Taylor Summation Flashcards
what controls intensity of skeletal muscle contraction
summation
type of summation that increases force of contraction by increasing frequency of action potentials
temporal summation
type of summation that increases intensity of contraction by increasing the amount of motor units
spatial summation
what are being summated during temporal summation
muscle twitches, NOT action potentials
smallest motor unit
small neurons innervating few type I muscle fibers
largest motor unit
large neurons innervating many type II muscle fibers
what increases when the load to be moved increases
firing frequency
how are additional motor units recruited
small to large
assessment of muscle activity through electrodes inserted into muscle
electromyography
what exactly does electromyography measure during contraction
motor unit action potentials (MUAPs)
low frequency and high amplitude indicative of what
neuropathy
low amplitude and short duration are sometimes indicative of what
myopathies
transient involuntary contractions; electrically active
cramps
failure to relax; electrically silent
contracture
why does myopathy show low amplitude and short duration
b/c some fibers are not participating
contracting at constant length (no shortening)
isometric contraction
increase muscle length increases what
forceand velocity
maximal force is achieved when
at optimal length
contraction at constant force (muscle shortens)
isotonic contraction
during isotonic contraction, what do you see initially before muscle shortens
isometric contraction
maximum force is seen at what muscle length
optimal (Lo)
increasing the load on the muscle does what to the velocity of shortening
decreases
decreasing initial length of muscle does what to velocity of shortening;increase length=
decreasing; increase length=increasing velocity
_____ is independent of initial length
Vmax
contracting while shortening (arm curl)
concentric contraction
contracting while lengthening (negative arm curl)
eccentric contraction
contraction most susceptible to injury
eccentric contraction
neural circuit at the level of the spinal cord providing automatic link between sensory input and a specific motor output (alpha motor neurons)
reflex arc
detects length and deals with stretch and speed of stretch; protects muscle from overstretch and has normal reflex arc
muscle spindle
not in muscle but in tendon; responds to contraction, make sure muscle doesn’t overcontract and deals with relaxation
golgi tendon organ
“knee jerk reflex”; stretches quad and stretch muscle spindle and causes normal reflex
myotatic reflex
0 (no response and deals with Westphal’s sign)
hypoactive
4+ and deals with clonus
hyperactive
often indicates neuropathy (upper motor neuron lesion)
clonus
these fibers are used during strenuous exercise
type I and II
these fibers are used during endurance and requires oxygen
type I
during a marathon, type I fibers are being used but what happens when glycogen stores and glucose have been depleted and person is just dependent on FA’s after this said event
“the wall”
the inability of muscle to maintain force
fatigue
during high intensity exercise, what stops muscle from contracting (fatigue)
low pH
temporary involuntary muscle contraction (spasms)
cramps
quick involuntary muscle twitches (random spasm)
fasciculations
broad involuntary muscle jerk
myoclonus
extended contraction due to inability of muscle to relax
contracture
