5.1&5.2 Flashcards
What do all living organisms need to maintain
A certain limited set of conditions in cells including temperature, pH, aqueous environment, no toxins and inhibitors
What happens when cells optimum condition isn’t maintained
Cells become inactive and die
What does it mean that multicellular organisms have specialised cells
Each cell relies on each cell, so they must communicate to coordinate their activity
What is the external environment of organisms
The constantly changing environment either air, water or soil
What stresses does a cold environment place on an organism
Greater heat loss
How does an organism counter cold conditions to stay active and alive
Changes in environment are monitored and organism changes its behaviour/physiology to reduce stress
What is environmental change to an organism
A stimulus and way in which organisms must change its behaviour/physiology is its response
What response is elicited if the environment changes slowly like between seasons
Gradual response
Give an example of a gradual response
Artic fox has thicker white coat in winter and thinner brown coat in summer, change in coat provides more insulation and camouflage in winter so it survives and in summer thin coat means it doesn’t over heat
Is everything in multicellular organisms exposed to the external environment
Not many tissues and cells exposed to external environment, they are protected by epithelial tissues and organs
What is the cell environment
Tissue fluid which bathes internal cells and tissues
What happens as metabolic reactions occur in cells
They use up substrate and create new products which can create unwanted bi-products which are toxic and these are moved out into the tissue fluid, so activity of cells alter their own environment
What happens as waste products build up in tissue fluid
May reduce cells activity so less waste produced but this response may not be good for whole organism
What is composition of tissue fluid maintained by
Blood, blood flows throughout body and transports substances to and from cells, waste/toxins accumulating in tissue fluid enter blood and carried away to prevent their accumulation in blood they are removed from body by excretion
Why is it important concentrations of waste products and substances in blood monitored closely
Ensures body doesn’t excrete too many useful substances but removes enough waste to maintain good health and that cells in body given substrate they need
Is multi or single celled organisms more efficient
Multicellular as it’s cells are differentiated so specialised cells can perform certain functions
What do groups of specialised cells performing a certain function become
Tissues and organs
Where may cells that monitor the blood be found
In different body part away from waste product and far from tissue or organ specialised to remove waste
What does a good communication system require
Go check these different parts of the body work together effectively
What are the features of a good communication system
Cover whole body, enables cells to communicate with each other, enable specific communication, enable rapid communication, enable long and short term responses
How do cells communicate with each other
By process of cell signalling
What is cell signalling
A process where one cell releases a chemical that’s detected by another cell, 2nd cell responds to signal released from 1st cell
What are the 2 major communication systems that rely on cell signalling
Neuronal system and hormonal system
What is the neuronal system
An interconnected network of neuronal that signal to each other across synapse junctions, neurones can conduct signals very quickly and enable rapid responses to stimulate that may be changing quickly
What is the hormonal system
System that uses blood to transport its signals, cells in endocrine system release signal (hormone) directly into blood , hormone is transported throughout body but only recognised by specific target cells, hormonal system enables longer-term responses to be coordinated
What must cell signalling molecules be to cell surface receptor
Complementary
What is homeostasis
Used in many living organisms to maintain conditions inside the body despite changes from external and internal factors
What aspects are maintained by homeostasis
Body temp, blood glucose concentration, blood salt concentration, water potential of blood, blood pressure, CO2 concentration
What does response to changes in the environment require
Requires complex mechanisms which may involve a series of tissues and organs that are coordinated through cell signalling
What is the standard response pathway to change in environment
Stimulus->receptor->communication pathway(cell signalling)->effector->response
What is needed for a response pathway to work
Number of specialised structures
What are the different aspects needed in a response pathway
Sensory receptors like temp receptor, on surface of skin, monitor changes in external environment, other receptors interns to monitor changes inside body, when 1 receptor detects change it sends message to effector (hormonal/nervous communication system), this acts by signalling between cells and transmuting message from receptor to effector via coordination centre (brain)
What is known as input and what’s output
Input-message from receptor to coordination centre, output-messages sent to effectors
Examples of effectors
Liver and muscle cells which bring about a response
What is feedback
When effectors respond to output from coordination centre, they bring a response that will change body internal conditions, these changes detected by recovers and had effect upon response pathway, so input changes known as feedback
How is constant internal environment maintained
Any change away from optimum must be reversed so conditions in body return to optimum
What is negative feedback
