Bss2085 Mastering A&p

Front 1

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.

Back 1

A. their fiber branch

Front 2

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

Back 2

C. skeletal

Front 3

Skeletal muscle does each of these except __________.
A. produce movement
B. ventilate the lungs
C. maintain posture
D. pump blood

Back 3

D. pump blood

Front 4

The capillaries that wrap around each muscle fiber are located within the __________.
A. sacrolemma
B. epimysium
C. perimysium
D. endomysium

Back 4

D. endomysium

Front 5

Muscles are attached to bones by tendons or __________.
A. aponeuroses
B. superficial fascia
C. ligaments
D. perimysium

Back 5

A. aponeuroses

Front 6

A thin layer of connective tissue that surrounds a muscle fascicle is called the __________.
A. endomysium
B. tendon
C. perimysium
D. epimysium

Back 6

C. perimysium

Front 7

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

Back 7

B. storage of calcium

Front 8

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

Back 8

D. houses the genetic material of the cell

Front 9

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

Back 9

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)

Front 10

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

Back 10

D. making of ATP - the "power house" of the cell

Front 11

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

Back 11

D. the region of the resting sarcomere that only contains thick filaments

Front 12

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

Back 12

A. the boundary between adjacent sarcomeres

(marks the boundary b/w neighboring sarcomeres)

Front 13

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

Back 13

D. It's a point of connection for adjacent thick filaments

Front 14

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

Back 14

B. the region of the sarcomere that contains only thin filaments

(central or middle portion of the sarcomere)

Front 15

Which thick filament binds to actin once its active binding sites are exposed?
A. myosin
B. tropomyosin
C. actin
D. troponin

Back 15

A. myosin

Front 16

The action potential in skeletal muscle fibers is generated by the __________.

Back 16

sarcolemma

Front 17

Titin is an ______________

Back 17

D. elastic protein

Front 18

Sarcomere is best defined as ___________

Back 18

a repeating unit of striated muscle

Front 19

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?

Back 19

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.)

Front 20

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?

Back 20

Acetylcholine is released by axon terminals of the motor neuron.

Front 21

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.

Back 21

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

Front 22

Calcium entry into the axon terminal triggers which of the following events?

Back 22

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

Front 23

Acetylcholine binds to its receptor in the sarcolemma and triggers __________.

Back 23

the opening of ligand-gated cation channels

(these channels permit sodium ions to diffuse inward and potassium ions to diffuse outward)

Front 24

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?

Back 24

The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients

Front 25

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?

Back 25

Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.

Front 26

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?

Back 26

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.)

Front 27

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?

Back 27

A series of proteins that control calcium release

Front 28

What is name given to the regularly spaced infoldings of the sarcolemma?

Back 28

transverse or T tubules


(T tubules penetrate a skeletal muscle fiber and provide a pathway for excitation into the interior)

Front 29

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?

Back 29

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.)

Front 30

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?

Back 30

Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.

Front 31

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?

Back 31

A myosin head bound to actin

(As soon as the activated myosin head forms a cross bridge with actin, the power stroke begins)

Front 32

What structure is the functional unit of contraction in a skeletal muscle fiber?

Back 32

The sarcomere

Front 33

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?

Back 33

Calcium ions are stored in the sarcoplasmic reticulum.

Front 34

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?

Back 34

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)

Front 35

How does the myosin head obtain the energy required for activation?

Back 35

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)

Front 36

What specific event triggers the uncovering of the myosin binding site on actin?

Back 36

Calcium ions bind to troponin and change its shape.

(the shape change shift tropomyosin away from the myosin binding sites on actin)

Front 37

When does cross bridge cycling end?

Back 37

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)

Front 38

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

Back 38

AcH

Front 39

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

Back 39

voltage-gated calcium channels

(action potential opens the gate, calcium rushes into the axon terminal leading to release of neurotransmitter)

Front 40

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

Back 40

exocytosis

Front 41

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

Back 41

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)

Front 42

How is acetylcholine (ACh) removed from the synaptic cleft?

Back 42

acetylcholinesterase (AChE, an enzyme)

(this enzyme is present in the synaptic cleft and breaks down acetylcholine)

Front 43

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?

Back 43

terminal cisternal of the sarcoplasmic reticulum

Front 44

The neuromuscular junction is a connection between a neuron and a __________.

Back 44

muscle fiber

Front 45

The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________.

