What is a myogram?
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A graphical representation of muscle contractions.
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What is a myogram?
A graphical representation of muscle contractions.
What is the state of a muscle when it is relaxed?
The muscle is in a relaxed state, with minimal tension.
What are thick filaments primarily composed of?
The protein myosin.
What are the characteristics of smooth muscle cells?
Elongated with tapered ends, lack striations, and have a relatively undeveloped sarcoplasmic reticulum.
What allows for the performance of daily activities?
Sustained contraction of muscles.
What is a myogram?
A graphical representation of muscle contraction over time.
What is hypertrophy in skeletal muscles?
Enlargement of a muscle due to repeated exercise.
How does low intensity exercise affect slow muscle fibers?
It increases mitochondria and capillaries, making them more fatigue-resistant while maintaining size and strength.
What is another term for oxygen debt?
Excess post-exercise oxygen consumption.
What is an example of isotonic contraction?
Lifting a weight.
Does the number of skeletal muscle fibers change with hypertrophy or atrophy?
No, the number of skeletal muscle fibers does not change.
Where is cardiac muscle found?
Only in the heart.
How does physical training affect muscle energy production?
It helps to increase a muscle’s capacity to improve energy production.
What is the structure of cardiac muscle cells?
Branching, striated cells that interconnect in three-dimensional networks.
What are twitches in muscle contraction?
A single, brief contraction of a muscle fiber.
Who is associated with the study of sarcomere shortening in muscle contraction?
H. E. Huxley.
What is tetany?
A sustained muscle contraction resulting from rapid stimulation.
What enzyme decomposes acetylcholine during muscle relaxation?
Acetylcholinesterase.
What is an isotonic contraction?
A contraction that involves shortening of the muscle while maintaining the same tension.
What happens to the heat produced during cellular respiration?
It is carried by the blood to other tissues to help maintain body temperature.
What type of energy is required for both smooth and skeletal muscle contraction?
ATP energy.
What characterizes isometric contraction?
Force generation without shortening of the muscle.
How does creatine phosphate help in energy production?
It transfers its phosphate group to ADP to regenerate ATP.
What is an example of isometric contraction?
Holding a weight in one position.
What does ATP stand for?
Adenosine triphosphate.
What are thin filaments primarily composed of?
The protein actin.
How are thick and thin filaments arranged in smooth muscle cells?
They are arranged more randomly compared to other muscle types.
What is multiunit smooth muscle?
Smooth muscle where fibers occur separately, found in blood vessels and the iris of the eye, stimulated by neurons and some hormones.
What is the significance of studying a myogram?
It helps in understanding the timing and strength of muscle contractions.
What neurotransmitter is released at the neuromuscular junction to initiate muscle contraction?
Acetylcholine (Ach).
What stimulates both smooth and skeletal muscle contractions?
Membrane impulses and an increase in calcium ions.
What is the response of a single muscle fiber to a single impulse called?
A twitch.
What structure releases calcium ions during muscle contraction?
Sarcoplasmic reticulum (SR).
What is glycolysis?
The first phase of cellular respiration that is anaerobic and occurs in the cytoplasm.
What is the role of calcium ions in muscle contraction?
They bind to troponin, exposing active sites on actin filaments.
What is the yield of ATP from glycolysis per molecule of glucose?
2 ATP.
What state does the muscle fiber remain in until it is stimulated again?
Relaxed, yet ready.
What powers the repeated cycles of cross-bridge binding during contraction?
The hydrolysis of ATP.
Where does aerobic respiration occur?
In the mitochondria.
What is summation in muscle fibers?
A process where a muscle fiber receives a series of stimuli of increasing frequency, leading to a greater force of contraction than a single twitch.
How much ATP does aerobic respiration yield per molecule of glucose?
28 ATP.
What are the three types of muscle tissue?
Skeletal, Smooth, Cardiac.
What provides energy for the cross-bridges during muscle contraction?
