- [narrator] when we're talking about the pathophysiology of a disease, we're trying to figure out howthat disease causes symptoms. so in the case of herpes,or the herpes simplex virus, we're trying to figure outhow the virus infects cells, and causes symptoms. so let's take a look atthis skin cell over here, this is a cell that may live on your lips, and here's the nucleus,
i'm gonna draw it dotted so we can see what's going on inside. and in there there's going to be some dna. and i'll draw it like thiseven though dna is a lot more tightly wound than it is here. then i'll label these thingsso this dotted line here, i mentioned was the nucleus. or we can also refer to itas the nuclear envelope. and then on the inside,
this guy is our cell's dna. it's our own dna or our nucleicacid that lives in there. now let's imagine thiscell's going to be infected by the herpes virus soi will use this triangle to symbolize herpes, and so this triangle or thisvirus will come and attach on to the cell membrane here. and within the cell, theherpes has its own dna. the viral dna that existsas well as some proteins
that are in here and i'llexplain in a few minutes what these proteins help it do. but just realize firstoff this green border, the triangle on the outside, is a nucleocapsid. this helps the virus injectthe dna and the proteins into the cell, like we'll see in a minute. right here we've got some proteins, as i'll mention in a few minutes.
these help incorporate the viral dna into the human or host dna. and finally this yellow strand right here is the viral dna. so this is the dna ofthe herpes simplex virus. and so our first step hereis that the nucleocapsid has proteins that helpinject the viral dna and these proteins into the human cell. which means that as i'll draw right here,
is to inject viral dna. so once we do that, letme just draw our cell again over here. now the viral dna willbe inside of the cell. and with it will be these viral proteins that the nucleocapsid injected as well. so at this point, the viral dna will use theseproteins to inject itself or incorporate itself,
which is a better word, into the human dna here. and so our next step isthat we will incorporate viral dna using these proteins. and so what you'll end up getting, and i'll bring in anothersample of the cell right here, so this is the cellwe've been working with, is the human dna here butnow it's also attached to the viral dna.
now at this point, this cell that now is under the control of the herpes virus, because the viral dna is now in the brain or the nucleus of the cell, this cell can do two things. and i'll draw that right here. here's one path that we can take, and then here's another path we can take.
so i'm trying to drawall this like a cycle, go let's complete thiscycle and talk about this step right here, which after we'veincorporated the viral dna, we will start to massproduce the herpes virus, which, as i'll draw this cell again, over here, you'll begin to see a lotof these nucleocapsids being formed again and sothey're going to swell up
in the cell. these guys will also have their own copies of the viral dna. and you might not be able to see it but i'll just mention theprotein is there as well. and in fact this occursat such a crazy extent that the cell can't handlethat type of viral production. and so what'll end up happening is that the cell will rupture.
it'll pop open. so i drew this cell herebut let's draw another one. up over here, and i'll really exaggerate this, there's going to be so manyof these viral nucleocapsids that are filled with dna and proteins that the cell will nothave any more nutrients for it to fortify its cell membrane or for it to grow on its own.
is that the cell membranewill fracture open, like that, it'll pop, it'll burst, and you'll begin to have anexodus of these viruses out here which then allows youto restart the cycle. and because the cell poppedopen here, or ruptured another term for rupture is lysis, the name of this phasefor the herpes life cycle is the lytic phase. this is the lytic phase.
and that's in contrastwith what's happening here. instead of killing the cell, what you'll see happeningis that the herpes virus will remain dormant, and so what you'll getare two of these cells, so there's one here,and here's another one. so the virus just kind of takes a backseat and allows the humancell to grow on its own. so here the virus willreproduce with the cell,
and this relatively moredormant phase of the virus, or the herpes virus life cycle is referred to as the lysogenic, the lysogenic phase. that's just to emphasizethat the cell is able to undergo the lytic phase, or undergo lysis of the cell, that's why lysogenicmeaning able to cause. so it has that potential butit's currently not doing that.
it's just going along for the ride. and for the time being, the herpes virus is dormant. meaning it's at restand not mass producing its viral nucleocapsids,proteins, or its dna. now an important thingabout herpes is that it likes to be dormantin nerve cell bodies, and the term for nerve cell bodies is ganglion.
so i'll write ganglion here. or if you're talkingabout multiple ganglions, there's no such word as ganglions so instead we say ganglia. and in fact we know whatspecific ganglion or ganglia herpes likes to go intothe lysogenic phase in, and that depends where it occurs. so remember herpes labialis is herpes that occurs on the lips,
on the inside of your cheeks, or even on the tip of the tongue, so it's oral herpes. that tends to go and become dormant in the trigeminal ganglion. the trigeminal ganglionwhich is a cranial nerve that helps you feel touch on your face. so that's for herpes labialis. now for herpes genitalis,
there are several ganglia that the herpes can become dormant in, and we group them together and call them the lumbosacral ganglia, which is a reference to the spinal cord. it can be in the lumbaror the sacral region of the spinal cord, so somewhere in there. but recall because this is lysogenic,
or able to cause lysis, these cells are able to pick right on up and enter the lytic phase. there are a couple of thingsthat are known to cause that. sunlight is one thing that'sbeen noted in some people to induce the lysogenic cycle to convert into the lytic cycle. decreased immune functionis another known cause. but what these all boil down to
is that anything that'san overload of stress, and that can alsoinclude emotional stress, can trigger a lysogenic virus to enter the lytic phase. which is such an interesting concept because the herpes virusmust be able to read how the cell is survivingrelative to its environment. so it has become one with the cell. and unfortunately once thatcell is overly stressed,
it's time for the virus to escape and reproduce and move on to another cell that'll be able to houseit and help it grow.