Homeostasis (Form 5)

Must remember these 3 (very important) :  

1. Blood osmotic pressure (involves water)
2. Blood glucose level
3. Body temperature 

Regulation of blood osmotic pressure : 

Situation A

Drink too much water

Blood osmotic pressure …………………………….

Osmoreceptor in hy………………………. less stimulated

P…………………………… less stimulated

Less …………….. is secreted into blood

Lower ……………….., d……………………………, c……………………………are less permeable to water

Less water is re…………………………………

Urine contains more …………………. means more d…………………….

Blood osmotic pressure increases back to normal 

Situation B 

Drink too little water

Blood osmotic pressure ………………………….

Os………………………………. in h………………………….. detect and is s…………………..

Stimulate p………………………………….

More ……………………….. is secreted into blood

Higher level of ……………………….. causes d…………………………….. & ………………………………. more permeable to water

M…………….. water is re…………………………

Urine contains less ……………………., more con………………………….

Blood osmotic pressure decreases back to normal 

Regulation of blood glucose level 

Pancreas secretes hormones i……………………. and g……………………….. 

Situation A 

Blood glucose level increases (Eg. After meal), pancreas secretes hormone ………………………..

I…………………….. transported by bloodstream to liver, muscle cells, adipose tissue

I…………………….. stimulates liver to : use glucose for respiration, convert excess glucose to

glycogen & stores excess glucose as glycogen

I…………………….. stimulates muscle cells to : use glucose for respiration, converts glucose to

glycogen & stores glycogen to build proteins

I…………………….. stimulates adipose tissue to : use glucose for respiration, use glucose to form fat 

Situation B 

Blood glucose level decreases (Eg. Fasting), pancreas secretes hormone ……………………

G…………………… transported by bloodstream to liver cells, adipose tissues

G…………………… stimulates liver to break down g…………………. into g……………….

G…………………… stimulates adipose tissue to break down l…………… which release fatty acids

that can be metabolised to generate energy 

Regulation of body temperature 

Normal body temperature 37⁰C (optimum temperature for metabolic reactions & enzyme

activities) 

Situation A

Surrounding temperature is hot 

Change in normal body temperature

T………………………………. in hypo…………………… detects blood temperature;

t…………………………. in s……………… detects external temperature

Both t………………………………. send nerve impulses to hypothalamus

Action? V…………………………………… (arterioles dilate), smooth muscles around arterioles relax,

more blood flows through skin, increase amount of heat radiated & loss via blood

Increase s…………………………., heat lost through surrounding when sweat evaporates, cools body down

Hair e………………………………… in the skin relax, warm air is not trapped &  free to escape

Adrenal gland & thyroid gland are less stimulated to secrete a…………………………….. and

t……………………………, thus metabolic rate is low & no excess heat generated

No shivering

Decrease body temperature 

Situation B 

Surrounding temperature is cold.

Change in normal body temperature.

T…………………………………. in hypo…………………… detects blood temperature; t………………………….. in s………………….. detects external temperature

Both ………………………………….. send nerve impulses to hypothalamus

Action? V………………………………… ( arterioles constrict), smooth muscles around arterioles

c…………………., d…………………… amount of blood flows through skin, d…………………….

amount of heat loss

Sweating does not occur

Hair e……………………………………… in the skin c…………….., trapping &  insulating air;

preventing air from e……………………

A……………………………….. & T…………………………. are stimulated to secrete more

a…………………………. & t………………, thus increases m………………………………. &  generates more h…………….

Skeletal muscles are stimulated; s……………………. occurs; heat is generated