Graded Muscle Contractions & fibers Flashcards
(33 cards)
What are the 2 criteria needed for contraction
ATP (will always have ATP unless death )
Calcium
Terminal cisternae contain membrane bound foot protein that is called
Ryanodine Receptor (RyR)
For a given set of Physiological conditions, a muscle fiber twitch always produces the same tension in response to an action potential — is called
A muscle twitch is an ______ response
All or None
Progressive activation of muscles motor units to achieve desired contraction strength
Motor unit recruitment
smaller motor neurons = small motor units
larger motor neurons= larger motor units
Smaller motor neurons have lower thresholds than larger motor neurons
size principal of recruitment
what motor unit is recruited first in terms of recruitment
The smaller motor units with the smaller thresholds.
In order to recruit the large ones you need a high Action Potential frequency
Which motor units are more fatigue resistant?
small motor units are slow and fatigue-resistant and are activated first and for longer periods of time than the large motor units that are fast and fatigable and recruited later and for shorter periods of time.
What is fiber type of motor units recruited first vs. those recruited last?
smaller motor units with the smaller thresholds working our way up to the large motor units with the large thresholds
What happens if you stimulate a muscle fiber again BEFORE the muscle relaxation is complete?
calcium levels spike
the second twitch is added on to the first twitch, resulting in wave summation
When calcium levels are high - what starts to occur?
Cross bridge cycling
if a muscle fiber is restimulated after it has COMPLETELY relaxed, what occurs?
The second twitch will be the same magnitude as the first twitch
if a muscle fiber is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli –
a maximal sustained contraction known as tetanus occurs
(when a graph is increased but then stays constant and levels out)
continuous cross bridge cycling
How do you stop tetanus
either you stop stimulating it OR it begins to fatigue out
Why does stimulating motor units at higher frequencies produce more tension than stimulating them at lower frequencies?
summation results in greater contraction of the motor unit
Why is there an optimal resting length of a muscle?
enables skeletal muscles to generate the maximum force possible when contracted or stimulated
when we took the frogs gastroc muscle out of the frog.. what did we ruin / take out?
we took out the frogs optimal resting length of the gastroc muscle (it was stretched in the body and now it is not)
if the resting length is longer or shorter
the contractions are compromised. The length tension relationship is altered
effect of resting fiber length on muscular contraction (term)
length-tension relationship
what instrument did we use in the frog lab that recorded how much contraction occurred
force transducer
what did we do to the frogs gastro muscle before stimulating it? we changed the …
resting length
tension is generated in muscle, but no shortening occurs
Isometric contraction
tension generated by muscle exceeds the resistance of object, muscle shortens and moves object
isotonic concentric contraction
why do our skeletal muscles need ATP?
- myosin / actin. crossbridge cycling
- drive the SERCA pumps to return calcium into the SR
