Physiology: The Muscular System Extra Info
Muscle is responsible for all of the following EXCEPT... - Guarding body entrances and exits - Maintenance of body temperature - production of Vitamin D - Supporting soft tissues
- production of Vitamin D
The post-synaptic reaction on the sarcolemma is short in duration. Which of the following explanations describes why the reaction of the sarcolemma is short in duration? (2 Answers) -The ACh receptors respond only for a short period of time. -ACh diffuses across the synaptic cleft toward the sarcolemma. -Muscle tissue has a smaller membrane potential than nervous tissue. -AChE acts to breakdown the ACh in the synaptic cleft. -ACh diffuses out of the synaptic cleft.
-AChE acts to breakdown the ACh in the synaptic cleft. -AND- -ACh diffuses out of the synaptic cleft.
Which of these statements about skeletal muscles is FALSE? -They store nutrient reserves. -Their fibers branch. -They support soft tissues. -They pull on tendons.
-Their fibers branch.
Skeletal muscle does each of these EXCEPT __________. -produce movement -pump blood -store nutrients -maintain posture
-pump blood
Put the following structures in order from superficial to deep. 1. muscle fiber 2. perimysium 3. myofibril 4. fascicle 5. endomysium 6. epimysium
6, 2, 4, 5, 1, 3
Which of the following is the dark band seen on the myofibrils
A band
The area where actin and myosin overlap
A-Band
Which of the following events most directly occurs due to an action potential generated by the motor neuron? -Na rushes into the sarcolemma. -An action potential is generated on the muscle fiber. -ACh is released at the synapse. -AChE breaks down ACh in the synaptic cleft. -ACh binds to ACh receptors.
ACh is released at the synapse.
The characteristic muscle stiffness associated with rigor mortis is due to the inability of myosin filaments to detach from the active site on actin filaments. What molecule is essential for this detachment?
ATP
What is required to occur to allow myosin to detach from actin
ATP
Vesicles in the synaptic terminal contain
Acetylcholine
Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine? -Acetylcholine is degraded by acetylcholinesterase. -Acetylcholine is transported back into the axon terminal by a reuptake mechanism. -Acetylcholine diffuses away from the cleft. -Acetylcholine is transported into the postsynaptic neuron by receptor-mediated endocytosis.
Acetylcholine is degraded by acetylcholinesterase.
What is the primary method for terminating the acetylcholine signal at the neuromuscular junction?
Acetylcholine is degraded by the enzyme acetylcholinesterase.
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction? -Acetylcholine is released and moves across the synaptic cleft bound to a transport protein. -Acetylcholine binds to its receptor in the junctional folds of the sarcolemma. Its receptor is linked to a G protein. -When the action potential reaches the end of the axon terminal, voltage-gated sodium channels open and sodium ions diffuse into the terminal. -Acetylcholine is released by axon terminals of the motor neuron.
Acetylcholine is released by axon terminals of the motor neuron.
Tamara's muscle weakness and fatigue becomes progressively worse over the course of the day. This is a hallmark sign of myasthenia gravis, an autoimmune disorder that affects the ability of a motor neuron to communicate with a muscle fiber. What synaptic events must happen first for excitation to occur?
Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate.
The injection that dramatically improved Tamara's symptoms was Tensilon, an acetylcholinesterase inhibitor. What is acetylcholinesterase, and why was this injection effective in relieving Tamara's symptoms?
Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors.
Thin Filaments are also called
Actin Filaments
During anaerobic glycolysis, -ATP is produced. -oxygen is not consumed. -pyruvic acid is produced. -carbohydrate is metabolized. -All of the answers are correct.
All of the answers are correct.
Which of the following is a function of skeletal muscle? All of these Maintain body temperature Maintain posture Produce movement
All of these
Which of these is/are true of cardiac muscle fibers? -Cardiac fibers have a long twitch duration compared to skeletal fibers. -Cardiac fibers branch. -Cardiac fibers have a single nucleus. -All of these are true of cardiac fibers.
All of these are true of cardiac fibers
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.
