Podcast
Questions and Answers
Which property of skeletal muscle allows it to respond to a neurotransmitter released by a motor neuron?
Which property of skeletal muscle allows it to respond to a neurotransmitter released by a motor neuron?
- Excitability (correct)
- Contractility
- Elasticity
- Extensibility
Why is elasticity an important property of skeletal muscle?
Why is elasticity an important property of skeletal muscle?
- It enables the muscle to shorten forcefully.
- It allows the muscle to return to its original length after being stretched. (correct)
- It allows the muscle to stretch without damage.
- It enables the muscle to transmit electrical signals.
During a bicep curl exercise, which property of skeletal muscle is primarily responsible for lifting the weight?
During a bicep curl exercise, which property of skeletal muscle is primarily responsible for lifting the weight?
- Elasticity
- Excitability
- Contractility (correct)
- Extensibility
In what way does the extensibility of skeletal muscle contribute to joint movement?
In what way does the extensibility of skeletal muscle contribute to joint movement?
Tendons are primarily composed of which type of connective tissue?
Tendons are primarily composed of which type of connective tissue?
Which connective tissue type primarily comprises the sheaths that connect muscle to bone?
Which connective tissue type primarily comprises the sheaths that connect muscle to bone?
Which characteristic enables a muscle to return to its original length after being stretched?
Which characteristic enables a muscle to return to its original length after being stretched?
Which of the following is the correct classification for skeletal muscle?
Which of the following is the correct classification for skeletal muscle?
Besides movement, what is another primary function of muscle tissue in the body?
Besides movement, what is another primary function of muscle tissue in the body?
Which property of muscle tissue allows it to receive and respond to stimuli?
Which property of muscle tissue allows it to receive and respond to stimuli?
What specific structures do the connective tissue sheaths of skeletal muscle form to attach muscle to bone?
What specific structures do the connective tissue sheaths of skeletal muscle form to attach muscle to bone?
Which muscle type is responsible for involuntary, rhythmic contractions in the heart?
Which muscle type is responsible for involuntary, rhythmic contractions in the heart?
What is the direct result of muscle contraction that allows the transfer of force to bone?
What is the direct result of muscle contraction that allows the transfer of force to bone?
During intense exercise, if oxygen supply cannot keep pace with energy demands, which metabolic pathway is primarily utilized, and what byproduct accumulates as a result?
During intense exercise, if oxygen supply cannot keep pace with energy demands, which metabolic pathway is primarily utilized, and what byproduct accumulates as a result?
Why does oxygen debt occur after strenuous exercise, and what processes require the additional oxygen?
Why does oxygen debt occur after strenuous exercise, and what processes require the additional oxygen?
How does increasing acidity due to lactic acid affect muscle contraction?
How does increasing acidity due to lactic acid affect muscle contraction?
What is muscle tone, and why is it important for overall muscle function?
What is muscle tone, and why is it important for overall muscle function?
If a muscle cell has 5 times more creatine phosphate (CP) than ATP, what is the primary role of CP during intense muscle activity?
If a muscle cell has 5 times more creatine phosphate (CP) than ATP, what is the primary role of CP during intense muscle activity?
Compared to anaerobic respiration, what is the net ATP production from aerobic respiration per glucose molecule?
Compared to anaerobic respiration, what is the net ATP production from aerobic respiration per glucose molecule?
Which of the following is the most direct cause of muscle fatigue during intense physical activity?
Which of the following is the most direct cause of muscle fatigue during intense physical activity?
How can increased breathing rate following intense exercise help reduce oxygen debt?
How can increased breathing rate following intense exercise help reduce oxygen debt?
During periods of rest, what is the primary benefit of maintaining muscle tone?
During periods of rest, what is the primary benefit of maintaining muscle tone?
Which energy system is primarily responsible for providing energy during short bursts of intense activity, such as a 100-meter sprint?
Which energy system is primarily responsible for providing energy during short bursts of intense activity, such as a 100-meter sprint?
What is the primary effect of increasing the frequency of stimuli (impulses) delivered to a muscle, eventually leading to tetanus?
What is the primary effect of increasing the frequency of stimuli (impulses) delivered to a muscle, eventually leading to tetanus?
How does increasing the strength of stimuli (impulses) impact muscle force through recruitment?
How does increasing the strength of stimuli (impulses) impact muscle force through recruitment?
A weightlifter is struggling to complete a final repetition. According to the text, what is the most likely limiting factor if their muscles continue to contract?
A weightlifter is struggling to complete a final repetition. According to the text, what is the most likely limiting factor if their muscles continue to contract?
