homeostasis chp 15 Flashcards
what is homeostais
- maintenance of a dynamic internal equilibrium, with small fluctuations over a narrow range of conditions
what are effectors
- muscles and glands that react to motor stimuli to bring about a change
What is negative feedback
- when a response to a stimuli works to reduce the effect of the stimuli and restore conditions
what are some examples of where negative feedback is used in humans
- controlling blood sugar levels by insulin and glucagon
- temperature control
- water balance of the body
What is positive feedback
- when a response to a stimuli reinforces and increase the effect of stimuli
What is an example of positive feedback in humans
- clotting cascade,
- ^when a blood vessel is damaged, platelets stick to the damaged region
- ^they release factors that initiate clotting and attract more platelets.
- oxytocin production in child birth
what is thermoregulation
it is the maintenance of a relatively constant core body temperature to maintain optimum enzyme activity
what are ectotherms
- animals that use their surroundings to regulate their body temperature as they do not regulate internal body temperature via metabolic processes
- They are ‘cold blooded’
- ectotherm litrally means outside heat
what are endotherms
- They rely on metabolic processes to warm up and usually maintain very stable core temperature
- They are ‘warmed blooded’
- Endotherm litrally means inside heat
What would an ecto and endo therms body temperature look like on a body temp, external temp graph
How do ectotherms regulate temperature
Behavioural responses
- may bake in sun
^orientating their body so maximum surface area is exposed
^can extend parts of body to increase surface area further, - ^do opposite to cool down
- press body against warm things
- ^when cooling press into mud or water
- get warmer thanks to exothermic metabolic reactions , shivering
- ^also minimise movement to help cool down
How do ectotherms regulate temperature
physiological responses
- Lizards living in colder climates tend to be darker so they can absorb more heat, vice versa
- some ectotherms also alter their heart rates to increase or decrease their metabolic rate
out of ecto and endo therms which is more suseptible to fluctuations in temperature
ectotherms are always more vulnerable to fluctuations in environment that endotherms.
what is an advantage of being an ectotherm
- don’t have to eat as much as lower metabolic demand as use less energy regulating their temperature
Where are the temperature receptors located in humans
- external temp receptors found in skin
- internal receptors found in hypothalamus
What is humans core body temperature and to within what degree does the hypothalamus maintain this
37°C ± 1°C
How do endotherms regulate their internal temperatures
Behavioural
- sun-bathing
- press against hot surfaces
- dig burrows to heat up/cool down
- wallow in water and mud
- animals can hibernate/aestivation to get through cold/hot weather
How do endotherms regulate their internal temperatures
physiological
- Vasodilation/constriction
- increased/decreased sweating
- reducing/increasing the insulating effect of hair or feathers (the erector pileup muscles in the skin relax to cool and contract to warm)
- shivering (only to warm up)
How does vasodilation/constriction help to cool/heat
VASODILATION:
- arterioles near surface of skin dilate
- shunt vessels contstrict forcing blood to surface
- heat from blood radiation off
VASOCONSTRICTION
- shunt vessles dilate to allow blood to pass through them
- artieoles constict to reduce blood flow to skin surface
- amount of heat lost via radiation is reduced
How does reducing the insulating effect of hair or feathers help with cooling and heating
- erector pili muslces contract to heat body, as traps insulating layer of air to reduce heat loss via radiation
- erector pili muscles relax to cool as insulting layer not present
What is a common anatomical feature of endotherms that live in hot climates
- relatively large SA:V
^e.g. large ears, wrinkles - pale fur/feathers
How does shivering increase body temperature
- Shivering is the rapid, involuntary contracting and relaxing of large voluntary muscles in the body. The metabolic heat from the exothermic reactions warm up the body.