Bringing conditions back to optimum after a change
What happens when conditions change in negative feedback
Receptor detects stimulus and sends input to coordination centre which send output to effectors and effectors respond to output
What happens when effectors bring about a change that reverses initial change in negative feedback
System moved closer to optimum and stimulus reduced, receptors detect reduction in stimulus and reduce input to coordination centre, output to effectors is also reduced so effectors reduce their activity, as system gets closer to optimum response is reduced
What is the negative feedback loop
Optimum condition->change away from optimum ->receptor detects change ->(input) ->communication system informs effectors->effectors react to reverse change->returns to optimum condition->optimum condition
Give an example of negative feedback
If temp rises too high in the body, response is to do something that brings body temp back to optimum resulting in stimulus reducing
What is the negative feedback loop for body temp
If temp rises:thermo-regulatory centre in hypothalamus detects change->nervous and hormonal system carry signal to skin, liver and muscles->less heat generated and more lost->temp too low: thermo-regulatory centre in hypothalamus detects change->nervous and hormonal system carry signal to skin, liver and muscles->more heat generated and less lost
3 steps for negative feedback to occur
1.change in internal environment must be detected 2.change must be signalled to other cells 3.must be an effective response that reverses change in conditions
Do negative feedback keep conditions 100%constant
Fairly constant but always some variation around the optimum
Why does negative feedback not keep same exact conditions
When stimulus occurs may take time to respond and responds may cause to much change but as long as conditions not too varied it remains acceptable
Why are negative feedback systems needed for temp control
To keep body warm enough for enzymes and cool enough to not damage proteins
Is positive or negative feedback more common
Negative
What is positive feedback
Response to increase the original change which destabilises system and usually harmful
Give an example of positive feedback (bad)
Below certain core temp enzymes less active and exergonic reactions are slower and release less heat, allowing body to cool more and slows enzymes controlled reactions more causing body temp to spiral down
Give an example of positive feedback (good)
At end of pregnancy to bring about cervix dilation, as cervix begins to stretch it causes posterior pituitary glands to secrete hormone oxytocin which increases uterine contractions which stretch cervix more causing more oxytocin secretion, once cervix fully dilated, baby can be born, birth ends oxytocin production, neurones also rely on positive feedback
What is the positive feedback loop
Optimum condition->change away from optimum->receptor detects change->(input)communication system informs effects->(output)effector reacts to increase change->change away from optimum
What effects does increases core temp have on body
Molecules have more kinetic energy, move quick and collide often, so essential chemical reactions occur quicker, affects structure of proteins (denature if temp too high), enzymes are globular w specific tertiary structure giving them specific 3D shape (complementary to substrate)
Why are some enzymes very temp sensitive
If body temp drops by 10degreesC some rate of enzyme controlled reactions half
What maintains heat in the body
Cellular reactions releasing heat but if temp drops reactions slow and less heat released allowing body to cool further (positive feedback), as body cools organism functions less
What is the difference between external and internal parts of the body
Core temp important as organs found in the centre, but external parts of body can change temp without effecting organisms overall survival
What are endotherms
Control their body temp within narrow limits and use variety of mechanisms to control body temp and largely independent of external temp
What are ectotherms
Can’t control body temp as effectively as endotherms, they rely on external sources of heat and body temp changes with external environment but using various behavioural mechanisms, some ectotherms can control their body temp in all but extreme conditions
What don’t ectotherms use to maintain their body temp
Don’t use internal energy sources to maintain body temp when cold but when active their muscles contract to generate heat from increased respiration
What does temp regulation in ectotherms rely on
Behavioural responses that alter heat exchange with environment
What happens if ectotherms too cold
They absorb heat from environment by moving to sunny area, lie on warm surface, expose large SA to sun
What do ectotherms do if they’re too hot
Avoid gaining heat by moving to shade, move underground, reduce body SA exposed to sun
What are advantages of ectotherms
Don’t use up energy to keep warm, so less food used in respiration and more energy gained from food used for growth, need to find less food, can survive long periods without food
Disadvantages of ectotherms
Less active in cold temps so at risk from predators whilst cold and unable to escape, can’t make use of available food while they’re cold
What are 2 examples of ectotherms and their adaption
Adder:(behavioural adaptation)lays in sun beside vegetation to absorb direct heat from sun, Horned lizard:(behavioural adaptation)can change shape by expanding/contracting ribcage increasing SA exposed to sun so more heat absorbed
What are endotherms
Use physiological and behavioural adaptations to control body temp and not environment
What does temp regulation rely on
Effectors in skin and muscles, as skin is organ in contact w environment many physiological adaptations to control body temp involves skin
