Unit 3.7 - Homeostasis and the kidney Flashcards
(342 cards)
1
Q
Homeostasis
A
The maintenance of a constant internal environment by negative feedback
2
Q
What does homeostasis prevent?
A
Wild fluctuations beyond the optimal range
3
Q
What does homeostasis allow to happen?
A
Cells and metabolism can function efficiently
4
Q
Give some examples of factors that are maintained by homeostasis
A
Core body temperature
pH
Water potential of blood and body fluids
5
Q
What should a human’s core body temperature be?
A
Approximately 37 degrees Celsius
6
Q
What could happen to some of the factors that have an optimal level in our body and when?
A
May change due to changes in our activity or external environment
7
Q
Does homeostasis keep factors at the optimal level all of the time?
A
The factors fluctuate about the set point
8
Q
Explain the homeostatic mechanism that occurs when we exercise
A
Core body temperature rises
The body responds to bring the temperature down again by producing sweat which evaporated from the skin and uses energy to cool us down
9
Q
What is the production of sweat when we’re hot an example of?
A
A homeostatic mechanism
10
Q
What happens if our core body temperature gets too high?
A
Denatured enzymes
11
Q
What happens if our core body temperature gets too low?
A
Metabolic reactions don’t happen fast enough, so metabolic processes in cells can’t be maintained
12
Q
In what condition is the body kept during homeostasis?
A
Dynamic equilibrium
13
Q
Why is the body described to be kept in “dynamic equilibrium”?
A
Constant changes occur but corrective mechanisms bring the internal environmental conditions back towards a set point
14
Q
How are internal environmental conditions brought back towards a set point when changes occur?
A
Corrective mechanisms
15
Q
Which system controls homeostatic responses?
A
The endocrine system
16
Q
How does the endocrine system control homeostatic responses?
A
With hormones operating by negative feedback
17
Q
What are the 4 stages involved in negative feedback?
A
Stimulus
Receptor
Co-ordination
Effector
18
Q
Explain the negative feedback system for when the body temperature exceeds 37 degrees Celsius
A
Stimulus = body temperature exceeds 37 degrees Celsius
Receptor = nerve cells in skin and brain
Co-ordinator = temperature regulatory center in brain
Effector = sweat glands throughout the body
19
Q
What does a receptor do during negative feedback?
A
Detects a deviation from the set point in the internal environment
20
Q
What does a receptor do during negative feedback?
A
Sends instructions to the co-ordinator or controller
21
Q
What does a co-ordinator or controller do during negative feedback?
A
Communicates with one or more effectors which make responses which are corrective
22
Q
How does a co-ordinator communicate with effectors during negative feedback?
A
By hormones circulating in the blood or nerve impulse
23
Q
Name for the “normal conditions” achieved by homeostasis?
A
The set point
24
Q
How is negative feedback stopped once a factor has returned back to normal (the set point)?
A
The factor changing is monitored by the receptor and information is fed back to the effectors, which stop making the correction
25
What do homeostatic systems use to control their levels?
Negative feedback
26
Why is negative feedback called negative feedback? Give an example
It gives the opposite result to the stimulus
E.g - decrease in temperature = brings temperature up
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2 main functions of the kidney
Excretion
Osmoregulation
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Excretion
The removal of nitrogenous waste from the body
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The removal of nitrogenous waste from the body
Excretion
30
Osmoregulation
The control of the water potential of the body’s fluids
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The control of the water potentials of the body’s fluids
Osmoregulation
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What is Osmoregulation an example of in the kidneys?
A homeostatic mechanism
33
What is an example of a homeostatic mechanism in the kidneys?
Osmoregulation
34
Why does excretion occur?
Due to metabolism
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4 excretory organs used by the mammalian body to excrete compounds
Lungs
Kidneys
Skin
Liver
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Compounds excreted by the lungs
CO2 and H2O in expired air
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Compounds excreted by the kidneys
Urea, creatinine and uric acid in urine (all nitrogenous waste)
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Compounds excreted by the skin
Urea in sweat
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Compounds excreted by the liver
Bile pigments in faeces
40
What are urea, creatinine and uric acid in urine all examples of?
Nitrogenous waste
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Main nitrogenous waste excreted by kidneys
Urea
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Give a detailed explanation on why urea is the main nitrogenous waste from the kidneys
In our diet, we eat proteins
Proteins are digested and absorbed in the body in the form of amino acids (amino acids are needed to make proteins)
Generally, we have too much protein in our diets
Therefore, we have an excess of amino a acids
If we can’t use them, the body can’t store them
So, amino acids are processed in the liver
Liver cells remove the amino group in a process called deamination
The rest of the amino acid is used in respiration for energy or converted into carbohydrate or fat
The amino group is converted into ammonia, then idea, the mai excreted product
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Can our bodies store amino acids?
