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Biology - Unit 3 > Homeostasis And The Kidney > Flashcards

Homeostasis And The Kidney Flashcards

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1
Q

What is homeostasis ?

A

The maintenance of a state of dynamic equilibrium in the body despite fluctuations in the internal and external conditions

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2
Q

Why is homeostasis important ?

A

Ensuring optimum conditions for enzymes and cellular processes in the body

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3
Q

Define negative feedback

A

Self regulatory mechanisms return the internal environment to the optimum when there is a fluctuation

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4
Q

Define positive feedback

A

A fluctuation which triggers changes that result in an even greater deviation from the normal level

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5
Q

What is a set point ?

A

A desired value or range of values determined by a coordinator

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6
Q

What are the components of a negative feedback system ?

A

Set point
Receptors
Coordinators
Effectors

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7
Q

What is osmoregulation?

A

Control of body fluid water potential via negative feedback

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8
Q

Why is osmoregulation so important ?

A
  • Prevents the cells from bursting / shrinking when water enter of leaves via osmosis
  • Cellular reactions occur in aqueous solution therefor water levels affect concentration and the rate of reaction in cells
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9
Q

Define excretion

A

The process of removing metabolic waste from an organism
(From lungs, kidneys, skin and liver)

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10
Q

How are excess amino acids secreted ?

A

Amino acids delaminated in the liver to form ammonia
Ammonia is converted into urea
Urea is transported into the blood plasma ( by facilitated diffusion )and eliminated by the kidneys

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11
Q

What is the function of the renal artery?

A

Supplies blood to the kidneys

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12
Q

What is the function of the renal vein?

A

Drain blood from the kidneys

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13
Q

What is the function of the ureter and urethra?

A

Ureter = Takes urine to the bladder from the kidneys
Urethra = Releases urine from the bladder, out of the body

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14
Q

Describe and explain the functions of the structures within a mammalian kidney

A

Cortex= outer region consists of the Bowman’s Capsule, convoluted tubules and blood vessels (ultrafiltration and selective reabsorption)
Medulla = inner region consists of collecting duct, loop of Henle and blood vessels (reabsorption of water )
Renal Pelvis = funnel shaped dilated section of ureter allows urine to be emptied to ureter
Fibrous Capsule = protects the kidney

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15
Q

What is a nephron ?

A

The functions unit of a kidney.

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16
Q

What part of the kidney is the nephron located in?

A

Bowman’s Capsule and Proximal & Distal convoluted tubule = Cortex
Loop of Henle = Medulla

17
Q

Describe Ultrafiltration

A

Occurring in the Bowman’s Capsule
1) Blood enter the glomerulus via the afferent arteriole (wider) and leaves via the efferent arteriole (narrower). This generated high hydrostatic pressure.
2) Small molecules pass through 3 layers and enters the Bowman’s Capsule and tubule as filtrate.

18
Q

What does Glomerular Filtrate contain?

A

Water
Glucose
Salts
Urea
Amino Acids

19
Q

What 3 layers separate the blood entering the glomerulus from the Bowman’s space?

A

1) Capillary Walls - one cell thick, tiny pores between cells called fenestrations allow solute to pass to the basement membrane
2) Basement Membrane - A selective molecular filter. Only allows small molecules to pass through, blood cells and platelets are too large.
3) Squamous Epithelial Layer - Podocytes have extensions called pedicels these wrap around capillary’s pulling it closer to the basement membrane. Gaps between pedicels are called filtration slits

20
Q

Define selective reabsorption

A

Process by which useful substances such as glucose, amino acids and salts are reabsorbed back into the blood plasma, taking place in the proximal convoluted tubule

21
Q

Describe how cells in the proximal convoluted tubule are adapted for selective reabsorption

A

MICROVILLI - provide large surface area for cotransporter proteins
MITOCHONDRIA - Lots to produce ATP for active transport of glucose into the intercellular space
FOLDED BASEMENT MEMBRANE - large surface area and also basement channels help
TIGHT JUNCTIONS - between cells to stop reabsorbed materials leaking back into the filtrate

22
Q

How are amino acids and glucose selectively reabsorbed back into the blood?

