Water and Electrolytes

Question 1

what gains water in the body

Answer 1

water ingested and water formed in metabolism

Question 2

what loses water

Answer 2

urine, faeces
sweat and expired air

Question 3

do we gain or lose more water every day

Answer 3

even

Question 4

what part of water balance is under homeostatic control

Answer 4

urination

Question 5

what are the features of the kidney

Answer 5

glomerulus
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting ducts

Question 6

label this

Answer 6

Question 7

what does the glomerulus do

Answer 7

involved in renal blood flow and filtration of plasma

Question 8

what is the renal blood flow rate

Answer 8

1200ml per minute

Question 9

what is ithe glomerular filtration rate

Answer 9

120ml per minute

Question 10

what are the filtration pressures

Answer 10

pressures that vary along the length of glomerular capillary form afferent arterioles

Question 11

what is the capillary hydrostatic pressure

Answer 11

45-50mmHg

Question 12

what is the plasma protein oncotic pressure

Answer 12

25-35mmHg

Question 13

what is the capsular pressure

Answer 13

10mmHg

Question 14

what is the net filtration pressure

Answer 14

10-15mmHg

Question 15

what does the proximal convoluted tubule absorb

Answer 15

60-70% of the glomerular filtrate

Question 16

what is absorbed in the proximal convoluted tubular

Answer 16

ions and small organic molecules

Question 17

what is secreted in the proximal convoluted tubule

Answer 17

hydrogen ions

Question 18

how are things absorbed in the proximal convoluted tubule

Answer 18

active transport and facilitated diffusion

Question 19

is there any control of reabsorption in the proximal convoluted tubular

Answer 19

very little

Question 20

what occurs in the loop of henle

Answer 20

this is important for concentration of urine
length of the loop correlates with the ability to concentrate urine

Question 21

what is the countercurrent exchange mechanism

Answer 21

this is how urine is concentrated in the loop of henle, and the concentration depends on active transport pumps in the thick ascending limb of the loop of henle

Question 22

what is the net reabsorption of liquid in the loop of henle

Answer 22

10%

Question 23

what is absorbed in the distal convoluted tubule

Answer 23

sodium
chloride
calcium

Question 24

what is secreted in the distal convoluted tubule

Answer 24

hydrogen
potassium

Question 25

what hormones control the activity of the distal convoluted tubular

Answer 25

aldosterone atrial natriuretic hormone ADH parathyroid hormone

Question 26

what happens in the collecting ducts of the kidney

Answer 26

water reabsorpiton, under the influence of ADH, and there are membrane channels for water reabsorption

Question 27

how does water move along the collecting ducts

Answer 27

along osmotic gradients created by the counter current exchange mechanism

Question 28

which hormones regulate water and electrolytes

Answer 28

antidiuretic hormone renin angiotension aldosterone system atrial natriuretic hormone

Question 29

what is vasopressin

Answer 29

ADH, produced in the hypothalamus and released from the posterior pituitary gland

Question 30

what does vasopressin act on

Answer 30

the distal convoluted tubule and collecting ducts to increase water and permeability by insertion of aquaporin channels water moves passively between the tubule lumen and the interstitial fluid

Question 31

what leads to an increase in ADH release in the posterior pituitary

Answer 31

decreased plasma volume decreased baroreceptor increased plasma osmorality increased osmoreceptor activation

Question 32

what is ADH secretion increased by

Answer 32

decreased extracellular fluid increased extraecllular fluid osmorality ADH also causes constriction of blood vessels

Question 33

how is a decreased in extracellular fluid detected

Answer 33

low pressure receptors in the atria and great veins

Question 34

how is an increase in extracellular fluid osmorality detected

Answer 34

osmoreceptors in the hypothalamus

Question 35

what are electrolytes

Answer 35

ions present in intracellualr and extracellular fluid

Question 36

what are electrolytes subject to the control of

Answer 36

homeostasis

Question 37

what are some important electrolytes

Answer 37

sodium potassium hydrogen calcium

Question 38

what does much of the homeostatic control of electrolytes involve

Answer 38

determining how much is excreted through the kidneys

Question 39

how is sodium controlled

Answer 39

RAAS and ANH

Question 40

describe how RAAS controls sodium levels

Answer 40

promotes reabsorption of sodium and water in distal convoluted tubule in exchange for potassium and hydrogen ions angiotensin is a potent vasoconstrictor

