Experiments with genetically altered mice showed that the mice would consume abnormally high amounts of bitter-tasting compounds in water after their

Experiments with genetically altered mice showed that the mice would consume abnormally high amounts of bitter-tasting compounds in water after their 

A) hormone receptors for digestive hormones were reduced or eliminated, showing that bitter tastes are reinforced by digestive responses.
B) salt-taste cells were altered to express receptors for bitter tastants, suggesting that animals have unregulated salt appetites.
C) visual sense was reduced or eliminated, suggesting that mice learn visual cues about bitter tastes.
D) olfactory sense was reduced or eliminated, suggesting that mice learn odor cues about bitter tastes.
E) sweet-taste cells were altered to express receptors for bitter tastants, suggesting that the sensation of taste depends only on which taste cell is stimulated.





Answer: E

Among these choices, the most energetically efficient locomotion per unit mass is likely

Among these choices, the most energetically efficient locomotion per unit mass is likely 

A) running by a 50-gram rodent.
B) running by a 40-kg ungulate.
C) flying by a 100-g bird.
D) swimming by a 10-g minnow (bony fish).
E) swimming by a 100-kg tuna (bony fish).





Answer: E

A ball-and-socket joint connects

A ball-and-socket joint connects 

A) the radius to the ulna.
B) the radius to the humerus.
C) the ulna to the humerus.
D) the humerus to the scapula.
E) the radius to the scapula.






Answer: D

An endoskeleton is the primary body support for the

An endoskeleton is the primary body support for the 

A) annelids, including earthworms.
B) insects, including beetles.
C) cartilaginous fishes, including sharks.
D) bivalves, including clams.
E) crustaceans, including lobsters.






Answer: C

Chitin is a major component of

Chitin is a major component of 

A) the skeleton of mammals.
B) the hydrostatic skeletons of earthworms.
C) the exoskeleton of insects.
D) the body hairs of mammals.
E) the skeleton in birds.







Answer: C

The hydrostatic skeleton of the earthworm allows it to move around in its environment by

The hydrostatic skeleton of the earthworm allows it to move around in its environment by 

A) walking on its limbs.
B) crawling with its feet.
C) swimming with its setae.
D) using peristaltic contractions of its circular and longitudinal muscles.
E) alternating contractions and relaxations of its flagellae.






Answer: D

Action potentials in the heart move from one contractile cell to the next via

Action potentials in the heart move from one contractile cell to the next via 

A) chemical synapses using acetylcholine.
B) chemical synapses using norepinephrine.
C) electrical synapses using gap junctions.
D) myelinated motor neurons.
E) non-myelinated motor neurons.





Answer: C

Calcium ions regulate contraction of smooth muscle cells by binding to

Calcium ions regulate contraction of smooth muscle cells by binding to 

A) troponin.
B) tropomyosin.
C) actin.
D) myosin.
E) calmodulin.






Answer: E

Skeletal, cardiac, and smooth muscle all have

Skeletal, cardiac, and smooth muscle all have 

A) A bands and I bands.
B) transverse tubules.
C) gap junctions.
D) motor units.
E) thick and thin filaments.







Answer: E

Sustained muscle contraction without relaxation between successive stimuli is called

Sustained muscle contraction without relaxation between successive stimuli is called 

A) tonus.
B) fused tetanus.
C) an all-or-none response.
D) fatigue.
E) a spasm.






Answer: B 

The lumen of the transverse tubules of skeletal muscles contains

The lumen of the transverse tubules of skeletal muscles contains 

A) extracellular fluid.
B) cytosol.
C) actin.
D) myosin.
E) sarcomeres.





Answer: A

Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber? 1. Tropomyosin shifts and unblocks the cross-bridge binding sites. 2. Calcium is released and binds to the troponin complex. 3. Transverse tubules depolarize the sarcoplasmic reticulum. 4. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP. 5. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.

Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber?
1. Tropomyosin shifts and unblocks the cross-bridge binding sites.
2. Calcium is released and binds to the troponin complex.
3. Transverse tubules depolarize the sarcoplasmic reticulum.
4. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP.
5. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane. 

A) 1 ? 2 ? 3 ? 4 ? 5
B) 2 ? 1 ? 3 ? 5 ? 4
C) 2 ? 3 ? 4 ? 1 ? 5
D) 5 ? 3 ? 1 ? 2 ? 4
E) 5 ? 3 ? 2 ? 1 ? 4




Answer: E

A skeletal muscle with abnormally low levels of calcium ions would be impaired in

A skeletal muscle with abnormally low levels of calcium ions would be impaired in 

A) ATP hydrolysis.
B) the initiation of an action potential.
C) maintaining its resting membrane potential.
D) initiating contraction.
E) its ability to sustain glycolysis.





Answer: D

Skeletal muscle contraction begins when calcium ions bind to

Skeletal muscle contraction begins when calcium ions bind to 

A) energized cross-bridges.
B) myosin.
C) actin.
D) tropomyosin.
E) troponin.





Answer: E

In a relaxed skeletal muscle, actin is not chemically bound to

In a relaxed skeletal muscle, actin is not chemically bound to 

A) myosin.
B) troponin.
C) tropomyosin.
D) Z lines






Answer: A

Muscle cells are stimulated by neurotransmitters released from the synaptic terminals of

Muscle cells are stimulated by neurotransmitters released from the synaptic terminals of 

A) T tubules.
B) motor neuron axons.
C) sensory neuron axons.
D) motor neuron dendrites.
E) sensory neuron dendrites.






Answer: B

Calcium ions initiate sliding of filaments in skeletal muscles by

Calcium ions initiate sliding of filaments in skeletal muscles by 

A) breaking the actin-myosin cross-bridges.
B) binding to the troponin complex, which then relocates tropomyosin.
C) transmitting action potentials across the neuromuscular junction.
D) spreading action potentials through the T tubules.
E) reestablishing the resting membrane potential following an action potential.






Answer: B

The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several hours, due to the lack of

The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several hours, due to the lack of 

A) phosphorylated myosin.
B) ATP needed to break actin-myosin bonds.
C) calcium ions needed to bind to troponin.
D) oxygen supplies needed for myoglobin.
E) sodium ions needed to fire action potentials.





Answer: B

The "motor unit" in vertebrate skeletal muscle refers to

The "motor unit" in vertebrate skeletal muscle refers to 

A) one actin binding site and its myosin partner.
B) one sarcomere and all of its actin and myosin filaments.
C) one myofibril and all of its sarcomeres.
D) one motor neuron and all of the muscle fibers on which it has synapses.
E) an entire muscle.





Answer: D

The calcium ions released into the cytosol during excitation of skeletal muscle bind to

The calcium ions released into the cytosol during excitation of skeletal muscle bind to 

A) troponin.
B) tropomyosin.
C) actin.
D) myosin.
E) transverse tubules.






Answer: A