chapter 15- homoestasis Flashcards
1
Q
What term is used to describe communication between adjacent cells or cells at a distance?
A
cell signalling
2
Q
what is homeostasis
A
Homeostasis is the maintenance of the internal environment within restricted limits.
3
Q
What two systems are used in animals to coordinate responses to changes in the environment?
A
the hormonal and the nervous system
4
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
5
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
6
Q
What is a receptor?
A
A cell or protein that detects one specific type of stimulus.
7
Q
what is steady or stable state
A
the reference point, the ideal
8
Q
what is dynamic equilibrium
A
changes and fluctuation about the norm/set point
9
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
10
Q
what is positive feedback
A
once a change is detected, the effectors reinforce that change increasing the response (keep increasing)
11
Q
what is the normal level
A
the range around the optimum/set point
12
Q
examples of positive feedback
A
childbirth
lactation
blood clotting
opening of voltage gated Na+ channel proteins in the axolemma
13
Q
examples of negative feedback systems
A
thermoregulation
blood glucose regulation
water balance in the body
14
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
15
Q
what is thermoregulation
A
Thermoregulation is the process by which organisms maintain a constant core temperature.
16
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
17
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
18
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./An ectotherm is an animal which thermoregulates using their surroundings.
19
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)
20
Q
examples of losses of heat
A
latent heat of evaporation of water (as sweat from blood)
conduction
convection
radiation
21
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
22
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
23
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
24
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
25
advantages of ectotherms
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
26
example of ectotherm: goldenrod crab spider
wait on flower for fly. fly is attracted to flower and so the spider gets the fly. waiting is a learnt response (behavioural)
27
physiological responses warming/cooling for ectotherms plus egs
lizards in cooler climates have darker skin so the skin absorbs radiant heat more easily
alter heart rate to inc or decrease metabolic rate
28
Sun basking and shade seeking are both examples of which type of response shown by ectotherms to help them control internal temperature?
behavioural response
29
What is meant by the term “endotherm”?
An animal that maintains a constant/stable internal body temperature regardless of the
external temperature by generating heat through metabolic processes.
30
In endotherms, temperature receptors are located in which two parts of the body?
skin and hypothalamus
31
In endotherms, which part of the brain is involved in thermoregulation?
hypothalamus
32
What is seen in endotherms in response to a rise in core body temperature?
vasodilation, sweating, loweing hair by relaxing erector muscles
33
What is seen in endotherms in response to a fall in core body temperature?
vasoconstriction, shivering, raising hair by contracting hair erector muscles
34
how is a camel adapted to living in the desert (thermoregulation wise)
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
35
adaptions of tuna fish (thermoregulation wise)
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
36
what are endotherms and how do they thermoregulate
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
37
what do metabolic processes include
anabolic and catabolic
38
what is core body temperature
abdomen, chest, and head excluding ears, nose
39
what is torpor
decreased activity
during the day
40
what is hibernation
minimal activity over a long period of time (eg over winter)
there is a decrease in body temperature, heart rate, breathing rate
41
what is aestivation
dormancy during summer when it gets too hot
hot and dry seasn
42
what are physiological responses of endotherms to cooling down
vasodilation, increased sweating, reducing insulation
43
how does vasodilation cool endotherms down
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
44
how does increased sweating cool endotherms down
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
release more water in the form of sweat. This increases heat loss because heat energy is used to turn the water released into water vapour.
45
how does reducing the insulating effect of hair or feathers cool endotherms down
erector pili muscles in skin relax-hair or feathers lie flat, avoids trapping an insulating layer of air. but has little effect in humans
46
what anatomical adaptations could some endotherms have if they live in hot or cold (extreme) environments
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
47
how can endotherms warm up
vasoconstriction, decreased sweating, rasing the body hairs/feathers, shivering
48
how does vasoconstriction warm up endotherms
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
49
how does a decrease in sweating keep endotherms warm
core body temp falls, sweat production will stop entirely, reducing evaporation of water from skin although some some lungs still continues
50
how does raising the body hair or feathers keep endotherms warm
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
51
how can shivering keep endotherms warm
rapid, involuntary contracting and relaxing of large voluntary muscles in the body. metabolic heat from exothermic reactions warm up the body
52
what are the 2 control centres involved in thermoregulation of endotherms
heat loss centre and heat gain centre
53
when is the heat loss centre activated, how and what is the response
The increase in temperature is detected by thermoreceptors and this is passed to the nervous system, which acts as the COORDINATOR
when temp of blood flowing through hypothalamus increases
sends impulses through autonomic motor neurones to effectors (stimulating them) in the skin and muscles triggering responses to reduce core temp
negative feedback system
54
when is the heat gain centre activated, how and what is the response
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
55
what do coordinators do
transfer information detected by receptors to different parts of the body.