The conversion of ATP to ADP by the enzyme ATPase.
What happens to acetylcholine in response to an impulse in the motor neuron?
It is released into the synaptic cleft.
What is the major function of smooth muscle?
Movement of viscera, peristalsis, vasoconstriction.
How do slow muscle fibers differ in terms of fatigue resistance?
They are resistant to fatigue and provide prolonged contraction.
How does the impulse travel within the muscle fiber after stimulation?
It travels over the surface and deep into the fiber through the transverse tubules.
What happens to creatine phosphate as ATP decomposes?
Its energy is transferred to ADP, converting it back to ATP.
What do liver cells convert lactate back into?
Glucose.
What are motor units composed of?
Motor neurons and the muscle fibers they innervate.
What feature do myosin molecules have that interacts with thin filaments?
Globular heads that extend toward nearby thin filaments.
What is the function of motor units?
To control muscle contractions.
What is visceral smooth muscle?
Smooth muscle that occurs in sheets, found in the walls of hollow organs, and can stimulate one another displaying rhythmicity.
What happens when a motor neuron fires?
All muscle fibers in that motor unit contract.
What happens to calcium ions during muscle relaxation?
They are actively transported into the sarcoplasmic reticulum.
What happens to fast muscle fibers during forceful exercise?
They increase the number of actin and myosin filaments, enlarging fibers and the entire muscle for stronger contractions.
What role does ATP play in muscle relaxation?
ATP binds to myosin heads, breaking the linkages between myosin and actin.
What is muscle fatigue?
The loss of a muscle's ability to contract during strenuous exercise.
Which neurotransmitters affect smooth muscle contraction?
Both acetylcholine (ACh) and norepinephrine.
What factors may contribute to muscle fatigue?
Electrolyte imbalances and decreased ATP levels.
How does smooth muscle contraction differ from skeletal muscle contraction in terms of hormonal influence?
Hormones can stimulate or inhibit smooth muscle contraction, but not skeletal muscle.
What does one motor neuron impulse release at the neuromuscular junction?
Sufficient acetylcholine (ACh) to bring a muscle fiber to its threshold.
How does the mechanism of contraction in cardiac muscle compare to skeletal and smooth muscle?
It is essentially the same, but with some differences.
Why is ATP important for muscles?
It provides energy for muscle contraction.
What is a key difference in the sarcoplasmic reticulum of cardiac muscle?
It is not well-developed and does not store much calcium.
What role do transverse tubules play in cardiac muscle?
They supply extra calcium from extracellular fluid, allowing longer twitches.
What is the role of the phosphate group released from creatine phosphate?
It is transferred to ADP to form ATP.
What is the neurotransmitter for skeletal muscle fiber contraction?
Acetylcholine.
What is the primary energy source for muscle fiber contraction?
ATP (adenosine triphosphate).
What neurotransmitter is released by the motor neuron during muscle contraction?
Acetylcholine (ACh).
How does summation affect muscle contraction?
It allows for a greater total contraction force by accumulating the force of each twitch.
What pathway is used during low to moderate intensity exercise?
Glycolysis leading to pyruvic acid formation and aerobic respiration.
What enzyme promotes the synthesis of creatine phosphate when ATP is sufficient?
Creatine phosphokinase.
What cellular characteristic is present in skeletal muscle?
Striations.
What is the primary function of slow muscle fibers?
To provide sustained, prolonged contractions.
What is the primary focus of the content?
Skeletal Muscle Contraction.
What are the two processes through which muscle cells produce ATP?
Glycolysis (anaerobic process) and the citric acid cycle (aerobic process).
What is the primary function of a sarcomere in muscle contraction?
To shorten and generate force during muscle contraction.
What is summation in muscle contractions?
The process where successive stimuli increase the strength of muscle contractions.
What continues the contraction of a muscle?
The continuation of the nerve impulse.
Why is muscle tone important?
For the maintenance of posture.
