
When muscle tension force is equal to external load +/- gravity
- Muscle length remains constant + no joint movement occurs
Describe an isokinetic contraction
When velocity of movement is constant as muscle shortens or lengthens
Differentiate b/t origin + insertion
Origin is the proximal muscle attachment whereas insertion is the distal muscle attachment
Describe an open kinetic chain in terms of origin + insertion
Origin is fixed + insertion moves towards origin
Describe a closed kinetic chain in terms of origin + insertion
Insertion is fixed + origin moves towards insertion
Describe the role of an agonist
Prime mover -
- can produce an isotonic or isometric contraction
Describe the role of an antagonist
Opposes action of agonist -
- must relax to allow movement to occur
- may act as a ‘brake’ at the end of rapid movement
Describe the role of an assistant agonist
Assists the agonist with the movement
Describe the role of the neutraliser
Limit unwanted movement by the agonist
eg. when walking upstairs rec fem wants to extend knee so hamstrings act as neutraliser to prevent this
- can also work in pairs as mutual neutralisers eg. flexor carpi ulnaris + flexor carpi radialis cancel out wrist deviation
Describe the role of stabilisers
Muscles that act in 1 segment so that a specific movement can occur at an adjacent joint
eg. rotator cuff ‘sucks’ ball of humerus into socket of scapula so its stabilised when shoulder abduction occurs
Describe the role of supporters
Similar to stabiliser but acts at a distance from moving joints to prevent movement by gravity
eg. abdominals during pushup
What is a force than can be used clinically to overcome gravity
Buoyancy
What is mass
Quantity of the physical property of the matter
What is weight
Object mass x acceleration due to gravity -> N
Describe centre of mass
The right angle intersection b/t all 3 cardinal planes
- Mass is equal superiorly + inferiorly, anteriorly + posteriorly + left + right
- Same as COG when weight distributed evenly
Describe centre of gravity
The point about which the body can balance perfectly against gravity
- can change or shift depending on orientation of body
- can lie inside or outside body
Other factors influencing COG are
Age - COG becomes lower as move to adulthood
Sex - females have lower COG due to mass distribution
Describe the line of gravity
Hypothetical line drawn through COG
- oriented downwards/ perpendicular to ground
- location coupled w/ COG
Describe base of support
The total area beneath an object or surface
- includes all points of contact (and area b/t them) between object/person + surface
Describe how to maintain stability
Line of gravity must remain inside base of support to remain upright
