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 connects the kidney to the bladder
The ureter
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 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
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 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
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
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 are the main ways water is lost and gained in the body
draw the negative feedback loop that controls the water potential of the blood
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 is the glomerular filtration rate affected with age
it decreases
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)