What does oxygen debt refer to?
The amount of oxygen required by liver cells to convert lactate back into glucose and by muscle cells to resynthesize ATP and creatine phosphate.
What happens to calcium after the nerve impulse stops?
Calcium is returned to the sarcoplasmic reticulum using ATP.
What is one method of studying muscle function?
Removing a single muscle fiber and connecting it to a device that records its responses to electrical stimulation.
How long may it take to repay the oxygen debt?
Several hours.
What does a myogram record?
An electrically-stimulated muscle contraction.
What occurs to actin after the muscle relaxes?
Actin returns to its original position.
What is the brief delay between stimulation and the beginning of contraction called?
The latent period.
Why is the return of calcium to the sarcoplasmic reticulum important?
It is a key step in muscle relaxation.
What follows the latent period in muscle contraction?
A period of contraction and a period of relaxation.
What is motor unit recruitment?
An increase in the number of activated motor units within a muscle at higher intensities of stimulation.
What is the relationship between isotonic and isometric contractions in most movements?
Most movements are a combination of both types of contraction.
What effect does recruitment have on muscle contraction?
It causes an increase in the strength of a contraction.
What happens if the stimulus does not reach the threshold in muscle fibers?
The muscle fiber will not respond at all.
When does a muscle achieve maximum tension?
When all of its motor units have been recruited.
What unique characteristic does cardiac muscle have regarding its contraction?
It is self-exciting and rhythmic.
Where is acetylcholine produced?
In the motor neuron.
Where is skeletal muscle primarily located?
In skeletal muscles.
What is the structure of myosin?
Myosin consists of two twisted strands with globular heads projected outward.
What does acetylcholine stimulate in the muscle fiber?
The muscle fiber itself.
Can complete tetany occur in the body?
No, it can only be accomplished in a lab.
What is the structure of actin?
Actin is a globular protein arranged in twisted filaments (a double helix).
What waste product is exhaled during low to moderate intensity exercise?
Carbon dioxide.
What pathway is used during high intensity exercise?
Glycolysis leading to lactic acid formation.
What must happen to oxygen debt?
It must be repaid.
What are summation and recruitment in muscle contractions?
They can produce a sustained contraction of increasing strength.
What is the role of myoglobin in muscle cells?
It stores oxygen.
What is muscle tone?
A continuous state of sustained contraction of a few motor units at a time within a muscle, even when at rest.
How do motor units contribute to muscle strength?
By recruiting more muscle fibers for stronger contractions.
What is atrophy in skeletal muscles?
Decrease in muscle size and strength due to disuse.
What enzyme decomposes acetylcholine at the motor end plate?
Acetylcholinesterase.
What physiological process is accomplished by visceral smooth muscle?
Peristalsis in tubular organs.
What happens to the transmembrane potential of the muscle fiber when Ach binds to its receptors?
It changes, leading to the production of an action potential.
What initiates the end of a muscle contraction?
The generation of action potential ceases as acetylcholine (ACh) is broken down by acetylcholinesterase (AChE).
What occurs to the myosin heads during the breakdown of ATP?
The myosin heads are 'cocked'.
What happens to calcium ions during the end of a muscle contraction?
The sarcoplasmic reticulum (SR) reabsorbs calcium ions, causing their concentration in the sarcoplasm to decline.
What molecules block the interaction between myosin and actin filaments during relaxation?
Troponin and tropomyosin.
What occurs when calcium ion concentrations approach normal resting levels?
The troponin-tropomyosin complex returns to its normal position, covering the active sites.
What is the role of acetylcholine (ACh) in muscle contraction?
It helps bring a muscle fiber to its threshold to trigger contraction.
What happens during the breakdown of creatine phosphate?
It releases a high-energy phosphate group.
What occurs when the myosin head bends?
It pulls on the actin filament, moving it toward the center of the sarcomere.
What is the relationship between heat production and cellular respiration?
