motor unit and fiber type Flashcards
There are 3 fiber types what are they?
1) type 1/aerobic
2) type 2a/anerobic glycolysis
3)type 2x /anerobic glycolytic /cp
how many muscle fibers, motor neurons are there approximately in a human?
~600 milly muscle fibers
~420k motor neurons 1428x less of them compared to fibers
~600 fibers/neuron
what are the characteristics of type 1 or aerobic?
Low force production
High mitochondria density
High blood supply/capillarization
Cellular adaptations
Oxidative capacity/high
Glycolytic capacity/low
Fuel / triglycerides
Slower calcium use=slower shortening speed
Large amounts of mitochondria
Less developed glycolytic capacity
use oxygen and glucose
produces 36-38 molecules of ATP
What process produce ATP in aerobic respiration/
1) oxidation phosphorylation -Glycolysis: Initially, glucose or glycogen is broken down into pyruvate in the cytoplasm of the muscle cell through glycolysis.
2) citric acid cycle- The pyruvate enters the mitochondria and is further processed in the citric acid cycle, producing electron carriers (NADH and FADH2) and some ATP.
3) electron transfer chain Electron Transport Chain: NADH and FADH2 transfer electrons to the electron transport chain, a series of protein complexes located in the inner mitochondrial membrane.
what are the characteristics type 2 a or anerobic glycolytic?
Resists fatigue
Long term Anaerobic
Moderately fast
Medium force production
High mitochondria density
Medium amount of capillarization
Cellular adaptations
Oxidative capacity/ high
glycolytic capacity/high
Fuel/creatine phosphate and glycogen in muscles
High electrical chemical transmission
High myosin atpase activity/ breakdown of fuel to sustain contractions
High rate of crossbridge turnover
what are characteristics of type 2x/ glycolytic cp fibers?
Fatigues rapidly (more fibers innervated)
Short term Anaerobic
Very fast
High force production
Medium mitochondria density
Low capillarization
Neural adaptations
Oxidative medium
Glycolytic capacity/high
Fuel/creatine phosphate and glycogen in muscles
High electrical chemical transmission
High myosin atpase activity/ breakdown of fuel to sustain contractions
High rate of crossbridge turnover
what color’s are the 3 fibers when stained with a basic alkaline preincubation?
type 1=white
type2a= grey
type2x=grey
what color’s are the 3 fibers when stained with an acidic preincubation?
type 1=dark
type2a=white
type2x=white
SDA and fibers?
type 1=darker blue due to ATPasepresent
type2a=light blue
type2x=wont stain due to minimal ATPase
List parts of a motor neuron?
action potential propagation
pre synaptic knob
neuromuscular junction
pre synaptic vesicles acetylcholine
synaptic cleft
post synaptic membrane
sarcolemma
t tubule
sarcolemma
tubule
muscle
Fiber Type is determined by 3 Characteristics what are they?
Determined by:
1. Myosin-ATPase activity
* Speed of contraction
2. Type of Metabolism
* Oxidative vs Glycolytic
* Determines resistance to fatigue
3. Fiber Diameter
* Maximal tension at any given length
How does a muscle contract?
1.The change in membrane potential generates an action potential that travels along the sarcolemma and penetrates deep into the muscle fiber through the transverse tubules (T-tubules).
2. It then triggers the SERCA pump to release calcium
3.The calcium binds to troponin to causing a change in postion allowing myosin heads to attach to actin
3.Power stroke occurs causing the myosin heads to pull actin “forming a crossbridge, this process requires atp.
4.Sarcomeres contract together causing an etrire muscle to contract
What does a motor neuron consist of?
1) An alpha neuron
2) and all the muscle its innervates
(type1, type 2a or fog and type 2x FG)
What is the function of a motor neuron?
The motor neurons are essential for the central nervous system to communicate with and control skeletal muscles, enabling us to perform voluntary and coordinated movements. They are a fundamental component of the neuromuscular system.
Does the size of a motor neuron make it superior?
No, its more about how the accuracy, precision and coordination of movement for example eye lids and fine motor skills versus gross motor
give an example of gross motor movement?
walking which requires large amounts of muscle to be activated and recruited so higher thresholds are needed.
give an example of fine motor skills
eye lids or picking up a pen less muscles need to be recruited so lower thresholds.
what is meant by the range of a motor unit?
The range can vary from fine to gross or a combination of both types of movements which may recruite a few to over 100 fibers
who studied a swedish ski team to determine fiber types?
Rusko h
what did Rusko h find?
1)Took muscle biopsies from finish national team over 8 years
2)Determined that high volume produced 11% increase in slow twitch fiber =1.5%/year
3)So yes it can be changed/slow process
4)Dictated by genetics
However the change can happen but not to the extent of a true fiber
Cross innervation studies are when they take an axon from a slow and attach it to a fast and vice versa
