G42LS05 Homeostasis (Better Quality)

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the human body is more complicated than

the most complex machine a power station

constantly burning fuel producing energy

doing work a Chemical Works taking in

food breaking down some molecules

building up

others but like any machine our body

needs control mechanisms to work

efficiently many of the body's vital

processes require a controlled

environment to work at all this is the

concept of homeostasis

the mechanisms that work together to

enable our bodies to maintain a constant

internal

environment but we often put our bodies

in situations that threaten this

delicate balance and in this program

we'll be looking at how our bodies

respond to one of the toughest tests of

all the marathon

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the place is Amsterdam in the

Netherlands the Time Early Autumn or to

be more precise 10:00 a.m. September

24th the morning of the Amsterdam City

Marathon as the runners limber up they

know how important it will be to

maintain the body's chemical and

physical balance in the race ahead

if at any point in the 42 km of the

Marathon course they go beyond their

limits disaster lies in weight and it

will for many of them but what are these

limits and what are the changes and

challenges our bodies face if we want to

run continuously over such a long

distance over 2 hours for the fastest

and more than twice as long for those at

the back of the

field there's only one way to find out

select a single run and follow her

through the course of the

race so what do we need to know about

our athlete she's 1 M 64 weighs 68 kg in

her running gear her resting heart rate

is around 62 beats per minute and she's

breathing at a rate of 14 decim cubed

per minute her core body temperature is

37.2 de C the skin temperature is lower

and the blood glucose level 90 mg per

100 cm

cubed right let's standardize them for

the start of the race this will be the

normal level and these are pretty normal

figures for a fit

person so weight heart rate breathing

rate temperature there'll all be good

indicators of the mechanisms at work in

her body as she

runs we'll keep an eye on them any

significant changes and we'll get a

warning but while Martina prepares for

the race there are a few things you

might want to think

about what changes would you

expect many people don't finish a

marathon what danger signs will you be

looking for and how will changes in one

indicator affect the

others okay 10 minutes before the start

and Martina and many others are having

trouble with one homeostatic me

mechanism it's hot and they know it's

going to get hotter so Martina is making

sure she drinks plenty of water she

doesn't want to become dehydrated later

in the

race but take on too much water and

there are inevitable

consequences like everything else we're

looking at it's all a question of

balance

just a few minutes to go and everyone's

getting

tense first warning light heart rate

time for a body

check weight temperature and blood

glucose levels no change there but there

is a slight increase in breathing rate

and a much bigger increase in her heart

rate to 90 beats per minute but she

hasn't done anything yet what's going

on the first of the control mechanisms

has kicked in it's located here these

are the adrenal glands one on each

kidney these glands are well supplied

with blood vessels and a hormone called

adrenaline is released from the adrenal

glands into these

capillaries the adrenaline is carried

around the body in the general

circulation it affects several organs

the heart speeds

up and the liver breaks down its energy

store glycogen into glucose more fuel

for the

muscles Martina hasn't asked her body to

do more work yet but already her body's

prepared more blood is being pumped more

fuel made available now you know why

commentators say the adrenaline's really

flowing now time to start the race and

just to show that we're not making this

up one last check on her weight 68

kg but will it be the same at the end 42

km to

go and there

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off the start of a marathon is very

