1. Homeostasis in mammals
title
Homeostasis in mammals

2. 17.1 What is homeostasis and why is it important?
content
Homeostasis in mammals
17.1 What is homeostasis and why is it important?
17.2 Regulation of the amounts of water and minerals by the kidneys
17.3 Regulation of body temperature by the skin
17.4 Regulation of blood glucose level by the liver and pancreas

3. 17.1 What is homeostasis and why is it important?
maintenance of a constant internal environment inside the body
the best internal environment for cells, tissues & organs to function efficiently and effectively is
provides
Homeostasis
examples
maintained by
kidneys
osmoregulation & excretion
skin & blood
regulation of body temperature
liver & pancreas
regulation of blood sugar level
negative feedback mechanisms

4. 17.2 Regulation of the amounts of water and minerals by the kidneys
Why important?
affect normal metabolic reactions
to avoid unnecessary total water movement into or out of cells
Which organs are responsible for that?
the kidneys
important components of the urinary system
Urinary system
kidneys
ureters
urinary bladder
urethra

5. The urinary system renal artery renal vein kidney ureters dorsal aorta
inferior vena cava
renal artery
carries blood from aorta to kidney
renal vein
returns blood from kidney to inferior vena cava
kidney
produces urine
ureters
carry urine to urinary bladder

6. The urinary system urinary bladder two sphincter muscles urethra
a muscular and elastic bag for temporary storage of urine
two sphincter muscles
these muscles relax when the bladder is full and urine is emptied to outside (urination)
urethra
passes urine from urinary bladder to outside

7. Examination of the urinary system of a mammal
Carry out Practical 17.1
Examination of the urinary system of a mammal

8. dark-red & bean-shaped organs
Kidneys
dark-red & bean-shaped organs
pelvis
cortex
a nephron
consist of
medulla
cortex (outer, lighter coloured)
medulla (inner, darker, with cone-like structures)
pelvis (central cavity into which the cones stick out)
each contains million nephrons (functional units of the kidneys)

9. Nephron first coiled tubule glomerulus second coiled tubule
a network of capillaries
second coiled tubule
Bowman’s capsule
cup-shaped
loop of Henle
U-shaped loop
collecting duct
allows urine to flow into pelvis

10. Nephron efferent arteriole capillary afferent arteriole renal artery
surrounding the coiled tubules and the loop of Henle
leaves a Bowman’s capsule
afferent arteriole
a branch of renal artery
renal artery
renal vein

11. Examination of a dissected mammalian kidney or a kidney model
Carry out Practical 17.2
Examination of a dissected mammalian kidney or a kidney model

12. How does a nephron work? Urine is formed by ultrafiltration
reabsorption
small molecules & water forced out from blood to Bowman’s capsule
glomerular filtrate
useful substances in glomerular filtrate are absorbed back into capillaries
Ultrafiltration and reabsorption

13. How does a nephron work? Nephron is adapted to ultrafiltration
efferent arteriole
The glomerulus and Bowman’s capsule
afferent arteriole
efferent arteriole is narrower than afferent arteriole
glucose
amino acids
water
urea
salts
high hydrostatic pressure
wall of capillaries of the glomerulus is differentially permeable
only small molecules can pass through

14. Regions where reabsorption occurs
How does a nephron work?
Substance reabsorbed
Regions where reabsorption occurs
Mechanism
Glucose (100%)
Active transport & diffusion
At first coiled tubule only
Amino acids (100%)
Mainly active transport
Active transport & diffusion
Salts (80%)
At first coiled tubule, loop of Henle, second coiled tubule & collecting duct
Water (99%)
Osmosis
Urea (50%)
Diffusion

15. smaller proportion of water is reabsorbed
The functions of the kidneys in homeostasis
Osmoregulation (3 cases)
Case A:
drink too much water
dilute blood
more & dilute urine
smaller proportion of water is reabsorbed

16. The functions of the kidneys in homeostasis
Osmoregulation (3 cases)
Case B:
concentrated blood
body lacks water
less & concentrated urine
greater proportion of water is reabsorbed

17. The functions of the kidneys in homeostasis
Osmoregulation (3 cases)
Case C:
higher concentration of salt in the filtrate
excess salts taken in
more urine with a higher salt concentration
water withdrawn from blood into the glomerular filtrate

18. The functions of the kidneys in homeostasis
Excretion
Metabolic wastes
removed by
high concentration is
example
excretion
urea
toxic
in form of
urine
produced by
kidneys

19. 17.3 Regulation of body temperature by the skin10 20 30 40
human body temperature (oC)
environmental temperature (oC)
Constant body temperature
skin
maintained by
enables
staying much more active at all times

20. Why is the regulation of body temperature important?
Do you remember ?
Enzymes
work efficiently only within a narrow range of temperature
Constant body temperature
Constant activity of enzymes and rate of metabolism

21. Beneath the dermis is a layer of subcutaneous fat
Structure and functions of the skin
Diagram showing a longitudinal section through mammalian skin
> 80% of total heat loss occurs through the skin
the skin consists of
epidermis
3 layers
dermis
subcutaneous fat
Beneath the dermis is a layer of subcutaneous fat