What do changes taking place at skin alter
Amount of heat lost to environment
What is an exergonic reaction and where do many occur
Release energy in form heat, many exergonic chemical reactions occur in human body
What can endotherms do to stay warm
Increase respiration (exergonic) in muscles and liver to release heat using their energy intake to stay warm
What other physiological adaptations do endotherms have
Directing blood towards or away from skin to alter amount of heat lost to environment
What are the physiological adaptations of skin when endotherms too hot
Sweat glands secrete fluid onto skin surface as it evaporates it uses heat from blood as latent heat of vaporisation, hairs lie flat to reduce insulation and allow greater heat loss, vasodilation of arterioles and precapillary sphincters direct blood to skin surface so more heat radiated away from body
What are the physiological adaptations of skin when endotherms too cold
Less sweat secreted so less evaporation means less heat loss, hairs stand erect to trap hair which insulates the body, vasoconstriction of arterioles and precapillary sphincters leading to skin surface, blood diverted away from surface of skin and less heat lost
What are the physiological adaptations of gaseous exchange system when endotherms too hot/cold
Hot-some animals pant, increasing evaporation of water from surface of lungs and airways, evaporation uses heat from blood as latent heat of vaporisation- cold-less panting so less heat lost
What are the physiological adaptations of liver when endotherms too hot/cold
Hot-less respiration occurs so less heat released, cold-increase respiration in liver cells means more food energy converted to heat
What are the physiological adaptations of skeletal muscles when endotherms too hot/cold
Hot-fewer contractions so less heat released, cold-spontaneous muscle contractions (shivering) to release heat
What are the physiological adaptations of blood vessels when endotherms too hot/cold
Hot-dilation to direct blood to extreme do more heat lost, cold-constriction to limit blood flow to extremities, so blood not cooled too much (can lead to frostbite)
What are the behavioural adaptations of endotherms when too hot
Move to shade, move body to reduce SA exposed to sun, remain inactive and spread limbs out to allow greater heat loss, wet skin to use evaporation to cool body
What are the behavioural adaptations of endotherms when too cold
Lie in sun, increase SA of body exposed to sun, move to generate heat in muscles or curl in ball to reduce SA and heat loss, remain dry
Advantages of endotherms
Can maintain constant body temp despite external environment, remains active in low external temp so take advantage of prey and escape predators, inhabit colder parts of planet
Disadvantages of endotherms
Use a lot of their energy to maintain body temp, need more food, low proportion of food and nutrient energy used for growth and many overheat in hot weather
What detects temp change in endotherms and what happens after
Receptors in hypothalamus detect change in temp and send out different impulses to reverse change, some receptors quick to prevent further temp change (neural system transmits output from hypothalamus to make response rapid) other responses are long term (hormonal system)
What will hypothalamus bring about if core body temp too low
Change in skin to reduce heat loss, release heat via muscle contractions, increase metabolic to release heat form exergonic reactions
What will hypothalamus bring about if core body temp too high
Change skin to increase heat loss, less muscle contractions, decreased metabolism (example of negative feedback)
What monitors blood temp and detects change in core body temp
Thermoegulatroy centre in hypothalamus
What receptors can detect temp change early to counter it
Peripheral temp receptors in skin as extremities get cooler before the core of the body
What happens if thermoregultary centre signals to brain external environment is too hot/cold
Brain can initiate behavioural mechanisms for maintaining body temp live moving into shade
What is excretion
Removal of metabolic waste from body
What products are excreted
All products formed in excess by chemical processes occurring in cells so they don’t build up and inhibit enzyme activity or become toxic
What are the main excretory products
CO2 from respiration, Nitrogen containing compounds like urea and bile pigments found in faeces
What are the excretory organs
Lungs, liver, kidneys, skin
How is the lungs an excretory organ
Every cell in body produces CO2 due to respiration, CO2 passes from respiring cells to bloodstream where transported most in form of hydrogencarbonate ions to lungs, in lungs CO2 diffuses to alveoli to be excreted as we exhale
How is the liver an excretory organ
Directly involved in excretion, has many metabolic roles and some substances produced passed to bile for excretion with faeces like pigment bilirubin, liver also converts excess amino acids to urea, amino acids broken down in process of deamination, nitrogen containing part of molecule then combines with CO2 to make urea
How is the kidneys an excretory organ
Urea passed to bloodstream to be transported to kidneys, urea transported in solution (dissolved plasma) in kidneys urea removed from blood to become part of urine, urine stored in bladder before excreted via urethra
How is the skin an excretory organ
Excretion not primary function but sweat containing substances like salts, urea, water, uric acid and ammonia. Urea, uric acid and ammonia are all excretory products, loss of water and salts important in homeostasis (maintains body temp and water potential of blood)
Why is it fatal to let metabolic products to build up
Some products like CO2 and ammonia are toxic, they interfere with cell processes by altering pH, so normal metabolism prevented, other metabolic products can act as inhibitors and reduce essential enzyme activity
