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alevel biology ocr > chapter 15- homoestasis > Flashcards

chapter 15- homoestasis Flashcards

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1
Q

What term is used to describe communication between adjacent cells or cells at a distance?

A

cell signalling

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2
Q

What two systems are used in animals to coordinate responses to changes in the environment?

A

the hormonal and the nervous system

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3
Q

What name is given to the type of homeostatic control in which the response to a stimulus restores a factor to its original set point?

A

negative feedback

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4
Q

What name is given to the type of homeostatic control in which the response to a stimulus causes a factor to deviate further from its original set point?

A

positive feedback

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5
Q

What is a receptor?

A

A cell or protein that detects one specific type of stimulus.

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6
Q

what is steady or stable state

A

the reference point, the ideal

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7
Q

what is dynamic equilibrium

A

changes and fluctuation about the norm/set point

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8
Q

what is negative feedback

A

something is switched off, work is done to reverse the initial stimulus and restore whatever to the base level, switching off a mechanisms once the baseline level has been rectified

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9
Q

what is positive feedback

A

once a change is detected, the effectors reinforce that change increasing the response (keep increasing)

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10
Q

what is the normal level

A

the range around the optimum/set point

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11
Q

examples of positive feedback

A

childbirth
lactation
blood clotting
opening of voltage gated Na+ channel proteins in the axolemma

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12
Q

examples of negative feedback systems

A

thermoregulation
blood glucose regulation
water balance in the body

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13
Q

homeostasis is dependent on variables eg ……
and they need to be regulated despite..

A

pH of extracellular fluid, body temp

despite changes in environment, diet, level of activity

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14
Q

what is the difference between terrestrial and marine ectotherms

A

many marine ectotherms dont need to thermoregulate because water has a high specific heat capacity so temp of environment doesnt change much

for terrestrial ectotherms the temp of the air changes dramatically over short periods of time (days/hours/seasons) so have developed behavioural and physiological responses to thermoregulation

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15
Q

why is thermoregulation important as a homeostatic process

A

for enzymes
activation energy
KE and the rate of chemical reactions
to maintain set point

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16
Q

what is an ectotherm

A

they cannot maintain body temp by themselves so rely on using the surroundings to warm their bodies, core body temp is heavily dependent on the environment

metabolic processes not enough to maintain constant body temp

inc invertebrates, fish, amphibians and reptiles

used to be known as cold blooded

An animal which depends on the environment to regulate its internal body temperature.

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17
Q

what can gains in heat come from

A

waste heat from cellular respiration.
conduction from the surroundings.(contact)
convection from the surroundings.(current)
radiation from the surroundings (emwaves)

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18
Q

examples of losses of heat

A

latent heat of evaporation of water (as sweat from blood)

conduction
convection
radiation

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19
Q

examples of behavioural responses for ectotherms for warming up (general)

A

basking in the sun, orientation of the body to maximise exposure to the sun (increase sa to the sun)

pressing their bodies against warm surface- conduction

increasing metabolic reaction eg movement, exercise

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20
Q

examples of behavioural responses for ectotherms for warming up (specific)

A

lizards bask to get warm enough to move fast and hunt prey

butterflies orientate for max exposure to the sun spread their wings

moth and butterflies vibrating their wings

galapagos iguanas contract and vibrate their muscles increasing cellular metabolism

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21
Q

examples of behavioural responses for ectotherms for cooling down (general)

A

sheltering in burrows
pressing body against cool surface- conduction
orientating body to expose the least sa to the sun.
minimising movement to reduce metabolic reactions

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22
Q

examples of behavioural responses for ectotherms for cooling down (specific)

A

seek shade, hiding in cracks of rocks, digging burrows, move into water or mud, cold rocks, stay still

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23
Q

advantages of ectotherms

A

need less food/feed on food of a lower calorific quality.
can have bigger population in a habitat.
allows sit and wait foraging strategy which uses less energy

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24
Q

example of ectotherm: goldenrod crab spider

A

wait on flower for fly. fly is attracted to flower and so the spider gets the fly. waiting is a learnt response (behavioural)

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25
Q

physiological responses warming/cooling for ectotherms plus egs

A

lizards in cooler climates have darker skin so the skin absorbs radiant heat more easily

alter heart rate to inc or decrease metabolic rate

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26
Q

Sun basking and shade seeking are both examples of which type of response shown by ectotherms to help them control internal temperature?

A

behavioural response

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27
Q

What is meant by the term “endotherm”?

A

An animal that maintains a constant/stable internal body temperature regardless of the
external temperature by generating heat through metabolic processes.

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28
Q

In endotherms, temperature receptors are located in which two parts of the body?

A

skin and hypothalamus

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29
Q

In endotherms, which part of the brain is involved in thermoregulation?

A

hypothalamus

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30
Q

What is seen in endotherms in response to a rise in core body temperature?

A

vasodilation, sweating, loweing hair by relaxing erector muscles

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31
Q

What is seen in endotherms in response to a fall in core body temperature?

