Skeletal Muscle Physio - Smith Flashcards
What is the order of events for a skeletal muscle contraction?
action potential through motor neuron
AP triggers acetylcholine release to synapse
acetylcholine diffuses across the cleft
End plate depolarizes because of the acetylcholine
End Pate triggers AP in the skeletal muscle cell that travels to the t-tubules
AP triggers Ca release from sarcoplasmic reticulum
Ca binds to troponin on the actin which shifts tropomyosin
energized myosin binds to actin and rotates causing shortening
calcium concentration falls and muscle relaxes
What are the 3 roles of calcium in skeletal muscle contraction?
Promotes presynaptic neurotransmitter release
Calcium released form the sarcoplasmic reticulum binds to troponin to initiate sliding fliaments
Calcium promotes glycogen breakdown and ATP synthesis by activating essential enzymes
What are the 3 sources of ATP in the body? How much ATP does each create?
Creatine Phosphate - 1 ATP - fast energy
Glycogenolysis - 2 ATP/Glucose - slower energy
Cellular respiration - 38ATP/Glucose - long term energy
What is oxygen debt?
the amount of O2 needed to convert the accumulated lactic acid to glucose and to restore the supplies of ATP and creatinine phosphate
What is the definition of multiple motor unit summation?
increasing the strength of the stimulus at a constant frequency
What is the definition of temporal summation?
increasing the frequency of a stimulus that is held at a constant intensity
what is the definition of treppe?
a form of incomplete fusion of the wave summation at a frequency just below tetanus
What is the definition of fatigue?
loss of tension despite continuing stimuli
What is the concept of fractionation?
all motor units in a muscle do not need to activate always. When more and more motor units are recruited the greater tension
What is Henneman’s size principle?
motor units are recruited in the order of the size of the motor unit - small to large
What is the order of the hennemen’s size principle?
Type I (slow twitch), Type IIa (fast twitch), Type IIb
What are the 6 basic components of the reflex arcs?
sensor receptor afferent neuron integration center (CNS) interneuron motor efferent neuron effector muscle
How does a stretch reflex work?
the muscle stretch is sensed by the receptor which stimulates the stretched muscle to contract (to resist stretch) through the spinal cord and the alpha motor neuron
What neuron innervates extrafusal fibers?
alpha motor neurons
what neurons innervate intrafusal fibers?
gamma-motor neurons
