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Biology🧬 > Homeostasis And The Kidney💦 > Flashcards

Homeostasis And The Kidney💦 Flashcards

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1
Q

What is homeostasis?

A

The maintenance of a constant internal environment within a living organism

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2
Q

What is negative feedback?

A

Where a stimulus causes an opposite output/brings about corrective mechanism in order to maintain an ideal level/restore norm

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3
Q

What must each control system have?

A
  • A receptor - detects a stimulus - a change from the norm
  • A coordinator - receives and controls information from receptor and triggers an action
  • An effector - carries out action (corrective mechanism)
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4
Q

What is osmoregulation?

A
  • Carried out by kidneys
  • Maintenance of set water potential of blood/homeostatic control of body water
  • Involved in excretion
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5
Q

What is excretion?

A
  • Removal of waste products produced during cellular metabolisms
  • Forms urine
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6
Q

What are the main organs in the urinary system?

A

The kidneys

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7
Q

What is the role of the kidneys?

A
  • To filter waste products out of the blood

* To regulate the water potential of the blood

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8
Q

Where does each kidney relieve it’s blood supply from?

A

The renal artery - a branch of the aorta

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9
Q

How does the filtered blood leave the kidneys?

A

Along the renal veins

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10
Q

Where does the urine travel?

A
  • Passes down a muscular tube called the ureter

* There is a ureter connecting each kidney to the bladder - a muscular sac that stores urine

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11
Q

What happens during urination?

A
  • Sphincter muscle relaxes

* Urine passes out of the body, along the urethra

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12
Q

What is the structure of the surrounding layer? (Kidney structure)

A
  • Layer of adipose (fat) tissue and a layer of fibrous connective tissue
  • These keep kidneys in position and protect them from mechanical damage
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13
Q

What is the structure of the cortex? (Kidney structure)

A
  • The dark outer region
  • Filtration is carried out by the nephrons here
  • Dense capillary network - receives blood from renal artery
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14
Q

What is the structure of the medulla? (Kidney structure)

A
  • The lighter inner region

* Each nephron extends across the medulla to form structures called renal pyramids

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15
Q

What is the structure of the pelvis? (Kidney structure)

A
  • The renal pyramids projects into the pelvis

* Urine passes out into the pelvis before it passes down the ureter

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16
Q

Describe the nephron blood supply

A
  • Renal artery branches to form arterioles
  • Each Bowman’s capsule is supplied with blood by an afferent arteriole
  • Afferent arteriole branches inside the Bowman’s capsule to form the glomerulus
  • Capillaries in glomerulus join up to form efferent arteriole, which takes blood away from the Bowman’s Capsule
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17
Q

What is the effect of the afferent arteriole being wider than the efferent?

A

•More blood is carried to the glomerulus than carried away

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18
Q

Describe the endothelium of the capillary (Microstructure)

A
  • First cell layer

* In the glomerulus, this single layer of cells has thousands of gaps (fenestrations)

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19
Q

Describe the basement membrane (Microstructure)

A

•Between two cell layers
•Composed of glycoprotein and collagen fibres
•Mesh-like structure acts as a filter
- water and small solutes are forced out of the blood
-blood cells and large solutes are prevented from leaving

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20
Q

Describe the podocytes (Microstructure)

A
  • The second cell layer - epithelial cells
  • Have foot-like processes that wrap around the capillaries
  • Gaps between them
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21
Q

What is deamination?

A

The break down of excess amino acids in the liver for:
•Building new proteins
•Produce waste (urea) - amino group combines with carbon dioxide to form urea

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22
Q

What is ultrafiltration?

