Under positive g, blood flow to the brain is reduced eventually leading to 'black out'. Under high negative g blood is forced into the head. Sustained negative g can produce blood-shot eyes and ruptures to small blood vessels in the face. There is in fact an over-supply of blood to the head.

Here is how I understand it. 

Negative G force means more blood is going to the head ( opposite to a +ve G )

There is a pressure sensor in the artery that goes from the heart to the head. It measures pressure so it is called a baroreceptor.

It then thinks, that more blood is going to the head and triggers a response. 

That response is a nerve response from a nerve called the vagus nerve. ( Vagus is wanderer where we also get vagabond from!)

If the vagus nerve is stimulated, it slows the heart rate down. 

So it is a feedback loop designed to control blood to the head. Negative G - More blood to head - Stimulates pressure receptor - triggers safeguard to lower blood to head  = vagus nerve activation = heart rate goes down

I hope this helps 

Haven't seen you about for a while, Ravi.   Trust life in the north is treating you well, good sir.    How is the flying progressing ?

Hi John, apologies, yes quite busy interspersed with flying and exams. Did a flight to Cooinda in Kakadu from Darwin the other day, very nice.

Im about to do the human factors exam whilst trying to organize the college of surgeons meeting in Darwin as I am the chair and trying to be an associate professor of surgery at the same time! Hectic.  

Flying is going well. This year whilst my son is in year 12, I will do the exams in parallel with him. Next year, when no children left, will start to use bigger toys with retractables, constant speed prop, and do some ratings night etc, then hopefully my commercial flight test. Fingers crossed. 

Ive completed 4 of the 7 exams. Human Factors, Performance and Law are left.

Ironically Im struggling with human factors! 

I dont think Im going to read the textbooks by Green and the other one. No one has told me its essential.

The casa website has a lot on human factors which is requisite reading material and also as well as Bob's books

Cheers and look forward to hearing from you

R

Ravi, suggest that the biggest problem for folks who have extensive subject knowledge outside of the flying game relates to overthinking things.   The exams are intended for folks with a relatively low index of subject expertise associated with the recommended study sources.   The CASA website is really useful for HF as it provides a lot of ICAO material upon which the subject stuff is based.   If you have a scan through, say, Bob's HF text (which is generally well regarded for the CASA requirements) and, likewise, the CASA material, you should be a dead cert to zoom through the exam.   As you would be aware from your day job, the expert often has some difficulty dumbing stuff down the level of a new, incoming undergrad student.