What is the basic function of all muscle tissue? |
generate muscle tension |
When the sarcomere contracts and shortens__________. |
the A band stays the same |
The storage and release of calcium ions is the key function of the: |
sarcoplasmic reticulum. |
A group of skeletal muscle fibers together with the surrounding perimysium form a(n): |
fascicle |
The Na+/K+ pump helps a muscle cell maintain a state of: |
resting membrane potential. |
A crossbridge forms when: |
a myosin head binds to actin. |
Which of the following steps of the crossbridge cycle occurs immediately before the power stroke? |
A crossbridge forms. |
As myosin heads complete the power stroke, actin filaments: |
slide toward the M line of the sarcomere. |
Which of the following causes myosin to detach from actin? |
An ATP molecule binds to myosin. |
In the absence of ATP in the muscle, which of the following is most likely to occur? |
Some myosin heads will remain attached to actin molecules, but are unable to perform a power stroke. |
The narrow space between the axon terminal and the motor end plate is called the: |
synaptic cleft |
Stimulation of acetylcholine (ACh) receptors by ACh will primarily result in: |
sodium ions entering the muscle fiber. |
The end-plate potential is: |
a depolarization caused by sodium ion movement into the cytosol. |
The neurons of patients with multiple sclerosis are unable to transmit action potentials down the axon. How will that affect skeletal muscle stimulation? |
The muscle will not be stimulated and therefore will not contract. |
The active ingredient of Botox, botulinum toxin, blocks the release of ACh from the axon terminal. An overdose of Botox will most likely result in: |
muscle paralysis at the site of injection. |
What are the components of a triad? |
Two terminal cisternae of the sarcoplasma reticulum (SR) and one T-tubule |
Excitation-contraction coupling results in an increase of calcium ion concentration: |
in the cytosol of the muscle fiber. |
Predict the effect of Tetrodotoxin, a powerful blocker of voltage-gated sodium ion channels: |
There will be no action potential generated in the muscle fiber. |
In preparation for contraction, calcium ions bind to: |
troponin |
The protein that binds to actin when tropomyosin moves off of the active sites of actin, is: |
myosin |
Which of the following can cause relaxation? |
End of neural stimulation |
When the sarcolemma repolarizes and returns to rest: |
the inside of the sarcolemma is more negatively charged than the outside. |
The progressive stiffening of muscles after death, known as rigor mortis, is due to: |
ATP depletion, which leads to high cytosolic calcium and inability of crossbridges to detach. |
Rank from the first to the last steps in stages involved in a twitch contraction |
latent, contraction, relaxation |
The main immediate source of ATP (lasting about 10 seconds) as muscle contractions begin comes from: |
creatine phosphate |
What is a necessary reactant for glycolytic, or anaerobic, catabolism to proceed? |
glucose |
Wave summation, in which the muscle can only partially relax between contractions, will lead to__________. |
unfused tetanus |
Compared to Type I fibers, Type II fibers__________. |
can generate faster, more powerful contractions |
The type of contraction that causes a skeletal muscle to lengthen is called__________. |
isotonic eccentric contraction |
Which type of contraction causes a skeletal muscle to shorten? |
isotonic concentric contraction |
Which of the following is not one of the factors that contribute to muscle fatigue? |
excess post-exercise oxygen consumption |
What do skeletal muscle contractions share in common with smooth muscle contractions? |
Both types of contractions result from thick and thin filaments sliding past one another. |
When muscle fibers contract, the tension is transmitted to the _____. |
fascicle |
Which of the following properties of muscle cells would you expect to be the most involved in producing Joe’s muscle spasms? |
Contractility |
What is the type of chemical reaction used to rebuild ADP into ATP? |
dehydration synthesis |
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products? |
glycolysis |
Which of the following processes produces 36 ATP? |
Krebs cycle and oxidative phosphorylation |
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________. |
Pyruvic acid is converted back to lactic acid. |
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP? |
white fast twitch fibers |
Complete the reaction below: ADP + creatine phosphate → creatine + __________ |
ATP |
If oxygen is not available, the muscle fiber will produce ATP by__________. |
anaerobic catabolism |
Which of the following proteins forms elastic filaments? |
titin |
Which of the following is NOT one of the three major components of a typical eukaryotic cell? |
ribosome |
Which of the following acts as the digestive system of the cell, breaking down materials? |
lysosome |
Where in a typical eukaryotic cell would you expect to find genes? |
in the DNA within the cell’s nucleus |
Which of the following statements about cells is FALSE? |
Cells join together to form organelles, which then form our organs and organ systems. |
Which of the following proteins is a component of thick filaments? |
myosin |
Which of the following is a characteristic of smooth muscle? |
contain actin and myosin |
Which of the following organelles synthesizes proteins? |
ribosome |