A

vasoconstriction, shivering, raising hair by contracting hair erector muscles

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32
Q

how is a camel adapted to living in the desert (thermoregulation wise)

A

long legs to keep body away from hot sand.
fat stored in hump(s) so that it only insulates a small proportion of the body.
sit down at night so body is near hot sand when its cool outside.
hairs/fur stands up on end, contraction of erector pili muscles

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33
Q

adaptions of tuna fish (thermoregulation wise)

A

constant motion/movement
high metabolism
all creates heat

but water has a high specific heat capacity so provides constant ish envrionment that heavily controls core body temp

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34
Q

what are endotherms and how do they thermoregulate

A

they use metabolic processes to warm their bodies, core temp is not usually influenced by the environment

theyre birds, animals, exceptions eg blue fish tuna

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35
Q

what do metabolic processes include

A

anabolic and catabolic

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36
Q

what is core body temperature

A

abdomen, chest, and head excluding ears, nose

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37
Q

what is torpor

A

decreased activity

during the day

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38
Q

what is hibernation

A

minimal activity over a long period of time (eg over winter)
there is a decrease in body temperature, heart rate, breathing rate

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39
Q

what is aestivation

A

dormancy during summer when it gets too hot
hot and dry seasn

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40
Q

what are physiological responses of endotherms to cooling down

A

vasodilation, increased sweating, reducing insulation

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41
Q

how does vasodilation cool endotherms down

A

arterioles near the surface of the skin dilate when temp rises, the arteriovenous shunt vessels constrict (vessels connecting arterioles and venules directly), forcing blood through the capillary networks close to the surface of the skin, cooling occurs due to radiation or if against a cool surface- conduction

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42
Q

how does increased sweating cool endotherms down

A

sweat evaporates from surface of the skin losing heat, cooling the blood below the surface.

humans and horses and sweat glands all over the body.

in some animals sweat glands are in less hairy areas eg paws. they also open their mouths and pant, losing heat as water evaporates

kangaroos and cats lick their front legs to keep cool

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43
Q

how does reducing the insulating effect of hair or feathers cool endotherms down

A

erector pili muscles in skin relax-hair or feathers lie flat, avoids trapping an insulating layer of air. but has little effect in humans

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44
Q

what anatomical adaptations could some endotherms have if they live in hot or cold (extreme) environments

A

hot large sa:v eg large ears, wrinkly skin
pale fur or feathers to reflect radiation

cold: minimise sa:v eg small ears, thick layer of insulating fat eg blubber, hibination

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45
Q

how can endotherms warm up

A

vasoconstriction, decreased sweating, rasing the body hairs/feathers, shivering

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46
Q

how does vasoconstriction warm up endotherms

A

the arterioles near the surface of the skin constrict, ateriovenous shunt vessels dilate so little blood flows through the capillary networks close to the surface of the skin,

skin looks pale and little radiation takes place

warm blood is kept below the surface

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47
Q

how does a decrease in sweating keep endotherms warm

A

core body temp falls, sweat production will stop entirely, reducing evaporation of water from skin although some some lungs still continues

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48
Q

how does raising the body hair or feathers keep endotherms warm

A

the erector pili muscles contract pulling the hair or feathers erect, traping an insulating layer of air and so reduces cooling through the skin

in humans has little effect

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49
Q

how can shivering keep endotherms warm

A

rapid, involuntary contracting and relaxing of large voluntary muscles in the body. metabolic heat from exothermic reactions warm up the body

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50
Q

what are the 2 control centres involved in thermoregulation of endotherms

A

heat loss centre and heat gain centre

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51
Q

when is the heat loss centre activated, how and what is the response

A

when temp of blood flowing through hypothalamus increases

sends impulses through autonomic motor neurones to effectors in the skin and muscles triggering responses to reduce core temp

negative feedback system

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52
Q

when is the heat gain centre activated, how and what is the response

A

when temp of blood flowing through hypothalamus decreases

sends impulses through autonomic motor neurones to effectors in the skin and muscles triggering responses to reduce increase temp

negative feedback system

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53
Q

what is nitrogenous waste in humans, insects and birds, fish

A

humans- urea
insects and birds- uric acid
fish- ammonia

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54
Q

differences between excretion and secretion

A

ex vs sec:
metabolic waste vs useful product
toxic/harmful vs used in cell comms
doesnt use vesicles vs does
substance to be removed vs remain in but released from glands exo and ecto

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55
Q

what is excretion

A

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

keeping it in the body would be harmful

Excretion is the process of removing the waste products of cell metabolism from the body.

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56
Q

3 examples of excretion

A

carbon dioxide
bile pigments
nitrogenous waste products (UREA)

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57
Q

explain the excretion of carbon dioxide

A

from cellular respiration is excreted from the lungs

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58
Q

explain the excretion of bile pigments

A

from the breakdown of haemoglobin from old rbcs,made in the liver, excreted from bile in the liver to small intestine via gall bladder and bile duct

stored in gall bladder

red/brown colouring the faeces

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59
Q

explain the excretion of urea

A

from breakdown of excess amino acids by the liver, excreted by the kidneys in urine

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60
Q

order of toxicity of nitrogenous wastes

A

ammonia (highly soluble in the blood)
urea
uric acid

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61
Q

what is ingestion

A

taking food into the digestive system via the mouth

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62
Q

what is digestion

A

breakdown of food into smaller molecules via hydrolysis using enzymes

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63
Q

what is egestion

A

removal of undigested “waste” faeces

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64
Q

what is secretion inc egs

A

transport out of a cell or gland (group of cells) usually a useful product (not waste)

eg:
hormones
enzymes
lubrication (eg mucus, oils)
antibodies
bile salts
neurotransmitter