What moves troponin and tropomyosin on the actin so that cross bridges can form?
Ca ions
Ca++ is stored in specialized pockets of the sarcoplasmic reticulum called
Cisternae
Which connective tissue layer wraps the entire muscle
Epimysium
The perimysium surrounds a bundle of muscle fibers called a
Fascicle
Which of the following produces ATP from glucose anaerobically
Glycolysis
The part of the sarcomere that contains thick filaments but no thin filaments is the
H band
The region of the sarcomere that always contains thin filaments is the
I band.
The area where actin and myosin do not overlap and only actin is found is called the
I-Band
Myasthenia gravis is an autoimmune disorder that results in the production of antibodies that either block or cause the destruction of the ACh receptor. Why do you think that Tamara's symptoms become worse as the day progresses?
In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse.
What is the type of contraction in which muscle does NOT change length
Isometric
How does neurotransmitter binding to it's receptor activate a muscle fiber?
It opens chemically-gated ion channels that allow sodium ions to diffuse into the junctional folds.
Heat released from contracting muscle functions to
Maintain body temperature
Why is control over leg muscles LESS precise than control over the muscles of the eye
Many muscle fibers are controlled by a single motor unit
Acetylcholine crosses the synaptic cleft and binds to the receptors on the
Motor End Plate
One neuron and all of the muscle cells it controls is called
Motor Unit
What structure most directly stimulates a skeletal muscle fiber to contract?
Motor neuron
All the muscle fibers and the single motor neuron that innervates them are called a
Motor unit
Myofibrils bundled together form
Muscle Fiber (Cell)
Muscle Cells are made up of
Myofibrils
Thick filaments are also called
Myosin Filaments
How does the muscle fiber become positively charged during depolarization?
Na ions flood into the cell
Why do bodies go into rigor after death?
No ATP to release myosin from actin
Inadequate calcium in the neuromuscular junction would directly affect which of the following processes? -Release of acetylcholine from the synaptic vesicles -Conduction of action potentials by the motor neuron -Depolarization of the junctional folds -Breakdown of acetylcholine by acetylcholinesterase
Release of acetylcholine from the synaptic vesicles
What is the functional unit of the muscle fiber (cell)?
Sacromere
The cell membrane of the muscle cell is called
Sarcolemma
The basic functional unit of skeletal muscle is the
Sarcomere
Myofibrils are made up of repeating sub-units called
Sarcomeres
The repeating functional units seen in the myofibrils are
Sarcomeres
A high blood concentration of the enzyme creatine kinase (CPK) usually indicates
Serious muscle damage
What are the three types of muscle tissue
Skeletal, cardiac, and smooth
Calcium entry into the axon terminal triggers which of the following events? -Cation channels open and sodium ions enter the axon terminal while potassium ions exit the axon terminal. -Acetylcholine is released into the cleft by active transporters in the plasma membrane of the axon terminal. -Acetylcholine binds to its receptor. -Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
Action potentials travel along the sarcolemma and reach the interior of the cell through
T-tubules
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
Which of the following statements is true? -The neurotransmitter is stored in the presynaptic motor neuron. -The sarcolemma is the presynaptic membrane. -The acetylcholine (ACh) receptors are located on the myofibril membrane. -Acetylcholinesterase (AChE) is stored in vesicles within the presynaptic motor neuron.
The neurotransmitter is stored in the presynaptic motor neuron.
Which of the following is not characteristic of smooth muscle? -The striations are due to the orderly arrangement of actin and myosin. -The thin filaments of smooth muscle fibers are attached to dense bodies. -Smooth muscles do not contain sarcomeres. -Neurons that innervate smooth muscles are under involuntary control. -Smooth muscle cells are uninucleate.
The striations are due to the orderly arrangement of actin and myosin.
Which of these statements about skeletal muscles is FALSE? -Their fibers branch. -They support soft tissues. -They store nutrient reserves. -They pull on tendons.
Their fibers branch.
An action potential at the axon terminal of a motor neuron opens what type of ion channels?
