Neuromuscular Physiology II Flashcards
What is a muscle twitch?
Contractile response of a muscle fiber to a single muscle AP
What happens if all muscle fibers within a muscle were activated?
Whole muscle twitch
Latent Period
delay between the arrival of the AP and initiation of contraction
Contraction period
When CA2+ binds to troponin and the actin-myosin cross-bridges are formed
Relaxation period
When Ca2+ is actively pumped back into the SR, myosin head detaches from actin and muscle tension decreases
Refractory period
the period of time when the muscle tissue is unable to respond to a subsequent AP
Wave summation
occurs when a second AP triggers muscle contraction before the first contraction has finished
Wave summation - result
stronger contraction; b/c the muscle fiber hasn’t had enough time to completely reset its self
What is tetanus
when repeated stimuli are sent in short durations that they can lead to an even greater summation of contraction force
Unfused (incomplete) tetanus
occurs when muscle fibers are stimulated at a rate where they don’t completely relax between stimuli
Fused (complete) tetanus
occurs when muscle fibers are stimulated at a rate where they don’t relax AT ALL between stimuli
Henneman’s size prinicple
- not all MN have same excitability threshold
- smaller, fatigue-resistant MU’s recruited first
What is fatigue?
reduction in the force output (or capacity) of a muscle in response to a voluntary effort
Where does peripheral fatigue occur?
at or below the level of the NMJ
Where does central fatigue occur?
above the level of the NMJ; motor cortex, spinal cord