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65
Q

similarities between excretion and secretion

A

requires atp
involved in homeostasis

compounds produced by cells by metabolism need to cross membrane and leave cell to may be transported in blood

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66
Q

the liver is responsible for producing enzymes which detoxify alcohol by breaking it down into smaller units, this uses NAD, wmt other reactions that use NAD are less likely to take place. the build up of fats in the liver is one of the 1st signs of liver damage due to excessive alcohol intake

explain why (3)

A

fats/fatty acids not respired
beta oxidation of fats requires nad
nad is used in the breakdown of alcohol
nad is in short supply

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67
Q

why are amino acids converted into urea

A

because the body cannot store excess amino acids like it can with carbs, the body doesnt want to waste the amino acids

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68
Q

what happens to excess amino acids

A

they are deaminated in the liver, excess from that are used in respiration or converted to lipids and then adipose tissue

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69
Q

how is urea formed

A

ammonia is reacted with carbon dioxide

ammonia+carbon dioxide -> urea + water

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70
Q

what is transamination

A

when 2 amino acids switch R groups
the conversion of one amino acid into another type

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71
Q

why can fish excrete ammonia

A

they live in an aquatic environment and so can have a constant supply of water to flush the ammonia out

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72
Q

why cant humans excrete ammonia/why is urea made

A

we are terrestrial, dont have enough water so cannot tolerate build up of ammonia, it is toxic

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73
Q

what is the small intestine also known as

A

the duodenum

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74
Q

what type of organisms is the liver found in

A

vertebrates

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75
Q

how many lobes does the liver have and compare them

A

2, left and right
left is bigger than the right

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76
Q

what is the only treatment for complete liver failure

A

liver transplant, could be transplanted right lobe from a living donor

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77
Q

what are5 general/important functions of the liver

A

detoxification of various metabolites
synthesis of proteins and biochemicals needed for digestion (BILE) and growth.
regulation of glycogen storage.
constant decomposition of rbcs.
production of hormones

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78
Q

function of the liver: control of … (3)

A

blood glucose levels
blood amino acid levels
blood lipid levels

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79
Q

function of the liver: synthesis of… (10 ish) dont need to know all

A

rbcs
bile
plasma proteins (especially albumin)
cholesterol
new aas
urea
glycogen from lactic acid
blood coagulation proteins
lymph
catalase

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80
Q

function of the liver: breakdown of …(8)

A

hormones
rbcs
bacteria
excess aas
toxins
alcohol
drugs
hydrogen peroxide

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81
Q

function of the liver: storage of…. (4)

A

vitamins
mineral ions
glycogen
blood

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82
Q

what is 80% of the liver made up of

A

hepatocytes

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83
Q

what are hepatocytes

A

cells of the main tissue of the liver

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84
Q

6 features of hepatocytes

A

have prominent nuclei
numerous mitochondria
prominent golgi apparatus
very metabolically active
large amounts of smooth er
have many free ribosomes

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85
Q

why is nuclei of hepatocytes prominent

A

because lots of genes are expressed, they are round with dispersed chromatin and prominent nucleoli

take up lots of stain

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86
Q

what are kupffer cells

A

remove foreign debris, pathogens, gut bacteria, endotoxins from bacteria that are in the blood when it passes through the liver

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87
Q

what are the 3 blood vessels that are linked to the liver

A

hepatic artery
hepatic vein
hepatic portal vein

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88
Q

describe the hepatic artery

A

carries oxygenated blood directly from the heart via the (descending) aorta to the liver.

narrow and only branched at the liver end

blood INTO liver (25%)

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89
Q

describe the hepatic portal vein

A

carries blood from gastrointestinal tract, gallbladder, pancreas and spleen to the liver

contains nutrients, toxins extracted from digested food

75% of total liver flow comes through hpv

wide and branched at both liver end and si end

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90
Q

describe the hepatic vein

A

drains deoxygenated blood from the liver into the inferior vena cava

only branched at the liver end

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91
Q

Name the blood vessel that supplies oxygenated, nutrient-poor blood.

Name the blood vessel that supplies deoxygenated, nutrient-rich blood.

Name the blood vessel that carries deoxygenated blood out of the liver.

A

hepatic artery
portal vein
vein

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92
Q

where is bile made

A

in the liver

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93
Q

what is the billary tract

A

the system of ducts that collect products from the liver and pancreas and drain them into the duodenum

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94
Q

what does bile consist of

A

water, electrolytes, bile acids, cholesterol, phospholipids and billirubin (gives colour)

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95
Q

where is bile stored

A

in the gall bladder

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96
Q

some bile is ……… by ……… and the rest are extracted from the blood by the liver

A

synthesised by hepatocytes

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97
Q

what are the small structures that make up the liver

A

lobules

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98
Q

what is the shape of a liver lobule

A

hexagonal

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99
Q

what specialised cells make up hepatic lobules

A

hepatocytes

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100
Q

how are the lobules in the liver arranged

A

irregular, branching, interconnecting plates around a central vein

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101
Q

in a liver lobule blood passes through large endothelium lined spaced called

A

sinusoids

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102
Q

in a liver lobule what happens to the blood coming from the HA and HPV

A

it mixes in the spaces called sinusoids

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103
Q

on each corner of a liver lobule what is there

A

a branch of the hepatic artery (arteriole)
a branch of the hepatic portal vein (venule)
branch of the bile duct (ductile)

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104
Q

lood from ha and hpv mixes in sinusoid and then entres a ………. leading to the …..