What are some anatomical adaptations of endotherms that live in cold climates
- smaller SA:V (reduces cooling by convection)
- thick layer of insulating fat underneath skin (blubber in whales and seals)
- hibernation
^build up fat stores, build well-insulated shelter, lower their metabolic rate so can pass winter
What are the 2 control centres that help to control thermoregulation, where are they found
- The heat loss centre
- The heat gain centre
- They are both found in the hypothalmus
What type of feedback takes place in the heat loss/gain centres
negative feedback
How does the hypothalumas actually regulate heat
- signals sent from heat receptors in skin to hypothalumas
- depending on temperature stims:
^vaso constriction/dilation
^onset of shivering/sweating
^increased/decreased metabolic rate
^raising/lowering of hair follicles
define excretion
The removal of the waste products of metabolism from the body
what are the main metabolic waste products in mammals
- carbon dioxide from cellular respiration
- Bile pigments via shit
- Nitrogenous waste products (urea), via urine
What arteries and veins supply and take blood away from the liver
- the hepatic artery supplys the liver with around 15% of al the blood supplied to the liver (it is oxygenated).
- The hepatic portal vein supplys around 75% of the blood the liver needs (This blood carries products of digestion straight from the intestines, so it can be used for metabolic activity in the liver).
- The hepativ vein takes the blood from the liver and sends it back to the heart
What are liver cells called
- Hepatocytes
What are the features of hepatocytes
- large nuclei
- prominent Golgi apparatus
- lots of mitochondria (this indicates they are very metabolically active)
- ^They divide and replicate rapidly (even if around 65% of the liver is lost, it will regenerate in months)
What occurs in sinusoids and where are they found
- found in liver surrounded by hepatocytes
- mixing of blood from hepatic artery and hepatic portal vein occurs in this space
What is the point in the mixing of blood within the sinusoids
The mixing increases the oxygen content of the blood from the hepatic portal vein, which supply hepatocytes with oxygen for their needs
What are kupffer cells, where are they found and what is their function
- Kupffer cells are found within the sinusoids
- They act as the resident macrophages of the liver, ingesting pathogens and protecting against disease.
What is the function of canaliculi
- Hepatocytes secrete bile from the breakdown of the blood into spaces called canaliculi,
- ^the bile then drains from these into bile ductules which takes it to the gall bladder
What are some of the main functions of the liver
- emulsification of lipids
- Deamination of excess amino acids
- Detoxification
- blood glucose level maintainence
How does the liver regulate blood glucose levels
hepatocytes can convert glucose to glycogen when stimulated to by inuslin
hepatocytes convert glycogen to glucose under the influence of the glucagon
What is transamination, why is it important
- The conversion of one amino acid into another
- Because the diet does not always contain the required balance of amino acids
What is deamination, why is it important
- The removal of an amine group from a molecule
- the body cannot store amino acids or proteins.
- and so if didnt undergo deamination whole molecule would go to waste
- Once the amine group is removed the remainder of the molecule can be used in cellular respiration or converted into lipids for storage
Once the amine group Is removed in deamination what happens to it
- It is first converted into ammonia then enters ornithine cycle to produce urea
Through what cycle is ammonia converted into urea
- It is converted in a set of enzyme controlled reactions called the ornithine cycle
What is meant by detoxification, and what is an example of it
making harmful substances harmless
- The liver detoxifies alcohol using alcohol dehydrogenase breaks down the ethanol to ethanal which can be used for respiration or fatty acid molecules
what occurs in cirrhosis of the liver
- Normal liver tissue is replaced by fibrous scar tissue
- ^Many hepatocytes die and can no longer divide and replace themselves, so the livers ability to deal with toxins decrease
- the most common cause of this is over consumption of alcohol
where are the kidneys found in the body
- Attached to the back of the abdominal cavity
- Usually surrounded by a thick, protective layer of fat and a layer of fibrous connective tissue.