56
what is nitrogenous waste in humans, insects and birds, fish
humans- urea
insects and birds- uric acid
fish- ammonia
57
differences between excretion and secretion
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
58
what is excretion
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.
59
3 examples of excretion
carbon dioxide
bile pigments
nitrogenous waste products (UREA)
60
explain the excretion of carbon dioxide
from cellular respiration is excreted from the lungs
61
explain the excretion of bile pigments
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
62
explain the excretion of urea
from breakdown of excess amino acids by the liver, excreted by the kidneys in urine
63
order of toxicity of nitrogenous wastes
ammonia (highly soluble in the blood)
urea
uric acid
64
what is ingestion
taking food into the digestive system via the mouth
65
what is digestion
breakdown of food into smaller molecules via hydrolysis using enzymes
66
what is egestion
removal of undigested "waste" faeces
67
what is secretion inc egs
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
68
similarities between excretion and secretion
requires atp
involved in homeostasis
compounds produced by cells by metabolism need to cross membrane and leave cell to may be transported in blood
69
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)
fats/fatty acids not respired
beta oxidation of fats requires nad
nad is used in the breakdown of alcohol
nad is in short supply
70
why are amino acids converted into urea
because the body cannot store excess amino acids like it can with carbs, the body doesnt want to waste the amino acids
71
what happens to excess amino acids
they are deaminated in the liver, excess from that are used in respiration or converted to lipids and then adipose tissue
72
how is urea formed
ammonia is reacted with carbon dioxide
ammonia+carbon dioxide -> urea + water
73
what is transamination
when 2 amino acids switch R groups
the conversion of one amino acid into another type
74
why can fish excrete ammonia
they live in an aquatic environment and so can have a constant supply of water to flush the ammonia out
75
why cant humans excrete ammonia/why is urea made
we are terrestrial, dont have enough water so cannot tolerate build up of ammonia, it is toxic
76
what is the small intestine also known as
the duodenum
77
what type of organisms is the liver found in
vertebrates
78
how many lobes does the liver have and compare them
2, left and right
left is bigger than the right
79
what is the only treatment for complete liver failure
liver transplant, could be transplanted right lobe from a living donor
80
what are5 general/important functions of the liver
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
81
function of the liver: control of ... (3)
blood glucose levels
blood amino acid levels
blood lipid levels
82
function of the liver: synthesis of... (10 ish) dont need to know all
rbcs
bile
plasma proteins (especially albumin)
cholesterol
new aas
urea
glycogen from lactic acid
blood coagulation proteins
lymph
catalase
83
function of the liver: breakdown of ...(8)
hormones
rbcs
bacteria
excess aas
toxins
alcohol
drugs
hydrogen peroxide
84
function of the liver: storage of.... (4)
vitamins
mineral ions
glycogen
blood
85
what is 80% of the liver made up of
hepatocytes
86
what are hepatocytes
cells of the main tissue of the liver
87
6 features of hepatocytes
have prominent nuclei
numerous mitochondria
prominent golgi apparatus
very metabolically active
large amounts of smooth er
have many free ribosomes
88
why is nuclei of hepatocytes prominent
because lots of genes are expressed, they are round with dispersed chromatin and prominent nucleoli
take up lots of stain
89
what are kupffer cells
remove foreign debris, pathogens, gut bacteria, endotoxins from bacteria that are in the blood when it passes through the liver
90
what are the 3 blood vessels that are linked to the liver
hepatic artery
hepatic vein
hepatic portal vein
91
describe the hepatic artery
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%)
92
describe the hepatic portal vein
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
93
describe the hepatic vein
drains deoxygenated blood from the liver into the inferior vena cava
only branched at the liver end
94
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.
