mastering a&p assignment 6 (exam 3)
The most common incubation period (time to onset of symptoms) for this disease is __________.
5-10 days
The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A myosin head bound to actin
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
A series of proteins that control calcium release.
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.
Which of the following best describes the interaction between transverse (T) tubules and the sarcoplasmic reticulum in skeletal muscle contraction?
Action potentials in T tubules are detected by DHP receptors, which are coupled to ryanodine receptors in the sarcoplasmic reticulum and open channels for calcium.
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
The main cranial nerve involved in jaw movement is __________.
CN V (trigeminal)
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.
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction.
Tetanus is a neuromuscular disease caused by the toxin of __________ and leads to __________ muscle tone.
Clostridium tetani; increased
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.
DNA is double stranded. It is arranged in nitrogenous base pairs, where a certain purine on one strand is covalently bonded to a pyrimidine on the other DNA strand. Along each DNA strand, the DNA is arranged in triplet codes. The triplet codes are comprised of 3 nucleotides in succession, arranged in a specific direction on the DNA molecule. Each triplet code codes for a particular amino acid. If one or two base pairs are deleted from DNA, it will disturb the order of the three nucleotides in succession after that point; it changes the triplet nucleotide set in each reading frame after the mutated point. This is type of deletion mutation is termed a "frame-shift" mutation; it is the type of mutation in __________. Since so many amino acids will be affected in this condition, it is more deleterious than some of the other forms of muscular dystrophy.
Duchenne MD
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
Hemoglobin in skeletal muscle acts as an oxygen buffer.
False
Skeletal muscle and cardiac muscle are multinucleated cells, whereas smooth muscle cells each have one nucleus.
False
Thick filaments have many protrusions along their middle (head of the myosin filaments) but none at their ends.
False
Which of the following transmits action potentials to the interior of the muscle cell to trigger calcium release? actin and myosin T-tubules sarcoplasmic reticulum sarcomeres motor end plate
T-tubules
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP
Which of the following statements about end-plate potentials is FALSE?
They are a result of acetylcholine binding to muscarinic cholinergic receptors.
What is the function of T tubules?
They conduct action potentials from the sarcolemma to the interior of the muscle cell.
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
The two most common forms of muscular dystrophy, Duchenne and Becker, are sex-linked recessive genetic problems involving the __________ chromosome.
X
Since Duchenne and Becker muscular dystrophy are __________ linked and recessive, it mainly affects __________.
X-linked; males
What is a motor unit?
a motor neuron and all the muscle fibers it innervates
__________ is the neurotransmitter used to carry a message from a motor neuron to a skeletal muscle fiber.
acetylcholine
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
A myosin head binds to which molecule to form a cross bridge?
actin
The contractile portion of the thin filament is composed of what protein?
actin
Troponin is a complex of three proteins that bind to tropomyosin, calcium, and
actin
How is acetylcholine (ACh) removed from the synaptic cleft? a reuptake pump on the axon terminal diffusion away from the synaptic cleft acetylcholinesterase (AChE; an enzyme) All of the above.
all of the above
What is the Z lines functional significance?
anchors the thin filaments together
What is the I bands functional significance?
area of actin not having a crossbridge
What is the H bands functional significance?
area of myosin not overlapped by actin
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
What causes the myosin head to disconnect from actin?
binding of ATP
In order for crossbridge cycling to occur, the actin-myosin complex must be broken by which of the following?
binding of ATP to myosin
Which of the following is the first step in the crossbridge cycle?
binding of myosin and actin
Death generally results from inability to __________.
breathe
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
calcium ions
The repeated binding and unbinding of myosin to actin is called __________ cycling.
crossbridge
Most commonly, the infection occurs after __________ become contaminated by soil and/or feces containing the microbe.
deep puncture wounds
DNA is double stranded. It is arranged in nitrogenous base pairs, where a certain purine on one strand is covalently bonded to a pyrimidine on the other DNA strand. Along each DNA strand, the DNA is arranged in triplet codes. The triplet codes are comprised of three nucleotides in succession, arranged in a specific direction on the DNA molecule. Each triplet code codes for a particular amino acid. If a mutation in DNA involves the loss of, at least, one base pair, it is termed a deletion. The type of mutation in both Becker MD and Duchenne MD is a __________.
deletion
Duchenne and Becker muscular dystrophy involves problems with the proper formation of a protein known as __________, which is important in attaching certain cytoskeletal proteins to the cell membrane (sarcolemma) of muscle, particularly skeletal muscle.
dystrophin
The sequence of events that links the muscles action potential to changes in skeletal muscle force development is called what?
excitation-contraction coupling
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
In muscle physiology, a bundle of muscle cells is known as a _________.
fascicle
A skeletal muscle is composed of a bundle of ________, each composed of many muscle fibers wrapped by connective tissue.
