Flashcards in MSK Session 2- Skeletal Muscle Structure, Morphology And Mechanics Deck (40)
Describe skeletal muscle.
-unbranched, long fibres
-multiple, peripheral nuclei.
What are the four functions of skeletal muscle?
Give an example of a unipennate muscle.
The lateral tibial muscle.
Give an example of a bipennate muscle.
Rectus femoris muscle
Give an example of a multipennate muscle.
Give an example of a fusiform muscle
Give an example of a convergent muscle
Give an example of a circular muscle
Orbicularis oris (mouth)
Give an example of a parallel muscle.
Describe the gross anatomy of skeletal muscle.
Muscle fibres are surrounded by endomysium and lie in parallel.
They form bundles to form fascicles, which are surround by perimysium.
Fascicles make up the muscle, which is surrounded by epimysium.
What do tendons do?
Attach muscle to bone
What is fasciculation?
It is muscle twitching due to fascicles making small twitching motions.
What is excessive muscle twitching a potential sign of?
Motor neurone disease.
What is the origin and insertion of the triceps brachii?
Origin- the scapula and humerus
Insertion- tendon inserts on the ulna
What is the origin and insertion of the biceps brachii?
Origin- the scapula
Insertion- the tendon inserts on the radius
Describe a first class lever and give an example.
Acts like a see saw.
An example is the skull- contraction of the muscle on the posterior wall of the neck pulls the skull back.
Describe what a second class lever is and give an example.
It acts like a wheelbarrow.
An example is the gastrocnemius muscle on the posterior of the lower leg. When it contracts and you are standing on tiptoes.
What is a third class lever and give an example.
It acts like a fishing rod.
An example is when the biceps contract and the arm is flexed about the elbow joint.
Which type of lever is the most: efficient, inefficient?
Efficient- first class lever
Inefficient-third class lever
What are agonist muscles?
They are prime movers and produce a specific movement.
What are antagonist muscles?
They oppose the action of prime movers.
What are synergistic muscles?
They are muscles that complement the movement of prime movers. They therefore keep the force in one direction.
What are fixator muscles and what do they do?
They stabilise the action of prime movers.
What is compartment syndrome?
When a blood haematoma forms in the in extensible compartment of a muscle. This puts pressure on the blood vessels and nerves within the compartment and can therefore cause a loss of nervous innervation and muscle contraction.
What is isotonic contraction, and what are the two types?
It is when there is constant tension, but the muscle length changes in relation to the production of movement to move the load.
-concentric- when the muscle shortens, causing movement
-eccentric- when the muscle lengthens and therefore relaxes, while exerting a force.
What is isometric contraction?
When the muscle length remains the same, no movement occurs, but the force is increased.
What are the three muscle fibre types?
Fast twitch IIa
Fast twitch IIb
What are the differences between fast twitch IIa and fast twitch IIb fibres? (7)
A- aerobic respiration, lots of myoglobin, red in colour, lots of mitochondria, rich capillary supply, can fatigue, used for walking/sprinting
B- anaerobic respiration, few myoglobin, white in colour, few mitochondria, poor capillary supply, fatigues rapidly, used for short intense movement.
What are slow twitch fibres used for? (2)
Which type of respiration do slow twitch fibres undergo?
Are slow twitch fibres easily fatigued?
What is proprioception?
It is an awareness of self. That proprioreceptors will recognise muscle stretch and tension and inform the brain, as well as informing it where the muscle is in 3D space.
What is a motor unit?
A motor neurone and the muscle fibres it Innervates.
If fine control is required, does a motor neurone innervate many or few muscle fibres?
What is cross talk?
It is the communication between neurones and muscles via signalling molecules.
When do muscles relax, with regards to calcium?
When calcium is taken up in the SR., or is bound by calmodulin.
What causes muscle cramp?
Anaerobic conditions cause pyruvate to be converted to lactate. If this builds up, it causes muscle cramps.
What is intermittent claudication?
It is intermittent muscle pain caused by a lack of blood flow to muscle, due to a partial blockage.
What is Rigor Mortis?
An example of continuous muscle contraction.
When death occurs, ATP is depleted, therefore myosin heads can't detach and muscles remain in a contracted state.