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Paper 3 - Bio > Homeostasis and the Kidney > Flashcards

Homeostasis and the Kidney Flashcards

1
Q

What is homeostasis?

A

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

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2
Q

Why is homeostasis important?

A

To ensure 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 the set point?

A

A desired value or range of values determined by a coordinator.

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6
Q

Describe receptors and effectors.

A
  • Receptors = specialised cells located in sense organs that detect a specific stimulus.
  • Effectors = muscles or glands which enable a physical response to a stimulus.
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7
Q

Describe the role of the coordinatior.

A

Coordinates info from the receptors and sends instructions to the effectors.

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8
Q

State the components of a negative feedback system.

A
  • Set point
  • Receptors
  • Coordinator
  • Effectors
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9
Q

What is the mammalian kidney?

A

One of a pair of organs in the abdomen that has a role in osmoregulation and nitrogenous excretion.

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10
Q

What is osmoregulation?

A

The regulation of the water potential of body fluids (e.g. blood, tissue fluid, lymph) by the kidney.

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11
Q

What is osmoregulation important?

A
  • Prevents cells bursting or shrinking when water enters or leaves by osmosis.
  • Cellular reactions occur in aqueous solution and so water levels affect concentrations and the rate of reactions in cells.
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12
Q

Define excretion.

A

The process of removing metabolic waste from an organism.

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13
Q

Describe how excess amino acids are excreted.

A
  • Amino acids deaminated in the liver (removal of amino group) to form ammonia.
  • Ammonia converted to urea (less toxic).
  • Urea transported into the blood plasma and eliminated by the kidneys.
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14
Q

What is the function of the renal artery?

A

Supplies blood to the kidneys.

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15
Q

What is the function of the renal vein?

A

Drains blood from the kidneys.

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16
Q

What is the function of the ureter?

A

Takes urine to the bladder from the kidneys.

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17
Q

What is the function of the urethra?

A

Releases urine from the bladder, out of the body.

18
Q

Describe the gross structure of a mammalian kidney?

A
  • Fibrous capsule (protects kidney).
  • Cortex (outer region consists of Bowman’s capsules, convoluted tubules, blood vessels).
  • Renal pyramids (cone-shaped subdivisions).
  • Renal pelvis (funnel-shaped dilated section of ureter).
  • Medulla (inner region consists of collecting ducts, loops of Henle, blood vessels).
19
Q

What is a nephron?

A

The functional unit of the mammalian kidney.

20
Q

Describe the blood vessels associated with a nephron.

A
  • Wide afferent arteriole from renal artery enters renal capsule and forms the glomerulus, a branched knot of capillaries which combine to form narrow efferent arteriole.
  • Efferent arteriole branches to form capillary network that surrounds.
21
Q

Define ultrafiltration.

A

The removal of smaller molecules, water and ions from the blood in the glomerulus of the kidney at high pressure.

22
Q

Describe the process of ultrafiltration.

A
  • Occurs in Bowman’s capsule.
  • High hydrostatic pressure in glomerulus forces small molecules (e.g. urea, water, glucose, ions) out of capillary fenestrations against osmotic gradient.
  • Basement membrane acts as a filter. Blood cells and large molecules (e.g. proteins) remain in capillary.
23
Q

Why is there a build-up of pressure in the glomerulus?

A

Afferent arteriole leading into the glomerulus is wider than the efferent arteriole taking blood from the glomerulus.

24
Q

How are cells of the Bowman’s capsule adapted for ultrafiltration?

A
  • Fenestrations between epithelial cells of capillaries.

- Fluid can pass between and under folded membrane of podocytes.

25
Q

What happens during selective reabsorption?

A
  • Useful molecules from glomerular filtrate (glucose, some water, some ions) are reabsorbed into the blood.
  • Involves membrane transport proteins.
26
Q

Where does selective reabsorption occur?

A

Proximal convoluted tubule.

27
Q

How are cells in the proximal convoluted tubule adapted for selective reabsorption?

A
  • Microvilli provide a large surface area for co-transporter proteins.
  • Many mitochondria produce ATP for active transport of glucose into intercellular spaces.
  • Folded basal membrane provides a large surface area.
  • Tight junctions stop reabsorbed materials leaking back into the filtrate.
  • Peritubular capillaries extend into the medulla enabling reabsorption of materials.
28
Q

By what mechanism are amino acids and glucose selectively reabsorbed into the blood?

A
  • Secondary active transport.

- Uses a co-transport mechanism involving sodium.

29
Q

By what mechanism are mineral ions selectively reabsorbed into the blood?

A

Active transport.

30
Q

By what mechanism is water selectively reabsorbed into the blood?

A

Osmosis.

31
Q

How are filtered proteins (and some urea) selectively reabsorbed into the blood?

A

Via diffusion.

32
Q

Describe the loop of Henle.

A

A loop consisting of a descending limb (dips into the medulla) and ascending limb (rises into the cortex) surrounded by blood capillaries.

33
Q

What is the function of the loop of Henle?

A

It creates a low water potential in the medulla, enabling the reabsorption of water.

34
Q

Describe what happens in the loop of Henle.

A
  • Active transport of sodium and calcium ions out of ascending limb.
  • Water potential of interstitial fluid decreases.
  • Movement of water out of descending limb via osmosis (ascending limb is impermeable to water).
  • Water potential of filtrate decreases going down descending limb (lowest in medullary region, highest at top of ascending limb).
  • Hairpin countercurrent multiplier.
35
Q

What is an endocrine gland?

A

A gland of the endocrine system that secrete hormones directly into the bloodstream.

36
Q

How is the concentration and volume or urine controlled?

A

Controlled by the secretion of antidiuretic hormone (ADH).

37
Q

Explain the role of the hypothalamus in osmoregulation.

A
  • Osmoreceptors in the hypothalamus detect the concentration of the blood plasma.
  • Hypothalamus secretes ADH.e
38
Q

Explain the role of the posterior pituitary gland in osmoregulation.

A

Stores and secretes the ADH produced by the hypothalamus.

39
Q

Describe how ADH affects the reabsorption of water from the kidney tubules.

A
  • ADH causes insertion of aquaporins into the plasma membranes of cells of the DCT and collecting duct.
  • Increases permeability of the DCT and collecting duct.
  • More water reabsorbed.
  • More concentrated urine produced.
40
Q

Describe the effects of kidney failure.

A
  • Build-up of toxic waste products (e.g. urea) causes symptoms such as vomiting.
  • Fluid accumulation leads to swelling.
  • Disruption to electrolyte balance can make bones more brittle.
  • High concentrations of renin may lead to hypertension.
  • Low concentration of EPO can lead to anemia.
41
Q

Outline the potential treatments for kidney failure.

A
  • Low protein diet.
  • Control of blood calcium and potassium levels using medication.
  • Drug to lower blood pressure.
  • Kidney transplant.
42
Q

What is a transplant?

A

A medical procedure in which an organ or tissue in an individual in replaced.

Paper 3 - Bio (5 decks)

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