Exam ! Flashcards
(52 cards)
Fast Motor Units (Type IIx)
high force production, fast contraction speed, low fatigue resistance, has a systematic increase in tension; fast glycolytic systems used
Fast Fatigue-Resistant Motor Units (Type IIa)
moderate force production, fast contraction speed, moderate fatigue resistance, has a systematic increase in tension, uses fast oxidative systems
Slow Motor Units (Type I)
low force production, slow contraction speed, highly fatigue resistant, no systematic increase in tension, slow oxidative; “dark meat” because of myoglobin; high oxidative capacity
High Oxygen Consumption =
higher VO2, higher aerobic capacity, more slow twitch fibers
Low Oxygen Consumption =
lower VO2, lower aerobic capacity, less slow twitch fibers
Motor Unit
a single nerve and every muscle fiber it innervates; come in different ratios of muscle fibers per motor neuron depending on how fine the movement is
Intensity v. Motor Units Recruited
as intensity increases, more motor units are recruited; force generation dictates motor units; light intensity/load means more type I motor units are available; heavy intensity means type IIa and IIx are much more available; moderate load means all three types are used equally
Size Principle
frequency of motor unit utilization is directly related to the size of the motor unit; smaller motor neurons are utilized more frequently and vice versa; motor units with smaller motor neurons (type I) will be recruited first
All or None Law
if you fire a motor neurons, all of their muscle fibers have to fire as well
Twitch
the smallest contractile response of a muscle fiber or a motor unit to a single electrical stimulus
Summation
a series of three stimuli is rapid sequence, before complete relaxation from the first stimulus, can elicit an even greater increase in force or tension
Tetanus
continued stimulation at higher frequencies can cause this, which results in the peak force or tension of the muscle fiber or motor unit
Rate Coding
the process by which the tension of a given motor unit can vary from that of a twitch to that of tetanus by increasing the frequency of stimulation of that motor unit
Asynchronous Recruitment
out of rhythm recruitment; “out of synch”; the motor units take turns, while some are contracting others are recovering; allows for endurance and resistance to fatigue; looks like a smooth contraction but all taking turns; sub max
Synchronous Recruitment
when you want to exert maximal force; all motor units fire at the same time; as we get stronger we get better at doing this;
Absolute Maximum Force
golgi tendon organs and muscle spindle prevent us from reaching this; but if we train hard enough we can overcome this; we also overcome this in fight or flight situations
Relative Maximum Force
When we perceive muscle fatigue; one rep max; we’ve all done this in the gym
Motor Unit Categorization
Two types based on speed of contraction (slow twitch and fast twitch) and three types because of metabolic capabilites (glycolytic or oxidative)
How is Muscle Fiber Type Determined
muscle biopsy or histochemical staining
Distribution of Fiber Types (Vo2 v. muscle fiber)
High oxygen consumption means higher VO2, higher aerobic capacity, more slow twitch fibers
Summation
a series of three stimuli in rapid sequence, before complete relaxation from the first stimuli; can elicit an even greater increase in force or tension
Absolute Maximal Force
golgi tendon organs and muscle spindle prevents us from reaching this; fight or flight response or extreme training can overcome these inhibitory forces
Relative Maximal Force
we all have done this when we’re in the gym; what we perceive as our muscle’s maximal force
Recruitment Order
motor units are recruited in sequential order and fired in this order; allows us to become very proficient at what we do; learned through repetitions