Question 41

describe how the atrial natriuretic hormone controls sodium

Answer 41

increases excretion of sodium and water, and has the opposite effects of aldosterone

Question 42

what stimulates atrial natriuretic hormone release

Answer 42

an increase in plasma volume which causes an increase in atrial distension

Question 43

why do cell membrane potentials rely on extracellular fluid

Answer 43

due to the presence of potassium

Question 44

what can small changes in potassium ions lead to

Answer 44

nerve and muscle function

Question 45

what regulates potassium levels

Answer 45

aldosterone

Question 46

what are the two disorders of ADH secretion

Answer 46

hyposecretion and hypersecretion

Question 47

describe hyposecretion of ADH

Answer 47

happens in diabetes inspidus, where there are large volumes of inspid, tasteless urine

Question 48

describe hypersecretion of ADH

Answer 48

syndrome of inappropriate ADH, which leads to excess ADH and water retention

Question 49

what are the effects of potassium electrolytes on nerve function

Answer 49

increasing extracellular fluid leads to depolarisation depolarisation causes axons to fire action potential membrane potential does not return to resting levels, the result is that the axon is in refractory period

Question 50

why are there potassium salts in toothpaste

Answer 50

to desensitise hypersensitive dentine

Question 51

what is the manufacturers claim in regard to potassium salts in toothpaste

Answer 51

potassium ions will diffuse from paste along the dentinal tubules and raise the potassium ion concentration at the end of the tubules. this leads to depolarised nerves, and inactivated sodium channels, causing a prolonged refractory period the issue is that potassium ion build up does not persist

Question 52

what causes an increase in renin secretion

Answer 52

- decreased plasma volume - increased sympathetic nerve activity - decreased renal blood flow, leading to a decrease in glomerular blood flow, leading to stretch of J-G baroreceptors and decreased sodium concentrations in tubular fluid - this affects the juxta glomerulosa apparatus, increasing renin secretion

Question 53

what are the two factors that increase renin secretion

Answer 53

increased sympathetic nervous activity and the macula densa

Question 54

what is the macula densa

Answer 54

lining of specialised cells in the kidney

Question 55

is there much control over the glomerular filtration rate

Answer 55

no because of the flow

Question 56

are there any hormonal impacts in the proximal convoluted tubule

Answer 56

no it happens despite any hormonal action

Question 57

describe the counter current exchange

Answer 57

flow is generated into the loop of henle, which works to concentrate the urine. the concentration depends on the active transport in the thick limb of the loop of henle, so there are working pumps

Question 58

what is the sodium ion involved in

Answer 58

depolarisation of nerves

Question 59

what are calcium ions involved in

Answer 59

cardiac conducting system, or as second messenger

Question 60

what are the chlorine ions involved in

Answer 60

saliva secretion, as they produce a concentration gadient with chloride in the lumen, to allow water flow into the lumen

Question 61

why do we excrete hydrogen ions

Answer 61

to prevent metabolic acidosis

Question 62

what does ADH do to allow water absorption

Answer 62

provides channels

Question 63

which hormone is involved in water absorption

Answer 63

ADH

Question 64

which hormone is involved in electrolyte reabsorption

Answer 64

RAAS and ANH

Question 65

what is octopressin

Answer 65

vasoconstrictor used in local anaesthetic

Question 66

how long after dirnking does fluid get lost through urine

Answer 66

half an hour

Question 67

which ions are exchanged when absorbing water and sodium

Answer 67

potassium and hydrogen

Question 68

what does sensitive toothpaste cause the production of

Answer 68

tertiary dentine by odontoblasts