A

central vein
hepatic vein

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105
Q

within sinusoids there are fixed phagocytes called …

A

kupffer cells

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106
Q

in which direction does the bile flow in a liver lobule, what does it drain into

A

inside to out
bile drains into bile canaliculi/canaliculus and then into a branch of the bile duct (ductile)

107
Q

what 2 types of metabolism is the liver involved in

A

carbohydrate: blood glucose reg, under control of insulin and glucagon

amino acid metabolism

108
Q

amino acid metabolism

A

hepatocytes synthesise most plasma proteins
H carries out transamination, deamination (H convert NH3 produced into urea in ornithine cycle and the remainder of aas is used in respiration or is converted into lipids for storage (adipose tissue).

109
Q

what amino acids is the body unable to store

A

excess aas and proteins that arent used in metabolism

110
Q

the excess aas must be broken down by 2 processes…

A

deamination and the ornithine cycle (stop energy form aas being wasted)

111
Q

what is deamination

A

the toxic amino/amine group NH2 is removed, requires O2
amino acid + oxygen ->keto acid + AMMONIA

the ammonia goes to ornithine cycle
keto acid can be used ether in cellular respiration to produce atp from adp and pi or is converted into lipids of cholersterol

112
Q

Which process in the liver removes the amine group from amino acids when breaking down excess proteins?

A

deamination

113
Q

Which process in the liver combines ammonia with carbon dioxide to produce urea?

A

the ornithine cycle

114
Q

How does the liver help to control blood glucose levels?

A

it converts glucose into glycogen for storage

115
Q

The breakdown of alcohol is an example of which important function of the liver?

A

detoxification

116
Q

what is ornithine

A

a non proteinogenic amino acid

117
Q

what happens in the fist stage of the ornithine cycle

A

NH3, CO2, ornithine and ATP produce citrulline and water

118
Q

what happens in the 2nd stage of the ornithine cycle

A

NH3, ATP and citrulline produce arginine and water

119
Q

what happens in the 3rd and final stage of the ornithine cycle

A

arginine and water produce urea and ornithine

120
Q

when is the ornithine cycle occuring

A

all the time unless youre fasting protein

they are enzyme controlled reactions

121
Q

where does H2O2/hydrogen peroxide come from and how/why is it toxic

A

toxic by-product of many normal catabolic processes in organisms that use O2 (especially the breakdown of long fatty acids chains)
it is produced by hepatocytes

toxicity comes from the oxidation of proteins membrane lipids and dna by h2o2

122
Q

how does the liver detoxify H2O2 (hydrogen peroxide

A

to prevent damage to cells and tissues H2O2 must be quickly converted into water and oxygen my catalase

catalase is located in a cellular organelle called the peroxisome

123
Q

how does the liver detoxify ethanol

A
124
Q

why is ethanol harmful what characteristics does it have (how does it behave in the body)

A

it can easily diffuse across plasma membranes
it enters the blood very rapidly after consumption.
it is toxic so causes serious damage to cells in high concentrations so must be broken down into harmless substances

125
Q

how does the liver detoxify the blood of ethanol

A

it has 2 enzymes: alcohol/ethanol dehydrogenase and aldehyde/ethanal dehydrogenase

ethanol is broken down into ethanal (acetaldehyde) via ethanol dehydrogenase making reduced NAD from oxidised NAD and then the ethanal is broken down into ethanoate (acetate) via ethanal dehydrogenase making reduced NAD from oxidised NAD

126
Q

when detoxifying ethanol what happens to the resulting ethanoate/acetate

A

it enters the krebs cycles to be metabolised synthesising atp and using “calories”

adipose tissues/fatty liver

127
Q

what affect does ethanol have on the body

A

it is a depressant so affects the brain and nervous system by slowing down the transmission of neurotransmitters across the synaptic cleft

128
Q

what is gout

A

a disease where the joints (mostly feet) become swollen and painful because of a build up of uric acid that is crystalised in the synovial fluid

129
Q

what is a nephron

A

the functional unit of the kidney

130
Q

what homeostatic roles does the kidney have

A

excretion of metabolic waste chemicals
osmoregulation (control of water potential)
controlling volume of water in the blood
controlling blood pH

131
Q

What is osmoregulation?

A

Osmoregulation is the process of regulating the water potential of the blood.

132
Q

what are the 5/6things that make up the kidneys gross structure

A

capsule
cortex
medulla
pelvis
pyramids

133
Q

describe the capsule of the kidney

A

a tough fibrous covering that itself is covered by fat, it provides protection

kidneys only protection is the adipose tissue

134
Q

describe the cortex of the kidney

A

dark outer layer, filtering of blood takes place, lots of capillaries, approx 1cm thick

nephron glomerulus, bowmans capsules and tubules are located here

135
Q

describe the medulla of the kidney

A

lighter in colour, the collecting ducts and loops of henle of the nephrons are here

middle of the kidney, contains renal pyramids

136
Q

describe the pelvis of the kidney

A

central chamber that the collecting ducts drain into, connected to the ureter

137
Q

what is the blood supply to the kidneys

A

renal arteries (branch directly from abdominal, descending aorta (kidneys receive 20% of cardiac output

renal veins- drain blood from the kidneys and drain into the inferior vena cava

138
Q

how long is a nephron

A

30mm long

139
Q

what are the components of a nephron

A

glomerulus
renal corpuscle/bowmans capsule/renal capsule
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting duct

