Lesson 6 Muscleskeletal System Flashcards
What are the main symptoms experienced by John after organophosphate poisoning?
Severe stomach cramps, double vision, difficulty breathing, spastic contractions of skeletal muscles.
How do organophosphate insecticides exert their effects?
By binding to the enzyme acetylcholinesterase within synaptic clefts, rendering it ineffective.
What neurotransmitter is affected by organophosphate poisons?
Acetylcholine.
What is the consequence of organophosphate poisoning on acetylcholine?
Increased concentration of acetylcholine due to ineffective degradation.
What is the primary function of acetylcholinesterase?
To degrade acetylcholine in the synaptic cleft.
What are the symptoms of Duchenne muscular dystrophy?
Muscle weakness, muscle atrophy, contractures.
What is a major complication of Duchenne muscular dystrophy related to the heart?
Heart failure occurs in many patients.
In Duchenne muscular dystrophy, what skeletal deformities can result from contractures?
Kyphoscoliosis.
What digestive issues can arise due to Duchenne muscular dystrophy?
Enlarged colon diameter and twisting of the small intestine leading to obstruction.
What is the effect of poliomyelitis on motor neurons?
It destroys motor neurons, causing loss of muscle function and flaccid paralysis.
What is the process of reinnervation in poliomyelitis recovery?
Axon branches from remaining motor neurons innervate paralyzed muscle fibers.
What are the components of a skeletal muscle fiber’s electrical structure?
Sarcolemma, transverse tubules (T tubules), sarcoplasmic reticulum (S R).
What is the basic functional unit of muscle fiber?
Sarcomere.
What is the role of tropomyosin in muscle contraction?
Regulates the interaction between active sites on G actin and myosin.
What are the four general properties of muscle tissue?
- Contractility
- Excitability
- Extensibility
- Elasticity
What type of muscle is responsible for locomotion and facial expressions?
Skeletal muscle.
What type of muscle is found in the walls of hollow organs?
Smooth muscle.
What is the primary function of cardiac muscle?
Pumping blood.
What condition is caused by the binding of antibodies to acetylcholine receptors in myasthenia gravis?
Flaccid paralysis.
What type of medication is used to treat myasthenia gravis by affecting acetylcholinesterase?
Neostigmine.
Fill in the blank: The _______ is a delicate filament holding myosin in place within a sarcomere.
M line
True or False: Smooth muscle is capable of spontaneous contraction.
True
What condition results from curare binding to acetylcholine receptors?
Flaccid paralysis
Flaccid paralysis occurs because muscle fibers cannot contract in response to nervous stimulation.
What is curare primarily used for in a medical context?
To relax muscles during certain kinds of surgery
Curare is administered in small doses for this purpose.
What autoimmune disorder is characterized by the production of antibodies that bind to acetylcholine receptors?
Myasthenia gravis
This disorder reduces the number of functional acetylcholine receptors.
What class of drugs is used to treat myasthenia gravis?
Neostigmine
Neostigmine partially blocks the action of acetylcholinesterase.
What phenomenon occurs shortly after a person dies due to calcium diffusion?
Rigor mortis
Rigor mortis is characterized by the body becoming rigid.
What type of transport is classified for the movement of Ca2+ from the sarcoplasm into the sarcoplasmic reticulum?
Active transport
Active transport requires energy to move ions against their concentration gradient.
What is malignant hyperthermia?
A hypermetabolic response to certain inhaled anesthetics
It leads to muscle rigidity and increased body temperature.
What condition results from organophosphate poisoning?
Spastic paralysis
This occurs because acetylcholine accumulates and causes constant muscle contraction.
What is the neuromuscular junction?
The point of contact between a motor neuron and a muscle fiber
It consists of presynaptic terminal, synaptic cleft, and postsynaptic membrane.
What neurotransmitter is released at the neuromuscular junction?
Acetylcholine (ACh)
ACh is contained in synaptic vesicles in the presynaptic terminal.