No
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Where are amino acids processed when we have an excess of them?
In the liver
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Why do we have an excess of amino acids?
Too much protein in our diets
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Deamination
Remove the amino group from an amino acid
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Process of removing the amino group from an amino acid
Deamination
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What type of cells cause deamination?
Liver cells
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What happens to the rest of the amino acid after deamination?
Used in respiration for energy or converted into carbohydrate or fat
50
What happens to the amino group removed from an amino acid after deamination?
The amino group is converted into ammonia, then urea, the main excreted product
51
Which system are the kidney part of?
The urinary system
52
Describe the location of the kidneys in the human body
Have 2 kidneys
One on each side of the back bone
Towards the back of the abdomen
Below the diaphragm
53
Describe the blood flowing from the heart to the kidneys
Oxygenated
High level of urea
54
How does oxygenated blood flow form the heart to the kidneys?
Via the aorta and renal arteries
55
Describe the blood returned to the heart form the kidneys
Deoxygenated
Lower levels of urea
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Where is nitrogenous waste removed in the body?
The kidneys
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How is blood returned to the heart from the kidneys?
Via the renal veins and vena cava
58
Explain how urine is passed out of the body
Urine containing a high concentration of urea is passed via the ureter to the urinary bladder for storage, until it is passed out of the body through the urethra
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How is urine passed to the bladder and why?
Via the ureter
For storage
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Through what is urine passed out of the body?
Through the urethra
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What are kidneys inside and what is this?
Tough renal capsules
Fibrous connective tissue
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Where is the blood from the renal artery filtered?
In the outer layer, the cortex, at the bowman’s or renal capsules
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Where is the Bowman’s capsule located?
At the cortex
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Where are the loops of Henle?
The medulla
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What does the medulla contain?
The loops of Henle
The collecting ducts that carry urine to the pelvis
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What do the collecting ducts in the medulla do?
Carry urine to the pelvis
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What lead to the renal pelvis?
Calixes
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What do calixes lead to?
The renal pelvis
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What does urine travel down to reach the bladder?
The ureter
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What does the renal artery do in the cortex?
Branches into narrow branches
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Where does the renal artery branch into narrow branches?
In the cortex
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What happens to blood in the cortex?
Blood is filtered to remove nitrogenous waste and excess water
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Where is blood filtered to remove nitrogenous waste and excess water?
In the cortex
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What happens to filtered blood once it’s been filtered in the cortex?
Travels through the renal vein to return to circulation
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Where does blood travel down from the cortex to return to circulation after it’s been filtered?
Through the renal vein
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Describe the network of blood vessels in the kidney
Very dense
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Why is there such a dense network of blood vessels in the kidney?
All the blood in or system passes through the kidney many times a day
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Where are most blood vessels found in the kidneys?
The cortex or the medulla
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Where does the process of filtering out waste from blood happen?
In the cortex and the medulla
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Nephron
One of the units used to filter blood
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What are nephrons?
Millions of tubes in the kidneys
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What is the nephron to the kidney?
The functional unit
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Which part of the nephron are the bowman’s capsule and the proximal and distal consulates tubules present?
In the cortex
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What are present in the cortex of the nephron?
Bowman’s capsule
The proximal and distal convoluted tubules
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Which part of the nephron is found in the medulla?
The loop of Henle
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Where is the loop of Henle found in the nephron?
In the medulla
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What carries blood to the nephron?
An afferent arteriole (a branch of the renal artery)
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What does an afferent arterials do?
Carries blood to the nephron
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Afferent arteriole
A branch of the renal artery
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What does the glomerulus contain?
About 50 parallel capillaries
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What’s enclosed in the Bowman’s capsule?
Glomerulus
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Wha encloses the Glomerulus in the nephron?
The Bowman’s capsule
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Where is blood filtered exactly in the nephron?
The glomerulus
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What happens in the glomerulus?
Blood is filtered
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What does the tubule do after the glomerulus has filtered the blood?
Returns needed substances the the blood and removed waste
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Where is filtered blood carried by an efferent arteriole to?
- a capillary network surrounding the proximal and distal convoluted tubules
-the vasa recta, a capillary network surrounding the loop of Henle
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What is filtered blood carried by?