What is the order head downwards of lungs, kidneys, urethra, bladder, ureter and liver
Lungs-liver-kidney-ureter-bladder-urethra
How is most CO2 transported in blood
As hydrogencarbonate ions, this also forms hydrogen ions
What is the equation for the production of hydrogencarbonate ions
CO2 + H2O -> H2CO3 (carbonic acid), carbonic acid then dissociates to release hydrogen ions. H2CO3 -> H+ + HCO3-
Where does the production of hydrogencarbonate ions occur and with the help of what
Occurs in red blood cells under enzyme carbonic anhydrase but also occurs in blood plasma
What can hydrogen ions effect and how
pH of cytoplasm in red blood cells, hydrogen ions interact with bonds in haemoglobin, changing its 3D shape reducing affinity of haemoglobin for oxygen and affecting oxygen transport
What happens to hydrogen ions in red blood cells to ensure they don’t effect oxygen transport
They combine with haemoglobin to form haemoglobinic acid
What happens to CO2 that’s not directly converted to hydrogencarbonate ions
Combines directly with haemoglobin to form carbaminohaemoglobin
What do haemoglobinic acid and carbaminohaemoglobin have in common
Both unable to combine with oxygen which reduces oxygen transport further
How does excess hydrogen ions in blood plasma effect blood plasma and how is this combatted
Excess hydrogen ions reduce pH of plasma and maintaining plasma pH is essential as changes could alter structure of proteins in blood that help transport substances around the body but proteins in blood act as buffers to resist pH change
If change of pH due to excess hydrogen ions in blood plasma is small what happens
Extra hydrogen ions detected by respiratory centre in medulla oblongata in brain causing an increased breathing rate to help remove excess CO2
What happens when blood pH drops below 7.35
Can cause headaches, drowsiness, restlessness, tremors and confusion, also rapid heart rate and changes in blood pressure (respiratory acidosis)
What can cause a lowering in blood pH
Disease or lung conditions like emphysema, chronic bronchitis, asthma, severe pneumonia, blockage of airway due to swelling, foreign object or vomit can also induce acute respiratory acidosis
What does the body do with excess amino acids as they can’t store them
Amino acids have almost as much energy as carbohydrates, so, wasteful to excrete amino acids, instead they’re transported to the liver and deaminated
What do the amino groups initially form after deamination and then what happens
Very soluble and highly toxic compound, ammonia which is then converted to less soluble and toxic compound, urea which is transported to kidneys for excretion
What happens to the deaminated amino acid
It becomes keto acid which is used directly in respiration to release energy or converted to carbohydrate or fat for storage
What is the deamination equation
Ammonia+carbon dioxide-> keto acid + ammonia
What’s the equation for formation of urea
Ammonia+ carbon dioxide -> urea + water
/2NH3 + CO2 -> (NH2)2CO + H2O
What are liver cells called
Hepatocytes
What do hepatocytes do
Carry out 100s of metabolic processes
What does liver have an important role in and what does this mean
In homeostasis, so it’s essential liver has good blood supply
What does livers internal structure ensures
As much blood as possible flows past as many hepatocytes as possible, enables hepatocytes to remove excess substances form blood and return substances to blood to ensure concentrations are maintained
What 2 sources supply liver with blood
Hepatic artery and hepatic portal vein
How does the hepatic artery supply liver with blood
Oxygenated blood from heart travels from arrow via hepatic artery to liver
What does the hepatic artery supply the liver with
Oxygen for aerobic respiration, liver cells very active as they do many metabolic processes, many processes require ATP so important to have good supply of oxygen for respiration
How does the hepatic portal vein supply liver with blood
Deoxygenated blood from digestive system enters liver via hepatic portal vein
What does the hepatic portal vein supply the liver with
Rich with digestive products, concentrations of various substances uncontrolled as entered body from digestive products in intestines and blood may also contain toxic compounds absorbed from intestines (important these substances don’t circulate body until their concentration adjusted)
Where does blood leave liver from
Via hepatic vein which rejoins inferior vena cava and blood returns to body’s normal circulation
What is the 4th vessel connected to the liver
Bile duct
What is bile
A secretion from the liver which has function in digestion and excretion
What does the bile duct do and what is role of bile
Carries bile from liver to gall bladder where urs stored till required to aid fat digestion in small intestines, bile also contains some excretory products like bile pigment bilirubin which leaves body with faeces
What is important about liver structure
That cells, blood vessels and chambers arranged to get greatest amount of contact between blood and liver cells
How is the liver divided
Into lobes which are further divided into lobules, lobules are cylindrical
What happens as hepatic portal vein and hepatic artery enter liver
They split into smaller and smaller vessels, these vessels run between and parallel to lobules and known as inter lobular vessels
What enters the lobules
At intervals branches from hepatic artery and hepatic portal vein enter lobules
What happens with the blood from the hepatic portal vein and hepatic artery enter the lobules
The 2 blood vessels mix and pass along a special chamber called sinusoid which is lined with liver cells
What happens as blood flows along sinusoid
It’s in close contact with liver cells, these cells able to remove substances from blood and return other substances to blood
