Which structure is responsible for setting the heart rate?

A) atrioventricular node
B) intercalated disk
C) sinoatrial node
D) pericardium
E) septum

Some drugs mimic a neurotransmitter's effect on a postsynaptic cell; for example, morphine and heroin bind to receptors for ____.

A) acetylcholine
B) dopamine
C) adenosine
D) serotonin
E) endorphins

Wastes would accumulate and most nutrients would stop cycling in the absence of ____.

A) plants and algae
B) bacteria and fungi
C) parasitic consumers
D) insects
E) vertebrates

Which of the following are components of the hepatic portal system?

A) Azygos vein
B) Inferior vena cava
C) Gastric vein
D) Inferior mesenteric vein
E) Both "Gastric vein" and "Inferior mesenteric vein" are correct.

The diagram illustrates sensory receptors in the skin. What structure does "A" represent?
A) Meissner corpuscles
B) Free nerve endings
C) Ruffini end organ
D) Pacinian corpuscle
E) Merkel disks

In pigs, the trapezius group of muscles is composed of three distinct muscles. How many muscle(s) make up the trapezius in humans?

A) three
B) two
C) one
D) four

Annelids are segmented worms.

closest relatives to animals

A) excavates
B) stramenopiles
C) alveolates
D) rhizarians
E) archaeplastidae
F) amoebozoans
G) choanoflagellates