Skeletal Muscle Flashcards
what are the 4 functions of skeletal muscle
- movement
- posture
- joint stability
- heat generation
what is fasciculation
small, local, involuntary muscle contractions and relaxations which may be visible under the skin
what are individual muscle cells wrapped in
endomysium
what are fascicles wrapped in
perimysium
what is epimysium
a CT layer covering skeletal muscle
what are the 3 types of arrangement of skeletal muscle
- circular
- parallel
- pennate
describe circular muscle
- A ring like band of muscle (concentrically arranged) that surrounds a bodily opening, constricting and relaxing to control flow (act as a sphincter)
- attach to skin, ligaments and fascia rather than bone
give a example of a circular muscle
orbicularis oris (mouth)
describe parallel skeletal muscle
- fascicles run parallel to eachother
- the most common type
- can be strap, fusiform or fan shaped
give an example of each of the 3 different types of parallel skeletal muscle
strap - Sartorius
fusiform - biceps brachii
fan shaped - pectoralis major
describe pennate skeletal muscle
one or more aponeuroses run through muscle body from tendons and fascicles attach to aponeuroses at an angle
give examples of the 3 different types of pennate skeletal muscle
- unipennate: is where all the fascicles are on the same side of the tendon e.g. extensor digitorum longus
- bipennate: where the fascicles are on both sides of the tendon e.g. rectus femoris
- multipennate: central tendon branches e.g. deltoid
what are muscle compartments
a section of the body which contains muscles and nerves and is surrounded by fascia
what is compartment syndrome
pressure withina compartment increases, restricting the blood flow to the area and potentially damaging the muscles and nearby nerves
what are the 2 different types of compartment syndrome
- acute: caused by injury and needs surgery
- chronic: caused by exercise and goes after a few minutes
what are symptoms of compartment syndrome
- pain
- paresthesia
- tense and firmness of compartment
- swollen, shiny skin
- prolonged capillary refill
what is used to treat compartment syndrome
fasciotomy (cutting the skin and fascia to relive the pressure in the compartment then attaching a skin graft)
what are agonist muscles
muscles which are responsible for a particular movement
what are antagonist muscles
muscle which oppose agonist muscles
what are synergist muscles
muscles which assist agonist muscles but cant act alone
what are neutraliser muscles
muscles which prevent unwanted actions that an agonist can perform
what are fixator muscles
muscles which immobilise a body part whilst another is moving
what are the 2 types of skeletal muscle contraction
isotonic and isometric
what is isotonic contraction
contractions where the muscle fibres change length but done change in tension
what are the 2 types of isotonic contraction
- concentric: where the muscle fibres shorten
- eccentric: muscle exerts a force whilst being extended
what is isometric contraction
where the muscle fibre contracts but remains the same length but have variable tension
what is a first class lever
where the effort and load are at either ends of the fulcrum
what is a fulcrum
where a lever is supported
what is a second class lever
where the fulcrum is at one end and the effort at the other with the load in the middle
what is a third class lever
where the fulcrum is at one end and the load at the other with the effort in the middle
what is rigor mortis
when ATP is depleted and the myosin heads cant detach from actin so the muscles are stiff
usually commences 3 hours after death and dissipates after 72 hours reaching maximum stiffness at 12 hours
what is a motor unit
a motor neurone and the skeletal muscle fibres it innervates
what is true about the muscle fibres making up a motor unit
they are all the same contractile type i.e. each motor unit is slow or fast contracting
what are the 3 main types of muscle fibres
- slow type I
- fast type IIA
- fast type IIX
what do the types of muscle fibres depend on
the myosin heavy chain expression
which type of skeletal muscle fibre is used in anaerobic glycolysis
fast type IIX
which skeletal muscle fibre is red
type 1 slow
which type of muscle fibre is the first to be recruited
slow type I
which type of skeletal muscle fibre has the highest levels of myoglobin
slow type I
what 2 things does the contractile force depend on
size principle and rate code
what is the size principle
the smaller motor neurones are recruited before the larger ones
what is the rate code
the frequency at which a muscle fibre is stimulated by a motor neurone
what is tetany
muscle spasms due to increased neural excitability
what is muscle tone
the degree of tension in muscles
what does muscle tone depend on
- degree of muscle elasticity
- low levels of motor neurone activity
what is hypotonia
lack of skeletal muscle tone
damage to what causes hypotonia
motor cortex, cerebellum, spinal cord or muscle degeneration
what is floppy baby syndrome a symptom of
hypotonia
permeability to which ion is most important for the resting membrane potential of skeletal muscle cells
chloride
what is myotonia congenita
mutations in chloride channels resulting in stiffness as chloride currents cant be produced
what is relaxation of skeletal muscle facilitated by
calcium being pumped back into the ER by the SERCA
what causes malignant hypothermia
anaesthetics blocking neuromuscular junctions so there is an increase in ATP production which releases heat in order for the SERCA to work
what are the 4 supplies of ATP
- creatine phosphate
- aerobic glycolysis
- anaerobic glycolysis
- oxidative phosphorylation