An efferent arteriole
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Vasa recta
A capillary network surrounding the loop of Henle
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The capillary network surrounding the loop of Henle
Vasa recta
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Name for the fluid travelling through the nephron
Filtrate
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Filtrate
Fluid travelling through he nephron
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What happens to the content of the filtrate along the nephron?
Changes
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When is filtrate called urine?
By the time it’s reached the renal pelvis
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when is filtrate called urine instead?
By the time it’s reached the renal pelvis
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Do nephrons exist individually?
No
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What does the efferent arteriole do?
Carries blood away from the glomerulus and divides up into many arteries
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What leaves the blood when filtrate is formed?
Waste but also some useful materials like glucose
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Why do we need selective re absorption?
To recover useful materials that left the blood when the filtrate was formed in the glomerulus
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Where does selective reabsorption happen mainly?
In the proximal convoluted tubule
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What happens mainly in the proximal convoluted tubule?
Selective re absorption
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What is the loop of Henle mostly concerned with?
The osmotic potential of the blood
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Ultrafiltration
Filtration under high pressure
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Filtration under high pressure
Ultrafiltration
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How many capillaries are in the glomerulus?
Numerous
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Describe capillary walls
1 cell thick
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Cells that make up capillary walls
Endothelial cells
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What are the cells of the capillaries set on?
A basement membrane
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What are between endothelial cells in the capillaries?
Fenestrations (pores)
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Where are fenestrations in the capillaries?
Between endothelial cells
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What do fenestrations in the capillaries do? Explain
Make the capillary semi-permeable
Don’t allow cells but allow small soluble molecules to leave the blood plasma (the rest can stay in the capillary)
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What do fenestrations allow small soluble molecules to leave?
The blood plasma
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How does blood arrive in the capillaries of the glomerulus?
From the afferent atriole
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Why does the blood from the afferent arteriole to the glomerulus have a high pressure?
The afferent atriole has a wider diameter than the efferent atriole
The heart’s contraction increases the pressure of arterial blood
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What does the high blood pressure to the glomerulus facilitate and why?
Facilitates ultrafiltration
High blood pressure forces filtrate out of the blood and into the nephron
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What does glomerular filtrate contain?
Water
Glucose
Salts (e.g - sodium)
Urea
Amino acids
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What do we want to do with the urea in globular filtrate?
Get rid of it as nitrogenous waste
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How is blood entering the glomerulus separated from the bowman’s space?
By 3 layers
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3 layers separating the blood entering the glomerulus from the Bowman’s space
Capillary walls
Basement membrane
Squamous epithelial cell layer of the Bowman’s capsule (podocytes)
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What is the name for the tiny pores between the endothelial cells of the capillary walls in the glomerulus?
Fenestrations
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Diameter of fenestrations
80nm
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What do fenestrations in the capillaries of the glomerulus allow to happen?
Allow solutes to pass to the basement membrane
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What is the selective molecular filter between the blood entering the glomerulus and the bowman’s space?
Basement membrane
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What is the basement membrane known as in the glomerulus?
Selective molecular filter
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Why is the basement membrane in the glomerulus known as the selective molecular filter?
It only allows small molecules to pass through
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What type of molecules would be too large to pass through the basement membrane in the glomerulus?
Blood cells
Placelets
Large proteins such as antibodies
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Extensions of podocytes
Pedicels
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Type of cell layer of the Bowman’s capsule
Squamous epithelial cell layer
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What do podocytes do?
Have extensions called pedicels, which wrap around a capillary, pulling it closer to the basement membrane. The gaps between the pedicels are called filtration slits
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Filtration slits
Gaps between the pedicels of podocytes
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What does the basement membrane behave as and what does this do?
As a molecular sieve
Stops larger molecules from entering the filtrate
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What does the basement membrane stop large molecules from entering?
The filtrate
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What do podocytes form?
The wall of the Bowman’s capsule
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What form the walls of the Bowman’s capsule?
Podocytes
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Explain how podocytes form filtration slits
Podocytes contain fingers tht plait together to form processes
Between the processes of the podocytes are the filtration slits
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What do filtration slits allow to happen?
Allow the filtrate to pass through easily
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Why do we need selective reabsorption?
After the literate is formed, the useful substances lost through ultrafiltration need to be re absorbed back into the blood plasma
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What are also lost through ultrafiltration?
Useful substances like glucose
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What is selective reabsorption?
The process by which useful substances such as glucose, amino acids and slats are re absorbed back into the blood plasma
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Give some examples of substances reabsorbed back into the blood plasma through selective reabsorption
Glucose
Amino acids
Salts
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Where does selective reabsorption take place?
