PURDUE BIO 203 EXAM 2 LECTURE 11 QUESTIONS AND ANSWERS || LATEST UPDATE 2025

Threshold stimulus - ANSWERThreshold-electrical stimulus needed for muscle fiber to contract All-or-nothing phenomenon - ANSWERFiber contracts or doesn't (applies to each individual muscle fiber) Motor unit - ANSWERMotor neuron and all the muscle fibers its connected to Motor recruitment - ANSWERProgressively activating more motor units Muscle tone - ANSWERTONE=partial contraction of muscle -some fibers are contracted and some are relaxed necessary for posture and balance Staircase effect (treppe) - ANSWERFrequency of stimulation: strength twitch progressively increases caused by a build up of Calcium in the sarcoplasm Not all the calcium is pumped back into SR so next twitch will be a little bigger than the last Multi-unit smooth muscle - ANSWERNot well organized Occurs as separate fibers Contract independently of each other Iris, arrector pili, blood vessels, alivary of lungs Visceral ("single unit") smooth muscle - ANSWERCells arranged in sheets Individual cells are close in contact and stimulate via gap junctions Wave of excitation travels along sheet