Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/90

Click to flip

90 Cards in this Set

  • Front
  • Back
Which of these statements about skeletal muscles is false?
A. Their fibers branch.
B. They pull on tendons.
C. They store nutrient reserves.
D. They support soft tissues.
A. their fiber branch
Which type of muscle tissue has the greatest effect on the body's heat production?
A. cardiac
B. smooth
C. skeletal
D. all of these muscle types have about the same effect on the body's heat production
C. skeletal
Skeletal muscle does each of these except __________.
A. produce movement
B. ventilate the lungs
C. maintain posture
D. pump blood
D. pump blood
The capillaries that wrap around each muscle fiber are located within the __________.
A. sacrolemma
B. epimysium
C. perimysium
D. endomysium
D. endomysium
Muscles are attached to bones by tendons or __________.
A. aponeuroses
B. superficial fascia
C. ligaments
D. perimysium
A. aponeuroses
A thin layer of connective tissue that surrounds a muscle fascicle is called the __________.
A. endomysium
B. tendon
C. perimysium
D. epimysium
C. perimysium
What is the function of the sarcoplasmic reticulum?
A. houses the genetic material of the cell
B. storage of calcium
C. making of ATP - the "power house" of the cell
D. part of coupling the action potential to contraction
B. storage of calcium
What is the function of the nucleus?
A. part of coupling the action potential to contraction
B. making of ATP - the "power house" of the cell
C. storage of calcium
D. houses the genetic material of the cell
D. houses the genetic material of the cell
What is the function of the T tubules?
A. part of coupling the action potential to contraction
B. houses the genetic material of the cell
C. storage of calcium
D. making of ATP - the "power house" of the cell
A. part of coupling the action potential to contraction

(T tubules are a conduit for the passage of the action potential from the sarcolemma to the sarcoplasmic reticulum)
What is the function of the mitochondria?
A. houses the genetic material of the cell
B. part of coupling the action potential to contraction
C. storage of calcium
D. making of ATP - the "power house" of the cell
D. making of ATP - the "power house" of the cell
Which arrangement of th esarcomere fives rise to the H band?
A. the boundary between adjacent sarcomeres
B. is the point of connection for adjacent thick filaments
C. the region of the sarcomere that contains only thin filaments
D. the region of the resting sarcomere that only contains thick filaments
D. the region of the resting sarcomere that only contains thick filaments
Which arrangement of the sarcomere gives rise to the Z line?
A. the boundary between adjacent sarcomeres
B. the region of the resting sarcomere that only contains thick filaments
C. is the point of connection for adjacent thick filaments
D. the region of the sarcomere that contains only thin filaments
A. the boundary between adjacent sarcomeres

(marks the boundary b/w neighboring sarcomeres)
Which arrangement of the sarcomere gives rise to the M line?
A. the region of the resting sarcomere that only contains thick filaments
B. the region of the sarcomere that contains only thin filaments
C. the boundary between adjacent sarcomeres
D. is the point of connection for adjacent thick filaments
D. It's a point of connection for adjacent thick filaments
Which arrangement of the sarcomere gives rise to the I band?
A. is the point of connection for adjacent thick filaments
B. the region of the sarcomere that contains only thin filaments
C. the boundary between adjacent sarcomeres
D. the region of the resting sarcomere that only contains thick filaments
B. the region of the sarcomere that contains only thin filaments

(central or middle portion of the sarcomere)
Which thick filament binds to actin once its active binding sites are exposed?
A. myosin
B. tropomyosin
C. actin
D. troponin
A. myosin
The action potential in skeletal muscle fibers is generated by the __________.
sarcolemma
Titin is an ______________
D. elastic protein
Sarcomere is best defined as ___________
a repeating unit of striated muscle
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.


(Acetylcholinesterase is an enzyme that degrades acetylcholine. This degradation results in a rapid cessation of the acetylcholine signal and a swift removal from the cleft.)
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 by axon terminals of the motor neuron.
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
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
the opening of ligand-gated cation channels

(these channels permit sodium ions to diffuse inward and potassium ions to diffuse outward)
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
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction.