What are Kupffer cells
Specialised macrophages move about with sinusoids, there primary function appears to be breakdown and recycling of old red blood cells
What is a product of red blood cel breakdown
Bilirubin
Where does the bile made to the liver go
Released into bile canaliculi which joins together to form bile duct which transports bile to gall bladder
What happens when blood reaches end of sinusoid
Concentrations of many components have been modified and regulated
What is at the centre of each lobule
A branch of the hepatic vein known as intra-lobular vessel
What happens at intra-lobular vessel
Sinusoids empty into this,
What joins to form hepatic vein and what’s hepatic veins function
Branches of hepatic vein, from different lobules, join together to form hepatic vein, which drains blood form liver
What is the structure of liver cells (hepatocytes)
Appear unspecialised, they have simple cuboid shape with many microvilli on surface
What is the function of hepatocytes
Many metabolic functions include protein synthesis, transformation and storage of carbohydrates, synthesis of cholesterol and bile salts, detoxification and many other processes
What does hepatocytes function mean about their cytoplasm
Cytoplasm must be very dense and specialised in number of certain organelles it contains
What functions does the liver carry out
Control of blood glucose, amino acid and lipid levels, synthesis of bile, plasma proteins and cholesterol, synthesis of red blood cells in foetus, storage of vitamins A,D and B12, iron, glycogen, detoxification of alcohol and drugs, hormone breakdown, destruction of red blood cells
What form does liver store sugars as
Glycogen
How much glycogen can liver store
100-120g which is 8%of weight of fresh liver
What does glycogen form in hepatocytes and what is glycogen broken down to
Forms granules and glycogen broken down to release glucose into blood as required
What are examples of substances the liver must detoxify
Hydrogen peroxide produced in the body, alcohol consumed as part of our diet pr drugs/medicines take for health or recreational use
How are toxic substances rendered harmless in liver
By oxidation, reduction, methylation or combination with other molecules, liver cells contain many enzymes that make them less toxic
What is role of catalase in liver
Converts hydrogen peroxide to oxygen and water, catalyse has high turn over number
What is cytochrome P450 role in liver
A group of enzymes used to breakdown drugs including cocaine and various medicinal drugs, also used in other metabolic reactions like electron transport in respiration, their role in metabolising drugs can interfere with other metabolic roles and cause unwanted side effects of some medicinal drugs
What does alcohol do to nerve activity and respiration
Depresses nerve activity, also contains a chemical potential energy used for respiration
How is alcohol broken down in hepatocytes
Broken down by enzyme dehydrogenase, resulting compound is ethanal which is dehydrogenated further by ethanal dehydrogenase to produce final product of acetate which combines with CoA to form acetyl CoA which enters aerobic respiration
What happens to hydrogen atoms released from alcohol
They combine with coenzyme NAD, to form reduced NAD
What is the equation for the breakdown of alcohol in the liver
Ethanol->(ethanol dehydrogenase and reduced NAD)->ethanal->(ethanal dehydrogenase and 2 reduced NAD)-> Ethanoic acid->acetyl CoA->respiration
What is required to oxidise and breakdown fatty acids needed for respiration
NAD
What happens when liver has to detoxify too much alcohol
It uses up NAD stores and has insufficient amount left to deal with fatty acids, these fatty acids then convert back to lipids and stored as fat in hepatocytes causing liver to become enlarged, known as fatty liver which causes alcohol related hepatitis or cirrhosis
Why can’t we store excess amino acids
Amino group makes them toxic
Why is it wasteful to excrete amino acids and so what happens
They contain a lot of energy so it’s wasteful, so excess amino acids undergo treatment in liver to remove and excrete amino components
What is the 2 processes of breaking down amino acids in liver
Deamination followed by ornithine cycle
What is the equation to remove and excrete amino components
Amino acid->(deamination)->ammonia+keto acid->(ornithine cycle)->urea
What does deamination do
It removes amino group and produces ammonia
What is the issue with production of ammonia in liver
It’s very soluble and toxic so it can’t accumulate,
What product does deamination also produce
Organic compound, keto acid, which enters respiration directly to release its energy
What is the equation of the breakdown of amino acids in liver
amino acid+oxygen->keto acid + ammonia
What must happen to ammonia due to its toxicity
Must be converted to less toxic form very quickly
What happens in ornithine cycle
Ammonia and CO2 combine with amino acids to form urea
What is the ornithine cycle in detail
Ammonia and CO2 combine with amino acid ornithine to produce citrulline which is converted to arginine by addition of further ammonia, arginine then reconverted to ornithine by urea removal
Why does ammonia turn to urea and then what happens to urea
as it’s less soluble and toxic than ammonia so can be passed back to blood and transported to kidneys, in kidneys urea filtered out of blood and concentrated in urine which is stored in bladder till released from body
What is the equation for ornithine cycle
Ammonia+CO2 -> urea+water
How many kidneys do we have and where are they located
2 kidneys 1 each side of spine just below lowest rib
Where do the kidneys get blood from and where does it leave from
Renal artery and leave from renal vein
What is kidneys role
Excretion, kidneys remove waste products from blood and produce urine