The proximal convoluted tubule in the cortex
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How does selective reabsorption happen in the proximal convoluted tubule in the cortex?
By facilitated diffusion and active transport
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What is the nephron closely associated with?
Blood capillaries called the vasa recta
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Where do reabsorbed substances from selective reabsorption pass from and to?
From the proximal convoluted tubule
Into the blood plasma contained in the vasa recta capillaries
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Which capillaries do the reabsorbed substances pass into after the proximal convoluted tubule during selective reabsorption?
The vasa recta capillaries
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What does glomerular filtrate represent?
Things that have left the blood
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Where is the basement membrane in the nephron?
Between the endothelial cells of the capillaries and the podocytes that form the Bowman’s capsule wall
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How does blood enter the glomerulus?
Through the afferent arteriole
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Where is filtrate formed?
In the glomerulus
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What happens to the blood that isn’t filtered in the glomerulus?
Carries on through the efferent arteriole
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What does the efferent arteriole do?
Splits up to form the capillaries of the vasa recta
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Where does most of selective reabsorption occur?
In the proximal convoluted tubule
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What type of cells does the proximal convoluted tubule have?
Cuboidal epithelium cells
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List the ways in which the cells of the proximal convoluted tubule have adapted for selective reabsorption
Microvilli
Many mitochondria
Tight junctions between cells
Basal channels
Closely associated with the blood capillaries of the vasa recta
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Purpose of the microvilli on the cells of the proximal convoluted tubule
Protrude into the lumen of the PCT to increase the surface area for selective reabsorption + absorb the contents of the filtrate for them to pass back into the blood
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Where are the microvilli of the cells of the proximal convoluted tubule?
Protruding into the lumen of the PCT
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What’s the purpose of the cells of the proximal convoluted tubule having many mitochondria?
Produces ATP for active transport
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Purpose of the tight junctions between the cells of the proximal convoluted tubule
Hold neighbouring cells together closely to prevent molecules diffusing between adjacent cells (in either direction)
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Purpose of the basal channels of the cells of the proximal convoluted tubule
Increase the surface area of the cell membrane at the basement membrane
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What are the cells of the proximal convoluted tubule closely associated with?
The blood capillaries of the vasa recta
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Are the materials that are reabsorbed into the blood via selective reabsorption absorbed back into the blood using the same processes?
No
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Give 2 reasons why proteins are not reabsorbed back into the blood during selective reabsorption
-proteins are too large to be reabsorbed
-no specific transport proteins for them
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How are salts reabsorbed during selective reabsorption?
Mainly active transport, but some facilitated diffusion
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How are glucose and amino acids reabsorbed during selective reabsorption?
Cotransport with sodium ions into the cell
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How is water reabsorbed during selective reabsorption?
Osmosis
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How are urea and small proteins reabsorbed during selective reabsorption?
Facilitated diffusion
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Why is some urea reabsorbed during selective reabsorption?
Is meant to be water but some is reabsorbed as it’s small enough to pass through channel proteins to be absorbed via facilitated diffusion
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Summarise what happens during the reabsorption of glucose during selective reabsorption
Cotransport with sodium through a carrier protein at one end of the cell
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What is the condition that has to be true for glucose to be cotransported?
Both glucose and sodium have to be present
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What type of process is the cotransport of glucose with sodium?
Passive process
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As cotransport is a passive process, what does it require?
A concentration gradient
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Which concentration gradients do we need for the cotransport of glucose and sodium ions?
Concentration gradient needed for both glucose and sodium ions between the filtrate and the cytoplasm on the other side of the membrane
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How do we obtain the concentration gradient for sodium for its cotransport with glucose?
Sodium is actively transported out through a sodium-potassium pump (sodium out, potassium in)
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How do we obtain the concentration gradient for glucose for its cotransport with sodium?
Glucose leaves by facilitated diffusion into the blood down its concentration gradient
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What do both the active transport of sodium and glucose leaving by facilitated diffusion ensure?
That the concentration of glucose and sodium ions in the cell is low
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What undergoes the same process as glucose in the cotransport of glucose and sodium?
Amino acids
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What happens to amino acids during the cotransport of glucose and sodium?
The same thing as the glucose (facilitated diffusion into the blood down its concentration gradient)
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In what form is the Na+ for its cotransport with glucose?
NaCl
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What ions are also present during the cotransport of glucose and sodium and why?
Cl- ions
Since Na+ is in the form of NaCl
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What happens to the Cl- during the cotransport of sodium and glucose?
Pass straight through the channel proteins down a concentration gradient
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What happens to H2O during the cotransport of sodium and glucose?
