Muscular System - Cellular Structure Flashcards
Muscle cells are also known as ___.
Muscle fibers
True or False: Muscle fibers are uninucleated.
FALSE. Muscle fibers are multinucleated (have many nuclei).
True or False: Muscle fibers tend to be smaller in larger muscles and larger in smaller muscles.
FALSE. Smaller muscles = smaller muscle fibers; larger muscles = larger muscle fibers.
Where do muscle fibers develop from?`
Myoblasts
These are converted to muscle fibers as contractile proteins accumulate within their cytoplasm.
Myofibrils
Muscle cells can range from ___ to ___ in length.
1mm - 4cm
True or False: Enlargement of muscles is an increase in muscle fiber size rather than number.
TRUE. Muscle fibers are amitotic (cannot undergo cell division), so they increase in size rather than dividing.
____ bands cause the light bands in skeletal muscle striations, while ____ bands cause the dark striations.
I bands; A bands
What are the 5 connective tissue coverings of muscle in order from innermost to outermost?
External lamina
Endomysium
Perimysium
Epimysium
Fascia
What is the cell membrane of the muscle cell?
Sarcolemma
The sarcoplasm is the muscle cell equivalent of the organelle called the ___.
Cytoplasm
It is a loose connective tissue with reticular fibers that surrounds groups of myofibrils.
Endomysium
It is a denser connective tissue surrounding a group of muscle fibers.
Perimysium
A group of muscle fibers is also called a ____.
Fasciculus/fascicle
It is a connective tissue that surrounds a group of fascicles.
Epimysium
What do you call a group of many fascicles?
Muscle
This connective tissue sheath forms a layer under the skin.
Fascia`
It holds muscles together & separates them into functional groups.
Fascia
Aside from muscles, what other body parts does the fascia carry?
Nerves, blood vessels, & lymphatic organs
The fascia is continuous with connective tissues of ___ and ___.
Tendons; periosteum
What are the components of the muscle in order from innermost to outermost?
Myofilaments, myofibrils, muscle fibers, fascicles, muscle
What are the two myofilaments?
Actin & myosin
Actin & myosin form highly ordered units called ___.
Sarcomeres
Sarcomeres are joined end to end to form ___.
Myofibrils
A ____ is composed of many myofibrils grouped together.
Muscle fiber
Groups of myofibrils are covered with an outer layer called the ___.
Sarcolemma
The ___ is found in between individual muscle fibers.
Endomysium
Fascicles are covered by the ___.
Perimysium
A muscle is covered by the outermost layer called the___.
Epimysium
These nerve cells have axons that extend to skeletal muscle fiber fibers through nerves.
Motor neurons
Muscle fibers are surrounded by ___.
Capillary beds
___is known as the thin myofilament, while ___ is known as the thick myofilament.
Actin; myosin
Actin is ____ in size; while myosin is ___ in size.
8nm; 12nm
What theory explains the shortening of muscle during contraction?
Sliding Filament Theory
True or False: According to the sliding filament theory, actin and myosin myofilaments change in length during contraction.
FALSE. Actin & myosin do not change in length during contraction.
True or False: In the sliding filament theory, actin & myosin myofilaments slide past each other in a way that causes sarcomeres to lengthen.
FALSE. Sliding of actin & myosin causes sarcomeres to shorten.
In the sliding filament theory, the ___ & ___ become narrower during contraction, while the ___ remains consistent in length.
I & H zones; A band
Once a muscle fiber begins to contract, it will contract maximally (meaning the entire muscle will contract). This is known as the ____.
All or none principle.
True or False: In the sliding filament model, actin slides over myosin, while myosin does not move.
TRUE
What causes sarcomeres to lengthen during relaxation?
External force
What are some external forces that may cause the lengthening of sarcomeres?
Forces produced by other muscles, gravity
They are muscles that are primarily responsible for producing a particular movement, such as flexion.
Agonists
Agonists are also called ___.
Prime movers
Muscles that oppose the action of the agonist are called ___.
Antagonists
What types of muscles aid the action of agonists by reducing undesirable/unnecessary movement?
Synergists
A special type of synergist that immobilizes the origin of the agonist.
Fixator/fixation muscle
A muscle’s more movable attachment is called its ___.
Insertion
A muscle’s fixed/immovable attachment is called its ___.
Origin
The junction between a nerve fiber & a muscle fiber is called a ___.
Neuromuscular junction/Myoneural junction
During flexion of the elbow, ___ is the agonist, while ___ is the antagonist.
