Frequently Asked Questions: Nervous System and Senses

Q. Is it true that men have bigger brains than women?
A. Yes. Men have more brain cells than women, probably to control their larger muscle bulk.

Q. What are brain waves?
A. When the brain is connected to a device called an EEG (electroencephalogram), it makes different waves depending on moods and levels of consciousness. For example, Alpha waves happen when we are day-dreaming, Beta waves when we are paying attention, Theta waves when the brain is getting tired, and Delta waves when the brain is in deep sleep.

Q. How long are our nerves?
A. A nerve is made of tiny nerve cells called neurones end to end. If all an adult's nerves were placed end to end, they would reach about 150 000 kilometres.

Q. Can bulls see red?
A. They are completely colour-blind and can only see shades of black, grey and white.

Q. Why do roosters crow at dawn?
A. They crow all day, but are more active at dawn and dusk.

Q. How often do we blink?
A. We blink our eyes approximately every 15 seconds when awake.

Q. What is curare?
A. Curare is a poison that affects the nervous system causing paralysis. One ten-thousandth of a gram is enough to kill a person. It is made by a South American frog which has it in its skin.

Q. Why don't marine sponges feel pain?
A. Marine sponges are animals, but they have no nervous systems.

Q. What voltage can an electric eel make?
A. An eel makes about 550 volts.

Q. Why do we get 'pins and needles'?
A. Usually we get 'pins and needles' when we have been sitting awkwardly and have stopped the blood circulation to a nerve receptor in the skin or joints. The pain nerve receptors react to the loss of blood by intermittently activating.

Q. How does a ballet dancer doing pirouettes stop herself from getting dizzy?
A. Our main balance mechanism is the semi-circular canals in our ears. Inside these is a fluid that moves to tell our brains if we are spinning or upside down and so on. To stop feeling dizzy, the ballet dancer focuses on a point on one wall that she sees once every turn. This sends another 'stable' message to the brain to stop feeling dizzy and to cancel out the 'spinning' message that our brains are receiving from the semi-circular canals.

Q. When someone suddenly shines a flashlight in our eyes, why do we keep seeing it after the torch has been turned off?
A. The image of the light on our retinas persists for an extra one-tenth of a second. That is why blinking lights also are often perceived by us as continuous.

Q. When we look at something colourful, why do we look directly at it?
A. The colour-sensitive cells called cones in the retina at the back of the eye are concentrated in the middle of the retina near the fovea, directly in line with the front of the eye.

Q. When we are in the dark, why can't we see colour very well?
A. The colour-sensitive cells on the retina at the back of the eye are called cones. Cones have higher stimulus threshold or need more light stimulation than the black-grey-white-sensitive cells called rods.

Q. Why do humans 'speak' and no other animal does?
A. There is a less constricted position of the voice-box or larynx in upright human compared with the constricted position in a quadriped such as a monkey or gorilla.

Q. Is it true that some deep-sea creatures have headlights?
A. The eyes of some deep-sea shrimp are reflective and are used as 'headlights' to find their way in the depths. Deep-sea shrimp protect themselves from predators by blinking. When their eyes are closed, they cannot be so easily spotted by predators.

Q. What animal has the best sense of smell?
A. A male Emperor moth can smell a female Emperor moth at a distance of 11 kilometres.