Heat production is a byproduct of cellular respiration.
What happens to the sarcomere when many sarcomeres shorten simultaneously?
The muscle fiber shortens.
What travels down a motor neuron axon to initiate muscle contraction?
An impulse.
What physiological activities can the generated ATP be used for?
Various activities, including muscle contraction.
What is the diameter of slow muscle fibers compared to fast fibers?
Slow fibers have a smaller diameter.
What role does creatine phosphate play in muscle contraction?
It helps regenerate ATP from ADP and phosphate.
What does the sarcoplasmic reticulum release upon receipt of a muscle impulse?
Stored calcium.
What opens when the impulse reaches the sarcoplasmic reticulum?
Calcium channels.
What is oxygen used for during strenuous exercise?
To produce ATP for muscle contraction.
What do troponin, tropomyosin, and actin together form?
Thin filaments.
How does smooth muscle contract compared to skeletal muscle?
Contracts and relaxes slowly; single unit type is self-exciting and rhythmic.
What is formed when a myosin head attaches to actin?
A cross-bridge.
What does a single muscle twitch represent?
A brief contraction of a muscle fiber in response to a stimulus.
What happens to the sarcomere during muscle contraction?
It shortens.
What is a similarity between smooth muscle contraction and skeletal muscle contraction?
Both involve a reaction between actin and myosin.
What percentage of energy released in cellular respiration is used to form ATP?
Less than half.
What role does ATP play in muscle relaxation?
It breaks cross-bridge linkages between actin and myosin filaments.
What is creatine phosphate?
A high-energy compound stored in muscles.
What happens to isolated muscle fibers when exposed to stimuli of various strengths?
They remain unresponsive until the threshold stimulus is reached.
What is a motor unit composed of?
A motor neuron and the muscle fibers it controls.
What is a threshold stimulus?
The minimum strength of stimulus required to generate an impulse through the muscle fiber, release calcium ions, activate cross-bridges, and contract the muscle.
What happens when a motor unit is stimulated?
The muscle fibers of the motor unit contract all at once.
How does lactic acid accumulation affect muscle fatigue?
It may decrease pH, contributing to muscle fatigue.
What prevents further cross-bridge interaction during muscle contraction?
The covering of active sites by the troponin-tropomyosin complex.
What is a muscle cramp?
A sustained, painful, involuntary contraction of a muscle.
What is the result of the absence of cross-bridge interactions?
Further sliding cannot take place, and the contraction ends.
What causes a muscle cramp?
Changes in the extracellular fluid around muscle fibers, leading to uncontrolled stimulation by motor neurons.
What happens to the muscle after contraction ends?
Muscle relaxation occurs, and the muscle returns passively to its resting length.
What does the all-or-none response imply about muscle fiber contraction?
A muscle fiber either contracts completely or not at all.
What is partial tetany?
A condition where relaxation time becomes very short due to higher frequency of stimulation.
What type of metabolism do fast muscle fibers primarily use?
Anaerobic metabolism.
What happens during 1-2 minutes of strenuous exercise?
Oxygen deficiency may develop.
What type of exercise has sufficient oxygen supply for cellular requirements?
Low to moderate intensity exercise.
What happens when ACh binds to its receptors in the muscle fiber membrane?
The sarcolemma is stimulated.
What do myosin molecules form?
A thick filament.
How much ATP is produced per glucose for skeletal muscle during low to moderate intensity exercise?
30 ATP per glucose.
What is the primary function of fast muscle fibers?
To perform rapid movements and reach maximum force quickly.
How many nuclei are present in smooth muscle cells?
Single nucleus.
What happens during high intensity exercise regarding oxygen supply?
Oxygen supply is not sufficient for cellular requirements.
What special feature is found in cardiac muscle?
Intercalated discs separating adjacent cells.
What type of control does skeletal muscle have?
Voluntary.
What waste product accumulates during high intensity exercise?
Lactic acid.