What is the sliding filament model?
The mechanism of muscle contraction where actin myofilaments slide over myosin
This process shortens sarcomeres without changing the length of actin and myosin.
What happens to the H zone during muscle contraction?
It disappears
The H zone vanishes as actin filaments slide past myosin filaments.
In a relaxed muscle, how do actin and myosin myofilaments overlap?
Slightly
This overlap is present when the sarcomere is at its normal resting length.
What is the primary role of motor neurons at the neuromuscular junction?
To carry action potentials that stimulate muscle contraction
This electrical signal initiates action potentials in muscle fibers.
What are the key components of cardiac muscle fibers?
Branching muscle cells, nucleus, intercalated disks, striations, T tubules, sarcoplasmic reticulum, mitochondrion, sarcolemma, connective tissue, sarcomere.
The structural organization is essential for the function of cardiac muscle, allowing for synchronized contractions.
What are the symptoms of Duchenne muscular dystrophy (DMD)?
Muscle weakness, muscle atrophy, contractures.
DMD primarily affects skeletal and cardiac muscles, leading to significant disability.
What is one of the leading causes of death for DMD patients?
Heart failure due to cardiac muscle involvement.
Cardiac involvement occurs in as many as 95 percent of DMD cases.
True or False: Duchenne muscular dystrophy affects the lymphatic system directly.
False.
Although the lymphatic system is not directly affected, damaged muscle fibers are phagocytized by macrophages.
What is the role of the sarcoplasmic reticulum in muscle fibers?
Surrounds T tubules and stores calcium ions for muscle contraction.
The sarcoplasmic reticulum is crucial for the excitation-contraction coupling process.
Fill in the blank: The connective tissue that surrounds each muscle fiber is called the _______.
Endomysium.
Endomysium provides structural support and houses blood capillaries and nerve fibers.
What are the three layers of connective tissue associated with skeletal muscles?
- Epimysium
- Perimysium
- Endomysium
These layers organize muscle fibers and provide pathways for nerves and blood vessels.
What is the function of the neuromuscular junction?
It is the site where a motor neuron communicates with a muscle fiber to initiate contraction.
This junction is critical for voluntary muscle movement.
Describe the structure of actin myofilaments.
Comprised of F-actin molecules, tropomyosin, and troponin.
These components are essential for muscle contraction regulation.
What is the difference between the I-band and A-band in a sarcomere?
- I-band: Contains only thin filaments (actin)
- A-band: Contains the entire length of thick filaments (myosin) and overlaps with thin filaments.
The I-band shortens during muscle contraction, while the A-band remains the same width.
What happens to the sarcomere during contraction?
The Z lines move closer together, the I band gets smaller, and the A band stays the same width.
This shortening of the sarcomere is essential for muscle contraction.
What structures are involved in the organization of sarcomeres?
- Z-disk
- A-band
- H-zone
- I-band
- M-band
These structures define the functional units of muscle fibers.
True or False: The H-zone contains both thick and thin filaments.
False.
The H-zone contains only thick filaments.
What is the primary function of myosin in muscle contraction?
Myosin heads bind to actin to facilitate muscle contraction.
Myosin is essential for the sliding filament theory of muscle contraction.
What is the role of tropomyosin in muscle contraction?
It blocks the binding sites on actin for myosin heads in a relaxed muscle.
Calcium binding to troponin causes a conformational change that moves tropomyosin, allowing contraction.
What happens to the Z lines during sarcomere contraction?
The Z lines move closer together.
What occurs to the I band during full sarcomere contraction?
The I band gets smaller.
What remains unchanged in width during sarcomere contraction?
The A band stays the same width.
Fill in the blank: The process of generating the resting membrane potential involves an uneven distribution of _______.
ions.
What ions primarily contribute to the resting membrane potential?
Sodium ions and potassium ions.
What is the role of the sodium-potassium pump in resting membrane potential?
It pumps sodium ions out and potassium ions in, using ATP.