Where does urine pass down Out of kidneys and to what
Passed down ureter and goes to bladder where it’s stored before release
What surrounds the kidneys
A tough capsule
What is the outer, middle and inner region of kidney called
Capsule, cortex, medulla
What is the centre that leads to the ureter in the kidney called
Pelvis
What does the bulk of each kidney have
Small tubules called nephrons, each kidney has around 1m nephrons
Where does each nephron start
In Cortex at cup shaped structure called bowmans capsule
What is the remainder of the nephron after bowmans capsules
A coiled tube that passes through cortex, forms loop down to medulla and back to cortex before joining a collecting duct that passes back down medulla
What does the renal artery split into
Many afferent arterioles which each lead to capillaries called glomerulus
Where does the blood go from the glomerulus
Continues to efferent arteriole which Carries blood to more capillaries surrounding the rest of the tubule and these capillaries flow into renal vein
What is each glomerulus surrounded by and what process occur here
Bowmans capsule, fluid from blood pushes into Bowmans capsule by process of ultrafiltration
How does ultrafiltration work
The filter is the barrier between blood in capillaries and lumen of Bowmans capsule, barrier consists of 3 layers all enabling ultrafiltration
What is the first layer of ultrafiltration and how does it filter
Endothelium of capillary-narrow gaps in endothelium of capillary wall, endothelial cells have pores called fenestrations allowing blood plasma and substances dissolved in it to pass out of the capillary
What is the second layer of ultrafiltration and how does it filter
Basement membrane-consists of fine mesh of collagen fibres and glycoproteins, mesh acts as filter to prevent passage of molecules with relative molecular mass above 69000, so lost proteins and all blood cells stay in capillaries of glomerulus
What is the last layer of ultrafiltration and how does it filter
Epithelial cells of Bowmans capsule (podocytes)- have specialised shape, have finger like projections called major processes and on each major process is a foot process that holds cells away from capillary endothelium, projections ensure gaps between cells, fluid from blood in glomerulus can pass between these cells into lumen of Bowmans capsule
What does Bowmans capsule lead to
Rest of the tubule which has 3 parts
What are the 3 parts of the tubule after Bowmans capsule
Proximal convoluted tubule, loop of Henle, distal convoluted tubule
What does fluid from many nephrons enter and where does that go
Enters collecting ducts which pass down medulla to pelvis at kidneys centre
What is in a nephron
Afferent arteriole to glomerulus to efferent arteriole, at glomerulus ultrafiltration to Bowmans capsule which goes to proximal convoluted tubule then descending loop of Henle moving from cortex to medulla and then ascending loop of Henle back to cortex, then distal convoluted tubule to collecting duct
What is ultrafiltration
Filtering of blood at a molecular level
How does ultrafiltration work
Blood flows into glomerulus through afferent arteriole which is wider than efferent arteriole that carries blood away from glomerulus, difference in diameters ensures blood in glomerulus maintains higher pressure than bowmans capsule, pressure difference pushes fluid from blood to bowmans capsule surrounding glomerulus
What is filtered out of blood in ultrafiltration
Blood plasma containing dissolved substances pushed under capillary pressure to bowmans capsules lumen, blood plasma contains water, amino acids, glucose, urea, inorganic mineral ions
What does concentration of dissolved solutes in blood depend on
Water balance in organism
How much glucose and amino acids found in urine and protein
0.0g dm-1 and almost 0 protein
What is left in capillaries after ultrafiltration and what does this mean
Blood cells and proteins, proteins means negative water potential in blood which ensures some fluid retained in blood containing some water and dissolved substances
Why is very low water potential needed in blood at capillaries
Helps reabsorb water at later stage
What happens to the composition of the filtrate as it passes along tubule from bowmans capsule
Altered by selective reabsorption, substances absorbed back to tissue fluid and blood capillaries surrounding nephron
What happens in proximal convoluted tubule
Filtrate altered by reabsorption of all sugars, most mineral ions and some water, 85% of fluid reabsorbed here and cells of tubule have highly folded surface to increase SA
What happens in descending loop of Henle
Water potential of fluid decreased by action of mineral ion and water removal
What happens in ascending limb of loop of Henle
Water potential increased as mineral ions removed by active transport
What happens in collecting duct
Water potential decreased by water removal, final product in collecting duct is urine, process ensures urine has low water potential so urine has higher concentration of solutes than in blood and tissue fluid, urine passes to pelvis and down ureter to bladder
What does reabsorption involve
Involves active transport and cotransport, cells lining proximal convoluted tubule specialised to achieve reabsorption
How are proximal convoluted tubule specialised to achieve selective reabsorption
Cell surface membrane in contact with tubule fluid is highly folded into microvilli which increase SA for reabsorption, cell surface membrane also contains special cotransporter proteins that transport glucose of amino acids, in association with sodium ions from tubule to cells
What is the structure of the cell surface membrane in proximal convoluted tubule that’s close to tissue fluid and blood capillaries