140
Q

where does the collecting duct go to

A

pelvis and the ureter

141
Q

which parts of the kidney are located in the cortex

A

glomerulus
renal corpuscle/bowmans capsule/renal capsule
proximal convoluted tubule
distal convoluted tubule

142
Q

which parts of the kidney are located in the medulla

A

loop of henle
collecting duct

143
Q

what does the bowmans capsule contain and what is this thing

A

glomerulus which is a bundle of capillaries

144
Q

what happens in the bowmans capsule/glomerulus

A

plasma is filtered from capillaries into renal tubules- ultrafiltration

145
Q

what are the names of the vessels that go to and from the glomerulus and how are they different

A

afferent arteriole (goes towards the G) this has a wider lumen then the efferent so that higher pressure is created in the G so that the rate of ultrafiltration is increased
efferent arteriole (goes away from the G)

146
Q

what does the renal capsule/bowmans space contain and what is the histology of this

A

glomerular filtrate, it is a colourless ring around glomerulus, there are no cells and so no stain is absorbed

147
Q

what is the difference between the proximal convoluted tubule and the distal convoluted tubule

A

the PCT is closer to the G and turns into the descending limb

DCT is further away from the G and comes from the ascending limb

148
Q

what happens in the PCT

A

selective reabsorption of many substances via active transport and diffuse
where 65% of the ions and water in tubular space are reabsorbed into the blood

149
Q

histology of PCT, what does it look like under a microscope and how can we tell what it is

A

lots of individual cells make one tubule, the cuboidal epithelial cells are large so that in a cross section not every nucleus will be visible making it appear that the pct has fewer nuclei than other tubules.

the cells have a apical brush border with microvilli to increase their surface area

150
Q

what happens at the loop of henle

A

the water is reabsorped into the blood via active transport, diffusion and osmosis
osmoregulation

somehow

151
Q

histology of the LOH

A

there is a descending and an ascending limb
ascending limbs lower end is very thin and lined with by simple squamous epithelium, upper end is very thick and is lined with simple cuboidal epithelium

therefore ascending limb might be seen has the larges lumen

152
Q

what happens in the DCT

A

the fine tuning of water balance in the blood by active transport and diffusion

153
Q

describe the volume conc /overall balance of the fluid in the collecting duct

A

volume and concentration of the urine and blood water balance is finally determined

waste metabolites, Cl^-, Na2+, K+, hormones, urea/ CO(NH2)2, H2O

154
Q

histology of DCT

A

smaller and more lightly stained than pct

more nuclei visible in a cross section compared to pct

lack of a brush border on their apical surface

much less space occupied compared to pct (because it is shorter and less convoluted)

155
Q

histology of the collecting ducts

A

prominent lateral borders of the epithelial cells

156
Q

where in the nephron does ultrafiltration take place

A

glomerulus/bowmans capsule

157
Q

where in the nephron does selective reabsorption occur

A

PCT, LOH, DCT, CD

158
Q

what are the capillaries like in the glomerulus and why is that usefyl

A

the cells that make up the capillary wall are leakier than normal- they have fenestrations and have a filtering function so the mass flow of plasma occurs

159
Q

in the process of ultrafiltration what happens to the plasma when it has diffused out of the capillaries in the G

A

is passes through a basement membrane that has a filtering function

160
Q

in the process of ultrafiltration what happens to the plasma when it has diffused through the basement layer

A

it diffuses through the inner wall of the bowmans capsule which is made from podocytes that have a filtering function because they create filtration slits (overall there is a triple filter)

161
Q

what are podocytes

A

cells that have psuedopodia which increase the sa

have pedicels that wrap around the glomerular capillaries, they have filtration slits between them

162
Q

glomerular filtrate is created in large amounts (5th of blood through kidney is filtered each cycle) why is this problematic

A

makes the blood viscous thats why pct is so close

163
Q

the filtration in the filtration splits stops…

A

rbcs and large plasma proteins such as albumin leaving the blood plasma

164
Q

the fluid that reaches the inside of the bowmans capsule contains almost the same ….

A

substances as the blood and at almost the same concs (water, glucose, amino acids, urea and inorganic ions) (plasma has higher conc of proteins whereas filtrate has none)

165
Q

which molecules/ions are reabsorbed/excreted

A

inorganic ions both
urea-excreted

166
Q

humans are terrestrial why is this important

A

cannot afford to loose water so gf undergoes changes (selective reabsorption)

167
Q

why does selective reabsorption happen why is ultrafiltration is bad

A

UT is not efficient enough because it filters everything based on molecular size doesnt know the difference between urea and eg glucose

168
Q

what are the vasa recta

A

STRAIGHT vessels (arterioles and venules) of the kidney, enter the medulla as straight arterioles and then enter cortex as straight venules

capillaries connect them and lie parallel to the LOH

at the hairpin (base of the vasa recta) the blood is slowed

creates countercurrent system which maintains concentration and diffusion gradients

169
Q

what is selective reabsorption and what processes are involved

A

the process that returns substances back to the blood

diffusion, osmosis and active transport

170
Q

SR in the PCT involves…

A

selectively reabsorbed from GF to blood…
all the amino acids, glucose, vitamins and hormones VIA ACTIVE TRANSPORT from GF into blood against conc gradient