Define muscle fascicle.
Bundle of muscle fibers within the entire muscle.
What surrounds a muscle fiber?
Endomysium.
What are myofibrils composed of?
Thick and thin myofilaments.
What are the two types of smooth muscle?
- Visceral
- Multiunit
True or False: Visceral smooth muscle cells function independently.
False.
What neurotransmitters are involved in the regulation of smooth muscle?
- Acetylcholine
- Norepinephrine
What is the latch state in smooth muscle contraction?
A period of sustained tension with slow cross-bridge release.
What condition is characterized by excessive contraction of smooth muscle in arterial walls?
Hypertension.
What is the significance of the optimal sarcomere length?
It produces maximum tension in response to a maximal stimulus.
What occurs during the depolarization phase of an action potential?
Sodium ions enter the cell.
Fill in the blank: The enzyme ______ catalyzes the conversion of ADP to ATP.
Adenylate kinase.
What happens to potassium ions during repolarization?
Potassium ions diffuse out of the cell.
What is wave summation?
Increased contraction force due to stimuli delivered more frequently.
Define tetanus in muscle contraction.
A smooth continuous contraction without any evidence of relaxation.
What are the phases of a muscle twitch?
- Lag phase
- Contraction phase
- Relaxation phase
What is the effect of prolonged stretching of a muscle on tension production?
It produces small tension due to little overlap between actin and myosin.
What does the term ‘smooth muscle tone’ refer to?
The relatively constant tension exhibited by smooth muscle.
What role does myosin phosphatase play in smooth muscle contraction?
It removes phosphate from myosin, leading to relaxation.
What happens to the muscle length when it is optimally stretched?
It produces maximal tension due to optimal overlap of actin and myosin.
What is the main function of the sodium-potassium pump?
To maintain the resting membrane potential by exchanging sodium and potassium ions.
What triggers the action potential in a neuron?
A stimulus that generates an action potential.
What is the significance of calcium ions entering the axon terminal?
They trigger the release of acetylcholine (ACh).
What is the result of acetylcholine binding to its receptor on the sarcolemma?
Opening of ligand-gated sodium channels.
What is the role of creatine kinase in ATP production?
It converts creatine and ATP to phosphocreatine and ADP.
What does creatine kinase catalyze?
The conversion of creatine and ATP to phosphocreatine (PCr) and ADP
This process takes 5 to 6 seconds to occur.
What is the anaerobic pathway in muscle metabolism?
Glucose undergoes glycolysis, producing ATP and pyruvate, which produces lactate
This process takes 30 to 40 seconds to occur.
What is the aerobic pathway in muscle metabolism?
Glucose undergoes glycolysis, producing pyruvate, which is used in aerobic respiration to produce ATP, CO2, and H2O
This process takes hours to happen.
What occurs during the recovery stroke in muscle contraction?
The myosin head returns to its original position and stores energy from ATP
This occurs after the contraction phase.
What happens during the power stroke of muscle contraction?
ATP is hydrolyzed to ADP and phosphate, causing the myosin head to pull actin
This is a critical step in cross-bridge cycling.
What is the role of calcium ions in muscle contraction?
Calcium ions bind to troponin, exposing active sites on actin for cross-bridge formation
This process is essential for muscle contraction to occur.
What is a motor unit?
A single motor neuron and all muscle fibers it innervates
An action potential in a motor unit causes all muscle fibers of that unit to contract.
What is the function of acetylcholinesterase at the neuromuscular junction?
It breaks down acetylcholine (ACh) into choline and acetic acid
This process is necessary to terminate the signal for muscle contraction.
Fill in the blank: The strength of muscle contractions varies from weak to strong, depending on the _______.
[force generated in individual muscle fibers]
What are the three major ATP-dependent events required for muscle relaxation?
- Active transport of sodium out and potassium into the muscle fiber
- Detachment of myosin heads from active sites
- Active transport of calcium into the sarcoplasmic reticulum
These events help restore resting membrane potential and prepare for the next contraction.
