Anatomy › Muscle Physiology
When measuring the heat generated by muscle contraction, there is an additional amount of heat, labelled as 'unexplained heat.'
What is the source of the 'unexplained heat' in the initial phase of muscle contraction?
Calcium that is released by the sarcoplasmic reticulum binds to parvalbumin in an exothermic binding reaction, producing the 'unexplained heat.'
The release of calcium from the sarcoplasmic reticulum is an exothermic reaction that produces large amounts of 'unexplained heat.'
All of the answers contribute to 'unexplained heat' production.
Parvalbumin directly catalyzes the breakdown of ATP, producing the 'unexplained heat' phenomenon that is observed.
There is no such thing as 'unexplained heat' related to muscle contraction.
The signal for muscle contraction causes the release of calcium from the sarcoplasmic reticulum. This calcium floods the cell and is necessary for causing muscle contraction. Parvalbumin, a protein in the cytoplasm, binds to calcium and acts as a slow-releaser of calcium. This binding reaction of calcium with parvalbumin causes the release of heat, which is termed as 'unexplained heat.' The 'unexplained heat' is also known as 'labile heat.'
When measuring the heat generated by muscle contraction, there is an additional amount of heat, labelled as 'unexplained heat.'
What is the source of the 'unexplained heat' in the initial phase of muscle contraction?
Calcium that is released by the sarcoplasmic reticulum binds to parvalbumin in an exothermic binding reaction, producing the 'unexplained heat.'
The release of calcium from the sarcoplasmic reticulum is an exothermic reaction that produces large amounts of 'unexplained heat.'
All of the answers contribute to 'unexplained heat' production.
Parvalbumin directly catalyzes the breakdown of ATP, producing the 'unexplained heat' phenomenon that is observed.
There is no such thing as 'unexplained heat' related to muscle contraction.
The signal for muscle contraction causes the release of calcium from the sarcoplasmic reticulum. This calcium floods the cell and is necessary for causing muscle contraction. Parvalbumin, a protein in the cytoplasm, binds to calcium and acts as a slow-releaser of calcium. This binding reaction of calcium with parvalbumin causes the release of heat, which is termed as 'unexplained heat.' The 'unexplained heat' is also known as 'labile heat.'
Which ion is quintessential for muscle contraction in skeletal muscle, but not in smooth muscle?
Calcium
Sodium
Chloride
Potassium
Bicarbonate
The sarcoplasmic reticulum of the muscle fiber is used to store calcium. When an action potential causes depolarization of the T-tubules, adjacent proteins cause the calcium channels of the sarcoplasmic reticulum to open. The released calcium binds to troponin, influencing a change in tropomyosin and allowing myosin to bind the active sites of actin. Without the presence of calcium, tropomyosin remains in place to block myosin binding and contraction cannot occur.
This process, however, does not occur in smooth muscle. Smooth muscle lacks both troponin and tropomyosin, and is thus not reliant on calcium for contraction.
A scientist is examining a sample of tissue taken from a skeletal muscle biopsy. Which of the following is most likely true of sample?
The cells have well-developed sarcoplasmic reticulum for storing calcium cations
The cells have well-developed sarcoplasmic reticulum for storing sodium cations
The cells have well-developed endoplasmic reticulum for storing calcium cations
The cells have well-developed sarcoplasmic reticulum for storing potassium cations
The cells have well-developed endoplasmic reticulum for storing potassium cations
The sarcoplasmic reticulum is a specialized cell structure, characteristic of skeletal muscle cells, that is used to store calcium ions.
Upon neural stimulation, depolarization of the T-tubules causes a cellular reaction to open ion channels in the membrane of the sarcoplasmic reticulum. Calcium is released into the cell, where it can bind to troponin and allow for muscle contraction.
The endoplasmic reticulum is found in most eukaryotic cells, and is used for lipid synthesis, detoxification, and several other functions. Sodium and potassium play significant role in regulating membrane potential, but are not stored in the muscle cell in large amounts as calcium is.
A scientist is examining a sample of tissue taken from a skeletal muscle biopsy. Which of the following is most likely true of sample?