Also folded to increase SA, membrane contains sodium-potassium pumps that pump sodium ions out of cell and potassium ions into cell, cell cytoplasm has many mitochondria indicating an active process is involved
How are glucose and amino acids selectively reabsorbed
By movement of sodium ions and glucose into cells driven by concentration gradient created by pumping sodium ions out of cell
How do sodium ions move into cell after they have been pumped out in reabsorption
By facilitated diffusion but as they move in the cotransport glucose and amino acids against their concentration gradient known as secondary active transport
What does the movement of glucose and amino acids out of tubule to these cell mean for the water potential in cells
It lowers the water potential of the cell meaning water from the tubule also leaves tubule by osmosis
What happens to larger molecules like small proteins that may have entered tubule
They can be reabsorbed by endocytosis
Where does selective reabsorption occur
Proximal convoluted tubule
What does the loop of Henle consist of
A descending limb that goes into medulla and ascending limb that goes back to the cortex
What does the arrangement for loop of Henle allow
Mineral ions (Na+Cl ions) to be transported from ascending limb to descending limb, overall effect to increase concentration of mineral ions in tubule fluid which has similar effect upon concentration of mineral ions in tissue fluid, giving medulla tissue fluid very low water potential
What happens as mineral ions enter descending loop of Henle
Concentration of fluid rises meaning water potential decreases and becomes more negative further descending limb goes to medulla
What happens as fluid rises up ascending limb
As base Mineral ions leave fluid by diffusion but higher up limb active transport used to move minerals out
What part of the ascending limb is impermeable to water
Upper portion
What is the effect of ionic movements in descending and ascending loop of Henle
Creates higher water potential in ascending limb and decrease water potential in medulla, water potential of tissue fluid becomes lower at bottom of loop of Henle
What happens as fluid passes down collecting ducts
Passes through tissue with decreasing water potential, so always a water potential gradient between fluid in collecting duct and that in tissue allowing water to move out of collecting duct and into tissue fluid by osmosis
What is the arrangement of the loop of Henle known as
Hairpin countercurrent multiplier system, overall arrangement is to increase efficiency of transfer of mineral ions from ascending limb to descending limb to create water potential gradient in medulla
From top of ascending limb where does the fluid go
Passes along short distal convoluted tubule where active transport used to adjust concentration of mineral ions, from here fluid flows to collecting duct but still has lots of water so high water potential
Where does collecting duct carry fluid to
Down through medulla to pelvis, tissue fluid in medulla has low water potential that gets even lower deeper into the medulla
What happens to water as tubule fluid passes down collecting duct
Water moves by osmosis from tubule fluid to surrounding tissue and then to blood capillaries by osmosis and it’s carried away
What does the amount of reabsorbed water depend on
Permeability of collecting duct wall
What is in urine by the time it reaches the pelvis
Very low water potential and concentration of mineral ions and urea is higher than in the blood
What happens to glucose during loop of Henle
It is all reabsorbed in the proximal convoluted tubule
What happens to sodium ions in loop of Henle
Diffuse into descending limb causing concentration to rise then pumped out of ascending limb so concentration falls
What happens to urea concentration in loop of Henle
Concentration rises as water withdrawn from tubule, urea also actively moved into tubule
Although sodium ions removed from tubule why does concentration still rise
Water is also removed from tubule and potassium ions increase concentration as water is removed, potassium ions actively transported to tubule to be removed in urine too
What is osmoregualtion
The control of water potential in the body
What does osmoregulation involve
Controlling levels of both salt and water in body
Why must correct water balance between cells and surrounding fluid be maintained
To prevent water entering cells causing lysis or leaving cells and causing crenation
What3 sources the the body gain water form and how is it lost
Food, drink and metabolism and lost by urine, sweat, water vapour in exhaled air and faeces
What does kidney act as to control water content of body and salt concentration of body fluid
An effector
On a cool day and u have drink lots of water what do kidneys produce
Large volume of dilute urine
On hot day and drunk little what do kidneys produce
Smaller volumes of more concentrated urine
How do kidneys alter volume of urine produced
By altering permeability of collecting duct wall, if need to conserve water collecting ducts more permeable and more water reabsorbed so smaller volume of urine, if don’t need to conserve water collecting duct less permeable and more urine produced
What do cells in collecting duct walls respond to in terms of becoming more or less permeable
Antidiuretic hormone (ADH) in blood
What do collecting duct membranes have for osmoregulation
Receptors for ADH
How does ADH work
Binds to receptor and causes a chain of enzyme-controlled reactions inside the cell like cell signalling, end result of these reaction is to cause vesicles containing water permeable channels (aquaporins) to fuse with cell surface membrane making walls more permeable to water
What happens when levels of ADH rise in the blood
More aquaporins inserted allowing more water to be reabsorbed by osmosis than in blood, less urine produced and has more negative water potential
What happens if levels of ADH fall in the blood