Biceps brachii; triceps brachii
During extension of the elbow, ___ is the agonist, while ___ is the antagonist.
Triceps brachii, biceps brachii
The nervous system controls muscle contractions via ___.
Action potential
Membrane voltage/electric charge difference across membranes.
Resting membrane potential
True or False: The inside of the muscle cell is more positive with more potassium, while the outside of the cell is more negative with more sodium.
FALSE. The inside is more negative, while the outside is more positive.
What must exist in order for action potential to occur?
resting membrane potential
What are two types of ion channels?
Ligand-gated & voltage-gated
They are molecules that bind to receptors.
Ligands
They are proteins/glycoproteins with a receptor site.
Receptors
What is the relationship between the shortening of a sarcomere and the contraction/shortening of a muscle?
Directly proportional
Resting membrane potential is maintain by ___.
Na/K Pump
Is a neurotransmitter an example of a ligand?
Yes
What are the building blocks of myofibrils?
Action & myosin
During flexion of the elbow, the biceps brachii ___, while the triceps brachii ___.
Contracts; relaxes
During extension of the elbow, the biceps brachii ___, while the triceps brachii ___.
Relaxes; contracts
True or False: Acetylcholine is an example of a neurotransmitter.
TRUE
Acetylcholinesterase breaks down acetylcholine into what components?
Acetic acid and choline
In the muscle cell, what attaches to the receptor in order to open the ligand-gated channels?
Acetylcholine
Acetylcholine is released into the muscle fiber by the use of what ion?
Calcium
This type of ion channel opens & closes in response to small voltage charges across plasma membrane.
Voltage-gated
True or False: Both ligand-gated and voltage-gated channels are specific for one type of ion.
TRUE
Action potential is also known as ___.
Impulse
What are the two phases of action potential?
Depolarization & repolarization
During this phase of action potential, the inside of the sarcolemma becomes less negative.
Depolarization
It is the return of resting membrane potential.
Repolarization
What restores the resting membrane potential?
Na/K pump
It is the spread from one location to another.
Propagate
True or False: During propagation, action potential moves along the membrane.
FALSE. Action potential does not move along the membrane; rather, there is new action potential at each successive location.
It is formed when an axon terminal rests on an invagination in the sarcolemma.
Synapse
What is the presynaptic terminal?
Axon terminal with synaptic vesicles
What is the postsynaptic terminal/membrane?
Sarcolemma or skeletal muscle.
The postsynaptic membrane is also known as ___?
Motor end-plate
What is the space between the axon terminal & the sarcolemma called?
Synaptic cleft
True or False: In a synapse, the axon terminal and sarcolemma attach to each other.
FALSE. They do not make contact with each other; there is a gap/space between them.
It separates muscle from another muscle
Fascia
What is the order of layers of tissue from skin to bone?
Skin
Subcutaneous Tissue
Fascia
Muscle
Peritoneum
What are the two synaptic vesicles?
Neurotransmitter & acetylcholinesterase
It is a substance released from a presynaptic membrane that diffuses across the synaptic cleft & stimulates/inhibits the production of an action potential in the postsynaptic membrane.
Neurotransmitter
It is a degrading enzyme in the synaptic cleft that prevents the accumulation of acetylcholine.
Acetylcholinesterase
What are 4 inhibitors of muscle contraction?
Neuromuscular-blocking drugs
Presynaptic inhibition
Postsynaptic inhibition
Non-depolarizing blocking agents
What prevents the synthesis/release of acetylcholine from the synaptic terminal?
Presynaptic inhibition
What acts at the neuromuscular junction to prevent/reduce action potential production?
Neuromuscular-blocking drugs
What prevents the production of action potential in the postsynaptic membrane?
Postsynaptic Inhibition
They block the movement of ions through ion channels in the postsynaptic membrane.
Non-depolarizing blocking agents
How can non-depolarizing blocking agents block the process of muscle contraction?
- Binding to Ach receptors in the Na+ channel (blocks Ach from binding to receptor)
- Blocking Na+ channel (prevents Na+ movement into muscle fiber)
What is an example of a presynaptic inhibitor?
Botulinum toxin (BOTOX)
Improper dosage of BOTOX may lead to what rare condition?
Botulism
What is an example of a non-depolarizing blocking agent?
Curare
It is the contraction of a muscle as a result of one or more muscle fibers contracting.
Muscle twitch
Muscle contraction is measures as___.
Force/tension
How long does muscle contraction take to occur?