Voltage-gated calcium channels
Myasthenia gravis is a disease resulting from an autoimmune attack on the ACh receptors of the motor end plate. Binding of antibodies to the ACh receptors results in generalized muscle weakness that progresses as more ACh receptors are destroyed. Which of the following medications would help alleviate the muscle weakness? -a drug that binds to and inactivates acetylcholinesterase (neostigmine) -a drug that binds to the acetylcholine receptor and prevents it from opening (curare) -a drug that blocks the release of acetylcholine (botulinum toxin) -a drug that prevents acetylcholine from being loaded into synaptic vesicles (vesamicol)
a drug that binds to and inactivates acetylcholinesterase (neostigmine)
Sarcomere is best defined as __________.
a repeating functional unit of striated muscle
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
Which structure of the neuromuscular junction is a chemically-gated ion channel that the neurotransmitter binds to?
acetylcholine receptor
The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter
acetylcholine.
Which filament moves during muscle contraction?
actin/thin
The most important factor in decreasing the intracellular concentration of calcium ion after contraction is
active transport of calcium into the sarcoplasmic reticulum (SR)
Creatine phosphate...
acts as an energy reserve in muscle tissue.
During the recovery period the body's need for oxygen is increased because
additional oxygen is required to restore energy reserves.
A resting muscle generates most of its ATP by
aerobic metabolism of fatty acids.
More efficient use of glucose molecule for ATP production
aerobic respiration
Used for long term, light-to-moderate exercise
aerobic respiration
Decreased blood flow to a muscle could result in all of the following except -an increase in intracellular glycogen. -a shift to anaerobic glycolysis. -an oxygen debt. -an increase in intracellular lactic acid. -muscle fatigue.
an increase in intracellular glycogen.
After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs.
an oxygen debt
Makes ATP faster (think)
anaerobic respiration
Used for strenuous exercises
anaerobic respiration
Where in the neuromuscular junction do you find voltage-gated calcium ion channels?
axon terminal
Active sites on the actin become available for binding after
calcium binds to troponin.
In response to action potentials arriving along the transverse tubules (T-Tubules), the sarcoplasmic reticulum releases
calcium ions.
Contraction where the muscle shortens
concentric
Contraction where the muscle shortens and does work
concentric
Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for...
contraction
Fatigued muscles signify __________.
decreased pH
When the muscle cell becomes positively charged, it has been _________.
depolarized
Contraction where the muscle lengthens and does work
eccentric
Individual muscle fibers are covered by which connective tissue?
endomysium
Muscle fibers are directly surrounded by which thin layer of connective tissue?
endomysium
The capillaries that wrap around each muscle fiber are located within the __________.
endomysium
The outer connective tissue layer surrounding a group of fascicles is called
epimysium
Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.
exocytosis
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
A group of muscle fibers are called
fascicles
Which of the following is not a function of smooth muscle tissue? -moving food materials along the digestive tract -elevating hairs on the arm -forcing urine out of the urinary tract -altering the diameter of the respiratory passageways -forcing blood from the heart into the major arteries
forcing blood from the heart into the major arteries
What is the function of the structure indicated by the arrow?
houses the genetic material (DNA) of the cell
Which of the following would not lead to increased oxygen consumption? -increased anaerobic respiration by muscle cells -increased conversion of lactic acid to glucose -increased heat production -increased muscle activity -All of the answers are correct; none would lead to increased oxygen consumption.
increased anaerobic respiration by muscle cells
A weight-lifter strains to lift a heavy weight and there is no movement of the person's arms holding on to the weight. This type of contraction is called a(n) ________ contraction.
isometric
Contraction of muscles that do not change length
isometric
What is the function of the structure indicated by the arrow?
making of energy (ATP), "power house" of the cell
Identify the structure labeled "1."
mitochondria
Organelle of ATP production
mitochondria
When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes
more permeable to sodium ions.
Receptors for acetylcholine are located on the
motor end plate.