While studying the properties of a muscle in the laboratory, you observe that the muscle is involuntary and does not have striations or T-tubules. You determine that this muscle is__________. |
smooth muscle |
The liver is an organ that can synthesize lipids, such as cholesterol, and detoxify poisons, such as alcohol. Which of the following organelles will be abundant in liver cells? |
smooth ER |
What structure is the functional unit of contraction in a skeletal muscle fiber? |
sacromere |
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? |
Calcium ions are stored in the sarcoplasmic reticulum. |
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment? |
ATP binds to the myosin head. |
How does the myosin head obtain the energy required for activation? |
The energy comes from the hydrolysis of ATP. |
What specific event triggers the uncovering of the myosin binding site on actin? |
Calcium ions bind to troponin and change its shape. |
When does cross bridge cycling end? |
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. |
What characteristic is not descriptive of cardiac muscle tissue? |
Voluntary muscle contractions |
Where are receptors for acetylcholine located? |
motor end plate |
During muscle contraction, myosin crossbridges bind to active sites on __________. |
actin filaments |
Deep inward extensions of the sarcolemma form a tunnel-like network inside the muscle cell known as __________. |
transverse tubules (T-tubules) |
When muscle fibers are stimulated so frequently they do not have an opportunity to relax, they are experiencing __________. |
fused or complete tetanus |
What is the functional contractile unit of the myofibril? |
Sarcomere |
The increase in muscle tension that is produced by increasing the number of active motor units is called __________. |
recruitment |
Through which ATP-generating mechanism can long-lasting muscle contractions be sustained? |
Oxidative catabolism |
Which statement best describes the function of myoglobin? |
Myoglobin stores oxygen in muscle cells. |
The degree to which a muscle cell can stretch depends on its __________. |
extensibility |
The fastest muscle contraction would be produced by a __________. |
type IIb fiber |
The storage and release of calcium ions is the key function of the __________. |
sarcoplasmic reticulum |
In response to physical inactivity, we expect to see muscles __________. |
atrophy |
The plasma membrane of a muscle cell is known as the __________. |
sarcolemma |
Type I fibers lack __________. |
speed |
Between the start of the latent period and the start of the contraction period, there is a time interval during which the muscle cannot respond to another stimulus. This brief period is known as the __________. |
refractory period |
The synapse of a motor neuron with a muscle fiber is known as the __________. |
neuromuscular junction |
A pathway of ATP production that results in the formation of lactic acid is __________. |
glycolytic catabolism |
The type of contraction in which length of the muscle fibers does not change is called __________. |
isometric |
Which of the following wraps and surrounds an individual skeletal muscle fiber? |
Endomysium |
What anchors thin and elastic filaments in place within the myofibril? |
Z-disc |
The end plate potential is generated by the influx of _______ into the motor end plate. |
sodium |
Acetylcholine is released from the synaptic terminus in response to |
An action potential arriving at the synaptic terminus |
The term "synaptic cleft" refers to |
The gap between the neuron and the muscle fiber |
The sodium channels of the motor end plate are |
Ligand-gated channels |
The end plate potential is |
A local depolarizaton |
The channels that open in the sarcolemma surrounding the motor endplate and generate an action potential are |
voltage gated channels |
The term "propagate" when referring to an action potential means |
spread |
In order to trigger a muscle contraction, an action potential must reach the |
triads |
A triad consists of |
Two terminal cisternae and a T-tubule |
________ is released from the SR in response to arrival of an action potential |
Ca++ |
Tropomyosin |
Covers actin active sites |
Troponin has three subunits. Which of the following does NOT bind to one of these subunits? |
myosin |
Choose the correct sequence of events that occur in preparation for contraction |
Action potential arrives at triad, calcium is released from the terminal cisternae, calcium binds to troponin, tropomyosin exposes the actin active sites |
Hydrolysis of ATP is responsible for |
Recocking of the myosin heads |
The binding of ATP to myosin is responsible for |
Release of the myosin heads from the actin active sites |
The release of ADP and Pi from myosin occurs during |
the power stroke |
The myosin heads return to their low-energy (relaxed) state during |
the power stroke |
The power stroke |
Pulls the thin filaments toward the M lines |
During muscle fiber relaxation, calcium channels in the SR close because |
The resting membrane potential is restored |
During muscle fiber relaxation |
Calcium is pumped back into the SR |
Acetylcholinesterase in the synaptic cleft degrades acetylcholine, allowing |
Ligand-gated sodium channels to close |
Sarcolemma repolarization during relaxation |
Restores the resting membrane potential |
Which aspect of muscle relaxation requires ATP? |
Pumping calcium ions back into the SR |
A & P chapter 10
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