Lecture 2: Muslce Function

Question 1

isometric contraction

Answer 1

muscle contraction but no shortening on the muscle

Question 2

at optimal length there is a greatest overlap of myosin and actin filaments thus the ….
a)
b)

Answer 2

a) the greatest number of cross bridges can be formed
b) the muscle and sarcomere can shorten

these occur at optimal length

Question 3

below optimum length as the muscle or sarcomere shortens the maximum tension falls off. this is due to what two factors?

Answer 3

1. below the optimum length , actin filaments begin to overlap decreasing the number of active cross bridges
2. myosin filaments become compressed against two Z lines

Question 4

tension is proportional to _________

Answer 4

tension is proportional to the number of crossbridges

Question 5

muscles tend to operate in the region of muscle length which optimizes force generation. what does this mean?

Answer 5

the relaxed length of the muscle is very close to the optimum length

Question 6

the slope of the line (distance/ time) is equal to the _____

Answer 6

velocity of shortening

Question 7

as load increases the velocity of shortening _____

Answer 7

decreases

Question 8

with no load on the muscle, there is a ____________

Answer 8

maximum velocity of contraction

Question 9

for each muscle, there is a load for which the muscle can not shorten at all. This is called the ____ or ______

Answer 9

maximum load or minimum tension

Question 10

maximum load or minimum tension

Answer 10

a load in which the muscle cannot shorten at all

Question 11

when you increase a load your velocity of contraction gets ____

Answer 11

slower

Question 12

motor unit

Answer 12

one motorneuron and all the muscle fibers it innervates

Question 13

all of the fibers innervated by the same motor neuron behave as ________, contracting and relaxing together.

Answer 13

one unit

Question 14

muscles performing fine motor skill and delicate movements have ______ fibers/motor neruon

Answer 14

muscles performing fine motor skill and delicate movements have FEWER fibers per motor neuron

Question 15

muscle that perform heavy work have how many fibers per motor neuron.

Answer 15

could be up to several hundred fibers per motor neuron

Question 16

asynchronous motor unit activity

Answer 16

different motor units are recruited at different times to produce a smoother muscle tension

Question 17

when does summation occur?

Answer 17

when a second stimulus is given to a muscle before it has completely relaxed

Question 18

twitch

Answer 18

single stimulation

Question 19

when a stimuli is repeated frequently and has not been allow to completely relax it is called ______

Answer 19

summation

Question 20

repeated continual stimulation

Answer 20

tetnus (if the stimuli is repeated fast enough)

Question 21

what are the 2 factors determining total muscle tension

Answer 21

1. the NUMBER of muscle fibers that are contracting

2. tension is produce by EACH CONTRACTING FIBER