4. Frog Muscle Physiology

basic muscle twitch

a single contraction of skeletal muscle, the response of skeletal muscle to stimulation

threshold stimuli

a stimuli that is just strong enough to change the membrane from resting potential to threshold

maximal stimuli

stimuli that are strong enough to produce action potentials in all motor units of a particular muscle

basic muscle twitch (events that cause)

1) ACh molecules bind to NICOTINIC RECEPTORS 2) Ion Channels Open 3) Sodium Ions Flow In → (Contraction Cycle Initiated)

intensity

1/3 Basic muscle twitch: Events -VOLTAGE CHANGE Increasing Stimuli = ↑Excited Motor Units, ↑Contraction Strength

Frequency

2/3 Basic muscle twitch: Events -PULSES/SECOND ↑ _____________ = ↑ Contraction Strength

Muscle Tissue Condition

3/3 Basic muscle twitch: Events -TEMPERATURE -O2 Level -ION CONCENTRATION

incomplete tetanus

5-10 shocks/second

twitch

A single electrical shock results in a _________.

action potential

A twitch produces an _________ __________ which leads to contraction.

contraction

A twitch produces an action potential which leads to _____________________.

increase

Increasing FREQUENCY of stimulus will _______________ MOTOR UNIT RECRUITMENT

Number of motor units reruited

Increasing VOLTAGE increases the __________________________.

force

Increasing the # of MOTOR UNITS firing will increase muscle _____________.

complete tetanus

Shows fatigue after 60 shocks/second

subthreshold stimuli

Stimuli below the minimum strength needed to trigger any of the muscle fibers to reach threshold and undergo an action potential

supramaximal stimuli

This is the strongest contraction and is due to longer period of time that all motor units respond

summation

When a second muscle twitch piggy backs on the first, it's called _______________, which leads to a STRONGER contraction.