Passes straight through via osmosis
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Which parts of the nephron does Osmoregulation take place?
Loop of Henle and collecting duct
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What happens during ultrafiltration?
Lots of blood is filtered
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What does how much water is taken back from ultrafiltration depend on?
The water levels in the body at the time
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Describe how water level is controlled in the loop of Henle at the descending limb
The descending limb of Henle is permeable to water; water leaves by osmosis since the water potential in the tissue fluid surrounding the nephron is lower than the filtrate.
Na+ and Cl- ions enter the descending limb by facilitated diffusion
195
Describe how water level is controlled in the loop of Henle at the ascending limb
The ascending limb of the loop of Henle is not permeable to water but does allow Na+ and Cl- to leave by facilitated diffusion and then active transport
As the NaCl in the filtrate goes into the tissue fluid in the medulla, it decreases the water potential of the tissue fluid since there’s more solutes in it. This helps water leave.
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Which limb of the loop do Henle is permeable to water?
Descending
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Why does water leave the descending limb of the loop of Henle via osmosis?
Success the water potential in the tissue fluid surrounding the nephron is lower than the filtrate
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How do Na+ and Cl- ions enter the descending limb of the loop of Henle?
Via facilitated diffusion
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How do Na+ and Cl- ions leave the ascending limb of the loop of Henle?
By facilitated diffusion and then active transport
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How is the water potential of the tissue fluid of the medulla decreased?
As the NaCl in the filtrate diffuses into the tissue fluid in the medulla, it decreases the water potential of the tissue fluid since there’s more solutes in it
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How is water helped to leave the filtrate in the loop of Henle?
By NaCl diffusing into the tissue fluid in the medulla to decrease its water potential
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What is the loop of Henle called?
A counter current multiplier
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Why is the loop of Henle called a counter current multiplier?
Because the filtrate flows in opposite directions (a counter current) and the concentration of solutes in the filtrate increases towards the apex (is multiplied)
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Why does the concentration of solutes in the loop of Henle increase towards?
The apex
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What leads to a higher concentration of solutes at the apex of the loop of Henle?
Longer loop of Henle
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What does a longer loop of Henle lead to?
A higher concentration of solutes at the apex
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What do the numbers represent on Loop of Henle diagrams?
The concentration of solutes in the filtrate
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At which point have most of the useful thing been reabsorbed back into the blood?
After the proximal convoluted tubule
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What are most of the solutes left unabsorbed by the blood after the proximal convoluted tubule?
NaCl in water
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Is there a change in concentration of the solutes in the proximal convoluted tubule? Why?
No, since there’s no concentration gradient
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What happens to the concentration of solutes down the descending limb of the Loop of Henle? Why?
Increases
Water is diffusing out
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Where does the concentration of solutes reach a maximum down the descending limb of the loop of Henle and why?
At the hair pin turn
Filtrate is most concentrated, with the lowest water potential
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What happens to the concentration of solutes up the ascending limb of the loop of Henle?
Decreases
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Why does the concentration of solutes decrease up the ascending limb of the loop of Henle?
Since the NaCl ions leave down their concentration gradient as they enter the tissue fluid via facilitated diffusion
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Why does facilitated diffusion not occur for NaCl ions to leave the ascending limb of the loop of Henle all of the way up? What happens instead?
As the concentration of solutes decreases, it eventually reaches equilibrium with the tissue fluid in the medulla. Now, there’s no concentration gradient so NaCl is pumped out by active transport.
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What does water do at the collecting duct in the nephron?
Diffuses out via osmosis
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What does water diffusing out of the collecting duct in the nephron do?
Recovers the water in the filtrate
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When is filtrate urine?
At the end of the collecting duct
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What is filtrate at the end of the collecting duct?
Urine
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What happens to the permeability of the walls of the collecting duct for water?
Can be changes due to a hormone
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What is the length of the loop of Henle positively correlated with?
The need for water conservation in animals
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Relationship between the length of the Loop of Henle and the need for water conservation in animals
Positively correlated
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Describe the loop of Henle for an animal in a very wet enviornment
Shorter loop of Henle
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Why does an animal have a shorter loop of Henle in a very wet environment?
No need to conserve water
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Describe the loop of Henle of an animal in a very dry environment
Longer
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Why do animals in very dry environments need longer loops of Henle?
For more water volume to be reclaimed
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Explain why is is beneficial for an animal in a very dry environment to have a longer loop of Henle
Can have a higher concentration of solutes in the medulla tissue fluid
More water recovered in the loop of Henle and collecting duct
More blood leaves filtrate and enters blood
Causes more water in the blood
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What are nitrogenous wastes?