A

•The filtering (under pressure) of small molecules out of the blood and into the Bowman’s capsule

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23
Q

Describe the process of ultrafiltration

A
  • Gaps in capillary endothelium and Bowman’s capsule wall allow most molecules to pass through
  • Basement membrane prevents large molecules from passing through
  • Blood pressure in kidney is higher than in the other organs - pressure maintained by glomerulus (wide afferent arteriole)
  • More blood goes into the glomerulus than leaves
  • Hydrostatic pressure builds up, forcing substances through the endothelial pores, across the B.membrane and into the B.capsule
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24
Q

What is the composition of glucose filtrate in comparison to plasma? (Reabsorption)

A
  • Water - both 900gdm-3
  • Protein - plasma 80gdm-3
  • Glucose - both 1gdm-3
  • Amino acids - both 0.5gdm-3
  • Urea - both 0.3gdm-3
  • Inorganic ions - both 7.2gdm-3
25
Q

What is selective reabsorption? (Reabsorption)

A

All glucose, amino acids, vitamins and many Na+ Cl- are actively transported out of the proximal convoluted tubule and back into the blood

26
Q

Describe the reabsorption of water (Reabsorption)

A
  • Uptake of substances means blood in capillaries surrounding the nephron have a low water potential
  • Large amounts of water passes out of the filtrate in the proximal convoluted tubule and back into the blood by osmosis
27
Q

What are the adaptations of the proximal convoluted tubule? (Reabsorption)

A
  • Microvilli - large S.A for absorption
  • Numerous mitochondria provide ATP for active transport
  • Close to capillaries - short diffusion pathway
  • Circulation of blood maintains a concentration gradient
28
Q

What is the function of the loop of Henle?

A

To create an area of high solute concentration deep in the medulla

  • Generates a water potential gradient between the filtrate and the tissue fluid of the medulla
  • This allows the concentration/volume of urine to be adjusted when necessary (osmoregulation)
29
Q

Describe the role of the loop of Henle as a counter current multiplier

A
  • Ascending limb more permeable to salts than water
  • As filtrate moves up, Na and Cl ions move out (passively first and the actively pumped) into surrounding tissue
  • Causes water to pass out of descending limb via osmosis
  • Filtrate becomes more concentrated as it passes down the descending limb
  • Net result - solute concentration at any part of loop is lower in the ascending limb than it is in the descending limb
30
Q

How does the role of the loop impact on the function of the collecting duct?

A
  • As the collecting ducts pass through the medulla to the pelvis they pass through the region of high solute concentration
  • Water is drawn out of the collecting ducts by osmosis
  • Creates more concentrated urine
31
Q

How is osmoregulation carried out? (Collecting duct)

A
  • Osmoreceptors In hypothalamus of brain react to changes in solute concentration of blood as it flows through the hypothalamus
  • Stimulates posterior pituitary gland to secrete more/lessADH
  • ADH makes walls of collecting duct and distal convoluted tubule more/less permeable through aquaporins
  • More water reabsorbed
  • Restores normal water potential of blood and produces small/large volume of hyper/hypotonic urine
32
Q

What does ADH stand for and what does it do?

A
  • Antidiuretic hormone

* Makes walls of CD and DCT permeable

33
Q

What is dialysis fluid?

A
  • Has same composition as that desired in the blood plasma
  • Wastes, toxic molecules and excess fluid diffuse from blood into dialysis fluid
  • Counter current flow of blood and dialysis fluid ensures a constant diffusion gradient is maintained
34
Q

How does haemodialysis work?

A
  • Blood passes through an artificial kidney machine (at hospital or home)
  • A shunt is used to access the bloodstream (tube that connects an artery to a vein)
  • Blood flows from this tube into the machine and back to the patient
  • Inside machine, blood flows over the surface of the partially permeable dialysis membrane
  • Wastes diffuse into dialysis fluid
  • Purified blood is returned to the patient
35
Q

Positives and negatives of haemodialysis

A 
POSITIVES 
•Patient can drink and eat what they want (to an extent)
NEGATIVES
•Restrictive
•Session lasts 2-6 hours
•2-3 sessions a week
36
Q

How does peritoneal dialysis work?