hepatic artery
portal vein
vein
95
where is bile made
in the liver
96
what is the billary tract
the system of ducts that collect products from the liver and pancreas and drain them into the duodenum
97
what does bile consist of
water, electrolytes, bile acids, cholesterol, phospholipids and billirubin (gives colour)
98
where is bile stored
in the gall bladder
99
some bile is ......... by ......... and the rest are extracted from the blood by the liver
synthesised by hepatocytes
100
what are the small structures that make up the liver
lobules
101
what is the shape of a liver lobule
hexagonal
102
what specialised cells make up hepatic lobules
hepatocytes
103
how are the lobules in the liver arranged
irregular, branching, interconnecting plates around a central vein
104
in a liver lobule blood passes through large endothelium lined spaced called
sinusoids
105
in a liver lobule what happens to the blood coming from the HA and HPV
it mixes in the spaces called sinusoids
106
on each corner of a liver lobule what is there
a branch of the hepatic artery (arteriole)
a branch of the hepatic portal vein (venule)
branch of the bile duct (ductile)
107
lood from ha and hpv mixes in sinusoid and then entres a .......... leading to the .....
central vein
hepatic vein
108
within sinusoids there are fixed phagocytes called ...
kupffer cells
109
in which direction does the bile flow in a liver lobule, what does it drain into
inside to out
bile drains into bile canaliculi/canaliculus and then into a branch of the bile duct (ductile)
110
what 2 types of metabolism is the liver involved in
carbohydrate: blood glucose reg, under control of insulin and glucagon
amino acid metabolism
111
amino acid metabolism
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).
112
what amino acids is the body unable to store
excess aas and proteins that arent used in metabolism
113
the excess aas must be broken down by 2 processes...
deamination and the ornithine cycle (stop energy form aas being wasted)
114
what is deamination
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
115
Which process in the liver removes the amine group from amino acids when breaking down excess proteins?
deamination
116
Which process in the liver combines ammonia with carbon dioxide to produce urea?
the ornithine cycle
117
How does the liver help to control blood glucose levels?
it converts glucose into glycogen for storage
118
The breakdown of alcohol is an example of which important function of the liver?
detoxification
119
what is ornithine
a non proteinogenic amino acid
120
what happens in the fist stage of the ornithine cycle
NH3, CO2, ornithine and ATP produce citrulline and water
121
what happens in the 2nd stage of the ornithine cycle
NH3, ATP and citrulline produce arginine and water
122
what happens in the 3rd and final stage of the ornithine cycle
arginine and water produce urea and ornithine
123
when is the ornithine cycle occuring
all the time unless youre fasting protein
they are enzyme controlled reactions
124
where does H2O2/hydrogen peroxide come from and how/why is it toxic
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
125
how does the liver detoxify H2O2 (hydrogen peroxide
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
126
how does the liver detoxify ethanol
127
why is ethanol harmful what characteristics does it have (how does it behave in the body)
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
128
how does the liver detoxify the blood of ethanol
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
129
when detoxifying ethanol what happens to the resulting ethanoate/acetate
it enters the krebs cycles to be metabolised synthesising atp and using "calories"
adipose tissues/fatty liver
130
what affect does ethanol have on the body
it is a depressant so affects the brain and nervous system by slowing down the transmission of neurotransmitters across the synaptic cleft
131
what is gout
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
132
what is a nephron
the functional unit of the kidney
133
what homeostatic roles does the kidney have
excretion of metabolic waste chemicals
osmoregulation (control of water potential)
controlling volume of water in the blood
controlling blood pH
134
What is osmoregulation?
Osmoregulation is the process of regulating the water potential of the blood.
