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biology > 3.4 - homeostasis + the kidney > Flashcards

3.4 - homeostasis + the kidney Flashcards

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1
Q

what’s homeostasis

A

maintenance of state of dynamic equilibrium in body despite fluctuations in internal + external conditions

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2
Q

why is homeostasis important

A

to ensure optimum conditions for enzymes + 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

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

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5
Q

what’s the set point

A

desired value or range of values determined by a coordinator

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6
Q

describe receptors + effectors

A

receptors - specialised cells located in sense organs that detect specific stimulus
effectors - muscles/glands which enable a physical response to a stimulus

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7
Q

describe the role of the coordinator

A

coordinated information from receptors + sends instructions to effectors

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8
Q

state the components of a negative feedback system

A
  • set point
  • receptors
  • coordinator
  • effector
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9
Q

what’s the mammalian kidney

A

one of a pair of organs in abdomen that has a role in osmoregulation + nitrogenous excretion

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10
Q

what’s osmoregulation

A

regulation of water potential of body fluids (eg: blood, tissue fluid, lymph) by the kideny

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11
Q

why is osmoregulation important

A
  • prevents cells bursting or shrinking when water enters or leaves by osmosis
  • cellular reactions occur in aqueous solution, water levels affect conc + rate of reactions in cells
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12
Q

define excretion

A

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 liver (removal of amino group) forming ammonia
  • ammonia converted to urea (less toxic)
  • urea transported into blood plasma + eliminated by kidneys
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14
Q

what’s the function of the renal artery

A

supplies blood to kidneys

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15
Q

what’s the function of the renal vein

A

drains blood from kidneys

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16
Q

what’s the function of the ureter

A

takes urine to bladder from kidneys

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17
Q

what’s the function of the ureter

A

takes urine to bladder from kidneys

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18
Q

what’s the function of the urethra

A

releases urine from bladder, out of body

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19
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 dilation section of ureter
medulla - inner region consists of collecting ducts, loops of henle, blood vessels

20
Q

what’s a nephron

A

functional unit of mammalian kidney

21
Q

where are nephrons found within kidneys

A

part of nephron located in medulla + part in cortex

22
Q

describe the blood vessels associated w/ a nephron

A

wide afferent arteriole from renal artery enters renal capsule + forms glomerulus, branched knot of capillaries which combine to form narrow efferent arteriole
efferent arteriole branches to form capillary network that surrounds tubules

23
Q

define ultrafiltration

A

removal of small molecules, water + ions from blood in glomerulus of kidney at high pressure

24
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 filter, blood cells + large molecules (e.g: proteins) remain in capillary
25
Q

why is there a build up of pressure in glomerulus

A

afferent arteriole leading into glomerulus is wider than efferent taking blood from glomerulus

26
Q

how are you cells of bowman’s capsule adapted for ultrafiltration

A
  • fenestrations between epithelial cells of capillaries
  • fluid can pass between + under folded membrane of podocytes
27
Q

what happens in selective re absorption

A
  • useful molecules from glomerular filtrate (glucose, some water, some ion) are reabsorbed into blood
  • involves membrane transport proteins
28
Q

where does selective re absorption occur

A

proximal convoluted tubule

29
Q

how are cells in PCT adapted for selective reabsorption

A
  • microvilli provide large SA for co-transporter proteins
  • many mitochondria produce ATP for active transport of glucose in intracellular spaces
  • folded basal membrane provides large SA
  • tight junctions stop reabsorbed materials leaking back into filtrate
  • peritubular capillaries extend into medulla enabling réabsorption of materials
30
Q

by what mechanism are amino acids + filtered glucose selectively reabsorbed into blood

A
  • secondary active transport
  • uses co-transport mechanism involving Na+
31
Q

by what mechanism are mineral ions selectively reabsorbed into blood

A

active transport

32
Q

by what mechanism is water selectively reabsorbed into blood

A

osmosis

33
Q

how are filtered protein (+some urea) selectively reabsorbed into blood

A

via diffusion

34
Q

describe the loop of henle

A

loop consisting of descending limb (dips into medulla) + ascending limb (rises into cortex) surrounded by blood capillaries

35
Q

what’s the function of the loop of henle

A

creates low water potential in medulla, enabling reabsorption of water

36
Q

describe what happens in the loop on henle

A
  • active transport of Na+ and Cl- 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
  • hair pin counter current mulitplier
37
Q

what’s an endocrine gland

A

gland of endocrine system that secretes hormones directly into bloodstream

38
Q

how is concentration + volume of urine controlled

A

controlled by secretion of anti-diuretic hormone (ADH)

39
Q

explain the role of the hypothalamus in osmoregulation

A
  • osmoreceptors in hypothalamus detect conc of blood plasma
  • hypothalamus secrets ADH
40
Q

explain the role of the posterior pituitary gland in osmoregulation

A

stores + secretes ADH produces by hypothalamus

41
Q

describe how ADH affects the reabsorption of water from kidney tubules

A
  • ADH causes insertion of aquaporins into plasma membranes of cells of DCT + collecting duct
  • increases permeability of DCT + collecting duct
  • more water reabsorbed
  • more concentrated urine produced
42
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 conc of renin may lead to hypertension
  • low conc of EPO can lead to anemia
43
Q

outline the potential treatments for kidney failure

A
  • low protein diet
  • control of blood calcium + potassium levels using medication
  • drugs to lower blood pressure
  • renal dialysis
  • kidney transplant
44
Q

describe renal dialysis

A
  • medical procedure that artificially filters blood
  • relies on partially permeable membrane between patients blood + dialysis fluid
  • 2 types: haemodialysis + peritoneal dialysis
45
Q

what’s a transplant

A

medical procedure in which an organ or tissue in an individual is replaced

46
Q

describe how animal excretory products can differ

A
  • freshwater animal species excrete ammonia
  • reptiles, birds + insects produce uric acid
  • mammals excrete urea
47
Q

how does length of loop of henle differ between mammals

A
  • length of loop varies depending on availability of water in mammals environment
  • longer loop in desert animals to allow greater time for reabsorption of water + salts

biology (24 decks)

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