What forms when myosin heads bind to active sites on actin?
Cross-bridges.
What type of respiration is aerobic respiration?
A complete breakdown of glucose that requires oxygen.
What is the significance of breaking the connection between myosin and actin?
It is necessary for muscle relaxation.
What is the all-or-none response in muscle physiology?
When a muscle fiber contracts fully or not at all, depending on whether the stimulus reaches the threshold.
What is the result of the repeated cycles of cross-bridge binding?
Filament sliding and muscle fiber shortening.
How are skeletal muscle fibers classified?
As fast or slow fibers.
What happens when a muscle fiber cannot relax completely?
It reaches a point where the force of individual twitches combines through summation.
What role does hemoglobin play in the body?
Carries oxygen to muscle tissue.
What supports aerobic respiration during rest or moderate activity?
Sufficient oxygen availability.
What are intercalated discs?
Complex membrane junctions that join cardiac muscle cells and transmit contraction force.
How is ATP regenerated for muscle contraction?
From creatine phosphate and cellular respiration.
What forms from pyruvic acid during anaerobic respiration?
Lactic acid.
What happens to the actin filament as the myosin heads repeatedly attach and pull?
The filaments increase their overlap and the sarcomere shortens from both ends.
What is the major function of cardiac muscle?
Pumping action of the heart.
Where does lactate diffuse after being produced in muscle cells?
Into the bloodstream and then to the liver.
What do actin filaments contain?
Myosin binding sites.
What happens to tropomyosin when calcium binds to troponin?
Tropomyosin moves and exposes specific sites on actin.
How much ATP is produced per glucose during high intensity exercise?
2 ATP per glucose.
What force does the muscle fiber exert during contraction?
A pulling force on its attachments.
Do muscles have to shorten to generate force?
No, muscles can generate force without shortening.
How does the speed of contraction compare between smooth and skeletal muscle?
Smooth muscle is slower to contract and relax.
How does smooth muscle maintain contraction compared to skeletal muscle?
Smooth muscle maintains a contraction longer with the same amount of ATP.
What unique ability does smooth muscle have regarding its length?
Smooth muscle can change length without a change in tautness.
What are the characteristics of fast muscle fibers?
They have a large diameter, fatigue quickly, and are best for rapid, short-term activities.
How quickly can ATP be generated from creatine phosphate?
It provides a rapid but short-term energy supply.
What is the function of myoglobin in muscle tissue?
Stores oxygen for aerobic respiration, increasing oxygen availability.
What is complete tetanic contraction?
A sustained contraction that lacks any relaxation, achievable only in a lab.
What causes the myosin heads to return to the 'cocked' position?
ATP breakdown.
What is the end product of anaerobic respiration?
Lactate.
What type of metabolism do slow muscle fibers primarily use?
Aerobic metabolism.
What interacts with troponin and tropomyosin to expose myosin binding sites?
High concentration of calcium in the sarcoplasm.
What must the cell rely on as the supply of creatine phosphate declines?
Cellular respiration to generate ATP.
What forms when myosin binding sites on actin filaments are exposed?
Cross-bridges.
What develops as lactate builds up during strenuous exercise?
Oxygen debt.
What is the result of the pulling of cross-bridges?
Thin filaments are pulled toward the center of the sarcomere.
What do calcium ions bind to after diffusing into the cytosol?
Troponin molecules.
What are the two proteins associated with the surface of actin molecules?
Troponin and tropomyosin.
What energy source is used by cross-bridges to pull on actin filaments?
ATP.
What is the result of cross-bridges pulling on actin filaments?
The sarcomere shortens.
What forms when myosin heads bind to exposed sites on actin?
Cross-bridges.
What is a key characteristic of cardiac muscle contraction?
Network of cells contracts as a unit; self-exciting; rhythmic.
What happens during muscle contraction according to the sliding filament model?
A myosin head attaches to a binding site on the actin filament, forming a cross-bridge.
