Ch 11: Behavior of whole muscle Flashcards
Length – tension relationship
Ideal length intention of sarcomere at rest that allows for maximum contraction and tension when stimulated
Myogram
Map of the timing and strength of a muscle contraction
Muscle twitch
Cycle of contraction and relaxation when action potential is fired
Phases of muscle twitch
- Latent phase
- Contraction phase
- Relaxation phase
Latent phase of muscle twitch
Time between stimulation and contraction occurring; AP has to travel down to tubules and release calcium and have sequence of events before next phase
Contraction phase of muscle twitch
Pulling of actin filaments by myosin heads towards M line to shorten sarcomeres
Relaxation phase of muscle twitch
Calcium re-sequestered, stimulation stops. Tropomyosin covers actin’s active sites and sarcomere lengthens
Duration of a muscle twitch
Between 7 -100 ms
Factors that affect contraction strength:
- Stretch
- Fatigue (lack of Ca^2+ or ATP)
- Temperature of muscle
- Stimulus frequency
Effect of stimulus intensity on muscle twitch
Greater voltage of the tumulus equals more muscle fibers recruited because more action potentials are sent along more muscle fibers. Or muscle fibers recruited equal stronger contraction
Effects of stimulus frequency on muscle twitch
Temporal summation (wave)
Fused to tetanus
Temporal (wave) summation
Build up of additional recruitment of neurons due to increasing frequency; each new twitch rides on the previous ones generating higher tension
Incomplete (unfused) tetanus
Contractions don’t fully relaxation before another contraction comes
Complete (fused) tetanus
Isolated muscle stimulated at such a frequency that all the twitch is fused into a single common on fluctuating contraction.
Only achievable in a laboratory setting
Isometric muscle contraction
Premovement
Important in postural muscle function
Ex: Pick up dumbbell, PLANK
Isotonic contraction
Muscle changes in length with no change in tension
Concentric isotonic contraction
Muscle shortens as it maintains tension
EX: bicep curl: curling weight up
Eccentric isotonic contraction
Muscle lengthens as it maintains tension
Ex: bicep curl: uncurling weight down
Muscle fatigue
Decrease in fiber tension of the fiber even a stimulation is occurring
Psychological muscle fatigue
“Mind over matter” Telling yourself you can’t do it even though it’s still physically possible
Physiological muscle fatigue
Fatigue from decreasing ATP concentration, increase in ADP
Cause: Constant stimuli, dietary deficiency, sickness, etc.)
Excess post Dash exercise oxygen consumption (EPOC)
Oxygen debt after exercise
Short term energy
Quick burst of energy (30-40 secs) from anaerobic respiration; buildup of lactic acid from glycolysis
Long-term energy
Reliant on cardio and respiratory systems catching up for oxygen delivery; aerobic respiration
Types of skeletal muscle fibers
- Type 1: Slow – oxidative fibers
- Type 2A: (intermediate) fast – oxidative – glycolytic fibers (animals)
- Type 2B: fast glycolytic fibers
Slow – oxidative fibers -type 1
Red fibers.
Slow twitch; endurance fibers
High myosin – ATPase activity and high oxidative capacity
Fast – glycolytic fibers (type 2B)
White fibers because lack myoglobin.
Fast twitch, no endurance. 
Hi myosin-ATPase activity and high glycolytic activity
Myasthenia gravis: Symptoms, cause, treatment
Symptoms: muscle fatigue and weakness that get progressively worse as muscle is used
Cause: autoimmune destruction of nicotinic ACH receptor proteins of the motor end plate
treatment:AChE inhibitors 
Rigor mortis: what is it? Cause of it, time
Hardening of muscles and stiffening of body, starts 3 to 4 hours after death.
Cause: Deteriorating of SR: calcium all released so muscle contracts, but can’t relax. Fibers remain contracted Until myofilaments decay. 
Peaks at 12 hours, diminishes over next 48 to 60 hours