During the first few seconds of intense muscle activity, which energy source is primarily utilized, and what is its limitation?
During the first few seconds of intense muscle activity, which energy source is primarily utilized, and what is its limitation?
During sustained muscle contraction, why are alternative energy pathways necessary after the initial few seconds?
During sustained muscle contraction, why are alternative energy pathways necessary after the initial few seconds?
A sprinter is running a 100-meter dash. How does the principle of muscle fiber recruitment apply as they accelerate?
A sprinter is running a 100-meter dash. How does the principle of muscle fiber recruitment apply as they accelerate?
A person is lifting progressively heavier weights. How does this activity relate to the relationship between stimulus strength and muscle force?
A person is lifting progressively heavier weights. How does this activity relate to the relationship between stimulus strength and muscle force?
In the context of muscle contraction, what distinguishes 'summation' from 'recruitment'?
In the context of muscle contraction, what distinguishes 'summation' from 'recruitment'?
In fine motor control, a single motor neuron typically innervates how many muscle fibers, and what is the functional consequence of this arrangement?
In fine motor control, a single motor neuron typically innervates how many muscle fibers, and what is the functional consequence of this arrangement?
What event directly triggers the release of acetylcholine (ACh) into the synaptic cleft at the neuromuscular junction?
What event directly triggers the release of acetylcholine (ACh) into the synaptic cleft at the neuromuscular junction?
Following the release of calcium from the sarcoplasmic reticulum, what is the next immediate step in initiating muscle contraction?
Following the release of calcium from the sarcoplasmic reticulum, what is the next immediate step in initiating muscle contraction?
During the sliding filament theory of muscle contraction, what role does ATP play in the detachment of myosin from actin?
During the sliding filament theory of muscle contraction, what role does ATP play in the detachment of myosin from actin?
What is the functional difference between fine motor control and gross motor control in terms of muscle fiber innervation?
What is the functional difference between fine motor control and gross motor control in terms of muscle fiber innervation?
What happens if the opening of $Na^+$ channels on the sarcolemma is blocked?
What happens if the opening of $Na^+$ channels on the sarcolemma is blocked?
During muscle contraction, what is the direct consequence of tropomyosin being moved off the myosin-binding site on actin?
During muscle contraction, what is the direct consequence of tropomyosin being moved off the myosin-binding site on actin?
Which step in the excitation-contraction coupling process directly links the action potential on the sarcolemma to calcium release within the muscle fiber?
Which step in the excitation-contraction coupling process directly links the action potential on the sarcolemma to calcium release within the muscle fiber?
A drug that interferes with the function of the enzyme acetylcholinesterase (which breaks down acetylcholine) at the neuromuscular junction would likely cause:
A drug that interferes with the function of the enzyme acetylcholinesterase (which breaks down acetylcholine) at the neuromuscular junction would likely cause:
What aspect(s) of skeletal muscle contraction are explained by 'graded responses'?
What aspect(s) of skeletal muscle contraction are explained by 'graded responses'?
Which connective tissue layer directly surrounds individual muscle fibers?
Which connective tissue layer directly surrounds individual muscle fibers?
What is the primary function of tendons in the context of skeletal muscle?
What is the primary function of tendons in the context of skeletal muscle?
Which of the following components is NOT a key feature of the microscopic anatomy of skeletal muscle cells?
Which of the following components is NOT a key feature of the microscopic anatomy of skeletal muscle cells?
What is the role of T-tubules in skeletal muscle fibers?
What is the role of T-tubules in skeletal muscle fibers?
Which structure within a muscle fiber is responsible for storing calcium ions?
Which structure within a muscle fiber is responsible for storing calcium ions?
What is the functional unit of a muscle called?
What is the functional unit of a muscle called?
Which protein primarily makes up the thin filaments in a sarcomere?
Which protein primarily makes up the thin filaments in a sarcomere?
During muscle contraction, what event directly precedes the binding of myosin to actin?
During muscle contraction, what event directly precedes the binding of myosin to actin?
Which of the following best describes the arrangement of myofilaments within a sarcomere?
Which of the following best describes the arrangement of myofilaments within a sarcomere?
What happens to the length of the I band during muscle contraction?
What happens to the length of the I band during muscle contraction?
If a muscle fiber has a reduced ability to store glycogen, what immediate effect would this have on muscle function?
If a muscle fiber has a reduced ability to store glycogen, what immediate effect would this have on muscle function?
Which of the following accurately describes the sequence of events in muscle contraction, starting with the arrival of an action potential?
Which of the following accurately describes the sequence of events in muscle contraction, starting with the arrival of an action potential?
