Misconceptions
1. The brain is coloured
Many people expect to see the brain in different colours since textbooks often portray them in that way for simplicity. The brain does not have any markers other than its ridges, and is not coloured differently, but rather homogeneously.
2. The Axons have sodium outside and potassium inside, Period
As students and teachers, were often shown the classic image of an axon having a positive charge on the outside and a negative charge on the inside at rest. Then we are told that there are Na+ ions on the outside and K+ ions on the inside. Aren't those BOTH positive? Where does the negative resting membrane potential of -70mV come from?
Spot the difference?
The diagram to the left has both positive potassium and positive sodium, but where does the negative potential of -70mV come from? If we look at the image on the right, we see that there are also large negatively charged proteins inside the cell, contributing to that resting potential. This is essential to explain to students!
The diagram to the left has both positive potassium and positive sodium, but where does the negative potential of -70mV come from? If we look at the image on the right, we see that there are also large negatively charged proteins inside the cell, contributing to that resting potential. This is essential to explain to students!
3. The brain has sensory receptors
While people assume that the brain has the ability to sense pain, the brain actually has NO sensory receptors. Your brain is extremely active, with millions of neurons sending action potentials at a given time. If we could feel every impulse, we would have a constant headache. The skull HAS receptors, the brain DOES NOT.
4. Neurons are irreplaceable
It is true that neurons in general do not reproduce, when someone receives damage to a particular area, they can recover to a certain extent. This is what we call brain plasticity. The more plastic or fluid the brain, the more likely you are to recover. Of course, no recovery is 100%.
Children under the age of 5 are more likely to recover from a brain injury than adults. The older you get, the less plastic your brain becomes.