169 Questions
Which type of muscle is involuntary and found in the walls of internal organs?
Smooth muscle
Which type of muscle forms the majority of the human muscular system?
Skeletal muscle
What is the main structural difference between skeletal and cardiac muscles?
Presence of intercalated discs in cardiac muscle
In terms of cellular structure, what distinguishes skeletal muscle fibers from cardiac muscle fibers?
Cardiac muscle fibers have a single nucleus, while skeletal muscle fibers are multinucleated
What is the main difference between a myofibril and a sarcomere?
The myofibril is the organized actin/myosin strands within the muscle fiber, while the sarcomere is a chunk of myofibril.
What cellular process leads to the formation of a muscle fiber from multiple myoblasts?
Fusion
What distinguishes the cellular structure of skeletal muscle fibers from cardiac muscle fibers?
The number of nuclei, with skeletal muscle fibers having multiple nuclei per cell and cardiac muscle fibers having a single nucleus.
Why do skeletal muscle fibers contain multiple nuclei?
To increase the capacity for protein synthesis and repair
What is the primary function of Transverse tubules (T tubules) in skeletal muscle fibers?
Facilitate the rapid conduction of action potentials to the interior of the muscle fiber
What distinguishes the sarcoplasmic reticulum from the smooth endoplasmic reticulum found in other cells?
Specialization in storing and releasing calcium ions for muscle contraction
Why do satellite cells only activate/differentiate if the muscle they're close to is strained or injured?
To ensure that new cells are only formed when there is a genuine need for repair or growth
How does muscle hypertrophy differ from the typical formation of new cells?
Muscle hypertrophy leads to the addition of more myocytes to existing cells, while typical formation of new cells does not involve myocyte addition
Why can't mature muscle cells (muscle fibers) regenerate on their own?
Mature muscle cells lack the ability to undergo mitosis and divide
What is the role of transverse tubules (T tubules) in skeletal muscle fibers?
Facilitate the release of calcium ions into the sarcoplasm during muscle contraction
What is the primary function of satellite cells in muscle tissue?
Repair and regenerate damaged muscle fibers
How do sarcomeres contribute to muscle function?
They generate force through the interaction of actin and myosin filaments
What is the primary significance of tongue fasciculations in the context of muscle health?
Indication of a lower motor nerve disease like ALS
In what situation would eye twitches (fasciculations) typically occur?
Due to fatigue or stress
What is the key characteristic of fasciculations in muscles?
Involuntary movement of one or more fascicles of a particular muscle
What is the primary function of satellite cells in muscle tissue?
To help regenerate injured muscle tissue
What distinguishes the cellular structure of skeletal muscle fibers from cardiac muscle fibers?
Presence of intercalated discs in cardiac muscle fibers
What is the main difference between a myofibril and a sarcomere?
Sarcomeres are contractile units within myofibrils
In terms of muscle contraction, what distinguishes the cellular structure of fast twitch fibers from slow twitch fibers?
The greater reliance on anaerobic metabolism in fast twitch fibers
What is the primary factor that contributes to the difference in muscle contraction speed between fast twitch and slow twitch fibers?
The ratio of myosin heavy chain isoforms in the muscle fibers
Which type of muscle fibers have low blood supply, fatigue rapidly, and are anaerobic?
Fast twitch type 2a
What is the primary characteristic of slow twitch type 1 muscle fibers?
High number of mitochondria
Which type of muscle fibers are primarily used by sprinters?
Fast twitch type 2b
What distinguishes the cellular structure of fast twitch type 2a and 2b fibers from slow twitch type 1 fibers?
Low number of capillaries and low blood supply
What is the primary function of myoglobin in muscle fibers?
To store and transport oxygen within the muscle fibers
Which type of neuron is associated with slow twitch muscle fibers?
Motor neuron
What distinguishes myoglobin from hemoglobin in terms of location and function?
Myoglobin stores oxygen within muscle fibers, while hemoglobin transports oxygen in the form of oxyhemoglobin.
How does the presence of myoglobin affect the appearance of muscle fibers?
Increases myoglobin makes the fibers appear darker in color
What is the primary function of myoglobin in Fast Twitch Type II muscle fibers?
Binds and stores oxygen for use during intense muscle activity
What distinguishes the primary energy production process in Fast Twitch Type II muscle fibers from Slow Twitch muscle fibers?
Heavy reliance on anaerobic respiration
Why are Fast Twitch Type II muscle fibers well-suited for sprinting activities?