85% of sodium ions via ACTIVE TRANSPORT

85% of chloride ions via DIFFUSION

85% of water via OSMOSIS

171
Q

by the end of the PCT what is the gf like

A

well 80% of the volume of the gf has been sred back into the blood

isotonic

172
Q

how is the diffusion gradient maintained in the nephron

A

because the blood is constantly moving

173
Q

how much gf is produced every min

A

100ml

174
Q

what does hypertonic mean

A

a solution outside the cell with a lower water potential compared to inside the cell so that the solution inside the cell is of a higher water potential

more negative

175
Q

what does isotonic mean

A

a solution outside the cell with the same water potential as inside the cell

0kpa

iso means same

176
Q

what does hypotonic mean

A

a solution outside the cell with a higher water potential compared to inside the cell so that the solution inside the cell is of a lower water potential

less negative

177
Q

what are the 2 functions of the LOH

A

creates high conc gradient of na and cl ions in the tissue fluid that is in between cells of the medulla (salt bath)

allows mammals to produce urine that is more concentrated that their blood (hypertonic) (avoiding water loss)

178
Q

what qualities does the LOH have that allow it to carry out its functions

(general)

A

different parts have different permeabilities to water.

uses counter current flow arrangement and atp

179
Q

what is special about the descending limb of the LOH (permeability wise) and why

A

permeable to water but relatively impermeable to sodium and chloride ions

so that the ions dont diffuse back into the filtrate from the medulla tissue fluid and the high conc of these ions is not lost

180
Q

what is special about the ascending limb of the LOH (permeability wise)

A

it is permeable to sodium and chloride ions but impermeable to water

181
Q

as the LOH descends into the medulla what happens to the interstitial fluid

A

it becomes more salty

182
Q

what is special about the blood vessels surrounding the LOH (apart from vasa recta)

A

they have a blood flow that is opposite to the filtrate flow in both limbs allowing a counter current exchange

cc- efficient, reabsorbing what we need

183
Q

the longer the LOH the ….. the urine ….

A

greater the urine concentration

lowers the water potential that can build up in the medulla by increasing the salt concentration, giving a greater wp gradient between the urine in the cd and the medulla, so more water is reabsorbed from the urine into the cds, hence a smaller volume of more concentrated urine is produced

desert rat

184
Q

no LOH would mean the urine would be …

A

hypotonic

185
Q

what happens in the lower part of the ascending limb of the LOH

A

sodium ions and chloride ions move from filtrate into tissue fluid of the medulla (and then blood) by DIFFUSION

186
Q

what happens in the upper part of the ascending limb of the LOH

A

sodium ions and chloride ions are pumped from filtrate to tissue fluid of the medulla (to blood) via ACTIVE TRANSPORT

because there is not enough of a gradient for it to occur passively

187
Q

what type of filtrate is produced at the top of the ascending limb (link to wp and conc)

A

a dilute filtrate that is hypotonic to blood plasma

this means that it has a lower water potential than the blood and it is more concentrated

188
Q

the gf entering the descending limb is …. to the blood plasma

A

isotonic

189
Q

what is the movement of water for descending limb

and why

A

water moves out of the filtrate into tissue fluid of medulla cells (and then into blood) via diffusion

osmosis??

because ascending limb has created high conc of na+ and cl- in the medullas tissue fluid

the water in the tissue fluid then diffuses back into the blood plasms in the vasa recta

190
Q

the descending limb is only permeable to water when…

A

it enters the medulla

191
Q

the filtrate at the bend of the LOH is ……. to blood plasma

A

hypertonic

192
Q

where in the nephron is the water balance regulated

A

the distal convoluted tubule

193
Q

why would active transport have to occur instead of diffusion

A

there is not enough of a diffusion gradient, not a steep enough concentration of eg charges (ions) so active transport has to occur

194
Q

the water permeability of the cells in the dct is controlled by …… which means that ….. controls

A

ADH so adh controls the water balance in the blood

195
Q

if the blood plasma has too little na+ and cl- then what happens in the dct

A

sodium ions are pumped in by active transport from the filtrate into the tissue fluid so that they move into the blood by diffusion, chloride ions follow by diffusion

196
Q

when is hypertonic urine produced

A

this is concentrated urine and so is produced when the body needs to reduce water loss

197
Q

what is also regulated in the dct

A

blood pH

198
Q

when is hypotonic urine produced

A

this is diluted urine and is produced when the body needs to increase water loss

199
Q

what is the permeability of the CD controlled by

A

adh just like dct

200
Q

what happens to animal cells when their water potential is too high

A

LYSIS

201
Q

what happens to animal cells when their water potential is too low

A

CRENATION

202
Q

what is hydrostatic pressure

A

the pressure caused by water potential

203
Q

can plasma membranes of animal cells withstand increased hydrostatic pressure

A

no because they cannot stretch easily and they have no mechanical strength

204
Q

what type of feedback is involved with ADH

A

negative feedback

205
Q

ADH has a very short half life (16-24 mins) why??

A

because it is only needed for a short amount of time in order to get the water potential to where it needs to be otherwise the wp will go the other way

206
Q

what does a presence of ADH cause

A

increases the permeability of the CD to water

207
Q

where is adh made

A

hypothalamus

208
Q

where is ADH stored

A

posterior pituitary gland

209
Q

when is adh released into the blood

A

when the water potential of the blood if too low/blood conc is too high

210
Q

what do osmoreceptors detect

A

concentration of inorganic ions in the blood in order to detect the water potential of the blood

Osmoreceptors detect changes in the water potential of the blood.

