Muscle 10 Flashcards
What is the comparison in terms of time between an action potential and muscle twitch?
A muscle twitch lasts a lot longer than the action potential
What is Summation?
When action potentials occur with less time in between them so that muscle tension does not have enough time between action potentials to relax back to the initial resting level
What does summation cause?
Tension to build
What are the twitches like in Summation?
Each additional twitch is superimposed on the next twitch causing an increase in tension each time
What occurs in in unfused tetanus?
The tension in the muscle builds and there is no time to to relax between action potentials so the tension does decrease a little bit between stimulation but tension remains at the same tension
What occurs in Fused Tetanus?
Muscle stimulation occurs so frequently that tension builds and there are no longer oscillations of force and the tension plateaus at a single tension level as the simulations are no longer distinguishable from one another
Why does Tetanus not occur in Cardiac muscle?
Due to different ion channels involved in the action potential
Why would Tetanus be dangerous in the heart?
Because a prolonged contraction won’t allow the heart chambers to fill with blood
How do Tetanic Contractions caused by neurotoxins from bacteria work?
The toxin inhibits synaptic vesicles released by interneurons that inhibit firing skeletal muscle
Why does Tetanus arise?
It arises because the time between successive action potentials is insufficient to return enough calcium to the sarcoplasmic reticulum to lower the intracellular calcium concentration
What is the meaning of at stimulation frequencies above the fusion frequency, muscle fiber tension increases very little?
Increasing a stimulus frequency past the frequency required to reach tetanus will not further increase the muscle fiber tension
What does the CNS determine in terms of muscle fibers?
- The frequency at which it stimulates the single muscle fiber
- The number of individual muscle fibers it stimulations at a given time
What occurs in man rather than a twitch?
The summation of action potentials from the spinal cord to the muscle
What are changes in the force of a muscle brought about by?
Recruitment of motor units
What is Recruitment?
The process of increasing the number of active motor units in a muscle