True or False: The recovery stroke occurs after the power stroke in muscle contraction.
True
What triggers the opening of sodium channels in an action potential?
Depolarization of the membrane
This leads to the propagation of the action potential along the plasma membrane.
What is the role of the sodium-potassium pump in muscle fibers?
To actively transport sodium out and potassium into the fiber to maintain resting membrane potential
This is essential for the muscle fiber’s readiness for contraction.
What is the significance of the triad in muscle fibers?
It consists of a transverse tubule and two terminal cisternae, facilitating calcium release
This structure is crucial for excitation-contraction coupling.
What happens during the lag or latent phase of a muscle twitch?
There is a delay from the stimulus to the beginning of contraction
This phase is critical for preparing the muscle for contraction.
What is the effect of poliomyelitis on motor neurons?
It destroys motor neurons, causing loss of muscle function and flaccid paralysis
Some patients may recover through reinnervation of muscle fibers.
What is the importance of the action potential in muscle contraction?
It stimulates the opening of voltage-gated channels, leading to calcium release and muscle contraction
This initiates the entire contraction process.
What neurotransmitter is released into the synaptic cleft by exocytosis?
Acetylcholine (ACh)
ACh diffuses across the synaptic cleft and binds to ligand-gated channels on the motor end plate.
What happens when ACh binds to ligand-gated channels on the motor end plate?
Channels open, allowing sodium (Na+) to enter the muscle fiber
This causes the postsynaptic membrane to depolarize.
What enzyme breaks down acetylcholine after it detaches from the receptors?
Acetylcholinesterase
It breaks down ACh into acetic acid and choline.
What process is described by the link between electrical and mechanical components of contraction?
Excitation-Contraction Coupling
It starts with an action potential in the sarcolemma and leads to muscle contraction.
What is the role of calcium in excitation-contraction coupling?
Calcium binds to troponin, initiating muscle contraction
Calcium is released from the sarcoplasmic reticulum upon action potential propagation.
What occurs when muscle fibers are stretched too far?
Fewer cross-bridges can form
This results in decreased muscle contraction force.
What is active tension in muscle contraction?
Force applied to lift an object during muscle contraction
It varies with muscle fiber length.
What is total tension in muscle contraction?
Sum of active and passive tension
Active tension changes with muscle length, while passive tension is due to muscle stretching.
What happens to metabolic rate and heat production during exercise?
Both metabolic rate and heat production increase
Post-exercise metabolic rate remains high due to oxygen debt.
What is muscle fatigue characterized by?
Decreased capacity to work and reduced performance efficiency
Mechanisms include acidosis, ATP depletion, oxidative stress, and local inflammation.
What is rigor mortis?
Development of rigid muscles several hours after death
Caused by calcium leaks into the sarcoplasm and cross-bridge formation.
What characterizes slow-twitch muscle fibers?
Contract slowly, have a smaller diameter, better blood supply, more mitochondria
More fatigue-resistant than fast-twitch fibers.
What is hypertrophy in muscle fibers?
Increase in muscle size
Involves an increase in myofibrils and nuclei due to satellite cell fusion.
What is the size principle in muscle recruitment?
Small motor units are recruited first, followed by larger ones
This affects the strength of muscle contraction.
Define isometric contraction.
No change in length but tension increases
Common in postural muscles.
Define isotonic contraction.
Change in length but tension remains constant
Includes concentric and eccentric contractions.
What distinguishes fast-twitch muscle fibers?
Respond rapidly to stimulation, fewer mitochondria, less blood supply
They can be further classified into oxidative (IIa) and glycolytic (IIb) types.
What is the role of calmodulin in smooth muscle contraction?
Regulates myosin kinase
It is activated by calcium ions to initiate contraction.
What is the primary outcome of muscle contraction?
Cross-bridge cycling
Involves the interaction of actin and myosin.