Back 45

synaptic terminal

Front 46

What is the synaptic cleft?

Back 46

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).

Front 47

Inside a neuron, acetylcholine is contained within __________.

Back 47

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)

Front 48

What causes the vesicles inside a neuron to fuse with the plasma membrane?

Back 48

an action potential in the neuron

Front 49

Acetylcholine receptors are primarily located __________.

Back 49

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.

Front 50

An action potential in the muscle fiber causes __________.

Back 50

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.

Front 51

The role of acetylcholinesterase in the neuromuscular junction is to __________.

Back 51

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

Front 52

Myofibrils are __________.

Back 52

made of a series of sarcomeres

Front 53

Z lines define the edges of which of the following?

Back 53

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)

Front 54

Myosin molecules form what part of the sarcomere?

Back 54

thick filament

Front 55

Which of the following is involved in the power stroke?

Back 55

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)

Front 56

Which of the following proteins contains the active site involved in cross-bridge formation?

Back 56

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.

Front 57

When the sarcomere is at rest, what is covering the active sites on actin?

Back 57

tropomyosin

(Covers active site on actin to prevent cross brides from forming)

Front 58

When calcium is released inside a muscle cell, what does it bind to?

Back 58

troponin

(the calcium binds to troponin and this initiates the exposure of the active sites on actin)

Front 59

Myosin molecules form cross-bridges when they attach to __________.

Back 59

actin

Front 60

What happens immediately after the myosin head binds to the active site on actin?

Back 60

The myosin head detaches from the active site on actin

Front 61

ATP binding leads to which of the following actions?

Back 61

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.)

Front 62

Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum?

Back 62

troponin

Front 63

Triads in skeletal muscle fibers function in __________.

Back 63

calcium ion release

Front 64

During neuromuscular transmission, the axon terminals release __________.

Back 64

acetylcholine

Front 65

The muscle action potential penetrates into a fiber along the __________

Back 65

transverse tubules

Front 66

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.

Back 66

sarcoplasmic reticulum

Front 67

Cycling of myosin cross-bridges results in ___________.

Back 67

Repeated cycling of cross-bridges causes all of these effects.

Front 68

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

Back 68

arrival of an action potential

Front 69

The binding of calcium to which molecule causes the myosin binding sites to be exposed?

Back 69

troponin

(when calcium binds to troponin, troponin releasees tropomyosin, exposing the myosin binding sites

Front 70

A myosin head binds to which molecule to form a cross bridge?

Back 70

actin

Front 71

What causes the myosin head to disconnect from actin?

Back 71

binding of ATP

Front 72

What energizes the power stroke?

Back 72

hydrolysis of ATP
(the energy is transferred from from ATP to the myosin head)

Front 73

A single muscle action potential will normally be followed by __________

Back 73

a single pulse of calcium ion release

Front 74

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.

Back 74

D. All of these can increase muscle tension.

Front 75

When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.

Back 75

isometric

Front 76

What is the type of chemical reaction used to rebuild ADP into ATP?

Back 76

dehydration synthesis

Front 77

Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?

Back 77

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

Front 78

Which of the following processes produces 36 ATP?

Back 78

Krebs cycle and oxidative phosphorylation

Front 79

The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.

Back 79

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.

Front 80

Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?

Back 80

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).

Front 81

The biochemical reaction that consumes the majority of a muscle's ATP is the __________.

Back 81

actin myosin cross-bridge cycle

Front 82

Muscle fatigue occurs due to a buildup of __________ and __________ in pH.

Back 82

lactic acid; decrease

Front 83

Anaerobic glycolysis provides energy for muscle contraction when the supply of __________ is limited.

Back 83

oxygen

Front 84

The __________ type of muscle fiber has relatively few mitochondria

Back 84

fast

Front 85

Which of these is not a property of slow muscle fibers?

Back 85

They are large in diameter.

Front 86

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.

Back 86

D. All of these are true of cardiac fibers.

Front 87

The intercalated disk is a not site of __________.

Back 87

neuromuscular transmission

Front 88

All of the following are found in both skeletal and cardiac muscle fibers except __________
A. striations
B. intercalated disks
C. sarcomeres
D. mitochondria

Back 88

B. intercalated disks

Front 89

Smooth muscle contracts when calcium binds to __________ and activates __________.

Back 89

calmodulin; myosin light chain kinase

Front 90

Which of these is not a function of smooth muscle?

Back 90

pushing blood into the arteries