- If you put your hands on your hips then your thumns will be around where your kidneys are
what is the function of the kidney
- excretion (especially urea but more things that just that)
- osmoregulation (maintain water balance and Ph of the blood and therefore the tissue fluid that surrounds all the cells)
what supples and takes blood away from the kidney
- Supplied with blood at arterial pressure by the renal arteries
- Blood is taken away from the kidney by the renal vein, which drains into the inferior vena cava
How much blood actually passes through the kidney
- All the blood In the body passes through the kidney once every hour
- It filters 180 dm^3 of blood a day
How much urine does the kidney produce a day
1-2 dm^3 a day
the final volume depends on many different factors
what makes up the majority of the kidney
- roughly 1.5 million nephrons make up each kidney
- They act as filtering units
- Each nephron is around 3 cm long
What connects the kidney to the bladder
The ureter
what is the bladder
- A muscular sac that holds urine ready for excretion
- it can store around 400-600 cm^3 of urine
Through what does the urine exit the body
Urine passes out the body down the urethra
what are the 3 main areas of the kidney you see after you’ve sliced it open
- The cortex (the dark outer layer)
- The medulla (is it lighter in colour)
- The renal pelvis (central part of kidney)
what is the cortex of a kidney
- This is where the filtering of blood takes place
- It has a very dense capillary network carrying the blood form the renal artery to the nephrons
What is the renal pelvis
- It is the central chamber of the kidney
- it is where the urine collects before passing out down the ureter
what is the medulla
- It contains the tubules of the nephrons that form the pyramids of the kidney and the collecting ducts
what is the function of the nephron
- Blood is filtered,
- ^the majority of the filtered material is returned to the blood, removing nitrogenous waste and balancing the mineral ions and water.
- They provide a massive surface area through which reabsorption can occur
what are the main structures of the nephron, list them in order of use (from blood waste to urine)
- Bowmans capsule
- proximal convoluted tubule
- loop of henle
- Distal convoluted tubule
- collecting duct
function and structure of bow-mans capsule
- cup-shaped structure
- contains glomerulus (a tangle of capillaries)
- filters large molcules out of blood
structure and function of proximal convoluted tubule
- first coiled region of tubule after Bowmans
- found in cortex of kidney
- where many substances needed by body are reabsorbed
structure and function of loop of henle
- long loop of tubule, creates region with very high solute concentration in tissue fluid in the medulla
- descending loop runs down the cortex through the medulla, bends at bottom, ascending limbs travels though medulla to the cortex
features of distal convoluted tubule
- second twisted tubule
- osmoregulation of blood takes place here
- maintainence of blood composition takes place (ion balance, Ph)
- permeability of walls depends of levels of ADH in the blood
structure and function of collecting duct
- urine passes down collecting duct through medulla to the pelvis
- further regulation of water potential takes place
- walls here are also sensitive to ADH
Where does the blood from the nephron go after it has been filtered, how can it diffuse back
- It flows back into network of capillaries surrounding the nephron, lead to the venule and to the renal vein
- maintain concentration gradient by constant blood flow through the capillaries
What are the features of blood after it has been cleaned by the kidney
- Greatly reduced level of urea
- levels of things such as glucose and amino acids are basically the same
- ^some glucose would be used during selective reabsorption
- mineral ion concentration is at ideal levels
what is ultrafiltration
- first stage of removal of nitrogenous waste and osmoregulation of the blood
- specialised form of process that results in formation of tissue fluid
where does blood enter and leave the glomerulus
- supplied with blood by relatively wide afferent (incoming) arteriole from the renal artery
- blood leaves through narrower efferent (outward) arteriole
- as a result blood in the glomerulus is under very high pressure
what does the high blood pressure in the glomerulus result in
- forces blood out through capillary wall, it acts like a sieve
structure of basement membrane
- made up of network of collagen fibres and other proteins
- make up second ‘sieve’
what can pass through the basement membrane
- platlets, water, salts, urea, amino acids, glucose
- blood cells, proteins cannot
what is the function of podocytes
- act as additional filter in the Bowmans capsule
- makes sure platelets or large plasma proteins that have gotten through glomerulus and basement membrane do not enter tubule
structure of podocytes
- have extensions called pedicels that wrap around capillaries
- ^this forms slits
once the fluid has passed the podocytes what does it contain
- Platelets
- Water