The cells have well-developed sarcoplasmic reticulum for storing calcium cations
The cells have well-developed sarcoplasmic reticulum for storing sodium cations
The cells have well-developed endoplasmic reticulum for storing calcium cations
The cells have well-developed sarcoplasmic reticulum for storing potassium cations
The cells have well-developed endoplasmic reticulum for storing potassium cations
The sarcoplasmic reticulum is a specialized cell structure, characteristic of skeletal muscle cells, that is used to store calcium ions.
Upon neural stimulation, depolarization of the T-tubules causes a cellular reaction to open ion channels in the membrane of the sarcoplasmic reticulum. Calcium is released into the cell, where it can bind to troponin and allow for muscle contraction.
The endoplasmic reticulum is found in most eukaryotic cells, and is used for lipid synthesis, detoxification, and several other functions. Sodium and potassium play significant role in regulating membrane potential, but are not stored in the muscle cell in large amounts as calcium is.
Which ion is quintessential for muscle contraction in skeletal muscle, but not in smooth muscle?
Calcium
Sodium
Chloride
Potassium
Bicarbonate
The sarcoplasmic reticulum of the muscle fiber is used to store calcium. When an action potential causes depolarization of the T-tubules, adjacent proteins cause the calcium channels of the sarcoplasmic reticulum to open. The released calcium binds to troponin, influencing a change in tropomyosin and allowing myosin to bind the active sites of actin. Without the presence of calcium, tropomyosin remains in place to block myosin binding and contraction cannot occur.
This process, however, does not occur in smooth muscle. Smooth muscle lacks both troponin and tropomyosin, and is thus not reliant on calcium for contraction.
A scientist is studying a type of cell and discovers that this cell uses kinesin to transport secretory vesicles down long cytoplasmic extensions. Upon further study, the vesicles are found to contain the substance acetylcholine. What is the most likely classification of this cell?
Efferent (motor) neuron
Inhibitory interneuron
Skeletal muscle cell
Smooth muscle cell
Cardiac muscle cell
Acetylcholine is transported in vesicles, via the protein kinesin, in excitatory motor neurons. Muscle cells typically do not transport secretory vesicles, as they are not active secretors of most proteins. Neurons, in contrast, function to release neurotransmitters from secretory vesicles at synapses.
This logic leaves us with either type of neuron specified in the question. The best answer is motor neuron, as acetylcholine is the primary excitatory neurotransmitter at the neuromuscular junction. Had the question specified that the vesicle was filled with GABA or glycine, inhibitory neuron would have been the better answer.
What is the role of creatine phosphokinase (CPK) in skeletal muscle?
CPK catalyzes the transfer of a phosphate from PCr (phosphocreatine) to ADP (adenosine diphosphate)
CPK catalyzes the transfer of a phosphate from ATP (adenosine triphosphate) to Cr (creatine)
CPK catalyzes the production of PCr (phosphocreatine) from two ATPs (adenosine triphosphate)
CPK catalyzes the breakdown of ATP during muscle contractions
None of the answers are correct.
When ATP is used during the muscle contraction process, it is regenerated through the transfer of phosphate from PCr (phosphocreatine) to ADP (adenosine diphosphate). This reaction is catalyzed by the enzyme CPK (creatine phosphokinase).
The net reaction that is catalyzed by CPK is: PCr + ADP -> ATP + Cr
Muscle myofibrils are arranged longitudinally into sarcomeres. Which of the following correctly lists the boundaries of a single sarcomere?
Z line to Z line
Z line to M line
Z line to H band
M line to H band
Each myofibril contains interdigitating thick and thin filaments arranged longitudinally in sarcomeres. Repeating units of sarcomeres account for the unique banding pattern in striated muscle. A sarcomere runs from Z line to Z line.
What is the role of creatine phosphokinase (CPK) in skeletal muscle?
CPK catalyzes the transfer of a phosphate from PCr (phosphocreatine) to ADP (adenosine diphosphate)
CPK catalyzes the transfer of a phosphate from ATP (adenosine triphosphate) to Cr (creatine)
CPK catalyzes the production of PCr (phosphocreatine) from two ATPs (adenosine triphosphate)
CPK catalyzes the breakdown of ATP during muscle contractions
None of the answers are correct.
When ATP is used during the muscle contraction process, it is regenerated through the transfer of phosphate from PCr (phosphocreatine) to ADP (adenosine diphosphate). This reaction is catalyzed by the enzyme CPK (creatine phosphokinase).
The net reaction that is catalyzed by CPK is: PCr + ADP -> ATP + Cr