211
Q

where are osmoreceptors located

A

in the hypothalamus

212
Q

osmoreceptors are near what and do they trigger

A

they are near neurones which when send action potentials trigger the release of adh

when the wp of the blood is too low then the nerve impulses to the post pit are reduced/stopped, inhibiting release of ADH

The hypothalamus contains osmoreceptors which are sensitive to changes in the water potential of the blood. They control the release of ADH by the posterior pituitary gland.

213
Q

explain the mechanism of ADH

A

it arrives in the blood near CD and is detected by cell surface receptors

binds with ssr
a series of enzyme reactions
vesicle containing aquaporins stimulates to move towards and fuse with csm on other side

the vesicle fuse to csm and the aquaporins allow more water to be reabsorbed into the cell where it is transported by osmosis into the capillary (of the vasa recta)

this leaves the urine in the CD

214
Q

what are aquaporins

A

transmembrane proteins (intrinsic) bind to csm but are stored on a vesicle and bind to csm when needed

215
Q

what are the target cells of ADH

A

the cells of the wall of the collecting duct (and dct)

216
Q

when adh binds with the ssr what happens to it

A

it becomes an active enzyme and of the cytoplasmic face of the csm and forms cAMP as a second messenger

217
Q

the more adh in the blood means more …… are embedded into the csm

A

aquaporins

218
Q

What happens when osmoreceptors detect an increase in the water potential of the blood? 2 things

A

The posterior pituitary gland produces less ADH.
urine becomes less concentrated.

219
Q

name the process by which the fluid passes from the glomerulus into the renal tubule (1)

A

ultrafiltration

220
Q

name the tissue that lines the pct (1)

A

cuboidal epithelium

221
Q

explain why protein in the urine is often a symptom of chronic high blood pressure (2)

A

glomerular bp is greater, proteins are forced through, damage to capillaries, damage to basement membrane

222
Q

the presence of protein molecules in the urine of an individual is a sign of kidney disease or damage.

explain why it is unusual for protein molecules to appear in the urine (2)

A

they are too large to pass through the basement membrane

223
Q

explain why the bp in the glomerular capillaries is considerably higher in the glomerular capillaries than in other capillaries (2)

A

wide/large afferent arteriole
narrow/small efferent arteriole

bottleneck effect build up pressure to achieve filtration

224
Q

explain how changes in gf conc and conc of urine leaving cd are brought about by the pct

A

selective reabsorption
of glucose and aas
co transport/facilitated diffusion
(uptake of glucose and aas by AT)
water follows by osmosis so conc of ions/urea increases

225
Q

what things can urine test for

A

pregnancy
use of illegal drugs
use of anabolic steroids

226
Q

what hormone is present in females urine if she is pregnant

A

HCG (human chorionic gonadotrophin)

227
Q

what are monoclonal antibodies

A

antibody molecules that will bind to a specific antigen and are produced from a single clone of a plasma cell so that they produce identical antibodies

228
Q

what is the design of the dipstick of a pregnancy test (what is in region 1 and region 2)

A

mobile antibodies that are specific to HCG and are bound to pink/blue beads are present at the base of the test strip in region 1

region 2 has immobile antibodies that are specific to HCG

region 2 also has immobile antibodies that are specific to the antibodies in region 1

229
Q

what is the control line in a pregnancy test and how does it appear

A

if the stick is working, a pink line always appears in the control region (2??) HCG antibody bound to pink is carried upwards and captured by antibody which is specific to it which was immobilised here.

230
Q

if HCG is present in the urine how does the 2nd pink line appear

A

HCG binds to HCG specific antibody and the pink at the end and is carried upwards, when this meets immobilised HCG specific antibody it is bound and a pink line appears = PREGNANT

231
Q

anabolic steroids are soluble in phospholipid bilayers what does this mean for movement across cell membranes

A

because they can just diffuse through because theyre made of cholesterol so no need for transmembrane protein ???? NEEDS CHECKING

232
Q

what are the main causes of kidney failure

A

type 2 diabetes
hypertension
infection of the kidney that leads to structural changes to the kidney.
genetic condition such as polycystic kidney disease (when the kidney has fluid filled cysts)

233
Q

what are the 3 types of kidney failure

A

chronic and acute

234
Q

how are chronic and acute kidney failure different

A

acute is fast development, short acting, more easily treated, quicker recovery

chronic is slower development longer acting and less easily treated so slower/no recovery

235
Q

some symptoms of kidney failure (caused by infection/hypertension)

A

protein in the urine (damage to basement membrane/podocytes)
blood in the urine

236
Q

if both kidneys fail this leads to…..

A

loss of electrolyte balance in the blood > death
inc urea conc in blood > death
hypertension/loss of osmoregulation > stroke>death.
weakened bones due to loss of electrolyte balance.
pain and stiffness in joints as proteins build up
anaemia because kidneys are involved in production of EPO which makes RBCs

237
Q

what can be used to measure the extend of kidney failure and how can it be measured

A

glomerular filtrate rate
measured indirectly from a blood test measuring creatine phosphate conc in blood to get estimated gfr

238
Q

how are creatine phosphate levels linked to gfr

A

creatinine is a breakdown product from creatine phosphate in muscles which is excreted by the kidneys, if blood conc of creatinine is high then kidneys are not removing it indicating lower egfr>kidney disease/failure

239
Q

levels of gfr indicated normal, chronic kidney disease and kidney failure

A

normal= 90mlmin-1
60 for 3 mths+ = chronic kidney disease
below 15 = kidney failure

240
Q

risk factors for kidney disease

A

diabetes
hypertension
family history
older age
ethnic group
smoking

241
Q

Urine samples can be used in medical diagnosis.

