2 - Skeletal Muscle Flashcards
Give four functions of skeletal muscle
MovementPostureStability of joints Heat generation
Why is a mechanical effiency of 20% useful for skeletal muscle?
Large amount of energy lost as heat e.g. shivering
Give 7 types of skeletal muscle
CircularConvergentParallelUnipennateMultipennateFusiformBipennate
What is a first class lever muscle?
Force —- Fulcrum — LoadLoad and force on opposing sides
Give an example of a first class lever muscle
The muscles in the posterior region of the neck attached to the skull
What is a second class lever?
Force – Load – FulcrumForce and load on same side of fulcrum, with load between force and fulcrum
Give an example of a second class lever
The muscles in the back of the calf flex the foot by exerting force on the calcaneus
What is a third class lever
Fulcrum – Force – Load
Give an example of a third class lever
Biceps
What is the most common type of lever? How efficient are they?
Third class, the least efficient
What is an agonist?
Prime movers (main muscles responsible for a particular movement
What is an antagonist?
Oppose prime movers (agonists)
What are synergists?
Assist prime movers (neutralise extra motion)
What are fixators?
Stabilize action of prime movers e.g. fixes non-moving joint when prime mover acting over two joints
What is a compartment?
Limbs are divided into comparments, which are lined and defined by fascia.
What is COMPARTMENT SYNDROME?
Trauma in a compartment can cause internal bleeding, which could exert pressure on blood vessels and nerves in the compartment. This can give rise to a variety of symptoms and is called compartment sydrome.
What is an isotonic contraction? What are the two types?
Constant tension, variable muscle length Concentric and eccentric
What is a concentric isotonic contraction?
Muscle shortens e.g. lifting a load with the arm
What is an eccentric contraction?
The muscle exerts a force while being extended
What is isometric contraction?
Constant length of muscle, variable tension e.g. hand grip
What are three types of muscle fibre?
Type 1, Type IIa and Type IIb
What is type I?
High oxidative capacity and are resistant to fatigue. Maintain contractions over long periods of time and are very important in postural muscles.
What is type IIb?
Mostly obtain energy via glycolysis and rapidly fatigue
What is proprioception?
touches noseFeedback control of movement
How is proprioception determined
By special nerve endings known as proprioceptors and muscle spindles in muscles, which sense the degree of stretch and tension in the muscle.
Why are muscle spindles clinically useful?
Give rise to some reflexes in the body which can be tested
What is a motor unit?
A motor neurone and the muscle fibres that it innervates
How many muscle fibres per motor neurone?
Anywhere between 2 and 2000 muscle fibres, depending on degree of fine control required
What is cross-talk?
Signalling molecules communicate between nerve and muscle. If one atrophys, so does the other
How do muscles increase force generated?
More motor units activated, via process known as recruitment. Termed spacial summation.
What aids in recruitment?
Motor neurones, feedback from muscle spindles, joint receptors and golgi tendon organs
What is temporal summation?
Increased frequency of action potentials causes summation and tetanus
What occurs in tetanus?
Toxin from bacterium clostridium tetani blocks inhibitors motor feedback control which leads to unopposed muscle contraction
What is EMG?
Method of measuring electrical activity in muscle, via method known as electromyography
How do muscle cells relax?
Ca 2+ pumped back into the SR via Ca 2+ pumpsSome Ca2+ binds to a protein known as calmodulin