Up to 1 second
What are the three phases of muscle contraction?
Lag/latent
Contraction
Relaxation
It is the contraction of equal force in response to each action potential.
All-or-None Law
What are the three levels of stimulus strength?
- Sub-threshold/Submaximal Stimulus
- Threshold/Maximal Stimulus
- Supramaximal Stimulus
In this stimulus, there is no action potential & no contraction.
Sub-threshold stimulus
It is the smallest amount of stimulation/action potential needed in order to produce a contraction.
Threshold stimulus
This stimulus strength has action potential and a contraction equal to that with threshold stimulus.
Supramaximal stimulus
Comprised of a single motor neuron & all muscle fibers innervated by it.
Motor unit
True or False: There must be relaxation of a muscle fiber before a second action potential can stimulate a second contraction.
FALSE. Relaxation is not required for stimulating succeeding contractions.
What is the relationship between frequency or action potential & frequency of contractions?
Directly proportional (as frequency of action potential increases, frequency of contraction increases)
Muscle fibers partially relax between contractions.
Incomplete tetanus
No relaxation between contractions.
Complete tetanus
Muscle tension increases as contraction frequencies increase.
Multiple-wave summation
What are the three types of muscular contractions?
Isometric, isotonic, muscle tone
In this type of muscle contraction, there is no change in length of muscle, but tension increases during contraction.
Isometric
In this type of muscle contraction, there is change in length but tension is constant.
Isotonic
What are the two types of isotonic muscle contractions?
Concentric & eccentric
In this type of isotonic contraction, tension is so great that t overcomes opposing resistance and muscle shortens.
Concentric
This type of isotonic contraction enables muscles to resist an increase in length.
Eccentric
It is the constant tension by muscles for a long period of time.
Muscle tone
Where can isometric contractions be seen?
Postural muscles of the body
Muscles holding the spine erect while a person is sitting/standing is an example of what type of contraction?
Isometric
What type of contraction is used when typing using a computer keyboard?
Isotonic
The raising of a weight during a bicep curl utilizes what contraction?
Concentric
When a person slowly lowers a heavy weight, what contraction is displayed?
Eccentric
True or False: Asynchronous contractions of motor units produce smooth, steady muscle contractions.
TRUE
It is the decreased capacity to work & the reduced efficiency of performance.
Fatigue
What are the three types of fatigue?
Psychological, muscular, synaptic
This type of fatigue depends on the emotional state of the individual.
Psychological fatigue
This type of fatigue results from ATP depletion.
Muscular fatigue
This fatigue occurs in the neuromuscular junction.
Synaptic
How does synaptic fatigue occur?
Lack of acetylcholine
A burst in activity of a tired athlete shows how ___ fatigue can be overcome.
Psychological
Fatigue in the lower limbs of marathon runners or the upper & lower limbs of swimmers are examples of ____ fatigue.
Muscular
This type of fatigue is rare and occurs only under extreme conditions.
Synaptic
What provides immediate energy for muscle contractions?
Adenosine triphosphate (ATP)
ATP can be produced from what 3 sources?
Creatine phosphate, anaerobic respiration, and aerobic respiration
It stores energy during resting conditions to synthesize ATP.
Creatine phosphate
Adenosine diphosphate (ADP) and Creatine phosphate react to produce ___.
Creatine and adenosine triphosphate.
What enzyme catalyzes the reaction between creatine phosphate and ADP?
Creatine Kinase
This energy source occurs in absence of oxygen and results in breakdown of
glucose.
Anaerobic respiration
What are the products of anaerobic respiration?
ATP and lactic acid
This energy source requires oxygen and breaks down glucose.
Aerobic respiration
What two energy sources break down glucose?
Anaerobic and aerobic respiration
What are the products of aerobic respiration?
ATP, carbon dioxide and water
True or False: Aerobic respiration is more efficient than anaerobic respiration.
TRUE
What are the two types of muscle fibers in terms of speed of muscle twitch?
Slow-twitch oxidative and fast-twitch
This type of muscle fiber contract more slowly, are smaller in diameter, better blood supply, have more mitochondria, are more fatigue-resistant, and have a large amount of myoglobin.
Slow-twitch oxidative
Slow-twitch fibers are also called oxidative because they carry out what energy source?
Aerobic respiration
A dark pigment which binds oxygen & acts as a muscle reservoir for oxygen when blood does not supply adequate amount.
Myoglobin
This type of muscle fiber can respond rapidly to nervous stimulation, contain myosin that can break down ATP
more rapidly than that in Type I, has less blood supply, and fewer and smaller mitochondria.