Rapid firing capability and quick energy production
What is the primary advantage of Fast Twitch Type II muscle fibers in extraocular muscles, speaking, and swallowing muscles?
Capability for rapid, forceful contractions
What is the primary reason for slow twitch Type I muscle fibers to use aerobic respiration?
To facilitate prolonged muscle endurance
Why are slow twitch Type I muscle fibers referred to as 'Red'?
Due to their high blood supply
What is the key characteristic that enables slow twitch Type I muscle fibers to stay energized for a long time?
Predominant reliance on aerobic respiration
How do slow twitch Type I muscle fibers differ from fast twitch Type II muscle fibers in terms of lactic acid production?
Slow twitch fibers produce negligible amounts of lactic acid
What is the primary role of Golgi tendon organs in muscle physiology?
Detecting stretch near muscle tendons
What distinguishes the primary function of the sarcoplasmic reticulum in skeletal muscle fibers from other cellular structures?
Regulation of calcium levels for muscle contraction
In terms of energy production, what sets Fast Twitch Type II muscle fibers apart from Slow Twitch muscle fibers?
Greater production of lactic acid
What is the primary characteristic of slow twitch Type I muscle fibers in terms of endurance?
Ability to sustain contractions for long periods
What is the primary role of troponin in muscle contraction?
Regulating the binding of myosin to actin
What is primarily responsible for the sliding of actin and myosin filaments during muscle contraction?
ATP
Which structure prevents myosin from binding to actin during muscle relaxation?
Tropomyosin
What is happening in a muscle that is working but maintaining its length?
The actin and myosin are forming new cross-bridges at the same rate as they are breaking down
What contributes to the maintenance of muscle length during contraction?
Simultaneous attachment and detachment of actin and myosin cross-bridges
What prevents the muscle from shortening during a contraction?
Continuous attachment of myosin heads to actin filaments
What is the significance of maintaining cross-bridges between actin and myosin in a functioning muscle?
Prevents muscle fatigue and prolongs endurance
Which term describes maintaining a constant tension while changing in length?
Isotonic
What term refers to constant length, even if tension is changing?
Isometric
How would you describe exercises that involve maintaining a constant speed of contraction?
Isokinetic
What term is used to describe a hypothetical type of muscle contraction that maintains a constant temperature?
Isothermal
What is the primary role of troponin in muscle contraction?
To change shape when it binds calcium and let go of tropomyosin
What happens when there is very little calcium around in muscle cells?
Tropomyosin is in the way of actin-myosin binding
What is the primary function of myosin in muscle contraction?
To grab actin and pull it against in a sliding motion
What is the main role of tropomyosin in muscle contraction?
To wrap around actin and cover up the sites where myosin likes to grab on
What is the primary role of troponin in muscle contraction?
To hold tropomyosin in place to cover the actin binding sites
What contributes to the maintenance of muscle length during contraction?
Tropomyosin moving out of the way
What is the main structural difference between skeletal and cardiac muscles?
Arrangement of actin and myosin filaments
Why can't mature muscle cells (muscle fibers) regenerate on their own?
Absence of satellite cells in mature muscle fibers
What is the primary role of satellite cells in muscle tissue?
To regenerate and repair muscle fibers
What is the main advantage of Fast Twitch Type II muscle fibers in extraocular muscles, speaking, and swallowing muscles?
High resistance to fatigue and anaerobic energy production
What is the primary role of myosin in a single sarcomere during muscle contraction?
Pulling the actin filaments closer to the M line
What is the effect of insufficient calcium in a muscle cell during contraction?
Decreased binding of myosin to actin
Which statement best describes the interaction of myosin with actin in a single sarcomere during muscle contraction?
Myosin pulls the actin filaments towards the M line, causing muscle shortening.
In terms of muscle contraction, what is the primary function of troponin?
Stabilizing the position of tropomyosin on actin filaments
What is the primary function of transverse tubules (T tubules) in skeletal muscle fibers?
Facilitate communication between sarcomeres
What happens when there is very little calcium around in muscle cells?
Myosin remains unattached to actin, preventing muscle contraction
What is the primary reason for slow twitch Type I muscle fibers to use aerobic respiration?
To support sustained, endurance activities with a steady supply of energy
What distinguishes the cellular structure of fast twitch fibers from slow twitch fibers in terms of lactic acid production?
Fast twitch fibers produce lactic acid more rapidly than slow twitch fibers
What will happen if Ca++ remains and more ATP is available in the muscle?
Myosin will release actin to bind a new ATP and change its shape to 'unflexed'
If Ca++ disappears in the muscle, what will happen to myosin?
