Q 01/05

Roughly how many neurons does the adult human brain contain?

A) 8.6 billion

B) 860 billion

C) 86 billion

D) 8.6 trillion

Answer · why

C) 86 billion

There are about as many non-neuronal glial cells again, and the whole organ is only about 2% of body weight.

Q 02/05

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

A) Up to 20%

B) About 5%

C) About 40%

D) About 60%

Answer · why

A) Up to 20%

More than any other organ, for something that weighs a little over a kilogram.

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

A neuron's sequence of them is called its spike train; some plant and pancreatic cells fire them too.

Q 04/05

Which animals are the only ones 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

The ability to fire electrical signals seems to have appeared 700 to 800 million years ago; plants and fungi never evolved it.

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

They come in chemical and electrical varieties; the electrical kind couples cells through gap junctions.