- Salts
- Urea
- Amino Acids
- Glucose
what is the volume of blood filtered through the glomerulus in a given time called
Known as the glomerular filtration rate
is the ultrafiltrate hypo, hyper or iso tonic compared to the blood plasma
hypotonic (less concentrated than)
what is the main function of the nephron after the blood has passed through the bow-mans capsule
- reabsorption of filtered substances back into blood
what is reabsorbed in the proximal convoluted tubule
- all the glucose, amino acids, vitamins and hormones are reabsorbed back into blood by active transport
- 85% of NaCl and water is reabsorbed
- ^Na+ ions move by active transport, Cl- ions and water move by osmosis
what adaptations do the cells lining the proximal convoluted tubule have
- covered with microvilli, greatly increasing surface area for reabsorption
- contain many mitochondria to provide ATP needed in active transport
is the filtrate at the loop of henle iso, hypo or hyper tonic compared to the tissue fluid surrounding the tubule and the blood
isotonic (same concentration) with both
at the loop of henle how much of the glomerular filtrate has been reabsorbed
- over 80% of the glomerular filtrate has been reabsorbed back into the blood
- remains the same regardless of the bodies condition
what does the loop of henle allow for
enables mammals to produce urine more concentrated than their own blood
what is the permeability of the descending limb of the loop of henle
permeable to water
what is the permeability of the descending limb of the loop of henle
- lower part is permeable
- upper part is impermeable
How does the concentration of the filtrate change as it goes through the loop of henle compared to the blood
iso, hyper, hypo
- as it enters descending limb isotonic
- at bottom hypertonic
- at top of ascending limb hypotonic
How does the concentration of sodium and chloride ions change through out the loop of henle
- concentration of sodium and chloride ions is high in tissue fluid in medulla
- high conc of ions in tissue fluid means water moves out from descending limb and at bend if hypertonic to tissue fluid
- ascending limb is permeable to ions and they diffuse out, upper portion actively pumps them out
What will occur in the distal convoluted tubule if that body lacks salt
sodium ions will be actively pumped out the tubule up a concentration gradient
what is the main site where the concentration and volume of urine is determined
- the collecting duct
- as fine-tuning of water takes place here
How can the urine become very concentrated while in the collecting duct
- water moves out by diffusion
- ^as low potential due to high sodium ion concentration in tissue fluid surrounding it
How does the environment an animal evolve in effect its loop of henle
- animals in high water environments have smaller loops of henle
- animals in low water environments have larger loops of henle to allow for more reabsorpotion
what is osmoregulation
this involves controlling the water potential of the blood within very narrow boundaries, regardless of the activities of the body
what are some factors that can put stress on your osmoregulatory system
- eating a salty meal
- drinking large volumes of liquid
- exercising hard
- running a fever
- visiting a very hot climate
What are the main ways water is lost and gained in the body
What controls the amount of water lost in the urine, where is it produced
- controlled by ADH in a negative feedback system
- produced in the hypothalamus, stored in posterior pituitary gland
what is the function of ADH in osmoregulation
increases the permeability of the distal convoluted tubule and the collecting duct to water
How does ADH increase then permeability of tubule cells
- it binds to receptors of tubule membrane and triggers formation of cyclic AMP (cAMP)
- ^cAMP is a second messenger inside the cell
What cascade of events does cAMP cause in the tubule
1)vesicles in cells lining collecting duct fuse with cell membrane
2)these vesicles contain protein based water channels (aquaporins), once inserted into cell membrane, it becomes water permeable
3)provides route for water to move out of tubule cells into tissue fluid of medulla and the blood capillaries by osmosis
draw the negative feedback loop that controls the water potential of the blood
what detects changes in water potential
- osmoreceptors in the hypothalamus
- sensitive to concentration of inorganic ions in the blood
what happens to the blood when water is in surplus of shortage
- in shortage, concentration of inorganic ions rises, water potential of blood rises, tissue fluid becomes more negative
- in surplus the blood becomes more dilute , concentration of inorganic ions decreases, water potential falls
what can urine tests be used for
- pregnancy tests
- drug testing
- general health of kidney
How can urine be used for testing
- urine contains the broken down products of toxins and other substances and these can be tested for
What does a pregnancy test actually test for
- The presence of human chorionic gonadotrophin (hCG)
- ^which is produced after the first 6 days