Myosin will hold its ATP, detached from actin, and await another chance to bind
What happens if Ca++ is present but no ATP is available in the muscle?
Myosin will remain attached to its actin binding site in its 'flexed' position
What is the consequence of myosin remaining attached to its actin binding site in the muscle when there is no ATP available?
The muscle remains in a contracted state
During a muscle contraction, which statement best describes the stacking up of multiple muscle fiber membrane potentials?
It enables rapid transmission of action potentials along the muscle fibers.
What is the primary role of titin in muscle fibers?
Acting as a molecular spring to resist over-stretching of the sarcomere
In terms of muscle contraction, what distinguishes the cellular structure of fast-oxidative-glycolytic fibers from slow-oxidative fibers?
Higher myosin ATPase activity
What is the primary role of the sarcoplasmic reticulum in muscle physiology?
A reservoir of calcium ions that can flood the sarcomeres when it's time to contract
What is the primary function of transverse (T) tubules in skeletal muscle fibers?
Relaying signals to rapidly activate the entire muscle cell for contraction
What happens when there is an insufficient amount of calcium ions in muscle cells?
The tropomyosin blocks myosin binding sites on actin, preventing muscle contraction
What distinguishes the primary energy production process in Fast Twitch Type II muscle fibers from Slow Twitch muscle fibers?
Fast Twitch fibers rely more on anaerobic glycolysis for energy
What is the specialized role of endoplasmic reticulum in muscle cells?
Storing calcium until it's needed
How is the release of Ca++ from the endoplasmic reticulum characterized in muscle cells?
It is faster compared to the reuptake of Ca++
What connects the endoplasmic reticulum to T Tubules in muscle cells?
DHP Receptor (specialized voltage sensor)
What is the characteristic of the reuptake of Ca++ by the endoplasmic reticulum in muscle cells?
It is faster compared to the release of Ca++
What is responsible for rapidly transmitting the depolarization message to the sarcoplasmic reticulum in muscle cells?
T-Tubules
If there is a lack of calcium ions in muscle cells, what will be affected?
Myosin binding to actin
Which structure primarily prevents myosin from binding to actin during muscle relaxation?
Troponin
In terms of cellular structure, what distinguishes skeletal muscle fibers from cardiac muscle fibers?
Presence of T-Tubules
Qual es le characteristic principal que distingue le contraction muscular del fibra musculare?
Le activation electric del fibra muscular es lente, e su contraction real es rapide
Qual es le resultato si le calcium non dispare in le musculo?
Le actina e myosina non pote ligar se pro iniciar le contraction
Qual es le principal function de myosina in un singule sarcomero durante le contraction muscular?
Initiar le contractile processus
In relation al contraction muscular, qual distingue le structura cellular del fibra muscular de contraction rapida-oxidative-glicolitic de fibra muscular de contraction lente-oxidative?
Le differentia in production de acid lact
During a muscle contraction, what best describes the relationship between the action of myofibrils and the message conduction of the plasma membrane?
The action of myofibrils lags behind the message conduction of the plasma membrane
What distinguishes the primary role of satellite cells in muscle tissue?
Regeneration of damaged muscle fibers
How are slow twitch Type I muscle fibers characterized in terms of blood supply, fatigue, and aerobic/anaerobic nature?
Low blood supply, rapid fatigue, aerobic
What is the consequence of myosin remaining attached to its actin binding site in the muscle when there is no ATP available?
Muscle fibers disintegrate without ATP
What is the consequence of myosin remaining attached to its actin binding site in the muscle when there is no ATP available?
The muscle will be unable to relax due to the continued formation of crossbridges.
What contributes to the maintenance of muscle length during contraction?
The presence of titin filaments in the sarcomere
What is primarily responsible for the sliding of actin and myosin filaments during muscle contraction?
Myosin crossbridge formation
What is the primary role of troponin in muscle contraction?
To bind calcium ions and initiate contraction
What is the primary factor contributing to the strength of muscle contraction?
The size of the motor units in a muscle
What distinguishes the primary role of satellite cells in muscle tissue?
Contributing to muscle regeneration and repair
In terms of energy production, what sets Fast Twitch Type II muscle fibers apart from Slow Twitch muscle fibers?
Increased capacity for anaerobic glycolysis
What is the primary function of titin in muscle fibers?
Anchoring myosin filaments in place within the sarcomere
What is the primary factor contributing to the contraction of skeletal muscles?
Stimulation by nerve cells
What distinguishes the primary role of motor neurons in stimulating skeletal muscle fibers?
