A normal healthy humans can maintain constant blood flow to their brain providing that the average arterial blood pressures is between 50 and 150 mmHg. Above 150 mmHg there is a risk that blood flow becomes too high, which can potentially cause a brain haemorrhage.  Below 50mmHg and there is a risk that blood flow will be inadequate to perfuse the brain.

Giraffes can grow to heights of 5m.  I think that the difference in cerebral blood pressure between standing fully erect and bending down to ground level to drink would be over 360mmHg. 

I have heard that giraffes have a system of one way valves in their neck veins to prevent pressure overload in the venous system when bending down to drink but it would be impossible to achieve this with their arteries because the blood has to travel in the direction of the head.  

How do giraffes maintain constant brain blood flow over such a huge range of blood pressures?

How do their cerebral arteries cope with such high pressures without bursting? 

Hypothetically, if a child was brought up without any reference to our human measurements of time (seconds, minutes, hours, days etc.), would it affect his/her concept of time passing?

For instance, we all have a general idea of how long 30 minutes is, but if someone was brought up without the ability to estimate how many minutes have passed, would they percieve time differently to the rest of us?

How much does RNA interference effect and consequently, affect human memory, if at all? What can be defined as natural and what cannot?

It can be argued that one of the reasons why humans love music with the same bpm as the human heart beat, is because it reminds us of being in the womb and can induce a relaxed state.

I have recently been reading up on self-sustaining criticality, the process by which the brain maintains a fine balance between boring and slow order, and exciting out of control thought propagation, to achieve a balance of speedy but stable thought / processing. A common example of self sustaining criticality in nature is the sand pile, where you can predict the average frequency and size of collapses, but where each one is still random and unpredictable.

There are similar events in nature that seem to be able to hold us humans in a trance, a burning fire, waves breaking, falling snow and of course avalanches in a sand pile. Do all of these events have an element of self-sustaining criticality to them?..and if they do, does our brain "enjoy" them because it fits in with its own processing system - similarly to how our body "enjoys" repetitive beats on the same frequency as our heartbeat?

Can watching too much television increase the risk of memory loss? If so, How much is too much? And what causes this?