14) Excretion and homeostasis Flashcards
(22 cards)
Excretion
Removal of Waste products of metabolic reaction, Excess substances and Toxic substances out of the body.
Examples of excretory products
- sweat, from skin, produced in sweat glands
- Urea, from kidney, produced in liver
- Carbon dioxide, from lungs, produced by respiring cells
Role of kidney in excretion
1.Filtration of blood
2.Urine formation and excretion of urea
3.Osmoregulation, by controlling amount of water in blood
Ureter
Carries urine from kidney to bladder
Urinary bladder
Stores urine
Urethra
Carries urine out of the body
Ultrafiltration
-Filtration of small molecules such as oxygen, glucose, amino acids, salts, water and urea.
-Under high pressure where they are forced out the blood through capillary pores in glomerulus to be collected in bowman’s capsule
-While large plasma proteins and blood cells cant pass through membrane because they are too large molecules
Selective reabsorption (Proximal convoluted tubule)
-Reabsorption of useful substances such as remaining glucose by ACTIVE TRANSPORT, some salts by active transport and diffusion and most of water by osmosis
-back to blood
Urine formation and osmoregulation(Collecting duct)
-More water is reabsorbed back to blood by osmosis under control of hormone ADH
-Urea and excess salts, dissolve in excess water to form urine to be excreted
Explain the role of kidney in excretion
- Ultra filtration, where the small molecules such as glucose, water, amino acids, urea are forced out under high pressure with plasma through capillary pores of glomerulus to be collected into Bowman’s capsule
- Selective reabsorption, of useful substances in proximal convoluted tubule, such as amino acid, glucose by diffusion and active transport and water by osmosis back to blood
- Excess salts and urea will dissolve in excess water to form urine to be excreted out of the body through kidney
Osmoregulation in hot weather/ exercise
-More water lost in sweat glands, less water lost in urine
-Urine is more concentrated with urea, dark yellow
-Small volume of urine
1. to keep amount of water in blood constant
2. Reducing dehydration
Osmoregulation in cold weather/drinking too much water
-Less water lost in sweat and more water lost in urine
-Urine is diluted, pale yellow colour , large volume
-Help get rid of excess water
Homeostasis
Maintaining the internal environment of body constant by negative feedback mechanism
Examples of homeostasis
- Temperature (controlled by skin arteriole, sweat glands, hair erector muscle)
- Blood glucose concentration (Pancreas and liver)
- Amount of water in blood (kidney)
- Blood pH (brain)
Why must body have a constant temperature
- To have constant metabolic rate
- For optimum temperature for enzyme activity
- To avoid denaturing enzymes
4.Lower temperature would slow down enzyme activity
5.High temperature denatures other protein molecules as carrier protein, cell membrane, haemoglobin, hormones and antibodies
Epidermis in skin
Prevents dehydration of skin, protects against entry of pathogens
Dermis
Has sweat glands, hair erector muscle, sensory neurone, blood vessels
Hypodermis
Adipose tissue/fatty layer
acts as thermal insulator
In case of increase in body temperature
-Skin receptors detect increase in body temperature
-Send electrical impulses through sensory neurone, to the relay
neurone in the brain, to motor neurone, to the effectors which are:
A) Skin arteriole:
1.Vasodilation of arteriole
2.Vasoconstriction of shunt vessel
3.More blood near surface
4.More heat loss by radiation
B)Hair erector muscle:
1. Hair erector muscle relax
2. Hair lies flat
3. Traps less heat
4. Better cooling
C) Sweat glands:
1.Increase in sweat production
2.More water of sweat evaporates
3.Leaving a cooling effect
In case of decrease in body temperature
-Skin receptors detect decrease in body temperature
-Send electrical impulses through sensory neurone, to the relay
neurone in the brain, to motor neurone, to the effectors which are:
A) Skin arteriole:
1.Vasoconstriction of arteriole
2.Vasodilation of shunt vessel
3.Less blood near surface
4.Less heat loss by radiation
B)Hair erector muscle:
1. Hair erector muscle contract
2. Hair stands up/erect
3. Traps more heat
4. Better insulation
C) Sweat glands:
1.Decrease in sweat production
2.No water of sweat evaporates
3.No cooling effect
D) Skeletal muscles, shivering
1.More contraction and relaxation of skeletal muscles
2.More aerobic respiration, releasing more heat energy
Response when blood glucose level is high
1.High blood glucose level detected by pancreas
2.Pancreas secretes insulin in blood plasma to the liver
3.Insulin stimulates glucose to be stored as glycogen in liver
4.Returning blood level back to normal
5. Negative feedback mechanism
Response when blood glucose level is low
1.Low blood glucose level detected by pancreas
2.Pancreas secretes glucagon hormone in blood plasma to the liver
3.Glucagon stimulates glycogen to be broken down into glucose
4.Returning blood level back to normal
5. Negative feedback mechanism