Origin of cell bodies in the CNS
Which characteristic sets motor neurons apart from other nerves in the body?
Large diameter
What is the essential requirement for skeletal muscle contraction?
Stimulation by motor neurons
What is the primary reason that skeletal muscles have to be stimulated by a nerve in order to contract?
No pacemaker cells for spontaneous electrical activity
What is the primary function of the neuromuscular junction in muscle physiology?
Generation of action potentials for muscle stimulation
What distinguishes the structure of skeletal muscles from cardiac muscles in terms of electrical activity?
Presence of T tubules in skeletal muscles
What is the primary role of myosin in muscle fibers during contraction?
Binding to actin and forming cross-bridges
What is the final result of the process where ACh binds to receptors on the motor end plate?
Contraction of the muscle fiber
What is the primary role of tropomyosin in muscle contraction?
Allowing myosin to bind to actin during muscle contraction
What is the consequence of calcium remaining bound to troponin in the muscle fiber?
Tropomyosin remains in place and blocks myosin from binding to actin
In the absence of ATP, what effect does myosin remaining attached to its actin binding site have on muscle contraction?
Muscle remains in a state of tetanus
Which type of acetylcholine receptor is also responsive to nicotine?
Nicotinic receptors
What type of acetylcholine receptor is found in skeletal muscle?
Nicotinic receptor
Which compound do muscarinic receptors also bind to?
Muscarine
What classifies acetylcholine receptors based on their responsiveness to specific substances?
Interaction with specific compounds
How is muscle contraction stopped?
By stopping the action potential and removing the ACh from the motor end plate
What is the primary method to get a muscle to stop doing what it's doing?
Stop the action potential and eliminate the ACh from the motor end plate
What is the role of IPSP for muscle in muscle contraction?
Inhibits muscle contraction
Why is it said that all neuromuscular junctions are excitatory?
Because they lead to muscle contraction through the release of ACh
What is the consequence of a muscle where ACh binds to receptors but does not open their ion channels?
Normal muscle function is inhibited, including breathing
What is the primary target of destruction in Myasthenia Gravis?
Acetylcholine receptors
What is the approximate ratio of women to men affected by Myasthenia Gravis in the United States?
2:1
What percentage of nicotinic ACh receptors in skeletal muscle's motor end plate can be destroyed by Myasthenia Gravis?
Up to 80%
What is the primary target for treatment of Myasthenia Gravis?
Reduce the activity of the immune system
Which treatment approach aims to make acetylcholine (ACh) last longer in the neuromuscular junction (NMJ) for patients with Myasthenia Gravis?
Inhibiting the breakdown of ACh in the NMJ
What is a treatment method that aims to remove circulating antibodies in Myasthenia Gravis?
Plasmapheresis to eliminate circulating antibodies
What type of receptors are skeletal muscle acetylcholine receptors?
Ionotropic
What is the primary neurotransmitter that binds to skeletal muscle acetylcholine receptors?
Acetylcholine
What is the specific responsiveness of skeletal muscle acetylcholine receptors to external substances?
Nicotinic
During which phase of a twitch contraction is tension developing due to the cross-bridge cycling?
Contraction Phase
Why is the relaxation phase longer than the contraction phase in a twitch contraction?
To sequester all the Ca2+
What is the primary reason for the time delay from the action potential to the onset of contraction during the latent period of a twitch contraction?
Excitation-contraction coupling
What is the primary difference between isometric and isotonic twitches?
Isometric twitches generate tension but do not change the length of the muscle, whereas isotonic twitches generate enough tension to shorten the muscle.
What happens when isotonic twitches occur in a muscle?
The tension generated is greater than the load, resulting in shortening of the muscle.
In terms of muscle contraction, what distinguishes the role of myosin during isometric and isotonic twitches?
Myosin remains attached to actin binding sites during isometric twitches but detaches during isotonic twitches.
What is the term for the increase in muscle tension from successive action potentials during the phase of mechanical activity?
Tetanus
What is the term for the phenomenon where a muscle fiber is stimulated again before it has fully relaxed from its last twitch?
Temporal summation
What is the term used for the increase in muscle fiber's tension due to multiple stimuli arriving before the muscle fiber has relaxed from its last twitch?
Wave summation
In the context of muscle contraction, what does tetany refer to?
A maintained contraction in response to repetitive stimulation
What is the primary effect of too much summation on muscle contraction?
Tetanic contraction
How does tetanic contraction differ from a single twitch contraction?
