Homeostasis

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Definition of homeostasis
The maintenance of a constant internal environment within a living organism
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Why is homeostasis important?
To maintain optimum pH and temperature for enzymes, to prevent damage to structures in the body
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Examples of homeostatic control
Osmoregulation, thermoregulation and blood glucose levels
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Function of kidneys
To remove nitrogenous bases (urea) and osmoregulation
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What happens to excess amino acids?
They are deaminated in the liver and converted to ammonia, then converted to urea which is transported to the kidneys through the blood
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Name the 10 elements of a nephron
Afferent arteriole, glomerulus, bowman's capsule, efferent arteriole, proximal convoluted tubule, descending limb, loop of henle, ascending limb, distal convoluted tubule, collecting duct
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Definition of ultrafiltration
Filtration under pressure that separates small molecules from the blood plasma
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What happens to these small molecules after ultrafiltration?
The small molecules are filtered from the knot of capillaries (glomerulus) to form a filtrate in the bowman's capsule
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How is hydrostatic pressure generated in the glomerulus?
Through the afferent arteriole is wider than the efferent arteriole
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Name the 6 labels that can be found on a glomerulus diagram
Cells of proximal convoluted tubule, squamous epithelial cells of bowman's capsule, afferent arteriole, efferent arteriole and podocyte cells
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How does filtration occur through a molecular sieve?
Pores in the endothelium of capillary, pores in basement membrane, the feet of podocytes
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During ultrafiltration what passes into the filtrate?
Water, urea, glucose, salt and mineral ions
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During ultrafiltration what remains in the blood?
Red blood cells, white blood cells, plasma proetins
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Definition of selective reabsorption
Useful products are reabsorbed from the filtrate into the blood
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What features do Proximal Convoluted Tubules have and why are they useful?
Intrinsic Proteins - selectively uptake substances from the filtrate, Microvilli - large surface area for absorption, Mitochondria - provide ATP for active transport
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What does the loop of henle do?
Concentrates ions in the tissue fluid of the medulla
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What principle does the loop of henle use?
hair-pin counter current multiplier
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What happens in the descending limb of the loop of henle?
It's permeable to water, so water moves out into the tissue fluid of medulla by osmosis, thereore increasing the water potential of the tissue fluid in medulla
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When in the loop of henle is the filtrate most concentrated?
In the apex
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What happens in the ascending limb of the loop of henle?
It's impermeable to water, so Na+ Cl- ions move out through active transport and lowers tissue fluid of medulla
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How does water leave the tissue fluid in the medulla?
It's carried away by the blood by the vasa recta
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What is the function of the loop of henle?
Create a concentration gradient/ lower water potential in the medulla
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What happens in the collecting duct?
Water leaves the collecting duct walls through osmosis from a low to high water potential
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Osmoregulation
The homeostatic control of body water - controls water potential of the blood
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How do humans gain water/lose water?
Gain it through eating/drinking and lose it by sweating/urine/faeces
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What is the excretory substance of fish?
Ammonia
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What are the features of the excretory substance of fish?
highly toxic, extremely soluble in water, diffuses across gills and is quickly diluted to non-toxic levels
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What is the excretory substance of birds?
Uric Acid
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What are the features of the excretory substance of birds?
Insoluble in water, small mass for storage to help organisms fly, important in conserving water (allows organisms to live in dry environments) low toxicity so safely build up in eggs, large energy cost for production, little water cost 4 excretion
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What is the excretory substance of mammals?
Urea
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What are the features of the excretory substance of mammals?
Production requires energy, long loop of henle, less toxic than ammonia, tissues can tolerate large concentrations for short period of time, can live in low water environment, more water reabsorbed into filtrate,seeds need oils to form metabolic H20
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Other cards in this set

Card 2

Front

Why is homeostasis important?

Back

To maintain optimum pH and temperature for enzymes, to prevent damage to structures in the body

Card 3

Front

Examples of homeostatic control

Back

Preview of the front of card 3

Card 4

Front

Function of kidneys

Back

Preview of the front of card 4

Card 5

Front

What happens to excess amino acids?

Back

Preview of the front of card 5
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