How would inhibiting the function of the sarcoplasmic reticulum affect muscle contraction?
How would inhibiting the function of the sarcoplasmic reticulum affect muscle contraction?
Predict the effect of a drug that blocks the activity of acetylcholinesterase at the neuromuscular junction.
Predict the effect of a drug that blocks the activity of acetylcholinesterase at the neuromuscular junction.
Consider a scenario where a person's muscle fibers have fewer mitochondria than normal. How would this most likely affect their physical performance?
Consider a scenario where a person's muscle fibers have fewer mitochondria than normal. How would this most likely affect their physical performance?
Flashcards
Excitability
Excitability
Ability to receive and respond to stimuli.
Contractility
Contractility
Ability to shorten forcibly when stimulated.
Elasticity
Elasticity
Ability to recoil and resume resting length after being stretched.
Extensibility
Extensibility
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Tendons
Tendons
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Tendons Function
Tendons Function
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Skeletal Muscle
Skeletal Muscle
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cardiac muscle
cardiac muscle
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Smooth muscle
Smooth muscle
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Muscle Movement
Muscle Movement
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Posture
Posture
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Joint Stabilization
Joint Stabilization
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Irritability
Irritability
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Fine Motor Control
Fine Motor Control
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Gross Motor Control
Gross Motor Control
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Neuromuscular Junction
Neuromuscular Junction
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Step 1 of Muscle Excitation
Step 1 of Muscle Excitation
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Step 2 of Muscle Excitation
Step 2 of Muscle Excitation
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Step 3 of Muscle Excitation
Step 3 of Muscle Excitation
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Step 4 of Muscle Excitation
Step 4 of Muscle Excitation
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Step 5 of Excitation-Contraction Coupling
Step 5 of Excitation-Contraction Coupling
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Step 6 of Excitation-Contraction Coupling
Step 6 of Excitation-Contraction Coupling
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Graded Response
Graded Response
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Frequency of Stimuli
Frequency of Stimuli
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Tetanus (Muscle)
Tetanus (Muscle)
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Recruitment (Muscle)
Recruitment (Muscle)
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Muscle Tension
Muscle Tension
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Initial Energy Source
Initial Energy Source
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Muscle Contraction Duration
Muscle Contraction Duration
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Strength of Stimuli
Strength of Stimuli
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Summation (Muscle)
Summation (Muscle)
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Anaerobic
Anaerobic
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Aerobic
Aerobic
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Glycolysis
Glycolysis
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Lactic Acid
Lactic Acid
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What is ATP?
What is ATP?
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Creatine Phosphate (CP)
Creatine Phosphate (CP)
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Muscle Fatigue
Muscle Fatigue
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Oxygen debt
Oxygen debt
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What causes muscle fatigue?
What causes muscle fatigue?
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Muscle Tone
Muscle Tone
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Endomysium
Endomysium
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Perimysium
Perimysium
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Epimysium
Epimysium
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Sarcolemma
Sarcolemma
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T-tubule
T-tubule
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Sarcoplasm
Sarcoplasm
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Sarcoplasmic Reticulum
Sarcoplasmic Reticulum
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Terminal Cisternae
Terminal Cisternae
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Sarcomeres
Sarcomeres
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Z-discs
Z-discs
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Myofilaments
Myofilaments
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Myoglobin
Myoglobin
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Glycogen
Glycogen
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Study Notes
- To recall the basic muscle types a review worksheet should be completed in Brightspace.
Functions of Muscle
- Muscles provide movement.
- Muscles maintain posture.
- Muscles stabilize joints.
- Muscles produce heat to maintain body temperature.
Properties of Skeletal Muscle Activity
- Excitability refers to the ability to receive and respond to stimuli.
- Contractility refers to the ability to shorten forcibly when stimulated.
- Elasticity refers to the ability to recoil after stretch.
- Extensibility refers to the ability to stretch.
Connective Tissue Wrappings of Skeletal Muscle
- Connective tissue sheaths are made of dense regular connective tissue.
- Connective tissue sheaths form tendons that connect muscles to bone and transfer contractile force to bone for movement.
- The muscle cell/fiber is covered by the Endomysium.
- A group of muscle cells, or fascicles are covered by the Perimysium.
- A group of fascicles are covered by the Epimysium.
Microscopic Anatomy of Skeletal Muscle
- One muscle cell/fiber contains many cells that are long and cylindrical.
- Myoglobin stores oxygen in the muscle cells.
- Glycogen stores energy in the muscle cells.
- Muscle cells contain more mitochondria.
- Sarcolemma is the membrane of the muscle cell.
