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Biology component 3 > homeostasis and the kidney > Flashcards

homeostasis and the kidney Flashcards

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1
Q

negative feedback

A

the mechanism by which the body reverses the direction of change in a system to restore the set point

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2
Q

What is homeostasis

A
  • the maintenance of an internal environment within tolerable limits
  • despite external and internal changes
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3
Q

How is homeostasis achieved

A
  • via negative feedback whereby the body respond in such a way as to reverse the direction of change
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4
Q

What is general body temperature

A

37 degrees celcius

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5
Q

What is the general glucose concentration in the body

A

90 mg per 100cm3 blood

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6
Q

Describe the negative feedback loop

A
  • input
  • receptor
  • control centre
  • effector
  • output
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7
Q

What is an input

A

a change away from set point or norm

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8
Q

What is a receptor

A

a sensor that detectd the change from the set point

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9
Q

What is the control centre / co ordinator

A

detect singals from receptors and coordinates a respone via effectorss eg hypothalmus

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10
Q

What is an effector

A

brings about changes which returns the body to set point

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11
Q

What are the two types of effectors and their functions

A
  • muscles - contract
  • glands -secrete
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12
Q

What is an output

A
  • the corrective procedure
  • eg evaporation of sweat cools skin
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13
Q

What is excretion

A
  • removal of wastes made by the body eg carbon dioxide , water , urea
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14
Q

How is urea formed and removed

A
  • from the deamination of excess amino acids in the liver
  • the amine group is removed and converted into ammonia then urea
  • urea is removed via the kidney
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15
Q

How are organic acids formed and how are they used

A
  • they are formed when the NH2 is removed from the amino acid
  • remains can be used in respiration or converted to lipids or glucose
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16
Q

osmoregulation

A

the control of the water potential of body fluid by the regulation of water content of the body

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17
Q

What are the two main functions of the kidney

A
  • excretion - excretion of nitrogenous waste - urea from the body
  • osmoregulation- control of water potential body fluids including blood
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18
Q

Describe the role of renal artery

A
  • supply kidneys with blood containing oxygen and waste
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19
Q

What is the role of the renal vein

A
  • filtered blood from kidney retyrns to the general circulation via renal vein
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20
Q

where do excess water, solutes and urea travel from the kidney

A
  • this is called urine
  • drains into the collecting ducts and pelvis which empties urine into the ureter
  • each ureter connects to the bladder n
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21
Q

Decribe the role of the capillaries in the nephron

A
  • surrounds the convoluted tubules and loop of henle
  • allowing substances to be reabsorbed into the blood
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22
Q

What are the capillaries surrounding the loop of henle referred as

A

vasa recta

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23
Q

What is ultrafiltration and where does it take place

A
  • bowmans capsule
  • where small molecules including water and urea are removed from the blood
24
Q

What is selective reabsorption and where does that take place

A
  • in the proximal concoluted tubule
  • useful substances such as water, glucose and amino acids are reabsorbed but urea is not
25
Q

What is osmoregulation and where does it occur

A
  • loop of henle and collecting ducts
  • water potential of the blood is regulated
26
Q

Describe ultrafiltration

A
  • afferent arteriole is wider than the efferent arteriole creates a higher blood pressure than normal in the glomerulus
  • substances <68000 relative molecular mass are forced out into the bowmans capsule
  • this includes glucose, amino acids ,salts, water , ureaa and forms the glomeuluar filtrate
  • most proteins in the plasma are >68000 so remain in the blood wiht cells
27
Q

What is the excpetion of the protein that can pass through the glomerulus into the bowmans capsule

A
  • HCG hormone
  • prescence used to detect pregnancy
28
Q

What is the movement in ultrafiltration resisted by

A
  • capillary epithelium which has pores called fenestrae
  • basement membrane of bowmans capsule which acts like sieve
  • walls of the bowmans capsule is made of highly pecialised squamous epitheliel cells called podpyctes
  • fultrate passes between their branches
  • hydrostatifc pressure in capsule
  • lower water potential of the blood in glomerulus (lowered by loss of water into capsule)
29
Q

Describe selective reabsorption

A
  • filtrate is reabsorbed in the proximal covoluted tubule which includes all glucose all amino acids and most water aand salts
  • urea and excess water forms urine
30
Q

How are glucose and amino acids selectivley reabsorbed

A
  • glucose and amino acids - secondary active transport using a co transport mechanism with sodium ions glucose is co transported with two sodium ions by facilitated diffusion into the cell sodium ions and glucose move seperatey into capillaries
31
Q

How are mineral ions and salts selectivley reabsorbed

A
  • mineral ions and salts - faacilitted diffusion and active transport into epithelial cells
32
Q

How is water selectivley reabsorbed

A

via osmosis

33
Q

How are some filtered proteins and urea selectivley reabsorbed

A

via diffusion

34
Q

How is the proximal concoluted tubule adapted for reabsorption

A
  • cells lining the tubule habe a large surface area due to the prescnce of microvilli and basal channels (infoldings of embrane in contact with the capillary) large numbers of nephrons
  • cells contain many mitochondria whcih provide ATP for active transport of solutes
  • close association with capillarie whcih create a short diffusion pathway between cells and peritubular capillarries
  • tight junctions are found between adjacent cells which prevent the seepage of reabsorbed materials back into filtrate
35
Q

How come glucose can be in the urine

A
  • if you have type I and type II diabetes as not glucose is reabsorbed in the tubule so it remains in the filtrate
36
Q

Why is it important controlling water potential of the body

A
  • mantains enzymes and metabolites
  • prevents cells from burting or crenating
37
Q