Tetanic contraction involves sustained and continuous contraction, while single twitch contraction is brief and isolated
What contributes to the rate of onset of muscle fatigue?
Intensity and duration of contractile activity
What is a characteristic of fatigued muscle in terms of shortening velocity?
Decreased shortening velocity
Which factor determines the type of muscle fiber that will be affected by fatigue?
Fitness level of the individual
What happens to relaxation time when squeeze intensity decreases?
It increases
What is the primary role of the stretch reflex in muscle physiology?
To elicit a monosynaptic response that causes the muscle to shorten
What is the main function of reciprocal innervation in muscle physiology?
To send inhibitory signals to the antagonist muscles
In terms of muscle physiology, what does the ascending information sent to the brain primarily serve for?
To process the information about the stretch at higher centers
What is the result of painful stimulation of the skin on the ipsilateral limb?
Flexor muscles are activated and extensor muscles are inhibited
What is the response of the contralateral limb to painful stimulation of the skin?
Extensors are activated while flexors are inhibited
What effect does painful stimulation of the skin have on both the ipsilateral and contralateral limbs?
Activates different muscle groups in each limb
Which type of pathways are considered sensory and afferent?
Motor pathways
What type of information do ascending pathways primarily carry?
Sensory and afferent information
Which of the following types of pathways are associated with autonomic functions?
Descending pathways
Which part of the cerebral cortex is responsible for the ongoing control of voluntary movements?
Sensorimotor cortex
What is the primary function of the neurons in the primary motor cortex and premotor cortex?
Motor control
Which area of the cerebral cortex is primarily made up of neurons that give rise to descending pathways for motor control?
Primary motor cortex
What is the primary source of input to the cerebellum from the sensorimotor cortex?
Relayed via brainstem nuclei
Which structure receives input from the vestibular system, eyes, skin, muscles, joints, and tendons?
Cerebellum
Where does the cerebellum send input to, ultimately impacting smooth motion and balance?
To the brainstem nuclei
Study Notes
Muscle Types and Characteristics
- Smooth muscle: involuntary, found in internal organs
- Skeletal muscle: majority of human muscular system, voluntary, attached to bones
- Cardiac muscle: involuntary, found in heart, striated
Muscle Fiber Structure
- Skeletal muscle fibers: multinucleated, voluntary
- Cardiac muscle fibers: single nucleus, involuntary
- Myofibrils: composed of sarcomeres, contractile units of muscle fibers
- Sarcomere: functional unit of muscle contraction, consists of actin and myosin filaments
Muscle Contraction
- Myofibril: composed of sarcomeres, contractile units of muscle fibers
- Sarcomere: functional unit of muscle contraction, consists of actin and myosin filaments
- Troponin: regulates muscle contraction, binds to calcium ions
- Tropomyosin: blocks myosin binding to actin, prevents muscle contraction
- Myosin: motor protein, responsible for muscle contraction
- Actin: protein filament, interacts with myosin during muscle contraction
Muscle Fiber Types
- Fast twitch (Type II) fibers: rapid contraction, high force, low endurance, anaerobic, low blood supply
- Slow twitch (Type I) fibers: slow contraction, low force, high endurance, aerobic, high blood supply
- Fast twitch Type II fibers: high power, short duration, low endurance
- Slow twitch Type I fibers: low power, long duration, high endurance
Muscle Physiology
- Satellite cells: precursor cells, differentiate into muscle fibers, repair damaged muscle tissue
- Sarcoplasmic reticulum: stores and releases calcium ions, regulates muscle contraction
- Transverse tubules (T-tubules): rapid transmission of depolarization message to sarcoplasmic reticulum
- Myoglobin: stores oxygen, facilitates muscle contraction
- Golgi tendon organs: sense muscle tension, regulate muscle contraction
Muscle Contraction Regulation
- Calcium ions: regulate muscle contraction, bind to troponin
- ATP: energy source for muscle contraction, needed for myosin to release from actin
- Titin: responsible for muscle elasticity, returns muscle to resting state
Muscle Function and Performance
- Muscle length: maintained during contraction, due to cross-bridges between actin and myosin
- Muscle contraction: sliding of actin and myosin filaments, regulated by calcium ions and ATP
- Muscle fatigue: results from decreased ATP and calcium ions, leads to muscle relaxation
- Muscle endurance: ability to sustain muscle contraction over time, dependent on muscle fiber type and energy production
Test your knowledge of muscle classification with this quiz. Determine whether a given type of muscle belongs to the categories of skeletal, cardiac, or smooth muscle, and understand their distinguishing characteristics.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