Cell surface membrane folds inwards to create new vesicle that removes aquaporins from the membrane making walls less permeable and less water reabsorbed by osmosis into blood, more water passes down collecting duct to form more urine with higher water potential
What does the hypothalamus contain
Specialised cells called osmoreceptors
How do osmoreceptors work
They’re sensory receptors that detect changes to water potential of blood, cells respond to effect of osmosis and shrink, as a result they stimulate neurosecretory cells in hypothalamus
What are neurosecretory cells
Specialised neurones that produce and release ADH, ADH manufactured in cell body which lives in hypothalamus
Where does ADH go after being secretared
Moved down axon terminal bulb into posterior pituitary gland where it’s stored in vesicles, when neurosecretory cells stimulated by osmoreceptors they carry action potentials down their axons and cause release of ADH any exocytosis
Where does ADH enter blood capillaries and where does it go from there
Enters through posterior pituitary gland and transported around the body and acts on cells of collecting ducts, once water potential of blood rises again less ADH is released
What is half life of ADH and what does this mean
20mins so once ADH in blood broken down, collecting ducts receive less stimulus and become less permeable
What is the negative feedback loop of control to bloods water potential
Increased water potential detected by hypothalamus->less ADH released from posterior pituitary gland-> collecting duct walls less permeable->less water reabsorbed to blood and more urine produced->decrease of water potential of blood (opposite of water potential too low in blood)
What happens if kidneys completely fail
They’re unable to regulate levels of water and electrolytes (substances that form charged particles in water) in body or remove waste products like urea in blood which quickly leads to detah
What are causes of kidney faliure
Diabetes mellitus (type 1/2 sugar diabetes), heart disease, hypertension and infection
What are the 2 treatments for kidney faliure
Renal dialysis and kidney transplant
How does renal dialysis work
Waste product, excess fluids and mineral ions removed from blood by passing it over partially permeable dialysis membrane allowing exchange of substances between blood and dialysis fluid, dialysis fluid contains correct concentrations of mineral ions, urea, water and other substances in blood plasma, any substances in excess diffuse into dialysis fluid and substances too low concentration diffuse into blood from dialysis fluid
What are the 2 types of renal dialysis
Haemodialysis, peritoneal dialysis
What is haemodialysis
Blood from artery or vein passed into machine that contains an artificial dialysis membrane shaped to form many artificial capillaries which cause increase SA for exchange, heparin added to avoid clotting, artificial capillaries surround dialysis fluid which flows opposite direction to blood (countercurrent) improving exchange efficiency, any bubbles removed before returned to veins
Where does haemodialysis happens
In a clinic 2/3 times a week for several hours each time, some patients do it at home
How does peritoneal dialysis(PD) work
Dialysis membrane in body’s own abdominal membrane (peritoneum), surgeon implants permeant tube in abdomen, dialysis solution poured through tube and fills space between abdominal walls and organs, after several hours used solution drains from abdomen
Where is peritoneal dialysis carried out
At home or work and patient can walk whilst having it and must be combined with carefully controlled diet
How does a kidney transplant work
Bets option for prolonging life for kidney failure, requires major surgery, surgeon implants new organ in lower abdomen and attaches to blood supply and bladder, patient given immunosuppressant to prevent immune system recognising new organ as foreign and rejecting it
4 advantages of kidney transplant over dialysis
Not time consuming, feel physically fitter, improved quality of life, improved self image
4 disadvantages of kidney transplant over dialysis
Must take immunosuppressive drugs, need major surgery, need regular checks for signs of infection, immunosuppressant side effects like high BP and susceptible to infection
Why can we detect some substances in urine
Substances with lower molecular mass than 69000 enter nephron, so any metabolic product or substance can pass to urine from blood if it’s small enough, if substances not reabsorbed further down nephron they’re detected in urine
What are example of things we can test for in urine
Glucose in diabetes diagnosis, alcohol for blood Alcohol in drivers, recreational drugs, hCG in pregnancy tests, anabolic steroids for doping in sport
Why do pregnancy tests work
Once embryo implanted in uterine lining it produces a hormone called hCG, it’s relatively small glycoprotein with molecular mass of 36700 and can be found 6days after conception, pregnancy testing kits use monoclonal antibodies which bind to hCG in urine
5 steps for how pregnancy tests work
1.urine poured onto test stick, 2.hCG binds to mobile antibodies attached to blue bead 3.mobile antibodies move down test stick 4.of hCG present it binds to fixed antibodies holding beads in place and blue lines form 5.mobile antibodies with no hCG attached bind to another fixed site show the test is working
What are anabolic steroids
Anabolic steroids increase protein synthesis in cells causing build up of tissue especially in muscles, they are controversial as they give sporting advantages and dangerous side effects and major sporting bodies ban them
How does testing for anabolic steroids work
Had life of 16hours and stay in body for many days, they’re relatively small molecules and easily enter nephron, testing involves analysis of urine in lab using gas chromatography
