motor unit summation, contraction and fiber types Flashcards
explain the motor unit?
its the somatic motor neuron and all muscle fibers it serves
describe the pattern of somatic motor neurons (SMN)
SMN leave spinal cord to muscle –> when it reaches the perimysium CT it branches onto collateral branches and serves individual muscle fibers
every muscle fibers can be contracted by how many SMN?
Every muscle fiber gets ONLY ONE connection to somatic muscle neuron
Number of fibers for each motor unit varies depending on movement for ex…
Small muscle / fine motor movement = less fibers / motor units
Large gross motor muscles /contract to cause movement = lotta fibers / motor units
why will every somatic neuron will only supply one fiber type?
b/c diff types of fibers have diff properties
ex. if you want strong forceful contraction or ones that will be sustained / last longer
summarize motor unit summation
drawn out
what are the types contractions?
isometric
isotonic
- concentric
- eccentric
what is an isometric contraction?
length of muscle doesnt change but tension increases
- myosin heads are pull omg on actin and the external force is equal to it so theres no change
what is an isotonic contraction?
constant amount of tension but muscle length changes
what are the types of isotonic?
concentric - muscle shortens when tension overcomes resistance . pulls actin towards the m line
eccentric - muscle lengthens when resistance is greater than tension. actin is pulled away from m line
what are the different fiber types?
type 1 muscle fibers
type 2a muscle fibers
type 2x muscle fibers
describe type 1 fiber
slow twitch (use energy slowly and fairly evenly to make it last a long time)
high oxidative
smaller in diameter b/c myofibrils inside fibers
better blood supply
more mitochondria
SLOW OXIDATIVE (SO)
describe type 2a fiber
fast twitch (use up a lot of energy very quickly, then get tired (fatigued) and need a break)
low oxidative
fast atp breakdown
less mitocondria
FAST OXIDATIVE GLYCOLYTIC
contract for long periods of time and be sustained
describe type 2X fiber
Largest
least mirochondria
least blood supply
strongest
Exercise training cant change from type 1 to type 2 b/c cant change type of myosin ATPase BUT we can change from type 2a to type 2x
Aerobic/endurance training can turn 2x to 2a (a is closer to type 1 fiber)
Resistance training can turn 2a to 2x - which gives them more strength
