They call it "Flight or Fright" Response. When peoples are faced with a sudden and traumatic situation, a series of changes occur in their bodies. Muscles are immediately prompted and ready for action, which is where the "flight" part comes in - our bodies prepare to run away. Our heart beats faster, there is an increase in arterial pressure, we breathe faster, our pupils dilate and our mouth goes dry.

This is what happened to Channel Nine news director John Sorell early on Wednesday morning as he watched live broadcasts from the United States. "I cried when the whole Diana thing happened, but I didn't cry with this one," he recalled on Friday. "I almost threw up, I just felt sick in the guts."

It also happened to Canon Stephen Ames of the Anglican Church. Canon Ames had not heard the news until he arrived at a breakfast meeting in North Melbourne. "I arrived at the same time as a colleague and he said, 'you've heard, of course, what's happened?' He told me they'd bombed New York and Washington and I just stood still. It froze me inside. There I was, on the corner of Peel Street and Victoria Street, just near the Vic Market, and I couldn't move. This was so hideous."

Since Wednesday, Melbourne has been able to talk of little else. And the saturation coverage - so sophisticated and immediate - has connected Australians to a news story in ways we have never previously experienced.

Internet news sites have reported massive traffic. (On Wednesday, The Age website registered two million page impressions. It also recorded many hits from Americans unable to access their own overloaded internal news services.) On Tuesday midnight, 1.69 million people were watching all five free-to-air TV networks, compared with 653,000 at the same time on the previous night. Add special edition newspapers and non-stop radio coverage, it's little wonder people can't stop talking.

But what are the effects of this saturation coverage? Despite geographical distance, many Australians have experienced physical and emotional fallout. Symptoms include sleep deprivation, inability to concentrate, anxiety, tears and the initial physiological "Flight or Fright" responses.

At 12.35am on Wednesday, my phone went. Middle of the night, your sleep is broken, and your first thought is: something has happened to my family. And so I frantically grabbed the receiver beside the bed. It was a friend, on her way home from a function. "They've just bombed the World Trade Centre and the Pentagon. Oh, Corrie, it's terrible."

I hung up the phone, threw on a dressing gown and turned on the television in the sitting room. For that first hour, I certainly experienced "Flight or Fright" syndrome. Uncontrollable shaking. My late-night fatigue was immediately replaced by an adrenalin surge. At one point in the coverage, tears. And a need to touch someone, to check the children. And to talk about it.

Thankfully, our society acknowledges the benefits of talking through a trauma, and there have been many opportunities for all of us to do this. As a family on the sofa, watching events unfold. In classrooms, in offices, in bank queues, people have shared their emotions in a collective, global way not seen since the death of the Princess of Wales in 1997.

Last week, the Association of Heads of Independent Schools of Australia circulated advice from Aaron Ebata of the Department of Human and Community Development, at the University of Illinois, regarding children's reactions to Tuesday's attacks.

"As many of us watch the news and talk to others about the day's events, our children will certainly notice that something is going on," he wrote. His advice included talking with older children about what the crisis might mean, and remembering that younger children (under seven or eight) may be disturbed by scenes on television or by listening in to adult conversation.

Professor Ebata urged adults to reassure children about their safety, and the safety of their loved ones.

Adolescent psychologist Michael Carr-Gregg is particularly concerned about the impact such a devastating world event might have on some teenagers, especially those struggling with peer group issues, suffering loneliness or isolation, or experiencing anxiety about life. "I'm encouraging the older ones to talk about it, and others to listen to them," he advised.

And yet despite the trauma, it has been difficult to turn off. John Sorell has worked for Nine for 26 years and can't recall a bigger story. "I've just never seen anything like the vision of those planes going into the World Trade Centre, and the post-traumatic stress that comes from just watching it again and again is incredible."

Canon Stephen Ames believes part of the reason we watched is because of reality that this could happen to any of us. "The horror you can see in people's faces, either when they're watching or retelling what's happened, tells you what an impact this has had. People, I think, identify with it, and therefore reel under it.

"It evokes a sense of no limits. Everything can be crossed here. And that extreme violence can cross those kinds of limits provokes terror and brings home how fragile our life is."

On Thursday at the Salvation Army's congress hall in Sydney, Lieutenant-Colonel Don Woodland spent time comforting people traumatised by the attacks. One young woman sat with him, put her head on his shoulder and sobbed. A professional nanny, she had just finished a three-year stint in New York, working for a family whose father worked on the 83rd floor of one of the World Trade Centre towers.

"She feels by association this horrendous loss," said Lieutenant-Colonel Woodland, who is no stranger to trauma. He attended the Port Arthur and Thredbo tragedies, as well as many other local and international crises. His advice is: don't be confused by the feelings you may experience. "People can be very disturbed by their responses. `I'm bursting into tears for no apparent reason.' It disturbs them that they don't seem to have control on their emotions.

"I don't think it's the right thing to say to somebody, `you need to see a counsellor'. They just need somebody to listen, someone to share in their emotional responses. They also need assurance that these are not abnormal responses. People think they are losing control, but what they are going through is very normal."

ABC radio presenter Jon Faine devoted his entire Wednesday program to the tragedy. There were the updates and interviews. But he also wanted to hear from listeners. As the calls flooded in, Faine and his audience listened to tears, anger, desolation. "I could keep my professional distance for the facts and emotional reports from America, but where I got a trembly lip was in talking to the people in Melbourne about their reactions."

The anecdotes were plenty, "but the stories that affected me personally was when people would say `my kids tell me they don't feel safe any more'. I can't comprehend what has gone on in New York, yet I can connect with comments like that, even though it's nothing like the scale of what has happened in America."

On Wednesday, I crept into my 12-year-old son's room an hour before he usually wakes. "I think you should get up," I whispered. "There is the most terrible news story on television, and I want you to see it."

So often over the past four days I have smiled, recalling his response. It says a lot about how the world has changed, yet reminds us we should cherish the simple routines of life.

My son blinked open his heavy eyes. Then he shot up straight. "Mum, what happened? Did Matty Lloyd get two weeks?"