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Biology Unit 3 > 3.7 Homeostasis and the kidney 5 > Flashcards

3.7 Homeostasis and the kidney 5 Flashcards

1
Q

What is homeostasis?

A

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 coordinator:

A

coordinates info from the receptors sending instructions to the effectors

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8
Q

state the components of a -ve 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 water potential of body fluids (e.g.blood, tissue fluid, lymph by the kidney)

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11
Q

why is osmoregulation important?

A

-prevents cells bursting or shrinking when water enters or leaves cells by osmosis
-cellular rctns occur in aqueous soln therefore water levels affect concs and the rate of rctn 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 were excreted

A

-amino acids deaminated in the liver (removal of amino grp) to form ammonia
-ammonia converted to urea (less toxic)
-urea transported into blood plasms and eliminated by the kidneys

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14
Q

function of renal artery?

A

supplies blood to the kidneys

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15
Q

function of renal vein?

A

drains blood from the kidneys

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16
Q

function of the ureter?

A

takes urine to the bladder from the kidneys

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17
Q

function of the urethra

A

releases urine from the bladder out of the body

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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, loop of Henle, blood vessels

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19
Q

what is nephron?

A

the functional unit of the mammalian kidney

20
Q

where are the nephrons found within the kidneys?

A

part of the nephron is located in the medulla and part in the cortex

21
Q

describe the blood vessels associated with a nephron?

A

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

22
Q

describe ultrafiltration

A

the removal of small molecules, water and ion from the blood in the glomerulus of the kidney at high pressure

23
Q

describe the process of ultrafiltration

A

-occurs in bowman’s capsule
-high hydrostatic pressure in glomerulus forces small molecules (urea, water, glucose, ions) out of capillary against osmotic gradient
-basement membrane acts as a filter, blood cells and large molecules (proteins) remain in capillary

24
Q

why is there a build-up of pressure in glomerulus?

A

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

25
Q

how are cells of the bowman’s capsule adapted for ultrafiltratioon?

A

-fenestrations bet epithelial cells of capillaries
-fluid can pass bet & under folded membrane of podocytes

26
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

27
Q

where does selective reabsorption occur?

A

proximal convoluted tubule (PCT)

28
Q

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

A

-microvilli provide 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 sa
-tight junctions stop reabsorbed materials leaking back into the filtrate
- peritubular capillaries extend into the medulla enabling reabsorption of materials

29
Q

by what mechanism are amino acids and filtered glucose selectively reabsorbed back into the blood?

A

secondary active transport
uses a co-transport mechanism involving Na+

30
Q

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

A

active transport

31
Q

by what mechanism is water selectively reabsorbed into the blood?

A

osmosis

32
Q

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

A

via diffusion

33
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

34
Q

function of the loop of Henle??

A

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

35
Q

describe what happens in the loop of 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 multiplier

36
Q

what is an endocrine gland?

A

gland of the endocrine system that secretes hormones directly into the bloodstream

37
Q

how is the conc and vol of urine controlled?

A

controlled by secretion of anti-diuretic hormone (ADH)

38
Q

explain the role of the hypothalamus in osmoregulation:

A

osmoreceptors in hypothalamus detect conc of blood plasma
hypothalamus secretes ADH

39
Q

explain the role of the posterior pituitary gland in osmoregulation

A

stores and secretes the ADH produced by hypothalamus

40
Q

describe how ADH affects the reabsorption of water from the kidney tubules

A

-ADH causes insertion of aquaporins into plasma membranes of cells of the DCT and collecting duct
-increases permeability of the DCT and collecting duct
-more water reabsorbed
more conc urine produced

41
Q

describe the effects of kidney failure

A

-build up of toxic waste products(e.g. urea) causes symptoms like vomiting
-fluid accumulation leads to swelling
-disruption to electrolyte balance can make bones more brittle
- high conc of renin may lead to hypertension
- low concs of EPO can lead to anaemia

42
Q

the potential treatments of kidney failure

A

-low protein diet
-control of blood calcium and potassium levels using medication
-drugs to lower blood pressure
-renal dialysis
-kidney transplant

43
Q

describe renal dialysis

A

-medical procedure that artificially filters the blood
-relies on a partially permeable membrane between the patient’s blood and dialysis fluid
-two types: haemodialysis and peritoneal dialysis

44
Q

what is a transplant?

A

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

45
Q

describe how animal excretory products can differ:

A

-freshwater animal species excrete ammonia
-reptiles, birds and insects produce uric acid
- mammals excrete urea

46
Q

how does length of the loop of Henle differ between mammals?

A

-length of the loop caries depending on availability of water in the mammal’s environment
-longer loop in desert animals (kangaroo rat) to allow greater time for reabsorption of water and salts

Biology Unit 3 (8 decks)

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