A patient has a high level of glucose in their urine.

What diagnosis might this lead to?

A

diabetes mellatus

242
Q

The rate at which the kidneys filter blood is called the

A

glomerular filtration rate

243
Q

How does haemodialysis treat kidney failure?

A

Haemodialysis involves passing the patient’s bloodthrough a dialysis machine. The machine contains an artificial partially permeable membrane that allows urea to diffuse out of the blood. The membrane also prevents glucose from diffusing out of the blood.

244
Q

What are the disadvantages of kidney transplants?

A

The patient’s body may reject the kidney.

There aren’t enough donors available.

245
Q

The efferent arteriole has a smaller diameter than the afferent arteriole. This causes ……. pressure to build up within the glomerulus.

A

hydrostatic (pressure exerted by a fluid eg blood)

246
Q

what are the barriers that substances need to pass through to reach the lumen of the Bowman’s capsule, where filtrate forms.
in order

A

endothelium
basement membrane
podocyte

247
Q

what substances pass into the Bowman’s capsule during ultrafiltration?

A

GLUCOSE
water
Na+
urea

248
Q

Describe the process of ultrafiltration.

A

There is high hydrostatic pressure in the capillaries that form the glomerulus. This forces out small molecules within blood to pass through the endothelium, the basement membrane, and podocytes into the Bowman’s capsule to form the glomerular filtrate. Small molecules that pass through include urea, water, glucose, and sodium ions, while larger molecules such as red blood cells are left behind in the blood.

249
Q

Name the part of the nephron that selective reabsorption takes place in.

A

proximal convoluted tubule

250
Q

During selective reabsorption, ………… are transported from the epithelial cell into the blood via ………….. ………. Sodium ions and other substances in the lumen are then transported into the epithelial cell via ………… …….using ………….. proteins. These substances then travel down their concentration gradient into the blood.

A

sodium
active transport
facilitated diffusion
co-transport

251
Q

Describe three adaptations of the proximal convoluted tubule for selective reabsorption.

A

The epithelial cells contain mitochondria to produce ATP for active transport.

The membrane contains a large number and variety of co-transport proteins.

Microvilli in the epithelial cells increase the surface area for diffusion.

There is a short diffusion distance through one epithelial cell.

252
Q

In the loop of Henle, ……. ions are actively transported out of the …….. limb. This decreases the water potential of the ………. , creating a water potential gradient. So, water moves out of the ………. limb by ………This is an example of a ……….. mechanism.

A

sodium
descending
medulla
ascending
osmosis
countercurrent

253
Q

what is reabsorbed into the blood from the loop of Henle

A

water
Na+

254
Q

Sodium ions are transported into the loop of Henle via

A

active transport out of the ascending limb.

255
Q

When sodium ions leave the ascending limb what happens to the wp of the area outside

A

the water potential of the medulla decreases

256
Q

where is water transported in the LOH

A

out of the descending limb by osmosis.

257
Q

The process that takes place in the loop of Henle is described as countercurrent mechanism because

A

filtrate flows in opposite directions in each limb.

258
Q

Describe how sodium ions and water are reabsorbed in the loop of Henle.

A

In the loop of Henle, sodium ions are actively transported out of the ascending limb and into the medulla. This decreases the water potential in the medulla, creating a water potential gradient. So, water moves out of the descending limb and into the medulla by osmosis. This is an example of a countercurrent mechanism. In the medulla, both sodium ions and water are reabsorbed into the blood.

259
Q

what is peritoneal dialysis

A

when the dialysis fluid is introduced directly into the abdomen using a catheter (so dialysis is done inside the body)

left for several hours for dialysis to take place (dwell time)

urea and excess ions pass out of blood into tissue fluid out across peritoneal membrane and into df which is drained and discarded

260
Q

benefits of peritoneal dialysis

A

can be done at home so patient can carry on with normal life ish eg diet as it as done times a day, can happen during sleep

makes use of natural dialysis membranes formed by the lining of the abdomen (peritoneum)

261
Q

disadvantages of peritoneal dialysis

A

patient has to be trained to be able to do it away from a hospital

overtime more expensive than a transplant

262
Q

disadvantages of haemodialysis

A

has to be done in a hospital (time, travel etc)

cant do anything whilst it takes place
has to be done several xs a week
takes about 3 hours
using shunt/cannula > infection
df has to be warm
eat relatively little protein and salt apart from before dialysis.
have to monitor your fluid intake
blood needs anticoagulant

263
Q

what is haemodialysis

A

using a dialysis machine blood leaves body via artery > shunt/catheter > machine + flows between partially permeable dialysis membranes that mimic bowmans capsule basement membrane

df and blood flow in opposite directions > countercurrent exchange system

df contains normal levels or glucose so not net movement

urea, excess mineral ions are lost

264
Q
A

alevel biology ocr (27 decks)

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