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(Answered) Human Anatomy and Physiology 1 Homework 20

Bio 201

Question 1

A motor unit is composed of a single one of these motorneurons  and many [2].  When a motorneuron is activated by the nervous system and fires an action potential along its axon, [3] of the muscle fibers it connects with are activated.  A motor unit can be a slow or a fast motor unit because [4] of its muscle fibers act the same way.  Motor units can also be considered small or large, depending on the number of muscle fibers in them.

When we produce forces to do things, we activate [5] motor units within a specific muscle.  Each time we activate a motor unit we get it to produce [6] force; that is the physiologically useful force that is built from the physiologically unuseful, smaller force building blocks, each called a [9].  If it is a fast motor unit, its force will tend to [7] if held for any length of time.  To maintain any force we need, we will use motor unit [8] to alternate motor unit activity and ensure a consistent force.
All Answer Choices

a few
muscle fibers

Question 2

This question should help you understand the difference between aerobic and anaerobic cellular respiration.

Oxygen is used during this type of cellular respiration.

All the steps of cellular respiration can be used in this.

Only glycolysis can occur for this type.

No biochemical steps in the mitochondrion will occur for this type of cellular respiration.

The blood contains gases and nutrients.  Any muscle cell that is poorly vascularized will not be able to exchange gases with the blood.  In that situation, when extremely active, the muscle cell will have to eventually only carry out this type of cellular respiration.

The molecule myoglobin can hold onto oxygen just like hemoglobin does in your blood.  Myoglobin also uses an iron atom to do this, just like hemoglobin, so it gives a reddish color to any cell that has it.  Some muscle fibers store a lot of myoglobin and look dark red; any muscle predominantly filled with these dark muscle fibers is what we call “dark meat.”  These dark muscle fibers must primarily use this type of cellular respiration.

Glycogen must be stored in some muscle fibers.  Basically, the ones that need tons of glucose and do mostly this type of cellular respiration.
anaerobic cellular respiration

This type produces the most ATP.

All Answer Choices
A. aerobic cellular respiration
B. anaerobic cellular respiration

Question 3

Match these occurrences with the correct portion of cellular respiration.

By the end of this step, only CO2 remains of the original glucose molecule.

This is the only portion of cellular respiration that can occur anaerobically.

Pyruvate is the product of this step. glycolysis

This happens in the inner membranes (cristae) of the mitochondrion and fuels ATP production.

This occurs in the cytosol of the muscle fiber.

When fatty acids from triglycerides enter cellular respiration, they enter at this point.

Lactic acid can arise as a result of carrying out this portion of cellular respiration.

Oxygen is only used during this portion of cellular respiration.

All Answer Choices
A. electron transport chain
B. glycolysis
C. citric acid cycle

Question 4

Muscle fibers cannot run out of ATP, or they run the risk of freezing up which we call rigor mortis. To make ATP most effectively, we need to break down the monomer [2] in the presence of oxygen gas within our organelles called [3]. Some muscle fibers store this monomer in the form of the polymer [4] in order to be able to make lots of ATP on demand. When the muscle fibers break down the polymer back into the monomers they use [8] reactions.

Although no cells can actually store ATP, muscle fibers can store the energy from ATP in another molecule called [5]; when needed, the muscle fibers can convert that energy back into an ATP molecule, which is a pretty amazing feat.

Not all ATP production involves oxygen gas in the breakdown of the monomer. If no oxygen is involved, it doesn’t break the monomer down completely, but leads to the production of pyruvate which cannot be stored. So pyruvate is then converted into [6], which then diffuses out of muscle fibers. That product goes to the [7] where it gets converted back to pyruvate and then back to the monomer. Although that is an energetically-costly process, it allows the muscle fibers to have the ATP when they need them.

All Answer Choices

amino acid
creatine phosphate
dehydration synthesis
rigor mortis

Question 5

Muscle fibers can be fast, slow, or some intermediate type.  When they are fast they appear as fatigable  fibers.  That is because they lack the [2] that is found in slow fibers.  Fast fibers also tend to do more [3] cellular respiration than slow fibers; because of this, they store a lot more [4] than slow fibers as well.  Slow fibers tend to be more heavily vascularized so that they can obtain more [5] from the blood.  Increased vascularization enables slow fibers to do more [6] cellular respiration than fast fibers and thus slow fibers make much more [7] than fast fibers.  Slow fibers are also very good for endurance tasks because they are [8].  White fibers cannot sustain a contraction as long because they build up too much [9] as they make cellular energy.  Finally, muscle fibers are also able to store energy in a different form than other cells because they contain [10].

All Answer Choices

creatine kinase
lactic acid
oxygen gas

Question 6

Complete these sentences with a word from the drop down menu.  A word might be used more than once or not at all.

Within each muscle fiber all of its myofibrils undergo the contraction cycle.

Tetanus results from the [4] of individual twitches.

This type of tetanus, [], is not used when we actually use our muscles, but can only be revealed in experimental settings.

A single motor unit that is activated to tetanus reaches its [] force.

When we activate multiple motor units their individual forces combine to produce a greater force for the overall muscle through [].

When an entire muscle contracts to maximum force, [] of its motor units are recruited.

Muscle contraction that leads to shortening of the muscle is also called [] contraction.  But sometimes a muscle might lengthen during contraction and that is a [] contraction.  Neither of those types of contractions, when muscle length changes, cannot be a/an [] contraction.  As long as both of those contractions occur when lifting the same amount of weight, they can be considered a/an [] contraction.
isometric contraction.  As long as both of those contractions occur when lifting the same amount of weight, they can be considered a/an   isotonic contraction.
All Answer Choices choose one:
fused tetanus
unfused tetanus
a majority

Question 7

Muscle produces force when it contracts. Use this image of force production to answer these questions. The purple arrows at the bottom represent when one motorneuron is stimulated. The force is being recorded from tendon to tendon across a muscle.

The X axis (marked X) indicates this.

This is a twitch (5 or 6)

This period would be when contraction is occurring (1, 2, or 3)

Summation is occuring in this contraction (5 or 6).

During which time period (1, 2, or 3) are the acetylcholine receptors activated?

True or False: The force level indicated by the number 4 is the maximal force from this motorneuron stimulation.

The forces shown here result from activation of a single ___ . motor unit

Calcium pumps are removing calcium from the cytosol during this period (1, 2, or 3).

All Answer Choices
A. 1
B. 2
C. 3
D. 5
E. 6
F. time
G. force
H. true
I. false
J. muscle fiber
K. motor unit

Question 8

Which of the following types of force production is used in our muscles for normal force production, like when you click your mouse or pick up your glass of water?


unfused tetanus

fused tetanus

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