135
what are the 5/6things that make up the kidneys gross structure
capsule
cortex
medulla
pelvis
pyramids
136
describe the capsule of the kidney
a tough fibrous covering that itself is covered by fat, it provides protection
kidneys only protection is the adipose tissue
137
describe the cortex of the kidney
dark outer layer, filtering of blood takes place, lots of capillaries, approx 1cm thick
nephron glomerulus, bowmans capsules and tubules are located here
138
describe the medulla of the kidney
lighter in colour, the collecting ducts and loops of henle of the nephrons are here
middle of the kidney, contains renal pyramids
139
describe the pelvis of the kidney
central chamber that the collecting ducts drain into, connected to the ureter
140
what is the blood supply to the kidneys
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
141
how long is a nephron
30mm long
142
what are the components of a nephron
glomerulus
renal corpuscle/bowmans capsule/renal capsule
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting duct
143
where does the collecting duct go to
pelvis and the ureter
144
which parts of the kidney are located in the cortex
glomerulus
renal corpuscle/bowmans capsule/renal capsule
proximal convoluted tubule
distal convoluted tubule
145
which parts of the kidney are located in the medulla
loop of henle
collecting duct
146
what does the bowmans capsule contain and what is this thing
glomerulus which is a bundle of capillaries
147
what happens in the bowmans capsule/glomerulus
plasma is filtered from capillaries into renal tubules- ultrafiltration
148
what are the names of the vessels that go to and from the glomerulus and how are they different
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)
149
what does the renal capsule/bowmans space contain and what is the histology of this
glomerular filtrate, it is a colourless ring around glomerulus, there are no cells and so no stain is absorbed
150
what is the difference between the proximal convoluted tubule and the distal convoluted tubule
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
151
what happens in the PCT
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
152
histology of PCT, what does it look like under a microscope and how can we tell what it is
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
153
what happens at the loop of henle
the water is reabsorped into the blood via active transport, diffusion and osmosis
osmoregulation
somehow
154
histology of the LOH
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
155
what happens in the DCT
the fine tuning of water balance in the blood by active transport and diffusion
156
describe the volume conc /overall balance of the fluid in the collecting duct
volume and concentration of the urine and blood water balance is finally determined
waste metabolites, Cl^-, Na2+, K+, hormones, urea/ CO(NH2)2, H2O
157
histology of DCT
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)
158
histology of the collecting ducts
prominent lateral borders of the epithelial cells
159
where in the nephron does ultrafiltration take place
glomerulus/bowmans capsule
160
where in the nephron does selective reabsorption occur
PCT, LOH, DCT, CD
161
what are the capillaries like in the glomerulus and why is that usefyl
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
162
in the process of ultrafiltration what happens to the plasma when it has diffused out of the capillaries in the G
is passes through a basement membrane that has a filtering function
163
in the process of ultrafiltration what happens to the plasma when it has diffused through the basement layer
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)
164
what are podocytes
cells that have psuedopodia which increase the sa
have pedicels that wrap around the glomerular capillaries, they have filtration slits between them
165
glomerular filtrate is created in large amounts (5th of blood through kidney is filtered each cycle) why is this problematic
makes the blood viscous thats why pct is so close
166
the filtration in the filtration splits stops...
rbcs and large plasma proteins such as albumin leaving the blood plasma
167
if kidney damage is suspected urine is likely to be tested for presence of the protein albumin. explain why the presence of albumin indicates kidney damage (1)
large proteins should remain in blood and not enter bowmans capsule/nephron
168
the fluid that reaches the inside of the bowmans capsule contains almost the same ....
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)
169
which molecules/ions are reabsorbed/excreted
inorganic ions both
urea-excreted
170
humans are terrestrial why is this important
cannot afford to loose water so gf undergoes changes (selective reabsorption)
171
why does selective reabsorption happen why is ultrafiltration is bad
UT is not efficient enough because it filters everything based on molecular size doesnt know the difference between urea and eg glucose
172
what are the vasa recta
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
173
what is selective reabsorption and what processes are involved
the process that returns substances back to the blood
diffusion, osmosis and active transport
174
SR in the PCT involves...
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
175
by the end of the PCT what is the gf like
well 80% of the volume of the gf has been sred back into the blood
isotonic
176
how is the diffusion gradient maintained in the nephron
because the blood is constantly moving
177
how much gf is produced every min
100ml
178
what does hypertonic mean
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
179
what does isotonic mean
a solution outside the cell with the same water potential as inside the cell
0kpa
iso means same
180
what does hypotonic mean
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
181
what are the 2 functions of the LOH
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)
182
what qualities does the LOH have that allow it to carry out its functions
(general)
different parts have different permeabilities to water.
uses counter current flow arrangement and atp
183
what is special about the descending limb of the LOH (permeability wise) and why
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
184
what is special about the ascending limb of the LOH (permeability wise)
it is permeable to sodium and chloride ions but impermeable to water
185
as the LOH descends into the medulla what happens to the interstitial fluid
it becomes more salty
186
what is special about the blood vessels surrounding the LOH (apart from vasa recta)
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
187
the longer the LOH the ..... the urine ....
