Unformatted text preview: Homeostasis
Glossary Maintain – keep up.
Constant – the same.
Internal – inside the body.
Environment – surroundings of the body. What is Homeostasis?
What is Homeostasis? Body cells work best if they have the correct
Temperature Water levels Glucose concentration Your body has mechanisms to keep the cells in a constant environment. What is Homeostasis?
What is Homeostasis? The maintenance of a constant environment in the body is called Homeostasis Controlling body temperature
Controlling body temperature All mammals maintain a constant body temperature.
Human beings have a body temperature of about 37ºC. E.g. If your body is in a hot environment your body temperature is 37ºC If your body is in a cold environment your body temperature is still 37ºC Controlling body temperature
Controlling body temperature Animals with a large surface area compared to their volume will lose heat faster than animals with a small surface area. Volume = _______ Volume = _______ Surface area = ______ Surface area = ______ Volume : Surface area ratio = ___________ Volume : Surface area ratio = ___________ Controlling body temperature
Controlling body temperature Volume : Surface area ratio = 1:6 For every 1 unit of heat made, heat is lost out of 6 sides Volume : Surface area ratio = 1:5 For every 1 unit of heat made, heat is lost out of 5 sides Controlling body temperature
Controlling body temperature Volume : Surface area ratio = 1:6 Volume : Surface area ratio = 1:5 The bigger the Volume : Surface Area ratio is, the faster heat will be lost. Penguins huddling to keep warm
Penguins huddling to keep warm What mechanisms are there to cool What mechanisms are there to cool the body down?
1. Sweating When your body is hot, sweat glands are stimulated to release sweat.
The liquid sweat turns into a gas (it evaporates)
To do this, it needs heat.
It gets that heat from your skin.
As your skin loses heat, it cools down. Sweating The skin What mechanisms are there to cool What mechanisms are there to the body down?
2. Vasodilation Your blood carries most of the heat energy around your body.
There are capillaries underneath your skin that can be filled with blood if you get too hot.
This brings the blood closer to the surface of the skin so more heat can be lost. This is why you look red when you are hot! This means more heat is lost from the surface of the skin If the temperature rises, the blood vessel dilates (gets bigger). What mechanisms are there to warm the What mechanisms are there to body up?
1. Vasoconstriction This is the opposite of vasodilation
The capillaries underneath your skin get constricted (shut off).
This takes the blood away from the surface of the skin so less heat can be lost. This means less heat is lost from the surface of the skin If the temperature falls, the blood vessel constricts (gets shut off). What mechanisms are there to warm the What mechanisms are there to warm the body up?
2. Piloerection This is when the hairs on your skin “stand up” .
It is sometimes called “goose bumps” or “chicken skin”!
The hairs trap a layer of air next to the skin which is then warmed by the body heat
The air becomes an insulating layer. Controlling Glucose levels
Controlling Glucose levels Your cells also need an exact level of glucose in the blood.
Excess glucose gets turned into glycogen in the liver
This is regulated by 2 hormones (chemicals) from the pancreas called: Insulin
Glucagon Glycogen I
nn Glucose in the blood If there is too much glucose in the blood, Insulin converts some of it to glycogen Glycogen If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose. l
g n Glucose in the blood Diabetes
Diabetes Some people do not produce enough insulin.
When they eat food, the glucose levels in their blood cannot be reduced.
This condition is known as DIABETES.
Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet. Glucose
Concentration Glucose levels
rise after a meal. Insulin is
glucose levels fall
to normal again.
Normal Meal eaten Time Glucose
Concentration Glucose levels
rise after a meal.
Insulin is not
stay high Meal eaten Time Glycogen I
nn Glucose in the blood The glucose in the But there is no Glucose blood increases.
insulin to convert concentration it into glycogen.
rises to dangerous levels. Controlling water levels
Controlling water levels The control of water levels is carried out by the KIDNEYS.
It is closely linked to the excretion of urea.
Urea is a waste product that is made when the LIVER breaks down proteins that are not needed by the body.
Urea contains the element Nitrogen. The kidneys
T h e kid ne ys “c le a n” th e b lo o d o f wa s te p ro d u c ts a n d c o n tro l h o w m u c h wa te r is ke p t in th e b o d y. T h e wa s te p ro d uc ts a nd wa te r m a ke u p urine wh ic h is e xc re te d via th e ure te r. “Dirty” b lo o d e n te rs th e kid ne y th ro ug h th e re n a l a rte ry. T h e n , s e ve ra l th ing s h a p p e n to c le a n th e b lo o d ... 1. Filtration
B lo o d e nte rs th e tu b ule a re a in a c a p illa ry.
T h e c a p illa ry fo rm s a s m a ll “kn o t” ne a r th e kid n e y tu b ule .
T h e b lo o d is filte re d s o a ll th e s m a ll p a rtic le s g o in to th e tub ule .
T h e c a p illa ry th e n c a rrie s o n to ru n n e xt to th e tu b ule . T h e kid ne y tub u le no w c o nta ins lo ts o f b lo o d c o m p o n e nts in c lud ing : G lu c o s e :
Io ns :
Wa te r:
Ure a : 2. Reabsorb sugar
T h e b o d y ne e d s to h a ve s u g a r in th e b lo o d fo r c e lls to us e in re s p ira tio n. S o a ll th e s ug a r is re a b s o rb e d b a c k into th e c a p illa ry. 2. Reabsorb sugar
T h e b o d y ne e d s to h a ve s u g a r in th e b lo o d fo r c e lls to us e in re s p ira tio n. S o a ll th e s ug a r is re a b s o rb e d b a c k into th e c a p illa ry. 3. Reabsorb water
Wa te r a nd io ns a re th e ne xt to b e a b s o rb e d . It d e p e n d s o n h o w m u c h is ne e d e d b y th e b o d y. 3. Reabsorb water
Wa te r a nd io ns a re th e ne xt to b e a b s o rb e d . It d e p e n d s o n h o w m u c h is ne e d e d b y th e b o d y. Reabsorbing water
If y o u h a ve to o little wa te r in y o ur b lo o d , yo u will p ro d uc e ve ry c o nc e ntra te d urine . If y o u h a ve to o m uc h wa te r in y o ur b lo o d , y o u will p ro d uc e ve ry d ilute urine . (ve ry little wa te r in it) (lo ts o f wa te r in it) 5. Excrete the waste
Eve ryth in g th a t is le ft in th e kid ne y tub u le is wa s te :
All th e ure a
• e s s wa te r
T h is wa s te is c a lle d u rine . It is e xc re te d via th e ure te r a nd is s to re d in th e b la d d e r.
T h e “c le a n ” b lo o d le a ve s th e kid ne y in th e re n a l ve in.
Ureter Summary of urine production
Summary of urine production Urea is a waste product made in the LIVER
Water content of the body is controlled in the KIDNEYS
Urea, water and other waste makes up URINE.
Urine travels down the URETER and is stored in the BLADDER
Urine is excreted through the URETHRA. This powerpoint was kindly donated to
www.worldofteaching.com http://www.worldofteaching.com is home to over a
thousand powerpoints submitted by teachers. This is a
completely free site and requires no registration. Please
visit and I hope it will help in your teaching. ...
View Full Document