What is the function of the loop of henle

A
  • responsible for reabsorption of some water from the descending limb
  • main function is to create an increase ion concentration within the interstitial region of medulla allows water water to be reabsorbed by the collecting duct
38
Q

Desribe the steps of osmoregulation

A
  • Na+ and Cl- ions are activley pumped out of the ascending limb
  • this creates and increasing ion concentration in the interstitial region
  • walls of the descending limb are permeable to water so water leaves by osmosis into the interstitial region before entering the capillaries (vasa recta)
  • water is progressivley down the descending limb typically at the base (longer loops can reach a much higher concentrations because more Na+ and Cl- ions are activley pumped out)
  • the concentration of the filtrate decreases in the lumen of the nephron in the ascending imb a Na+ and CL - ions are activley pumper out
  • this creates an increasing ion concentration gradient in the interstitial region towards the base of the loop
  • water passes out of the collecting duct via osmosis into the interstitial region before entering the vasa recta
  • as water passes out of the filtrate in the collecting duct the concentration of the filtrate increases but it is always lower than the fluid in the interstitial region of the medulla so water will continue to leave via osmosis
  • the two liquid flow in opposite directions past each other resulting in a greater exchange of substances between them than if they flowed in the same direction
  • this is referred as counter current multiplier this enures that the concentration of the filtrate is always lower than the interstitial fluid in the medulla
39
Q

How does the water potential of the blood vary in animals

A
  • over hydrates due to excess water intake or low salt intake
  • dehydrated due to low water intake sweating or high salt intake
40
Q

How is thw water potential of the blood controlled

A
  • by receptors called osmoreceptors in the hypothalmus which respond by triggering release of more or less ADH into the blood from the posterior pituitary gland
41
Q

What mechanism controls osmoregulation

A

negative feedback

42
Q

What does ADH stand for

A

antidiuretic hormone

43
Q

Describe how negative feedback restores and over hydrated person

A
  • osmoreceptors in the hpothalmus
  • posterior pituitary gland
  • decreased ADH secretion
  • decreased permebaility of the distal convoluted tubule and collecting duct
  • less water reabsorbed into the blood and dilute urine produced
44
Q

Describe how negative feedback restores a dehydrated person

A
  • osmoreceptors in the hypothalmus
  • posterior pituitary gland
  • increased ADH secretion
  • increased permeability of distal convoluted tubule and collecting duct
  • more water reabsorbed into trhe blood concentratedd urine produced
45
Q

What is the role of ADH

A
  • ADH binds to membrane receptor proteins found on the surface of cells lining the distal convoluted tubule and collecting duct wall
  • the binding of ADH triggers vesicles containing intrinsic membrane proteins called aquaporin containing pores that allow water to move fuse with the cell membrane
  • the aquaporins allow water to pass through the walls down the water potential gradient when ADH concentration falls aquaporins are removed from the cell membrane
46
Q

What are the main causes of kidney failure

A
  • diabetes
  • hgih blood presure
  • auto immune disease
  • infection
  • crushing injuries
47
Q

Describe the treatments for kidney failure

A
  • medication to controll blood calcium and potasssium levels which can lead to kidney stones and heat disease
  • a low protein diet reduce the concentration of excess amino acids aand hence concentration of urea
  • drugs to lower pressure: beta blockes which reduce the effect of adrenaline , calcium channel blockers which dilate blood vessels lowering blood pressure, ACE inhibitors which reduce the effect of angiotensin. Angiotensin causes blood vessels to constrict
  • dialysis
  • kidney transplant
48
Q

What is dialysis

A
  • involves dialysis fluis which contains glucose same concentration as the blood no urea and low ion concentraations
  • result is urea and some ions and water diffuse out of the blood but some glucose remains
49
Q

What is a kidney transplant

A
  • involves transplanting one kidney from a donor who is closely matched to ensure tissue compatability
  • immunosuppressants have to be used afterwards to prevent organ rejection
50
Q

What is haemodialysis

A
  • takes blood from artery passes it through a dialyser containing thousands of fibres each consisting of selectivley permeable dialysis tubing and dialysis fluid
  • ensure maximum transfer a counter current is used where blood and dialysis fluid move in opposiute directions
  • hepain is used to prevent the blood from clotting
  • several hours repeated several times each week
51
Q

What is peritoneal dialysis

A
  • involves passinf dialysis fluid into the peritoneum through a catheter
  • the peritoneum contains capillaries which exchange materials with dialysis fluid whcih is changes after about 40 minutes and the process repeater several times a day
  • caan move around but it is less effective than haemodialysis so fluid retention is likely
52
Q

What do freshwater fish excrete and how is it handled

A
  • ammonia
  • highly soluble but is very toxic o it cannot be stored
  • it must be excreted immediatley using large volumes of water to dilute it
53
Q

What do mammals excrete and how is it handled

A
  • urea
  • less toxic than ammonia
  • less water to dilute it
  • stored for shorts periods of time
  • requires energy to conver ammonia to urea so prevent dehydration as less water is needed to excrete it
54
Q

What do birds, reptiles and insects excrete and how is it handled

A
  • uric acid
  • non toxic little water to dilute it
  • conversion requires energy from ammonia to uric acid
  • birds - small amount of water to dilute it so reducing weight in flight
55
Q

How has the loop of henle adapted to different environments

A
  • aquatic animals - short loops of henle - large volumes of dilute urine
  • arid enviromments - large loop of henle produce small volumes of highly concentrated urine - large amounts of nephron
  • longer loops of henle - higher ion concentration in the medulla creater by counter current multiplies
56
Q

What animals rely on more metabolic water

A
  • arid environements - eg camel largely respures fat in its hump
  • nocturnal conditions - behavioural adaptations

Biology component 3 (3 decks)

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