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
188
no LOH would mean the urine would be ...
hypotonic
189
what happens in the lower part of the ascending limb of the LOH
sodium ions and chloride ions move from filtrate into tissue fluid of the medulla (and then blood) by DIFFUSION
190
what happens in the upper part of the ascending limb of the LOH
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
191
what type of filtrate is produced at the top of the ascending limb (link to wp and conc)
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
192
the gf entering the descending limb is .... to the blood plasma
isotonic
193
what is the movement of water for descending limb
and why
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
194
the descending limb is only permeable to water when...
it enters the medulla
195
the filtrate at the bend of the LOH is ....... to blood plasma
hypertonic
196
where in the nephron is the water balance regulated
the distal convoluted tubule
197
why would active transport have to occur instead of diffusion
there is not enough of a diffusion gradient, not a steep enough concentration of eg charges (ions) so active transport has to occur
198
the water permeability of the cells in the dct is controlled by ...... which means that ..... controls
ADH so adh controls the water balance in the blood
199
if the blood plasma has too little na+ and cl- then what happens in the dct
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
200
when is hypertonic urine produced
this is concentrated urine and so is produced when the body needs to reduce water loss
201
what is also regulated in the dct
blood pH
202
when is hypotonic urine produced
this is diluted urine and is produced when the body needs to increase water loss
203
what is the permeability of the CD controlled by
adh just like dct
204
what happens to animal cells when their water potential is too high
LYSIS
205
what happens to animal cells when their water potential is too low
CRENATION
206
what is hydrostatic pressure
the pressure caused by water potential
207
can plasma membranes of animal cells withstand increased hydrostatic pressure
no because they cannot stretch easily and they have no mechanical strength
208
what type of feedback is involved with ADH
negative feedback
209
ADH has a very short half life (16-24 mins) why??
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
210
what does a presence of ADH cause
increases the permeability of the CD and dct to water
211
where is adh made
hypothalamus
212
where is ADH stored
posterior pituitary gland
213
when is adh released into the blood
when the water potential of the blood if too low/blood conc is too high
214
what do osmoreceptors detect
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.
215
where are osmoreceptors located
in the hypothalamus
216
osmoreceptors are near what and do they trigger
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.
217
explain the mechanism of ADH
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
218
what are aquaporins
transmembrane proteins (intrinsic) bind to csm but are stored on a vesicle and bind to csm when needed
219
what are the target cells of ADH
the cells of the wall of the collecting duct (and dct)
220
when adh binds with the ssr what happens to it
it becomes an active enzyme and of the cytoplasmic face of the csm and forms cAMP as a second messenger
221
the more adh in the blood means more ...... are embedded into the csm
aquaporins
222
What happens when osmoreceptors detect an increase in the water potential of the blood? 2 things
The posterior pituitary gland secretes less ADH.
urine becomes less concentrated.
223
suggest why homeostatic control of osmoregulation may not be sufficient to prevent dehydration (2 marks)
homeostatic control of osmoregulation does not increase blood water potential/only prevents the blood water potential from decreasing further
further intake of water needed to prevent dehydration
224
name the process by which the fluid passes from the glomerulus into the renal tubule (1)
ultrafiltration
225
name the tissue that lines the pct (1)
cuboidal epithelium
226
explain why protein in the urine is often a symptom of chronic high blood pressure (2)
glomerular bp is greater, proteins are forced through, damage to capillaries, damage to basement membrane
227
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)
they are too large to pass through the basement membrane
228
explain why the bp in the glomerular capillaries is considerably higher in the glomerular capillaries than in other capillaries (2)
wide/large afferent arteriole
narrow/small efferent arteriole
bottleneck effect build up pressure to achieve filtration
229
explain how changes in gf conc and conc of urine leaving cd are brought about by the pct
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
230
what things can urine test for
pregnancy
use of illegal drugs
use of anabolic steroids
231
what hormone is present in females urine if she is pregnant
HCG (human chorionic gonadotrophin)
232
what are monoclonal antibodies
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
233
what is the design of the dipstick of a pregnancy test (what is in region 1 and region 2)
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
234
what is the control line in a pregnancy test and how does it appear
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.
235
if HCG is present in the urine how does the 2nd pink line appear
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
236
hcg affects many different tissues.
susceptible cells have glycoprotein receptors on their cell surface.
these receptors are complementary to the shape of hcg molecules
what can be concluded from this information (3)
hcg is a peptide hormone/not lipid based/nonsteroid.
hcg binds to a cell surface receptor.
cell signalling is involved in the action of hcg.
hcg used camp/second messanger to bring about a response in a cell
237
oestrogen is lipid soluble, which molecule does oestrogen interact with when it changes cell activity
DNA
238
anabolic steroids are soluble in phospholipid bilayers what does this mean for movement across cell membranes
because they can just diffuse through because theyre made of cholesterol so no need for transmembrane protein ???? NEEDS CHECKING
239
what are the main causes of kidney failure
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)
240
what are the 3 types of kidney failure
chronic and acute
241
how are chronic and acute kidney failure different
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
242
some symptoms of kidney failure (caused by infection/hypertension)
protein in the urine (damage to basement membrane/podocytes)
blood in the urine
243
if both kidneys fail this leads to.....