Which one of the following components stimulates contraction of a skeletal muscle?
motor neuron
A nerve that stimulates a muscle fiber
motor neuron (NOT motor unit)
A motor neuron and all the fibers it stimulates
motor unit
A single motor neuron together with all the muscle fibers it innervates is called a(n)...
motor unit
Interactions between actin and myosin filaments of the sarcomere are responsible for...
muscle contraction
Interactions between actin and myosin filaments of the sarcomere are responsible for
muscle contraction.
In an isotonic contraction,
muscle tension exceeds the load and the muscle lifts the load.
The ability of a muscle to stay in a slightly contracted state is
muscle tone
In which of the following would the motor units have the fewest muscle fibers? -postural muscles of the back -muscles of the neck -thigh muscles -muscles that control the eyes -calf muscles
muscles that control the eyes
Cross-bridges are portions of
myosin molecules.
Each skeletal muscle fiber is controlled by a motor neuron at a single
neuromuscular junction.
What starts the 'relaxation' phase after a muscle contraction
no impulse sent down motor neuron
Why does muscle fatigue occur?
not enough ATP
Which muscle is indicated by the arrow?
orbicularis oculi
Amount of oxygen the muscle needs to restore itself for contraction
oxygen debt
Fascicles are covered by a layer of connective tissue called
perimysium
Resting smooth muscle can be stretched without affecting tension development because of its __________.
plasticity
The advantage of having many nuclei in a skeletal muscle fiber is the ability to
produce large amounts of muscle proteins.
Which of these is NOT a function of smooth muscle? -pushing blood into the great vessels of the heart -elevating skin hairs -adjusting airway diameter -churning the stomach contents
pushing blood into the great vessels of the heart
The increase in muscle tension that is produced by increasing the number of active motor units is called
recruitment
A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?
reduces the muscle's ability for contraction
The plasma membrane of a skeletal muscle fiber is called the...
sarcolemma
The plasma membrane of a skeletal muscle fiber is called the
sarcolemma.
The repeating unit of a skeletal muscle fiber is the
sarcomere.
In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.
sarcoplasmic reticulum
Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber
shortens.
How is acetylcholine (ACh) removed from the synaptic cleft?
simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
Movement of the eyeball would be controlled by _________ motor units.
small
What type or muscle tissue do NOT contain sarcomeres?
smooth
When acetylcholine reaches receptors on the sarcolemma of muscle fiber, ______ channels open
sodium (Na)
What is the function of the structure indicated by the arrow?
storage of calcium
The narrow space between the synaptic terminal and the muscle fiber is the
synaptic cleft.
Infoldings of the sarcolemma are called
t tubules
Which muscle is indicated by the arrow?
temporalis
At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a...
tendon
The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n)...
tendon
At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a
tendon.
Muscles are held to bones by
tendons AND aponeuroses
The contraction of a muscle exerts a pull on a bone because muscles attach to bones by
tendons.
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisterns (cisternae) of the sarcoplasmic reticulum
An infection by the bacterium Clostridium tetani can cause the disease called
tetanus.
Which region of the sarcomere gives rise to the structure (band or line) indicated by the arrow?
the boundary between adjacent sarcomeres
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
the opening of ligand-gated cation channels
Which region of the sarcomere gives rise to the structure (band or line) indicated by the arrow?
the region of the resting sarcomere that only contains thick filaments
Which region of the sarcomere gives rise to the structure (band or line) indicated by the arrow?
the region of the sarcomere that contains only thin filaments
Which of the following best describes the term Z line? -storage site for calcium ions -largely made of myosin molecules -protein that accounts for elasticity of resting muscle -repeating unit of striated myofibrils -thin filaments are anchored here
thin filaments are anchored here
Which of the following best describes the term Z line? -thin filaments are anchored here -protein that accounts for elasticity of resting muscle -largely made of myosin molecules -storage site for calcium ions -repeating unit of striated myofibrils
thin filaments are anchored here
The action potential is conducted into a skeletal muscle fiber by
transverse tubules (T-Tubules)
The release of Ca ions triggers the movement of
troponin/tropomyosin complex
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels (not chemically-gated)
When a skeletal muscle fiber contracts, the...
zones of overlap get larger
