Flashcards in MSK 4 - Skeletal Muscle Deck (51)
What are the three types of muscle?
- skeletal (striated)
- cardiac (striated)
- smooth (non-striated)
Give some characteristics of skeletal muscle?
- fused cells
- attached to skeleton
Give some characteristics of cardiac muscle
- branched uninucleated
- heart only
- intercalated discs
Give some characteristics of smooth muscle
- distance cells
- spindle shaped
- wall of internal organs
What are the functions of skeletal muscle?
- joint stability
- heat generation
What is fasciculation?
Small, local, involuntary muscle contractions and relaxation. May be visible under skin.
What attaches a muscle to a bone?
What is the function of circular muscles?
They act as sphincters to adjust opening.
How are circular muscles arranged?
They have concentric fibres, and attach to skin, ligaments and fascia rather than bone. Eg. orbicularis oris, which is around the mouth
What are the three main categories of parallel muscles?
- Strap (fibres run longitudinally to contraction direction) eg. Sartorius
- Fusiform (wider and cylindrical shaped at centre) eg. Biceps brachii
- Fan-shaped (fibres converge at one end and spread over) eg. Pectoralis major
What is a pennate muscle?
One or more aponeuroses run through the muscle body from the tendon
Give an example of a multipennate muscle
Deltoid (this has central tendon branches)
What is the origin of a muscle?
A point on bone, typically proximal, which has greater mass and is more stable during contraction than the muscle's insertion
What is a muscle's insertion?
This is the structure (bone, tendon or connective tissue) that the muscle attaches to. Usually distal and moved by contraction.
What are compartments in limbs?
Limbs are divided into compartments by fascia - eg. The lower leg has four compartments
What is compartment syndrome?
When trauma in one compartment causes internal bleeding which exerts pressure on blood vessels and nerves.
What are the symptoms of compartment syndrome?
- deep constant, poorly localised pain
- aggravated by passive stretch of muscle group
- paresthesia (pins and needles)
- compartment feels tense/firm
- swollen shiny skin with bruising
- prolonged capillary refill time
How is compartment syndrome treated?
Fasciotomy, which can be covered by a skin graft
What are agonist muscles?
'Prime movers' - the main muscles responsible for a particular movement
What are antagonist muscles?
These oppose prime movers
What is the role of synergist muscles?
They assist prime movers. They cannot perform the movement alone, but their angle of pull assists
What is the role of neutraliser muscles?
They prevent the unwanted actions of a joint that would otherwise occur with an agonist
What is the role of fixators?
These act to hold a body part immobile whilst another body part is moving
What is the difference between isotonic and isometric contraction?
Isotonic - constant tension, variable muscle length
Isometric - constant length, variable tension, eg. hand grip
What is the difference between concentric and eccentric isotonic contraction?
Concentric - muscle shortens
Eccentric - muscle exerts a force while being extended eg. walking downhill
What are the three types of levers in the human body?
- first class lever "see-saw" (effort at one end, load at the other, fulcrum in the middle) eg. head
- second class lever "wheelbarrow" (effort at one end, fulcrum at other, load in middle) eg. standing on tip toes
- third class lever "fishing rod" (effort in middle, load at one end, fulcrum at other) eg. biceps in elbow flexion
What is the name given to what happens when ATP is depleted after death, causing myosin heads to be unable to detach?
What is a motor unit?
An alpha-motor neurone and the muscle fibres it innervates
True or false - muscle with less fibres are usually better at fine control, while muscles with more fibres are usually more powerful?