The breakdown products of proteins and amino acids
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What do different animals do in terms of nitrogenous waste?
Excrete it in different forms
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How are proteins converted into amino groups?
Proteins —> amino acids —> amino groups
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How are nucleic acids converted into amino groups?
Nucleic acids —> nitrogenous bases —> amino groups
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Different forms of excreting nitrogenous waste
Ammonia (NH3)
Urea
Uric acid
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What animals excrete nitrogenous waste as ammonia?
Most aquatic mammals, including most bony fish
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What animals excrete nitrogenous waste as urea?
Mammals, most amphibians, sharks and some bony fish
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What animals excrete nitrogenous waste as uric acid?
Many reptiles (including birds), insects, land snails
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Explain why aquatic mammals excrete ammonia directly as their nitrogenous waste
Excrete it directly into large amounts of water
Ammonia is the most soluble in water compared to other urea and uric acid, therefore a lot of water is needed to get rid of it, which is fine for aquatic mammals
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What type of nitrogenous waste is the most soluble and what does this mean?
Ammonia
The most water is needed to get rid of it
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How do aquatic mammals excrete nitrogenous waste?
As ammonia
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How do mammals excrete nitrogenous waste?
Use energy to covert ammonia into less toxic urea, which is excreted in urine
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How is urea excreted?
In urine
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What is the most toxic - ammonia or urea?
Ammonia
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How do we get urea?
Amino acids —> ammonia —> urea (in liver cells)
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Give 2 reasons why urea is a better form of nitrogenous waste for mammals compared to ammonia
-urea is less toxic than ammonia
-urea is less soluble than ammonia, so less water is needed to get rid of it
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How do birds and insects excrete nitrogenous waste?
Convert ammonia into uric acid
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Disadvantage of producing uric acid as nitrogenous waste?
Required even more energy than producing urea
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2 advantages of uric acid as nitrogenous waste
-insoluble in water
-can be excreted as a waster with little water loss
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Do birds produce urine?
No
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How does uric acid help keep much more water in the body compared to having urea as nitrogenous waste?
Uric acid is much less soluble
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What does the fact that Uric acid is much less soluble than urea lead to?
It keeps more water in the body
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Explain why having uric acid as nitrogenous waste is useful to birds
They need less water to get rid of nitrogenous waste = they’re lighter = it’s easier to fly
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Explain why having uric acid as nitrogenous waste is advantageous for the fact that reptiles and birds lay eggs
As the embryo develops, it absorbs nutrients and produced nitrogenous waste
As this is in the form of uric acid, it ensures that the embryo isn’t poisoned in the egg
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Why is water able to diffuse out of the collecting duct in the nephron?
It passes through the medulla, which has a low water potential
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Where is water reabsorbed after it passes out of the collecting duct in the nephron?
Into the vasa recta
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Why is filtrate urine at the end of the collecting duct?
More concentrated than blood
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Name for concentration of solutes in the filtrates
Osmolarity
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Osmolarity
Concentration of solutes in the filtrate
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Why is the concentration of solutes in the filtrates referred to as Osmolarity?
Since it’s not just one compound
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What does ADH stand for?
Antidiuretic hormone
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What does ADH do?
Changes osmolarity
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Where is ADH produced?
In the hypothalamus
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Where is ADH secreted?
By the posterior lobe of the pituitary gland
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Where is ADH stored?
In the pituitary gland
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What does ADH increase the permeability of?
The cells of the collecting duct and distal convoluted tubule to water
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What does increased permeability of the collecting duct and distal convoluted tubule due to ADH lead to?
More water is reabsorbed by osmosis
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Results of the collecting duct walls being more permeable to water due to ADH
More water is reabsorbed from filtrate into the tissue fluid and into the blood
= lower volume of concentrated urine
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Hormone that increases the permeability of the cells of the collecting duct and distal convoluted tubule
ADH
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Where does water go when the collecting duct walls are more permeable to water due to ADH?
Reabsorbed form filtrate into the tissue fluid and into the blood
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What does more water being in the blood lead to?
Lower volumes of concentrated urine
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What are aquaporins?
Intrinsic protein channels which transport water across the phospholipid bilayer during osmosis
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Intrinsic protein channels which transport water across the phospholipid bilayer during osmosis
Aquaporins
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ADH
Anti diuretic hormone
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Diuretic
Anything that increase urine quantities in the body
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Example of a diuretic
Caffeine in tea and coffee
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Anti diuretic
Hormones that suppress the production of urine (lower volume produced)
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When does the blood water potential decrease?