fascicles
Muscular dystrophy is a(n) __________ disorder.
genetic (inherited)
If the microbe causing tetanus is subjected to a __________ oxygen environment, it will __________.
high-; die
Currently, __________ is (are) the best protection against tetanus.
immunizations
Heavy intensity exercise generates what byproduct that contributes to fatigue?
lactic acid
What is the A bands functional significance?
length of myosin attached to an M line
Muscular dystrophy is a medical condition that is somewhat opposite to tetanus, in terms of cause and presentation; muscular dystrophy involves problems with the __________ and gives muscle __________.
muscle itself; flaccidity (decrease in muscle tonus)
There is __________ for muscular dystrophy. Physical therapy helps to delay the progression of __________ and anti-inflammatory drugs may decrease the progression.
no cure; contractures
A reading frame is one triplet code on a strand of DNA that is being read by messenger RNA; it codes for one particular amino acid. Thus, the triplet code determines which amino acid will be inserted into the protein or polypeptide. If one complete triplet code (all three nucleotides in succession) is removed, it is termed a deletion type mutation. Because a complete reading frame was removed __________ will not be present in the protein or polypeptide.
one amino acid
Duchenne and Becker muscular dystrophy mainly involve problems with __________ muscles; when muscles __________ and start to form __________.
postural; atrophy; contractures
What causes the power stroke?
release of ADP and Pi
The fundamental repeating unit of the myofibril, called a ________, gives skeletal muscle its striated appearance and is bordered by ________.
sarcomere : Z lines
What is the functional unit of skeletal muscle?
sarcomeres
An action potential spreading from the motor end plate on a skeletal muscle fiber causes opening of calcium channels in the __________.
sarcoplasmic reticulum
Which of the following stores calcium to be released for muscle contraction? actin and myosin sarcoplasmic reticulum tendons sarcomeres motor end plate
sarcoplasmic reticulum
During skeletal muscle contraction, as the muscle shortens, the thick and thin filaments
slide past one another
Postural muscles of the legs and back tend to have a high proportion of what fiber type?
slow oxidative
Because of the correlation between the size of a motor unit and the type of fiber it contains, recruitment of fibers happen in a specific order. Which of the following fibers are recruited first?
slow oxidative fibers
What are the three types of muscle fibers that are found in all skeletal muscles?
slow oxidative, fast oxidative, and fast glycolytic
Binding of a neurotransmitter onto the motor end plate of a skeletal muscle fiber results in the opening of __________ channels, causing a depolarization.
sodium
The neuronal circuitry to skeletal muscles involves neurons that stimulate contractions and those that inhibit contractions. The muscle spindles and Golgi tendon organs are involved in maintaining the proper muscle tonus (resting muscle tension); they work by signaling the CNS. Since tetanus involves __________, the neurons involved in muscle contraction __________ are affected.
somatic motor neuron hyperexcitability; inhibition
The most frequent early systemic symptom of tetanus is __________.
stiffness of the jaw
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisternae of the sarcoplasmic reticulum
Summation happens whenever muscle twitches occur at such high frequencies that calcium cannot be removed from the cytosol as rapidly as it is released. If sustained at a high enough frequency, summation could lead to a condition known as ______ (also a term that also refers to a condition in which bacterial toxins cause inappropriate motor neuron stimulation).
tetanus
__________ will determine whether only local muscles close to the wound are affected or distant muscles are affected as well.
the extent of toxin spread
What is the sarcomeres functional significance?
the functional unit of muscle contraction whose length is changed as a muscle shortens and lengthens
The binding of calcium to troponin will directly allow which of the following?
the movement of tropomyosin, thereby exposing the myosin-binding site on the actin molecule
During the cross-bridge cycle, ATP binding to myosin causes which of the following?
the myosin head to detach from actin
What structure is the functional unit of contraction in a skeletal muscle fiber?
the sarcomere
The shortening of a skeletal muscle fiber during contraction involves which of the following? the Z lines not changing their position the A bands shortening the sarcomeres shortening the thick filaments shortening the thin filaments shortening
the sarcomeres shortening
What is name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules
What is the protein component of the thin filament that blocks the myosin-binding site on the actin monomer?
tropomyosin
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
When calcium is released into the cytoplasm of a skeletal muscle fiber, it binds to __________.
troponin
Which of the following proteins binds Ca++ to initiate skeletal muscle crossbridge cycling?
troponin
Creatine phosphate provides an immediate source of high energy phosphate to donate to ADP at the onset of muscle activity.
true
The primary source of calcium that drives skeletal muscle contraction is the sarcoplasmic reticulum.
true
There are no slow glycolytic fibers.
true
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
What is the M lines functional significance?
where the tails of the myosin molecules are bound to one another