22. Structure and functions of the skin
Epidermis
Diagram showing a longitudinal section through mammalian skin
innermost layer
produces new cells by cell division
contains melanin
protects the body by absorbing UV light
a dark pigment

23. Structure and functions of the skin
Epidermis
Diagram showing a longitudinal section through mammalian skin
middle layer
consists of living cells produced from the innermost layer
cells
being pushed towards the surface
die & flatten
form
outermost layer

24. Structure and functions of the skin
Epidermis
Diagram showing a longitudinal section through mammalian skin
outermost layer
made up of dead cells
reduces water loss from evaporation
protects the body from mechanical injury
prevents the entry of pathogens

25. Structure and functions of the skin
temperature receptor
Dermis
pain receptor
Diagram showing a longitudinal section through mammalian skin
sensory receptors
touch receptor
detect stimuli
such as
touch
pressure
pain
heat and cold
pressure receptor

26. Evaporation of sweat helps in regulating the body temperature
Structure and functions of the skin
sweat pore
Dermis
sweat gland
Diagram showing a longitudinal section through mammalian skin
sweat glands
secrete sweat
sweat duct
sweat passes through sweat duct to sweat pore on skin surface (sweating)
Evaporation of sweat helps in regulating the body temperature

27. Helps in regulating the body temperature
Structure and functions of the skin
O2 and nutrients
Dermis
blood vessel
Diagram showing a longitudinal section through mammalian skin
blood vessels and capillaries
supply useful materials to living skin cells and remove waste products
Helps in regulating the body temperature

28. Structure and functions of the skin
Dermis
hair follicle
Diagram showing a longitudinal section through mammalian skin
hair follicles
produce new hair cells from the base of each follicle
surrounded by nerve endings

29. Helps in regulating the body temperature
Structure and functions of the skin
Dermis
hair
erector muscle
Diagram showing a longitudinal section through mammalian skin
erector muscles and hair
muscle contracts
hair erects
muscle relaxes
hair lies flat
Helps in regulating the body temperature

30. Structure and functions of the skin
Dermis
sebaceous gland
Diagram showing a longitudinal section through mammalian skin
sebaceous/oil glands
secrete sebum or oil
keeps the hairs and skin supple and waterproof
reduces the growth of micro-organisms

31. Helps in heat insulation
Structure and functions of the skin
Beneath the dermis
Diagram showing a longitudinal section through mammalian skin
subcutaneous fat
made up of fat-storing cells
Helps in heat insulation
subcutaneous fat

32. What happens when a mammal is
The role of the skin in regulating body temperature
What happens when a mammal is
cold / hot?
The role of the skin in regulating body temperature

33. Examination of a skin model and a slide of mammalian skin
Carry out Practical 17.3
Examination of a skin model and a slide of mammalian skin

34. 17.4 Regulation of blood glucose level by the liver and pancreas
Why is the regulation of blood glucose level important?
glucose may also be lost
in urine
cells lose
water by
osmosis
affects normal metabolism
too high
Blood glucose level
too low
brain cannot function properly
kept constant
( mg/100cm3 of blood)

35. changes in insulin level
The roles of the liver and the pancreas in regulating blood glucose level
work together
liver
pancreas
releases insulin
glycogen  glucose
changes in insulin level
brings blood glucose level to suitable level

36. for a normal person, glucose is 100% reabsorbed
What happens if the body fails to regulate blood glucose?
glucose reabsorption in kidneys
insufficient insulin
excess glucose in urine
for a normal person, glucose is 100% reabsorbed
cannot be cured,
but can be controlled by
Diabetes mellitus
injecting insulin regularly
regulating intake of carbohydrates

37. blood glucose level (mg/ 100cm3)
What happens if the body fails to regulate blood glucose?
diabetic 1 2 3
100
150
200
time (hours)
blood glucose level (mg/ 100cm3) 1 2 3
100
150
200
time (hours)
blood glucose level drops very slowly with no injection of insulin
injection of insulin
blood glucose level drops fast after injection
normal person
normal level
glucose solution ingested

38. Concept diagram Homeostasis in mammals constant internal environment
is the maintenance of a
is controlled by
includes
constant internal environment
negative feed-back mechanisms
osmoregulation
regulation of blood glucose level
excretion
regulation of body temperature

39. constant water potential of cells and body fluid
Concept diagram
osmoregulation
maintains a
constant water potential of cells and body fluid
controlled by
consist of
kidneys
nephrons
salt
reabsorption
maintain constant levels of
work by
water
ultrafiltration

40. remove metabolic wastes
Concept diagram
excretion
maintains a low level of
controlled by
metabolic wastes
kidneys
which
remove metabolic wastes in
urine

41. Concept diagram regulation of body temperature skin, blood
maintains a
skin, blood
controlled by
constant body temperature by
the degree of
the degree of
the amount of
vasodilation/ vasoconstriction
erection of hair
sweating
subcutaneous fat (long-term response)

42. Concept diagram regulation of blood glucose level
maintains a
caused by
constant blood glucose level
liver
controlled by
level of insulin
released by
pancreas