When losing more water than normal (e.g - sweating, not drinking enough) and we become dehydrated
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What detects low water potential levels of the blood?
Osmoregulators
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What are osmoregulators?
Specialised cells in the hypothalamus in the brain
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When do osmoregulators detect blood water potential changes?
When blood flows through the hypothalamus in the brain
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What do osmoregulators do once they detect blood water potential changes?
Send a nerve impulse to the pituitary gland
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What do pituitary glands do once they receive nerve impulses from osmoregulators?
Secrete ADH into the blood
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What secrete ADH into the blood?
The posterior lobe of the pituitary gland
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What effects does ADH have?
Increases the permeability of the walls of the collecting duct + distal convoluted tubule to water
Triggers a feeling of thirst
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How can we tell from our urine if we’re dehydrated?
Darker urine = more concentrated —> sign of dehydration
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What is the pituitary gland?
A type of endocrine gland
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Give a detailed description of how the ADH hormone works
ADH is transported in the blood from the pituitary gland to the kidneys
ADH attaches to receptors in the cel wall of the collecting duct
Receptors stridulate aquaporin versicles to move towards the membrane of the cells of the collecting duct
As aquaporin pores are inserted into the cell membrane, there’s an increased number of channels, so an increasing flow of H2O out of the tubule and so the permeability of the collecting duct increases
More water possess from the lumen of the collecting duct (since the water potential of the filtrate is higher than the cells of the walls of the collecting duct) into the cells in the cell wall of the collecting duct and into the blood via osmosis
= ADH makes the collecting duct more permeable to water
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What does ADH do to the collecting duct?
Makes it more permeable to water
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Where are receptors for ADH to attach to?
In the cell wall of the collecting duct
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What do receptors in the cell wall of the collecting duct?
Stimulate aquaporin vesicles to move towards the membrane of the cells of the collecting duct
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What stimulates aquaporin vesicles to move towards the membrane of the cells of the collecting duct?
Receptors
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What happens as aquaporin pores are inserted into the cell membrane of the cells of the walls of the collecting duct?
Increased number of channels
Increasing flow of H2O out of the tubule
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What happens as ADH makes the collecting duct more permeable to water?
More water passes from the lumen of the collecting ducts into the cells in the cell walls of the collecting duct and into the blood via osmosis
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Why are the cells in the walls of the collecting duct the only ones to react in the presence of ADH?
As they contain aquaporins that can be absorbed into the membrane
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Give a detailed description of the kidneys response to water deprivation (Osmoregulation)
1. Low water levels (low water potential) in the blood caused by water deprivation
2. Detected by osmoreceptors in the hypothalamus
3. Nerve impulses are sent to the pituitary gland (endocrine gland)
4. The pituitary gland secretes the hormone ADH (anti diuretic hormone)
5. ADH carried in the bloodstream to kidneys
6. Increased ADH levels in kidney increases permeability of wall of the collecting duct and distal convoluted tubule to water
7. Water leaves the collecting duct and distal convoluted tubule by osmosis due to the low water potential in the medulla
8. This results in a small volume of more concentrated urine being produced
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Why is more concentrated urine produced during Osmoregulation - the kidneys response to water deprivation?
Water leaves the collecting duct and distal convoluted tubule by osmosis due to the low water potential in the medulla
This results in s a sell volume of more concentrated urine being produced
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Explain what will happen if the water levels in the blood become too high?
The opposite occurs…
The osmoregulators will detect the high blood water potential
The pituitary glands released less ADH
Thirst suppressed
Decreased permeability of walls of the collecting duct and distal convoluted tubule to water
Less water reabsorbed from kidney tubules
Large volumes of dilute urine forms
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What forms in terms of urine when the water levels in the blood become too high and why?
Large volumes of dilute iurine
Less water reabsorbed from kidney tubules since there’s a decreased permeability of the walls of the collecting duct and the distal convoluted tubule from kidney tubules with less ADH being released by pituitary glands
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Explain why Osmoregulation is a homeostatic mechanism
Stimulus: low water potential in the blood
Receptor: osmoreceptors in hypothalamus
Co-ordinatior: hypothalamus
Effector: pituitary gland (releases the hormone)
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What is the effector in a homeostatic mechanism usually?
A gland or a muscle
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Can we live healthily with one kidney? How do you know?
Yes
People often donate one of their kidneys as kidney donors
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What can a kidney do if there’s only one healthy kidney?
Can grow in size in order to work as hard as 2 kidneys
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Why will treatment be needed if both kidneys fail?
