BIO 436 Exercise 6 (Properties of Human
Skeletal Muscle) Questions and Correct
Answers
Skeleton provides __ and __ for the body. ✅Support; Articulation
Skeletal muscle are connected to the bones by __, which are strong bundles of __
fibers. ✅Tendons; Collagen
Skeletal muscle is composed of long, __ cells called __ grouped into ___.
✅Multinucleate; Fibers; Fascicles
__ or __ muscles usually work __. ✅Two or more; Antagonistically
An AP in a motor neuron induces an AP in all the muscle fibers it innervates by
releasing __ into the NMJ. This muscle AP causes a brief increase in the intracellular
concentration of __ ions and activates the contractile molecular machinery inside the
fiber (requires use of ATP). ✅Neurotransmitter Acetylocholine; Ca
Define a Twitch. ✅Single AP from a motor neuron thus producing a brief contraction of
the muscle
Define Tetanus. ✅Multiple rapid APs sent to the muscle fibers allow the muscle to
produce a sustained continuous contraction (muscle can't relax inbetween)
Define Recruitment. ✅Process of activating more motor units
At stimulation intervals greater than 200 msec, intracellular __ is restored to baseline
levels between APs and the contraction consists of separate twitches. ✅Ca
At stimulation intervals between 200 and 75 msec, __ in the muscle is still above
baseline levels when the next AP arrives. (Muscle fiber hasn't completely relaxed and
next contraction is stronger than a single twitch) ✅Ca
As contractions continue to increase with these stimulation intervals, eventually you will
reach the max force attainable, which is __. ✅Tetanus
Define Summation. ✅Additive effect of increasing strength up to tetanus; If 2nd
stimulus occurs before muscle relaxes from 1st, the 2nd twitch will be greater
, At even higher stimulation frequencies (less than __ msec), the muscle has no time to
relax between successive stimuli. ✅75
Define Tetanic contraction. ✅High frequencies are typical of the frequencies normally
used by the body and result in a smooth contraction many times stronger than a single
twitch (Muscle is said to be in a state of tetanus)
In the experiment, the stimulator was placed over the __ nerve at the __. ✅Median;
Wrist
The bending of the wrist is due to the __ and __ muscles. ✅Flexor carpi radialis
Flexor carpi ulnaris
The bending of the last segments of the fingers is due to the __ muscles. ✅Long finger
flexor
The movement of all fingers, combined with the pulling of the thumb towards the index
finger is due to the __ muscles. ✅Intrinsic muscles of the hand innervated by the ulnar
nerve
Flexion of the thumb is due to the __ muscles. ✅Muscles at the base of the thumb
innervated by the median nerve
What is the first response recorded? ✅A person's stimulus threshold for their smallest
motor unit
What were the 6 experiments done in lab? ✅1. Single twitch
2. Summation & Tetanus
3. Fatigue
a. Fatigue w/verbal encouragement
b. Fatigue w/rest
c. Pseudo-Fatigue
What % grip strength were utilized in the fatigue experiments? ✅Fatigue w/verbal
encouragement = 100%
Fatigue w/rest = 100%
Pseudo-Fatigue = 40%
What were the 8 labeled graphs from the experiment? ✅1. Single muscle twitch
2. Single muscle twitch w/latent period
3. Single muscle twitch w/overlay of motor unit recruitment
4. Summation of contraction
5. Identifying max contraction
6. Sustained contraction w/verbal encouragement
7. Sustained contraction w/rest periods
Skeletal Muscle) Questions and Correct
Answers
Skeleton provides __ and __ for the body. ✅Support; Articulation
Skeletal muscle are connected to the bones by __, which are strong bundles of __
fibers. ✅Tendons; Collagen
Skeletal muscle is composed of long, __ cells called __ grouped into ___.
✅Multinucleate; Fibers; Fascicles
__ or __ muscles usually work __. ✅Two or more; Antagonistically
An AP in a motor neuron induces an AP in all the muscle fibers it innervates by
releasing __ into the NMJ. This muscle AP causes a brief increase in the intracellular
concentration of __ ions and activates the contractile molecular machinery inside the
fiber (requires use of ATP). ✅Neurotransmitter Acetylocholine; Ca
Define a Twitch. ✅Single AP from a motor neuron thus producing a brief contraction of
the muscle
Define Tetanus. ✅Multiple rapid APs sent to the muscle fibers allow the muscle to
produce a sustained continuous contraction (muscle can't relax inbetween)
Define Recruitment. ✅Process of activating more motor units
At stimulation intervals greater than 200 msec, intracellular __ is restored to baseline
levels between APs and the contraction consists of separate twitches. ✅Ca
At stimulation intervals between 200 and 75 msec, __ in the muscle is still above
baseline levels when the next AP arrives. (Muscle fiber hasn't completely relaxed and
next contraction is stronger than a single twitch) ✅Ca
As contractions continue to increase with these stimulation intervals, eventually you will
reach the max force attainable, which is __. ✅Tetanus
Define Summation. ✅Additive effect of increasing strength up to tetanus; If 2nd
stimulus occurs before muscle relaxes from 1st, the 2nd twitch will be greater
, At even higher stimulation frequencies (less than __ msec), the muscle has no time to
relax between successive stimuli. ✅75
Define Tetanic contraction. ✅High frequencies are typical of the frequencies normally
used by the body and result in a smooth contraction many times stronger than a single
twitch (Muscle is said to be in a state of tetanus)
In the experiment, the stimulator was placed over the __ nerve at the __. ✅Median;
Wrist
The bending of the wrist is due to the __ and __ muscles. ✅Flexor carpi radialis
Flexor carpi ulnaris
The bending of the last segments of the fingers is due to the __ muscles. ✅Long finger
flexor
The movement of all fingers, combined with the pulling of the thumb towards the index
finger is due to the __ muscles. ✅Intrinsic muscles of the hand innervated by the ulnar
nerve
Flexion of the thumb is due to the __ muscles. ✅Muscles at the base of the thumb
innervated by the median nerve
What is the first response recorded? ✅A person's stimulus threshold for their smallest
motor unit
What were the 6 experiments done in lab? ✅1. Single twitch
2. Summation & Tetanus
3. Fatigue
a. Fatigue w/verbal encouragement
b. Fatigue w/rest
c. Pseudo-Fatigue
What % grip strength were utilized in the fatigue experiments? ✅Fatigue w/verbal
encouragement = 100%
Fatigue w/rest = 100%
Pseudo-Fatigue = 40%
What were the 8 labeled graphs from the experiment? ✅1. Single muscle twitch
2. Single muscle twitch w/latent period
3. Single muscle twitch w/overlay of motor unit recruitment
4. Summation of contraction
5. Identifying max contraction
6. Sustained contraction w/verbal encouragement
7. Sustained contraction w/rest periods