what are the main stages of pregnancy tests
1)Wick is soaked in first urine passed in the morning (has highest levels of hCG)
2)mobile monoclonal anitobodis attached to coloured beads form complex with hCG
3)Urine carries along test structure until window is reached
4)hCG\antibody complex binds to immobilised monocloonal antibodies that are in pattern that mean pos result
5)Urine continues up through test to second window
6)control line always binds to monoclonal antibodies in complex or not & show test is working
How are monoclonal antibodies made
- produced from single clone of cell
- mouse is injected with hormone/pathogen so right antibodies are made
- b-cells that make antibody, taken and fused to myeloma (cancer cell) to produced hybridoma
^millions of cells made - these are purified before use
how can you test for steroids in urine
testing urine using:
- gas chromatography (urine vaporised with known solvent and passed along tube to produce a chromatogram that can show presence of drugs )
- mass spectrometry
what tests are used to test for drugs in urine
- immunoassay (using monoclonal antibodies to bind to drug breakdown)
- gas chromatography/mass spectrometry
what are some factors that can cause kidney damage
- kidney infections (podocytes and tubules may be damaged)
- raised blood pressure can damage epithelial cells and basement membrane
- genetic conditions such as polycystic kidney disease (healthy kidney tissue replaced by cysts or damaged by cysts)
what are some ways the kidney could be effected by high blood pressure or infection
- proteins in the urine (if basement membrane is damaged proteins could be let passed)
- blood in the urine (if filtered damage, red blood cells could be let through)
what could be the effect of a build up of urea and mineral ions in the blood be
- loss of electrolyte balance (cannot remove mineral ions)
- build up of toxic urea in the blood
- high blood pressure (cannot get rid of water so pressure increases)
- weakened bones (calcium/phosphorus balance lost)
- pain and stiffness in joints (protein build up in blood)
- Anemia (cannot produced eryhropoietin which stimulate production of red blood cells)
what is glomerular filtrate rate used for
can indicate kidney diseases
How do you measure the Glomerular filtration rate
- it is not measured directly
- a measure of the levels of creatinine in the blood is used to estimate GFR
- cm^3/min
How is the glomerular filtration rate affected with age
it decreases
What does a GFR of below 60 mean
- if below 60 for 3 months, indicates moderate to severe chronic kidney disease
- if falls below 15 that is kidney failure
what are the 2 main ways in which kidney failure can be treated
- renal dialysis
- transplantation
what are the 2 main types of dialysis
- haeomodialysis
- peritoneal dialysis
what is haemodialysis
- involves use of machine
- usually carried out in hospital (sometimes at home)
- blood leaves patients body goes to dialysis machine,
- ^flows between dialysis membranes
- on other side of dialysis membrane, dialysis fluid = blood composition (isotonic) expect no urea at all
- blood and dialysis fluid flow in counter current system
What is peritoneal dialysis
- done inside the body
- makes use of natural dialysis membrane formed by lining of abdomen (peritoneum)
- usually done at home, patient can carry on with normal life while treatment happens
- dialysis fluid introduced via catheter, left for several hours for dialysis to take place (urea and excess mineral ions pass out of blood capillaries)
- fluid is then drained off and discarded, leaving blood balanced and waste removed
what is the main problem with organ transplants
- risk of rejection (antigens on donor organ differ from antigens on cells of recipient, immune system could recognise this and attack it)
what are some ways to reduce the risk of rejection on transplantation
- match the antigens of donor and recipient, same tissue type (same blood group)
- recipient given immunosuppressants for the rest of their lives (reduce need for matching tissue types)
What are the disadvantages of transplants
- patient become vulnerable to infectious diseases due to immunosuppresants
- ^they have to take great care if they become ill
- transplanted organs don’t last forever (around 9-10 years)
- once organ fails patient has to go back to old treatment (dialysis)
dialysis or transplant ??
pros and cons of both
- dialysis much more available than donor organs
- patients on dialysis can lead relatively normal lives
- patients on dialysis have to monitor diet carefully, and need regular sessions on the machine
- Long-term dialysis is much more expensive than a transplant and can cause damage to the body
- if a patient gets a transplant they are free from dialysis sessions and restricted diet
- as people get healthier there are less people dying suddnely to give donor organs (shortage of donor organs)
what could be done to overcome the problem of a shortage of donor organs
- organs could potentially be grow from stem cells, even without the antigens that cause rejection
- ^so no need for immunosuppresants