Fast-twitch
Fast-twitch fibers adapted to perform what energy source?
Anaerobic respiration
Where can slow-twitch fibers be found?
Postural muscles, more in lower than upper limbs, dark meat of chicken.
Where can fast-twitch fibers be found?
Lower limbs in sprinter, upper limbs of most people, white meat in chicken
The functions of this type of fiber include maintenance of posture & performance in endurance activities.
Slow-twitch
The functions of this type of fiber include rapid, intense movements of short duration.
Fast-twitch
What are the effects of exercise on muscle fibers?
Change in size
What are the two forms of fast twitch fibers?
Oxidative and glycolytic forms
True or False: In exercise, weight lifting enlarges fast-twitch & aerobic training enlarges slow-twitch.
TRUE
What is the distribution of fast-twitch and slow-twitch muscle fibers?
Most muscles have both but varies for each muscle.
What are the two types of change in muscle size in relation to exercise?
Hypertrophy and atrophy
It is an increase in muscle size.
Hypertrophy
Is is a decrease in muscle size.
Atrophy
Besides size, what also increases during hypertrophy?
myofibrils, nuclei (due to fusion of satellite cells), strength
*reverse is true for atrophy
True or False: Cells can die from atrophy.
TRUE. Only in severe situations.
What are the effects of aging on skeletal muscles?
- Reduced muscle mass
- Increased time for muscle to contract in response to nervous stimuli
- Reduced stamina
- Increased recovery time
- Loss of muscle fibers
Attach muscles to bones.
Tendons
A very broad tendon.
Aponeurosis
Muscle end attached to more stationary of two bones.
Origin or head
Muscle end attached to bone with greatest movement.
Insertion
Largest portion of the muscle between origin and
insertion
Belly
Muscles that work together to cause a movement
Synergists
Plays major role in accomplishing movement.
Prime mover/agonist
Muscle causing an action when contracts.
Prime mover/agonist`
A muscle working in opposition to agonist.
Antagonist
Stabilize joint/s crossed by the prime mover.
Fixators
What are the four patterns of fibers in the muscle?
Circular, convergent, parallel, pennate
Fibers arranged concentrically around an opening.
Circular muscle
Triangular muscle with common attachment site.
Convergent
Functions as a sphincter to close a passageway or opening.
Circular
Direction of pull of muscle can be changed.
Convergent
Does not pull as hard as equal-sized parallel muscle.
Convergent
Fascicles are parallel to the long axis of the muscle.
Parallel
Muscle body has one or more tendons.
Pennate
Body of muscle increases in diameter with contraction.
Pennate
Fascicles at oblique angle to tendon.
Pennate
High endurance, not very strong
Parallel
Pulls harder than a parallel muscle of equal size.
Pennate
What are the three types of pennate muscles?
Unipennate, bipennate, multipennate
What are some examples of circular muscles?
Orbits, mouth (obicularis oris), anus
What is an example of a convergent muscle?
Pectoralis major
What are some examples of parallel muscles?
Rectus abdominis or sartorius
This type of muscle has fibers same side of tendon.
Unipennate
This type of muscle has fibers on both side (interosseous).
Bipennate
This type of muscle has tendon branches within the muscle.
Multipennate
Give an example of a unipennate muscle.
Extensor digitorum
Give an example of a bipennate muscle.
Rectus femoris
Give an example of a multipennate muscle.
Deltoid
Muscles are named according to ___.
– Location
– Size
– Shape
– Orientation of fasciculi
– Origin and insertion
– Number of heads
– Function
Muscle contractions are a pull or force by relative positions of ___
Lever, fulcrum, and weight/resistance
It is a shaft or bone.
Lever
It is a pivot joint/joint.
Fulcrum
How many classes of levers are there?
3 (Class I, Class II, Class III)
In this class of lever, the fulcrum is between force and weight there is a seesaw or head movement.
Class I
In this class of lever, the weight is between fulcrum and pull wheelbarrow, standing
on toes.
Class II
In this class of levers, the pull located between the fulcrum and weight.
Class II
What is the most common class of levers?
Class III
A person using a shovel is an example of what class of levers?
Class III
Standing on toes is an example of what class of levers?
Class II
Muscle ache is known as ___.
Myalgia
What are the two types of range of motion?
Passive and active
Passive range of motion prevents___?
Contractures (shortening & hardening of muscles)
Active range of motion prevents ___?
Atrophy
