Muscles Flashcards
What is the orgin of a muscle?
The stationary anchor point and is usually sited proximally in the limb
What is the insertion of a muscle?
The insertion is the mobile attachment point and is usually sited distally in the limb.
Why is muscle contraction describe as symmetrical?
Equal force excerted on the origin and insertion. It is the stabilisation of the ‘origin’ (e.g. by contraction of other muscles) that leads to the ‘insertion’ becoming the only mobile attachment point. If the usual insertion point becomes fixed and the usual origin becomes mobile, the position of the origin and insertion will become inverted.
Using the pectoralis major describe insertion and origin and the orientation of the muscle fibres in order to understand the action of the muscle
Origin - Medial half of the clavical and anterior surface of the sternum and first six costal cartilages
Insertion - lateral lip of the biciptal groove of the humerus
Contraction of the sternocostal head pulls the humeral insertion towards the fixed sternocostal origin, and therefore adducts the arm if it is abducted at the shoulder joint.
Alternatively, if the upper limb starts in the anatomical position (by the patient’s side, palm of the hand facing forwards), contraction of the clavicular head will flex the arm at the shoulder joint.
If instead, the humerus is already externally rotated at the shoulder joint, contraction of pectoralis major will internally rotate it.
With regards to muscular movement, describe the meaning of agonist, antagonists, synergists, neutralisers and fixators?
Agonists - Prime muscle responsible for a paticular movement
Antagonists - Oppose agonist action
Synergists - assist the prime mover
Neutraliser - prevent unwanted action of a muscle
Fixators - stabilise joints
What are concentric contractions?
Cause the muscle to shorten as it contracts.
Example - flexing the elbow from full extension to full flexion by concentric contraction of the Biceps Brachii muscle.
Most common type of contraction
What are eccentric contractions?
The opposite of concentric and occur when the muscle lengthens as it contracts. This occurs when lowering the dumbbell down in a bicep curl exercise .
The fibres within the Biceps brachii muscle are still contracting to control the rate at which the dumbbell is lowered, but the muscle is lengthening
What are isometric contractions?
Occurs when there is no change in the length of the contracting muscle.
Example - when carrying an object in front of you as the weight of the object is pulling your arm downwards, but your muscles are contracting to hold the object at the same level.
Label the following skeletal muscle fibres
What is a fascial compartment?
aAregion of the limb that contains muscles, nerves and blood vessels, surrounded by deep fascia