A
  • Insert dialysis fluid into peritoneal cavity using a catheter
  • Waste products and excess water pass through the peritoneal membrane into this cavity
  • After several hours, fluid is drained out and discarded
37
Q

Positives of peritoneal dialysis

A
  • During period of drainage of fluid, patient can carry on with normal activities
  • Usually carried out at home
38
Q

What are some causes of kidney failure?

A
  • Diabetes
  • High-blood pressure
  • Auto-immune disease
  • Infection
  • Injury
39
Q

What are some treatments of kidney failure?

A
  • Low-protein diets
  • Medication to reduce blood pressure
  • Medication to control K+ and Ca- levels
40
Q

What are the pros of kidney transplant? (over dialysis)

A
  • Most straightforward transplant
  • Reasonable chance of success(80%)
  • Less expensive in long term
41
Q

What are the cons of kidney transplant? (Over dialysis)

A
  • Similar tissue and blood type
  • Rejection means returning to dialysis
  • Have to take immunosuppressants for rest of life
  • Long waiting list(4000)
  • More expensive in short term
42
Q

Describe nitrogenous waste in fish

A
  • Release nitrogen as ammonia
  • This is extremely soluble
  • Quickly diffuses out of gills and dilutes
43
Q

Describe nitrogenous waste in reptiles, birds and insects

A

•Excrete nitrogen and uric acid which requires energy
•This is almost insoluble in water and is non-toxic
•Very little water is needed to excrete uric acid
- conserve body water and live in arid environments

44
Q

Describe nitrogenous waste in mammals

A
  • Excrete as urea
  • Requires less water than ammonia
  • Energetically expensive, but prevents dehydration
45
Q

How does the length of the loop of Henle link to the environment?

A
  • In hot conditions, there will be a longer loop
  • The thicker the medulla, the longer the loop
  • The longer the loop, the greater the solute concentration set up in the medulla - more water is reabsorbed - more concentrated urine
46
Q

Explain how ADH works

A
  • ADH binds to receptors in membrane of CD epithelial cells
  • Stimulates formation of vesicles containing aquaporins
  • These move to inner membrane of CD epithelial cells and fuse with it, inserting aquaporins into membrane
  • Water can now move along a water potential gradient, through the epithelial cells and into medulla tissue fluid, and then into capillaries - raises water potential of blood
47
Q

Approximately what percentage of the plasma leaves the blood and enters the glomerula filtrate?

A

20%

48
Q

What percentage of urea is reabsorbed and why?

A

50%

-Because a concentration gradient exists

49
Q

What percentage of water is reabsorbed?

A

85%

50
Q

What is the function of the ascending limb?

A

To create a water potential gradient between the filtrate and the tissue fluid of the medulla

51
Q

Why is the hydrostatic pressure of the blood in the glomerulus very high?

A
  • Contraction of the left ventricle (renal artery branches from the aorta)
  • Efferent arteriole leaving the glomerulus is narrower - creating a bottleneck effect
52
Q

What is the descending limb highly permeable to? (Loop of Henle)

A

Water

53
Q

What is the ascending limb highly permeable to? (Loop of Henle)

A

Ions

54
Q

What are the walls of the blood capillaries surrounding the loop permeable to? (Loop of Henle)

A

Freely permeable to both water and ions

55
Q

As the filtrate moves down the descending limb it…

A

Loses water - lower water potential

56
Q

As the filtrate moves up the ascending limb it…

A

Loses ions - higher water potential

57
Q

At the apex of the loop…

A

The filtrate reaches a maximum ion concentration

58
Q

As the filtrate enters the DCT…

A

It has a higher water potential than the tissues of the medulla

59
Q

As the filtrate moves down the collecting duct…

A
  • It meets tissue fluid with a lower water potential
  • So water moves out of filtrate via osmosis along entire length of CD
  • Produces urine that is reduced in volume and has a lower water potential than blood

Biology🧬 (24 decks)

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