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
244
what can be used to measure the extend of kidney failure and how can it be measured
glomerular filtrate rate
measured indirectly from a blood test measuring creatine phosphate conc in blood to get estimated gfr
245
how are creatine phosphate levels linked to gfr
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
246
suggest 2 characteristics of a patient that must be taken into account when using GFR measurement to diagnose kidney damaged, explain why each characteristic must be considered (4)
(gfr is vol of blood can be filtered by kidneys per min, estimated by monitoring blood conc of creatinine, which is a breakdown product of creatine phosphate in muscles)
age cus gfr/kidney function declines with age (2)
gender cus men and women have diff muscle mass (2)
exercise/activity/fitness/pregnancy/body mass cus will alter metabolism of creatine phosphate > production of creatinine (2)
diet cus affects levels of creatinine in the blood (2)
ethnicity/genetic makeup cus different alleles > production of creatinine (2)
247
levels of gfr indicated normal, chronic kidney disease and kidney failure
normal= 90mlmin-1
60 for 3 mths+ = chronic kidney disease
below 15 = kidney failure
248
risk factors for kidney disease
diabetes
hypertension
family history
older age
ethnic group
smoking
249
The rate at which the kidneys filter blood is called the
glomerular filtration rate
250
How does haemodialysis treat kidney failure?
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.
251
suggest why peritoneal dialysis requires the df to be replaced 4 times a day but haemodialysis only needs doing 3 times a week (2)
PD can remove less waste than HD
HDF is constantly refreshed/changed but not in PD.
HD uses countercurrent flow.
HD maintains conc gradient/PD the conc gradient is lower.
PDF reaches equilibrium with the blood
252
What are the disadvantages of kidney transplants?
The patient's body may reject the kidney.
There aren’t enough donors available.
253
The efferent arteriole has a smaller diameter than the afferent arteriole. This causes ....... pressure to build up within the glomerulus.
hydrostatic (pressure exerted by a fluid eg blood)
254
what are the barriers that substances need to pass through to reach the lumen of the Bowman’s capsule, where filtrate forms.
in order
endothelium
basement membrane
podocyte
255
what substances pass into the Bowman’s capsule during ultrafiltration?
GLUCOSE
water
Na+
urea
256
Describe the process of ultrafiltration.
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.
257
Name the part of the nephron that selective reabsorption takes place in.
proximal convoluted tubule
258
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.
sodium
active transport
facilitated diffusion
co-transport
259
Describe three adaptations of the proximal convoluted tubule for selective reabsorption.
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.
260
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.
sodium
descending
medulla
ascending
osmosis
countercurrent
261
what is reabsorbed into the blood from the loop of Henle
water
Na+
262
Sodium ions are transported into the loop of Henle via
active transport out of the ascending limb.
263
When sodium ions leave the ascending limb what happens to the wp of the area outside
the water potential of the medulla decreases
264
where is water transported in the LOH
out of the descending limb by osmosis.
265
The process that takes place in the loop of Henle is described as countercurrent mechanism because
filtrate flows in opposite directions in each limb.
266
Describe how sodium ions and water are reabsorbed in the loop of Henle.
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.
267
what is peritoneal dialysis
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
268
benefits of peritoneal dialysis
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)
269
disadvantages of peritoneal dialysis
patient has to be trained to be able to do it away from a hospital
overtime more expensive than a transplant
270
why does the df in PD contain dextrose solution rather than water alone (2)
dextrose reduced wp of df (1)
water diffuses by osmosis into df/prevent water into blood (1)
if water alone > cell lysis (1)
replicating kidney function that is to remove excess water from blood (1)
271
how might the peritoneum differ in its function from the artificial membrane in a dialysis machine used in HD (1)
it can perform active transport/facilitated diffusion
272
disadvantages of haemodialysis
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
273
what is haemodialysis
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
274
which of the following relate to the exocrine function of the liver:
stores bile in the gall bladder
contains sinusoids
receives blood from the gut and heart
only
stores bile in the gall bladder
275
