Q 01/05

Roughly how many neurons does the adult human brain contain?

A) 8.6 billion

B) 86 billion

C) 860 billion

D) 8.6 trillion

Answer · why

B) 86 billion

86 billion: a 2009 count that replaced the round 100 billion textbooks had long quoted, and found about as many non-neuronal cells again, not ten time...

Q 02/05

The brain uses roughly what share of the body's energy?

A) About 1%

B) About 5%

C) About 20%

D) About 50%

Answer · why

C) About 20%

About 20%: the brain makes up only about 2% of body weight, yet it burns a fifth of the body's energy, more than any other organ.

Q 03/05

The electrical signals neurons fire are called what?

A) Resting potentials

B) Synaptic vesicles

C) Ion gradients

D) Action potentials

Answer · why

D) Action potentials

Action potentials last only a few thousandths of a second in a neuron, and they are not unique to animals: a Venus flytrap snaps shut when touch sets ...

Q 04/05

Which two groups of animals get by with no neurons at all?

A) Jellyfish and corals

B) Sponges and placozoans

C) Flatworms and roundworms

D) Sea squirts and lancelets

Answer · why

B) Sponges and placozoans

Sponges and placozoans: a sponge filters water without a single nerve cell, yet its genome already holds most of the genes other animals use to wire n...

Q 05/05

The junction across which one neuron signals to another cell is called what?

A) A dendrite

B) A synapse

C) A node of Ranvier

D) A ganglion

Answer · why

B) A synapse

A synapse: the word dates from 1897 and comes from the Greek for 'to clasp together', coined while scientists were still arguing over whether nerve ce...