A&p 2-Essay exam 1 Study Guide 3

Describe the relationship between number of muscle fibers present and amount of tension produced by a motor unit.

All muscle fibers controlled by a single motor neuron -all fibers in a motor unit contract together The more fibers in a unit the more tension produced.

Recall the major events that occur in each phase of a muscle fiber twitch

Latent period-no tension produced Contraction phase-tension peaks Relaxation phase-tension falls

Briefly describe three mechanisms by which contracting muscles return to resting length

"passive" 1. opposing muscle contractions -quickest way 2. elastic forces -tendons and organelles "recoil" 3. Gravity

Describe the relationship between muscle tone and resting metabolic rate

"resting" muscle tension -produced by a few active motor units The greater the muscle tone, the higher one's resting metabolic rate. -the more calories burned, even at rest

Compare and contrast concentric and eccentric muscle contractions. Give examples of each

Isotonic Concentric-muscle shortens as the tension increases Isotonic Eccentric-muscle lengthens as the tension increases

Compare and contrast isotonic and isometric contractions. Give examples of each

Isotonic contractions -produce movement -muscle shortens(or lengthens) as the tension increases ex-walking, running, moving objects Isometric Contractions -produce NO movement -muscle does NOT shorten as the tension increases ex-maintaining posture, holding objects in fixed positions

Compare and contrast tension production in a single muscle fiber and in an entire muscle

Single muscle fiber Depends on -degree of overlap -frequency of stimulation Entire Muscle Depends on -number of stimulated muscle fibers

Compare and contrast large and small motor units

Small motor units-only a few fibers, produce precise movements Large motor units-1000s of fibers, produce more powerful but less precise movements

Describe the relationship between stimulation frequency and tension production

Stimulation Frequency The faster the stimulation the more tension produced -twitch -treppe -wave summation -incomplete tetanus -complete tetanus Tension Production Single Muscle fiber depends on -degree of overlap -frequency of stimulation Entire muscle depends on -number of stimulated muscle fibers

Differentiate between twitch, treppe, wave summation, incomplete tetanus, and complete tetanus

Twitch-a single "stimulus-contraction-relaxation" sequence in a muscle fiber Treppe-occurs when fiber is re-stimulated immediately after relaxation phase, slight increase in tension, due to gradual increase in Ca2+ Wave summation-occurs when fiber is re-stimulated before it completely relaxes, larger increase in tension Incomplete tetanus-occurs when stimulation continues (fiber is not allowed to relax completely). "near" maximum tension produced (during rapid cycles of contraction/relaxation Complete Tetanus-Stimulation frequency prevents any relaxation, Ca2+ levels remain high. Maximum amount of tension produced(continuous contraction)