A

Glucose and amino acids enter the PCT by cotransport with sodium ions.
Once inside the cell they diffuse to the opposite cell membrane
Glucose leaves via facilitated diffusion and secondary active transport
Amino acids leave by facilitated diffusion

23
Q

How are chloride ions selectively reabsorbed ?

A

Chloride ions enter by facilitated diffusion
They then leave via facilitated diffusion

24
Q

What mechanism allows mineral ions to be selectively reabsorbed back into the blood ?

A

Active Transport

25
Q

By what mechanism is water selective,g reabsorbed into the blood?

A

Osmosis

26
Q

Describe the different parts of the loop of Henle

A

Descending Limb (dips into the medulla )
Ascending Limb ( rises into the cortex )

27
Q

What is the overall function of the loop of Henle ?

A

Creates a low water potential in the medulla, allowing reabsorption of water to occur

28
Q

Describe the process that occurs in the loop of Henle

A
  • Water moves out of the descending limb ( permeable to water ) and into the blood via osmosis
  • Na and Cl ions diffuse into the descending limb at the same time from the medulla
  • Filtrate becomes more concentrated as it gets towards the apex
  • The ascending limb expels the Na and Cl ions by facilitated diffusion and then active transport. ( AT takes over when concentration of solutes decreases too much) into the tissue fluid of the medulla
29
Q

What hormone controls the concentration and volume of urine?

A

Anti-diuretic hormone (ADH)

30
Q

Explain the roles of the hypothalamus in osmoregulation

A

Osmoreceptors in the hypothalamus detect the concentration in blood plasma
ADH is secreted from the hypothalamus

31
Q

Explain the role of the posterior lobe of the pituitary gland in osmoregulation

A

Signals are sent here
Stores and secreted the ADH produced by the hypothalamus

32
Q

How does ADH affect the reabsorption of water from the kidney tubules?

A

Release of ADH causes insertions of Aquaporins into the cell membranes of the DCT and collecting duct
This increases the permeability of the DCT and collecting duct
More water is reabsorbed and therefore a more concentrated urine is produced

33
Q

How do the length of the loop of Henle differ between different animals ?

A

Long loop = Desert Animals
- more ions can be pumped into the medulla, lowering the water potential and as a result more water to be reabsorbed into the blood stream
Shorter loop = fresh water e.g otters

34
Q

Describe the effects of kidney failure

A
  • build up of toxic waste products
  • fluid accumulation
35
Q

Outline the potential treatments for kidney failure

A
  • Low protein diet
  • control blood calcium and potassium levels using medication
  • kidney transplant
  • dialysis
36
Q

How is dialysis carried out?

A
  • Blood taken out of artery in patients arm entering dialysis machine.
  • blood is passed through thousands of long narrow strands of selectively permeable dialysis tubing.
  • waste passes through the pores into the dialysis fluid
  • fluid and blood flow in opposite directions, maintaining a strong concentration gradient
  • clean blood is returned via veins
37
Q

What are the 2 types of dialysis ?

A
  • haemodialysis
  • peritoneal dialysis
38
Q

What is a kidney transplant ?

A
  • organ from living or dead donor is given to the patient
  • needs to be correct tissue types and blood
  • patient will be on immunosuppressants for rest of life to decrease chance of rejection
39
Q

How do animals excrete nitrogenous waste?

A

Fish = excrete ammonia into surrounding water via diffusion across gills. Ammonia is toxic but highly soluble in water
Birds & Insects = uric acid, little water needed to excrete so save water loss
Mammals = Urea, requires ATP less toxic then ammonia

Biology - Unit 3 (11 decks)

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