Twitch
What are the 3 stages of a twitch?
Latent period, Contraction Phase, Relaxation Phase
what is the length-tension relationship? (Extra: optimum overlap?)
-depends on overlap between thick and thin fibers
-optimum overlap: greatest tension. Not necessarily at most relaxed or contracted.
What term describes tension at rest?
tone
Describe frequency vs strength of stimuli:
(effect?)
Frequency: how often (increased twitches, increased tension)
Strength: how strong (increased motor unit response)
What is another name for a muscle fiber? (extra: why is this important to know/ what happens here?)
Muscle Cell. A cell so it has cell elements: mitochondria, nuclei, sarcolemma (cell membrane), sarcoplasmic reticulum (ER, Ca2+). Innervated by a branch of a somatic motor neuron (synapses).
*show image
what is wave summation?
adding twitches creating a wave-like relationship. (shows increasing tension)
sustained contractions require_______
many repeated stimuli
What are the two main patterns of tension?
Isometric and Isotonic
Why are human muscles pink? What kind of fibers?
Mix of
White fibers (mostly fast fibers) and
Red fibers (mostly slow fibers)
Somatic motor neuron and the muscle fibers it innervates.
Incomplete Tetanus vs Complete tetanus:
Incomplete: twitches reach max tension. most common
Complete: Continuous contraction, cant stop, not common. (excessive energy and strength required)
The process in which the number of active motor units increases is called:
recruitment
What contraction is describes as:
Muscle contraction without length change
isometric
why do we have muscle tone?
-helps us to hold our bodies upright.
-ready for motion
What triggers Ca2+ channels to open?
Action potential form synapse to muscle. Goes along Sarcolemma and t tubules.
holding a heavy object that is not heavy enough to eliminate relaxation: what kind of twitch twitch?
Incomplete tetanus
How are motor units able to sustain contractions for
longer periods of time?
motor units contract alternately
what are the 2 parts of isotonic:
(tension is constant while muscle length
changes)
Concentric:
when muscle tension greater than load (resistance):
• Muscle shortens
Eccentric:
when muscle tension less than load (resistance):
• Muscle lengthens
Describe Anaerobic vs Aerobic activity:
Anaerobic (example:50-meter dash weightlifting)
• fast fibers, Fatigue quickly, Causes hypertrophy
• Improved by frequent, brief, intensive workouts
Aerobic (prolonged activity)
• Supported by mitochondria and Require oxygen and nutrients
• Improves: Endurance and Cardiovascular performance
What are the 3 binding sites of troponin (a component of actin)? Which one is most important for contraction?
1- binds to tropomycin (band that blocks active sites)
2- binds to Ca2+ (pulls tropomycin bands out of teh way of active sites) (allows contraction)
3-binds/anchors to actin
What stage of twitch refers to action potential moving along sarcolemma causing Ca2+ release?
Latent Period
What term describes the effect of elastic forces, opposing muscle contractions, and gravity?
relaxation
What happens when muscle tension greater than load (resistance)? What is this called?
-Muscle shortens
-Concentric
describe stimulus, tension, twitch, tone relationship:
stimulus causes twitch that lead to tension. Tone is tension at REST
What causes sarcomere shortening? Do myosin and Actin lengths change?
Myosin heads pull on actin filaments.
No the distance between z lines to get closer.