To balance fluids
To remove waste
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Reasons for kidney failure
Bacterial disease
Injury
Inherited condition (kidneys may get worse with age)
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List the different cations taken against kidney failure
-medication taken to control blood potassium and calcium levels (kidneys normally do this)
-low protein diet —> will reduce the need for deamination in the liver and less urea will be produced
-drugs taken to reduce blood pressure
-dialysis and a kidney transplant
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Why is medication taken during kidney failure?
To control blood potassium and calcium levels, which kidneys usually do
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What type of diet are those with kidney failure expected to go on and why?
Low protein
Will reduce the need for deamination in the liver + less urea will be produced
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What does a haemodialysis column do?
Gets rid of excess water from the blood like kidneys would
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What is the rest of the machinery apart from the haemodialysis column, used during haemodialysis, used for?
As a sophisticated pump that pumps blood from the arm of the patient to the haemodialysis column and back into the patient’s body
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Dialysis fluid name
Dialysate
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Purpose of dialysate during haemodialysis
Pumped through the machine and through the column to remove waste from the body, which diffuses into the dialysate
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Haemodialysis
When a dialysis machine removes waste products and excess salts form the blood
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Where is blood taken from during dialysis?
An artery in the arm
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Where does blood travel through once it’s been taken from an artery in the arm during haemodialysis?
Is passed through thousands of long narrow strands of selectively permeable dialysis tubing
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What are dialysis fibres surrounded by?
Dialysis fluid
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Where do waste products pass from and to during haemodialysis and how?
Out of the blood plasma, through the pores in the dialysis tubing, into the dialysis fluid
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How is clean blood returned to a patient during haemodialysis?
Through a vein
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How frequently is haemodialysis carried out?
3 days a week, with each session lasting 4 hours
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why does each haemodialysis session have to last 4 hours?
To allow the whole volume of blood in the body to pass through to complete dialysis
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What else diffuses into dialysis fluid apart from waste and why?
Water to remove excess water from the blood to avoid oedema
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What does dialysis fluid leave the top of the haemodialysis column with?
Waste and excess water from the blood
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What are the ways in which a dialysis machine makes filtration more efficient?
Counter current flow between blood and dialysis filter through the haemofilter
Dialysis fluid is continuously replaced
Blood flows through hundreds of thin, hollow membrane fibres
Temperature at about 40 degrees Celsius
Dialysis fibres made out of a semi-permeable membrane
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Why is the counter current flow between blood and dialysis fluid important?
Ensures that the concentration gradient of urea between blood and dialysis fluid is maintained along the length of the filter
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Why is dialysis fluid continuously replaced during haemodialysis?
To maintain a steep concentration gradient
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Why is it beneficial that blood flows through hundreds of thin, hollow membrane fibres during haemodialysis?
Provides a large surface area for dialysis to occur
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Why is a temperature of about 40 degrees used during haemodialysis?
Maximum possible
Higher than body temperature
Prevents temperature shock
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Why is it important that dialysis fibres are made out of a semi-permeable membrane?
Large enough for urea to diffuse out
Too small for proteins + blood cells to leave the blood
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What does a patient have to do when kidneys fail?
Undertake dialysis regularly
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Why can someone be forced to undertake dialysis for the rest of their life?
Since there’s a shortage of kidneys for kidney transplants
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What do the mitochondria in the cells of the proximal convoluted tubule do?
Produce ATP for active transport (not energy)
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What is the most toxic type of nitrogenous waste and what needs to be done therefore?
Ammonia
Needs to be diluted
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What needs the least amount of water for excretion - ammonia or urea?
Urea
331
When is the most amount of water lost - with urea or ammonia?
Ammonia
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What can be stored the best- ammonia or urea and why?
Urea
Less toxic
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What does ADH do in terms of aquaporin?
Makes *more* aquaporin insert into the membrane
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What are we describing everything occurring on when explaining the effects of ADH?
The *membrane* of the collecting duct
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what type of gland is the posterior lobe of the pituitary gland?
endocrine gland
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endocrine gland
secretes the hormone directly into the blood
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exocrine gland
secretes hormones via a duct
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where in the brain is the pituitary gland?
the base
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give the negative feedback loop of osmoregulation
stimulus = different water potential levels in the blood
detector = osmoregulators in the hypothalamus
coordinator = hypothalamus
effector = posterior lobe of the pituitary gland
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key word when talking about osmoregulation
negative feedback
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what does the rate of water réabsorption into blood depend on?
water potential gradient
number of aquaporins
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What does ADH do in terms of aquaporin?
Inserts *more* aquaporin into the membrane
