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biology alevel ocr > homeostasis > Flashcards

homeostasis Flashcards

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1
Q

Homeostasis definition

A

maintaining a constant internal environment despite external changes

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2
Q

Negative feedback definition

A

the reversing of a change in an internal environment

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3
Q

negative feedback pathway is

A

stimulis –> receptor –> coordination centre —> effector —> response

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4
Q

positive feedback definition

A

increases orignal change detected by receptors

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5
Q

ectotherm definition

A

an animal that relies on the external environment for temperature control instead of generating their own body heat

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6
Q

endotherm def.

A

a warm-blooded animal that generates its own body heat through metabolism

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7
Q

give examples of thermoreceptors in the body

A

hypothalamus, skin, arterioles

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8
Q

where is the thermoregulatory centre

A

in hypothalamus

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9
Q

list some examples of effectors if temp too high

A

sweat glands secrete more, smooth muscle in the walls of arterioles vasodilate to radiate heat, arrector pili muscles contract

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10
Q

list some examples of effectors if temp too low

A

shivering skeletal muscles contract, vasoconstriction, shunt vessels dilate (blood diverted away from surface of skin)

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11
Q

what is excretion?

A

removal of metabolic waste from the body. the removal of by products or unwanted substances from normal cellular processes

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12
Q

what does the hepatic artery do

A

carries oxygenated blood directly from the heart via the aorta

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13
Q

what does the hepatic portal vein do

A

this takes blood, rich in the products of digesions from the intestine to the liver

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14
Q

what products are needed to be excreted from the body

A

CO2 from cellular respiration
urea from excess amino acids

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15
Q

what does the hepatic vein do

A

this rejoins to vena cava taking the products of liver metabolism away

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16
Q

what does the bile duct in the liver do?

A

carries the non blood products out of the liver into the associated place e.g. gall bladder or small intestine

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17
Q

what are hepatic sinusoids?

A

adapted capillaries for exchange between hepatocytes and blood

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18
Q

describe the blood flow in the liver blood vessels

A

branch of hepatic artery & hepatic vein –> sinusoids where exchange takes place –> central canal/vein

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19
Q

what is the function of canaliculus?

A

to secrete and to transport the bile out of the interior of the hepatocytes to the branch of bile ducts

20
Q

what do kupffer cells do?

A

specialised macrophages which destroy worn out RBC, WBC, bacteria, foreign matters arriving from digestive tract. (they also break down haemoglobin to bilirubin)

21
Q

what happens in the process of deamination

A

the amino acid breaks into NH2 and CRHCOOH. NH3 and keto acids. the NH3 is changed to urea and excreted. keto acids enter the krebs cycle and respired and to lipids and cholesterol

22
Q

what are the inputs of the ornithine cycle?

A

ammonia, CO2, ATP, water, ornithine

23
Q

what are the outputs of the ornithine cycle?

A

urea and water

24
Q

what is the process of detoxification in the liver?

A

in the SER of the hepatocytes, liver produces hydrogen peroxide. liver produces catalase enzyme to break hydrogen peroxide down

25
Q

how is ethanol detoxified by the liver?

A

ethanol -> ethanal (this uses the enzyme alcohol dehydrogenase and oxidised NAD to reduced NAD)
ethanal -> ethanoate (uses same enzyme and oxidised NAD to NADH)

26
Q

what happens to ethanol after being oxidised to ethanoate?

A

enters the kreb cycle

27
Q

why is ethanol dangerous for the liver?

A

because ethanol is small and lipid and can enter the cell easily and is toxic and will cause serious damage to cells in high concentration so must be broken down into simple harmless molecules

28
Q

what are the three main functions of the kidneys

A

excrete urea and removal of urea, osmoregulation (controlling of blood), removal of excess ions

29
Q

how is blood supplied to and from the kidneys?

A

oxygenated blood comes through the aorta -> renal arteries. deoxygenated blood leaves through the renal veins -> vena cava

30
Q

what are the four layers of the kidney?

A

renal capsule -> renal cortex -> renal medulla -> renal pelvis

31
Q

what is the renal capsule?

A

the fibrous connective tissue that surrounds each kidney

32
Q

what is the top region of the nephron called?

A

renal cortex

33
Q

what is the bottom region of the nephron called?

A

renal medulla

34
Q

what is a nephron?

A

tiny tubes and the functional unit of the kidney – the nephrons are responsible for the formation of urine

35
Q

describe the process of the nephron

A

bowman’s capsule -> proximal convulated tubule -> descending limb -> loop of henle -> ascending limb -> distal convoulated tubule -> collecting duct

36
Q

what are vasa rectas in the kidney?

A

capillaries that wrap around the nephron (where selective reabsorption takes place)

37
Q

where does ultrafiltration take place in the nephron?

A

in the bowman’s capsule

38
Q

describe the structure of bowman’s capsule

A

afferent arterioles -> glomerulus -> efferent arteriole. also has podocytes

39
Q

how are the epithelium cells effective in the bowman’s capsule?

A

pores in epithelium cells reduce pressure

40
Q

how does ultrafiltration take place in the in the pct, loop of henle and collecting duct in the nephron?

A

in pct the fluid id altered by the reabsorption of all the sugars, most salts and some water -> in loop of henle salt is added to the fluid and Ψ is decreased -> in collecting duct the Ψ is decreased as more water removed so urine has a low Ψ

41
Q

what is the process of ultrafiltration int he bowman’s capsule?

A

high flow -> high hydrostatic pressure as affarent arterioles r wider than efferent -> high volume -> low space -> pressure gradient so substances can exchange

42
Q

what are the three layers in the ultrafiltration pathway?

A
  1. endothelium of blood capillary
  2. basement membrane made of collagen fibres (chooses based on size)
  3. podocytes which forms the lining
43
Q

what are some substances that the glomerular filtrate?

A

ions, glucose, urea, amino acids, water ,small proteins (rfm <69000)

44
Q

what are some substances that the glomerular cannot filtrate?

A

large proteins, plasma proteins, red blood cells

45
Q

why does not all water filtrate out of the nephron?

A

because blood requires water to travel substances (think about the water potential or concentration rather than volume)

biology alevel ocr (13 decks)

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