(Sarcoplasmic reticulum is the specific name given to the smooth endoplasmic reticulum in muscle cells. It is especially abundant and convoluted in skeletal muscle cells. It functions in the storage, release, and reuptake of calcium ions.)
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
A series of proteins that control calcium release
What is name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules


(T tubules penetrate a skeletal muscle fiber and provide a pathway for excitation into the interior)
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Calcium ions.

(Action potentials propagating down the T-tubule cause a voltage-sensitive protein to change shape. This shape change opens calcium release channels in the sarcoplasmic reticulum, allowing calcium ions to flood the sarcoplasm. This flood of calcium ions is directly responsible for the coupling of excitation to contraction in skeletal muscle fibers.)
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A myosin head bound to actin

(As soon as the activated myosin head forms a cross bridge with actin, the power stroke begins)
What structure is the functional unit of contraction in a skeletal muscle fiber?
The sarcomere
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
Calcium ions are stored in the sarcoplasmic reticulum.
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
ATP binds to the myosin head.

(The binding of ATP to the myosin head weakens the bond between myosin and actin, forcing the myosin head to detach. ATP also provides the energy for the next power stroke)
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP.

(Myosin is a large, complex protein with a binding site for actin. It also contains an ATPase. The energy released during the hydrolysis of ATP activates the myosin head)
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.

(the shape change shift tropomyosin away from the myosin binding sites on actin)
When does cross bridge cycling end?
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

(The sarcoplasmic reticulum contains Ca2+-ATPases that actively transport Ca2+ into the SR. Without Ca2+, troponin returns to its resting shape, and tropomyosin glides over and covers the myosin binding sites on actin)
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
AcH
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels

(action potential opens the gate, calcium rushes into the axon terminal leading to release of neurotransmitter)
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
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.

(sodium enters cell and causes depolarization. A small amount of potassium also leaves the motor end plate)
How is acetylcholine (ACh) removed from the synaptic cleft?
acetylcholinesterase (AChE, an enzyme)

(this enzyme is present in the synaptic cleft and breaks down acetylcholine)
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 cisternal of the sarcoplasmic reticulum
The neuromuscular junction is a connection between a neuron and a __________.
muscle fiber
The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________.
synaptic terminal
What is the synaptic cleft?
the space between the synaptic terminal and the motor end plate

(The synaptic cleft is the gap between the neuron and muscle fiber into which acetylcholine is released. The acetylcholine is released from vesicles in the neuron's synaptic terminal. Acetylcholine then binds to receptors embedded in the muscle fiber's motor end plate (a specialized region of the sarcolemma).
Inside a neuron, acetylcholine is contained within __________.
vesicles

(When an action potential arrives at the synaptic terminal, these vesicles fuse with the neuronal plasma membrane, releasing acetylcholine into the synaptic cleft. A single vesicle contains thousands of acetylcholine molecules)
What causes the vesicles inside a neuron to fuse with the plasma membrane?
an action potential in the neuron
Acetylcholine receptors are primarily located __________.
on the motor end plate


Receptors for acetylcholine are located on the motor end plate -- the portion of the muscle fiber's sarcolemma that faces the neuron's synaptic terminal. Binding of acetylcholine to acetylcholine receptors increases the sodium permeability of the motor end plate. This causes sodium to rush into the muscle fiber, which generates a muscle action potential.
An action potential in the muscle fiber causes __________.
the muscle fiber to contract\

Once the muscle fiber is excited by an action potential, it contracts through the process of excitation-contraction coupling. Cells that generate action potentials, such as muscle fibers and neurons, are known as "excitable" cells.
The role of acetylcholinesterase in the neuromuscular junction is to __________.
remove acetylcholine from the synaptic cleft


It breaks down acetylcholine soon after acetylcholine is released from the synaptic terminal. This breakdown is the primary mechanism for clearing acetylcholine from the synaptic cleft
Myofibrils are __________.
made of a series of sarcomeres
Z lines define the edges of which of the following?
sarcomeres

(Z-lines define the outer border of each sarcomere. When sarcomeres are connected end to end, the Z lines represent the link from one sarcomere to the other)
Myosin molecules form what part of the sarcomere?
thick filament
Which of the following is involved in the power stroke?
myosin

(The myosin head pivots at the head after it binds to actin, causing the thin filament to be pulled towards the center of the sarcomere. This motion causes the muscle to shorten during contraction)
Which of the following proteins contains the active site involved in cross-bridge formation?
actin