- Inward extensions of the sarcolemma form the T-tubules.
- Sarcoplasm is the intracellular fluid of the muscle cell
- Sarcoplasmic reticulum is a smooth endoplasmic reticulum in the muscle cell.
- Terminal cisternae are end sacs that store calcium.
- The muscle fiber/cell has hundreds or thousands of myofibrils.
- Myofibrils are made of chains of sarcomeres.
- Sarcomeres are functional units of muscle and are the spaces between two Z-discs.
- Z-discs divide sarcomeres.
- Sarcomeres have a specific arrangement/pattern of proteins called myofilaments.
- There are two types of myofilaments: actin and myosin.
- A-bands are dark bands containing actin and myosin.
- I-bands are light bands containing actin.
Myofilaments: Myosin and Actin
- Myosin is a thick filament that contains contractile proteins.
- Each myosin head has two binding sites: one to attach to actin to form a cross-bridge, and another to bind an ATP molecule.
- Actin is a thin filament which is a chain of proteins (G-proteins)
- Each G-protein has a site for myosin.
- The binding site is normally covered by a thin protein called tropomyosin.
- Attached to tropomyosin is troponin, which has an affinity for calcium.
Excitation-Contraction Coupling
- Muscle must be stimulated by a motor neuron in order to contract.
- A motor neuron has axon terminals that connect to many muscle fibers/cells.
- Stimulation of a motor unit causes a weak contraction of the entire muscle.
- Fine motor control occurs when one motor neuron controls 3-6 fibers/cells giving more accuracy, but less strength like controlling eyes and fingers.
- Gross motor control occurs when one motor neuron controls up to 1,000 fibers giving accuracy like using quadriceps muscle.
Neuromuscular Junction and Excitation of Muscle
- Step 1: A nerve impulse travels down the motor neuron to axon terminal.
- Step 2: The nerve impulse triggers movement of calcium from the extracellular fluid (ECF) to the intracellular fluid (ICF) of axon terminal.
- Step 3: Calcium triggers the release of acetylcholine (ACh) into the synaptic cleft.
- Step 4: ACh binds to receptors on the sarcolemma, which triggers the opening of sodium (Na+) channels.
- Step 5: An action potential occurs in the sarcolemma and travels down the T-tubule.
- Step 6: The action potential travels past the terminal cisternae of the sarcoplasmic reticulum, which releases Ca2+ into sarcoplasm.
- Step 7: Ca2+ binds to troponin, which moves tropomyosin off of the myosin-binding site on actin.
- Step 8: ATP binds to the myosin head, the myosin head changes shape ("cocked"), and myosin binds to actin forming a cross-bridge.
- Step 9: Actin then 'slides' past myosin, and the sarcomere shortens.
- Step 10: Another ATP binds to myosin head, and the head detaches from actin, allowing the cycle to continue.
Graded Responses of Muscle Contraction
- Graded response refers to different degrees of skeletal muscle contraction (different forces).
- Graded contractions are produced by changing the frequency and strength of stimuli.
- By changing the frequency is known as Summation, and refers to how fast a stimulus is sent to a muscle.
- Muscle force depends upon the number of fibers stimulated.
- More fibers contracting means more muscle tension.
- More force means stimulating/recruiting more motor units.
- Muscles can continue to contract unless they run out of energy.
Energy for Muscle Contraction
- Initially, muscles use stored ATP for energy, but there are only 4-6 seconds worth of this, so other pathways are needed to get energy.
- Direct phosphorylation of ADP by creatine phosphate (CP) provides energy for about 15 seconds.
- Anaerobic glycolysis and lactic acid formation provides energy for about 30-60 seconds.
- Aerobic respiration provides energy for hours.
- Muscle fatigue is the physiological inability for a muscle to contract.
- Oxygen debt is the oxygen owed to liver cells to rid lactic acid, and to muscle cells to restore ATP and CP.
Muscle Tone
- Muscle tone is the maintenance of partial contraction of a muscle when the muscle is at rest.
- Muscle tone maintains posture and comes from reflexes coming from the spinal cord, which come from signals from the brain.
Points of Attachment
- Muscles have at least two points of attachment:
- The origin is on the least movable bone of joint.
- The insertion is on the more movable bone of joint.
- When muscles contract, the insertion moves towards the origin.
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Description
This lesson reviews basic muscle types and their functions, including movement, posture maintenance, joint stabilization, and heat production. It covers properties of skeletal muscle activity like excitability, contractility, elasticity, and extensibility. Connective tissue wrappings such as Endomysium, Perimysium and Epimysium are also discussed.