important with so many Runners around

it's difficult to start at the correct

Pace too quick in you suffer later on to

too slow and you get a poor

time we're getting more warning signs

she's only one kilometer into the race

so what's happened let's look at the

chart a slight drop in blood glucose

levels she's obviously using

fuel but a big increase in heart rate to

140 beats per minute and her breathing

rate has gone up too it's almost doubled

so her heart and her lungs are working

harder what's the

connection as soon as Martina started

running her muscles were working they

needed more oxygen and produced more

waste

gas so the oxygen supply from the lung

lungs must be involved she breathes more

rapidly and more

deeply in the air sacs in the lungs the

rate of gas exchange increases more

blood more oxygen more carbon dioxide

more work for the

lungs but also more blood needed to

carry oxygen to the muscles the heart

has to work harder it beats more quickly

the heart rate increases it's also

pumping more with each beat the output

is four times greater than at the

start so Martina's body has responded to

the first challenge of the race Before

the Race her heart rate and breathing

rate were balanced to supply sufficient

oxygen to her body while it was at

rest but as soon as she started running

she knocked the system out of balance by

making her muscles work harder now her

body is responded her breathing and

heart rate have stabilized at a higher

level

it's the same for the other Runners the

question is at the quarter distance Mark

can they keep it

up at 10 km most of the runners take

their first drink usually just plain

water although some choose drinks

containing glucose but most of them

don't feel particularly thirsty so why

bother after all it isn't that easy

think about it it'll become important

later

on here's Martina at the feeding station

and we've got another warning it's a

temperature warning so what's going on

time to use a bit of

Technology this thermographic image of

Martina was taken at the start of the

race it shows the temperature of her

body surface the hottest area shown in

red and orange her face neck and arms

cooler regions show up in yellow the

coldest parts of her body her hair and

fingertips show up as green or blue the

blue and green on her body is in fact

her running vest

now compare that with an image taken

just after the feeding station at 11 km

Spot the

Difference the exposed areas of

Martina's body are hotter more red areas

or white where the body is hottest most

obviously the shoulder arms and legs

where the muscles work

hardest when muscles contract they

produce a lot of heat energy that's what

we're seeing here

and that heat causes the body some

serious

problems this is a blood vessel heat

from the surrounding muscle warms the

blood it's carried into the general

circulation raising the temperature of

the vital

organs this is the core body temperature

and if this becomes too high the body's

chemical reactions will cease to

function so so the body has conflicting

demands the muscles need the increased

blood supply to keep working but the

heat they generate will warm the body to

Dangerously high levels so how do you

stop that happening well you could stop

running but that would defeat the whole

object of the race any better

ideas well let's start with the blood

this is where it flowed before Martina

started running muscles 20% digestive

system 25 % kidneys 20% the brain 15%

the skin 5% heart 5% rest of the body

10% What's Happening Now Brain still 15%

heart 20% muscles 50% skin 10% rest of

the body 5% so the body has responded

and sent blood to where it's needed most

the muscles heart and

skin but Martina needs to cool down so

why not send even more blood to the skin

so that excess heat is conducted to the

surface and lost into the atmosphere a

good idea but there's a snag send more

blood to the skin and there's less

available for the muscles no blood for

the muscles and you can't carry on

running any better

ideas well Cooling the body down must

involve the skin it's where the body

comes into contact with the world

outside if more blood can't be sent to

the skin how can it help to cool the

body

down there are two ways for a start

radiation and

convection this is an infrared image the

body looks as if it's glowing heat is

radiating from its surface but obviously

not enough

heat what about

convection as she moves through cooler

air heat is carried away from her body

surface run faster and more heat is lost

but move faster and you generate more

heat Catch

22 so what's left heat loss by

evaporation good old

sweating these are sweat glands in the

skin the brain senses any increase in

temperature and stimulates the sweat

glands

moisture is released moisture

evaporation and evaporation carries heat

away from the body it causes

cooling back to the thermograph

Martina's body is

hot but her running vest is much cooler

a result of the evaporation of the sweat

collecting in the

fabric that sounds great turn on the

sweat glands and lose the heat generated

by the muscles easy

well not quite sweat and you lose

water that makes the blood thicker and

harder to pump this is dehydration let

it continue and your body would cease to

function and that's why Martina is so

Keen to replace water as quickly as

she's losing it and remember she drank a

lot before the race now it's paying off

she's moving through the field

we're now over half distance and some of

the less experienced Runners are

struggling too hot too

dehydrated too little training it's hard

to say

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why back in the race more and more

Runners are choosing glucose

drinks another warning light this time

fuel muscles depend upon a constant

supply of fuel particularly glucose but

where does it come from there's a little

in the liver and the muscles most of it

in the form of glycogen but 30 km in and

the glycogen has been used

up Martina is now depending on another

source of fuel fat fat stored Under the

Skin and inside the body when the level

of glucose in the blood runs low fat is

broken down to produce glucose which can

be used by the

muscles when they started the race these

Runners used their primary fuel

carbohydrate in the form of glucose now

they've switched to the reserve tanks

they'll finish the race running on fat

the leading Runners are approaching the

Finish 42 km covered a Triumph for each

of them other Runners are still on the

course as much as 20 km

behind but for Martina it's looking good

only a few Runners ahead of

her a change of

weight Martina's weight has dropped from

68 kg at the start to 6 3 Kg she's lost

5 kg enough to trigger our alarm

why it's all that sweating she's lost 5

kg that's 5 decim cubed of water but if

she doesn't sweat she'll

overheat the answer lies in the

kidneys sensors in the brain detect that

the blood is becoming too

concentrated these are the receptors

a hormone is released into the

bloodstream this causes a response in

the kidneys the

infectors as a result urine production

is

reduced this means a reduction in water

loss blood levels return to normal an

example of negative feedback

for these Runners the test is almost

over their bodies have overcome the

challenge the Finish is in sight and

here comes Martina her Pace over the

final stages bringing her up to third in

the women's race

but as she takes a well-earned drink

replacing the 5 decim cubed of fluid

she's lost let's recap on the

homeostatic mechanisms that have brought

her this

far first the brain that's what made her

run in the first place it also houses

the temperature receptors and detects

changes in blood

concentration a adrenaline released into

the blood to give the

kickart then there's the muscles they

upset the balance in the first

place the heart and lungs increase their

activity to supply oxygen via the

bloodstream the liver to store glucose

to break down fat the secondary source

of

fuel the kidneys The Regulators of water

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loss in fact the whole

body and this particular body has done a

whole lot of work

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oh

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