The active site on actin is where myosin heads bind. In the absence of calcium, these active sites are covered by the regulatory protein tropomyosin.
When the sarcomere is at rest, what is covering the active sites on actin?
tropomyosin

(Covers active site on actin to prevent cross brides from forming)
When calcium is released inside a muscle cell, what does it bind to?
troponin

(the calcium binds to troponin and this initiates the exposure of the active sites on actin)
Myosin molecules form cross-bridges when they attach to __________.
actin
What happens immediately after the myosin head binds to the active site on actin?
The myosin head detaches from the active site on actin
ATP binding leads to which of the following actions?
detaching and resetting cross-bridges

(ATP binding causes the myosin head to detach from actin. The energy from ATP hydrolysis is then used to reactivate the myosin head. This energy use is similar to setting a mouse trap, where the energy is used to set the trap, not to release the trap.)
Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum?
troponin
Triads in skeletal muscle fibers function in __________.
calcium ion release
During neuromuscular transmission, the axon terminals release __________.
acetylcholine
The muscle action potential penetrates into a fiber along the __________
transverse tubules
In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.
sarcoplasmic reticulum
Cycling of myosin cross-bridges results in ___________.
Repeated cycling of cross-bridges causes all of these effects.
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin

(when calcium binds to troponin, troponin releasees tropomyosin, exposing the myosin binding sites
A myosin head binds to which molecule to form a cross bridge?
actin
What causes the myosin head to disconnect from actin?
binding of ATP
What energizes the power stroke?
hydrolysis of ATP
(the energy is transferred from from ATP to the myosin head)
A single muscle action potential will normally be followed by __________
a single pulse of calcium ion release
To increase muscle tension, the nervous system can __________.

A. increase the number of active motor units
B. recruit larger motor units
C. increase the stimulation frequency
D. All of these can increase muscle tension.
D. All of these can increase muscle tension.
When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.
isometric
What is the type of chemical reaction used to rebuild ADP into ATP?
dehydration synthesis
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
glycolysis

glucose is broken down in the process called glycolysis. This process takes place in the cytoplasm and does not require oxygen – hence it is called anaerobic respiration. If oxygen is available, the pyruvic acid moves into the mitochondria and glycolysis contributes to aerobic respiration
Which of the following processes produces 36 ATP?
Krebs cycle and oxidative phosphorylation
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.
Pyruvic acid is converted back to lactic acid.


this is NOT a part of the “rest and recovery” period. When oxygen is available, lactic acid is converted back to pyruvic acid (not vice versa) that then enters the Krebs cycle. Lactic acid is the end product of the anaerobic pathway.
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
white fast twitch fibers


white fast twitch fibers have high glycogen content for a readily available source of glucose for glycolysis. They appear white because of the reduced amount of myoglobin and fewer capillaries surrounding them. Because these fibers have reduced myoglobin and very few capillaries surrounding them, they have very little oxygen available for the Krebs cycle and oxidative phosphorylation. They also have fewer mitochondria (where the Krebs cycle and oxidative phosphorylation would take place).
The biochemical reaction that consumes the majority of a muscle's ATP is the __________.
actin myosin cross-bridge cycle
Muscle fatigue occurs due to a buildup of __________ and __________ in pH.
lactic acid; decrease
Anaerobic glycolysis provides energy for muscle contraction when the supply of __________ is limited.
oxygen
The __________ type of muscle fiber has relatively few mitochondria
fast
Which of these is not a property of slow muscle fibers?
They are large in diameter.
Which of these is true of cardiac muscle fibers?
A. Cardiac fibers branch.
B. Cardiac fibers have a long twitch duration compared to skeletal fibers.
C. Cardiac fibers have a single nucleus.
D. All of these are true of cardiac fibers.
D. All of these are true of cardiac fibers.
The intercalated disk is a not site of __________.
neuromuscular transmission
All of the following are found in both skeletal and cardiac muscle fibers except __________
A. striations
B. intercalated disks
C. sarcomeres
D. mitochondria
B. intercalated disks
Smooth muscle contracts when calcium binds to __________ and activates __________.
calmodulin; myosin light chain kinase
Which of these is not a function of smooth muscle?
pushing blood into the arteries