MSK - Muscle physiology Flashcards
whats the difference in terms of initiation and propagation of contraction in skeletal and cardiac muscle
skeletal = neurogenic cardiac = myogenic
skeletal has NMJs, cardiac does not
skeletal has no gap junctions, cardiac does
skeletal has motor units, cardiac does not
which muscle gets Ca2+ entirely from SR? cardiac or skeletal
skeletal
cardiac muscle gets Ca2+ from extracellular fluid also
what is a motor unit
a single ALPHA motor neurone and all the skeletal muscle fibres it innervates
muscles used for fine movements have more fibres per motor unit. true?
false - muscles used for fine movements have fewer fibres per motor unit
what does the surface action potential have to spread down in order for Ca2+ to be released from SR
transverse (T)- tubules
what does skeletal muscle tension depend on
- no of motor fibres contracting within muscle
2. asynchronous motor unit recruitment during sub maximal contractions
how is it possible to summate twitches to bring about a stronger contraction
the duration of AP is much shorter than duration of resulting twitch
therefore, repetitive fast stimulation of skeletal muscle gives a stronger contraction
what can too much twitch summation result it
tetanus
not possible in cardiac muscle due to long refractory period
when can maximal tetanic contractions be achieved
when muscle is at optimum length
this is at resting length in humans (the point of optimal overlap of actin and myosin binding sites)
which type of muscle contraction is used in YOGA
isometric
what are the 3 metabolic pathways that supply ATP in muscle fibre
- transfer of high energy phosphate from creatine phosphate to ADP (this makes ATP) (the creatine transports the phosphate to muscle)
- oxidative phosphorylation (when O2 present)
- glycolysis (when O2 not present)
which glycolytic fibres use anaerobic metabolism only
fast glycolytic (type IIx) fibres
what does the stretch reflex aim to maintain
optimal muscle resting length
how does the stretch reflex maintain optimal muscle resting length
by resisting passive change - the muscle that is being stretched contracts
how does tapping muscle tendon with hammer elicit a response
it rapidly stretches muscle, causing contraction
what are the special sensory receptors that detect that the muscle is being stretched and what motor neurones are they supplied by
intrafusal muscle spindles
supplied by gamma motor neurones
which lumbar segment does the knee jerk assess
L3 - L4 (femoral)
which sacral segment does the ankle jerk assess
S1-S2 (tibial)
which cervical segment does the biceps jerk and brachioradialis test
C5 - C6
biceps = musculocutaneous nerve brachioradialis = radial nerve
which cervical segment does the triceps jerk test
C6-C7 (radial)
what is the most common type of hyaline cartilage
type II collagen
what is the main difference between trabecular and cortical bone
trabecular bone has spaces in and around it, cortical doesn’t
what is the purpose of the terminal bouton
it is found at the end of every branch of motor neurones
when AP reaches terminal bouton, ACh is released
where is ACh synthesised from choline and acetyl CoA and by what enzyme
cystol
by choline acetyltransferase
when ACh arrives at terminal of neurone, what channels open
Ca2+ channels open and Ca2+ gets into terminal
what happens when Ca2+ gets into terminal
ACh diffuses into synaptic cleft
what receptors does ACh activate after it travels across synapse? what affect does this have
nicotinic ACh receptors
causes the gate to open, causing Na+ to enter cell and K+ to exit
this depolarises membrane and generates an END PLATE POTENTIAL
how does Lambert Eaton syndrome affect NMJ
AI antibodies against voltage activated Ca2+ channels
causes muscle weakness
what pulmonary association does Lambert eaton syndrome have
associated with small cell lung cancer
