Fast and Slow Muscles, Muscle disorders Flashcards
when a motor neuron is excited what fibers contract?
all of the fibers in the motor unit contract
how is the force of muscle contraction increased?
- by activating more motor units - recruitment
- by activating motor units more by increasing stimulus frequency to cause summation or tetanus of individual motor units
what does an EMG (electromyogram) record?
it measures the electrical activity of skeletal muscle
What are fast and slow muscles adapted for?
- slow muscles are adapted for slow, sustained, tonic, fatigue-resistant contractions ex) postural muscles
- fast muscles are adapted for rapid, intense, phasic, easily fatigued contractions ex) gastrocnemius
wat makes a muscle fast or slow?
the reason a muscle is fast or slow is simply dependent on the duration of the twitch - the contraction phase and relaxation phase are the start and endpoint of the speed of contraction
are fast and slow metabolism designed for the same metabolism?
slow muscles - constantly used so they are adapted for aerobic metabolism - they require lots of ATP
fast muscles are adapted for anaerobic metabolism- they need to twitch quickly they don’t have tim for anaerobic metabolism
*slow muscles are red due to mitochondria, myoglobin, and vascularity where as fast muscles are white due to lack of the above -
*this is why in a chicken, the white meat is found in the chicken wings -b/c they are not used for flight, however the legs are dark meat due to their constant use and presence, therefore, of vasculature/myoglobin/mitochondria
what is the difference between type1, 2a, and 2b muscle fibers?
Type1 = small, long twitch with lots of blood supply (slow oxidative fibers)
Type 2a= intermediate - fast twitch but both oxidative and glycolytic - they’re the bets of both worlds … contracts rapidly but is still aerobic (fast oxidative fibers)
Type 2b= Fast contractions, sparse in capillaries, low oxidative capacity - used for short bursts of energy usage - high glycogen capacity though for anaerobic metabolism (fast glycolytic fibers)
do some muscles have all fast or all slow cells?
no! the muscles are composed of a mix of cells - it’s the majority of cells that determines if a muscle is fast or slow
ex) soleus muscle is known as a slow muscle, but it has a number of both fast and slow fibers
*individual cells are either fast or slow*
what is the difference in the motorneurons between slow and fast fibers?
the motorneurons to slow fibers are smaller than those to fast fibers - their cell bodies are more excitable and are the first to be recruited during moderate contractions - fast fibers will be recruited during more intense contractions
What did the Buller experiment tell us about muscles and nerves?
the nerve has a profound influence on our muscle - if you get the fast nerve and stick it into the slow muscle, then the muscle will turn fast - so the nerve determines the type of muscle ( slow or fast)
can you train your muscle cells to be fast or slow?
no - mainly predetermined
elite sprinters have high numbers of fast fibers =
elite endurance athletes have high numbers of slow fibers
what are fasciculations after denervation?
visible twitching caused by release of ACh from degenerating motorneurons -
the nerves start to die after you cut them and they are releasing ACh as a result - therefore they produce a visible contraction as a result of spontaneous ACh release
What can cuase Type 1 and Type 2 atrophy?
both of these occur in peripheral neuropathies, disuse (bedrest, spaceflight, immobilization), parkinson’s disease, or myasthenia gravis
mainly type 2 atrophy found with Duchenne muscular dystrophy and ageing (sarcopaenia)
type 2 hypertrophy occurs with weight training
how can we reverse age related sarcopaenia?
we can reverse sarcopaenia with weight training
