physiology Flashcards
1
Q
What is osmolarity?
A
The concentration of osmotically active particles present in a solution
2
Q
What is needed to calculate the osmolarity?
A
The molar concentration of the solution
The number of osmotically active particles present
3
Q
What is Tonicity?
A
The effect a solution has on cell volume
4
Q
What happens to a cell in a hypotonic solution?
A
Too much water
Induces cell lysis
5
Q
In which forms does total body water exist?
A
Intracellular fluid (67% of total body water)
Extracellular fluid (33% of total body water)
6
Q
What are the components of extracellular fluid?
A
Plasma (20%)
interstitial fluid (80%)
Lymph and trans cellular fluid (negligible)
7
Q
How are the fluid compartments measured?
A
TBW- 3H20
ECF- inulin
Plasma- labelled albumin
8
Q
What is insensible loss of water?
A
Skin
Lungs
9
Q
What is sensible loss of water?
A
Sweat
Faeces
Urine
10
Q
What causes the biggest loss of water?
A
Urine
11
Q
Are there always more Na and Cl ions outside the cell compared to inside?
A
Yes
12
Q
What alters the composition and volume of ECF?
A
Kidneys
13
Q
What is the primary function of the kidney?
A
Regulate the volume, composition and osmolarity of the body fluids
Controlled excretion of ions
14
Q
What is the functional unit of the kidneys?
A
The nephron
15
Q
What are the functions of nephrons?
A
Filtration
Reabsorption
Secretion
16
Q
What is urine?
A
Modified filtrate of blood
17
Q
What are the renal processes?
A
Glomerular filtration
Tubular reabsorption
Tubular secretion
18
Q
How much of plasma that enters the glomerulus is filtered?
A
20%
80% is unfiltered and leaves through the efferent arteriole
19
Q
is the diameter of the afferent arteriole bigger or smaller than the efferent arteriole?
A
bigger
20
Q
what acts as a barrier to RBC in glomerular filtration?
A
the glomerular capillary endothelium
21
Q
what acts as a barrier to plasma proteins in glomerular filtration?
A
the basement membrane
22
Q
what is glomerular filtration rate?
A
rate at which protein free plasma is filtered from the glomeruli into the bowmans capsule per unit time
23
Q
what is the major determinant of GFR?
A
glomerular capillary blood pressure
24
Q
what is the intrinsic regulation of GFR?
A
myogenic mechanism
tubuloglomerular feedback mechanism
25
what is the extrinsic control of GFR?
sympathetic control via baroreceptor reflex
26
what affect does an increase in arterial BP have on glomerular capillary blood pressure?
increased glomerular capillary BP, therefore increased net filtration pressure and then increased GFR
27
what affect does a decrease in urine production have on arterial blood pressure?
it helps compensate for the drop in BP
28
what happens in myogenic autoregulation?
if vascular smooth muscle is stretched (arterial pressure is increased) it contracts, thus constricting the arteriole
29
what happens in tubuloglomerular feedback autoregulation?
involves the juxtaglomerular apparatus (mechanism remains unclear)
if GFR rises then more NaCl flows through the tubule leading to constriction of the afferent arterioles
30
what senses NaCl in the tubular fluid of the juxtaglomerular apparatus?
macula densa cells
31
what can cause an increase in bowmans capsule fluid pressure?
a kidney stone
results in a lower GFR
32
what can cause an increase in capillary oncotic pressure?
diarrhoea
results in a lower GFR
33
what can cause a decrease in bowmans capsule oncotic pressure?
severe burns
results in an increase in GFR
34
what is plasma clearance?
a measure of how effectively the kidneys can 'clean' the blood of a substance
35
what is inulin clearance equal to?
GFR
36
what are the features of inulin?
freely filtered at the glomerulus
neither absorbed nor secreted
not metabolised by the kidneys
not toxic
easily measured in urine and blood
37
what is used as the gold standard to clinically determine GFR?
inulin
38
what is the clearance for a substance that are filtered, completely reabsorbed and not secreted in urine eg. glucose?
0
39
what is the clearance in a substance that is filtered, partially reabsorbed and not secreted eg. urea?
clearance< GFR
40
what is the clearance for a substance that is filtered, secreted but not reabsorbed eg H?
clearance>GFR
41
what is used to measure renal plasma flow?
para-amino hippuric acid (PAH)
42
what kind of fluid is reabsorbed in the proximal tubule?
iso-osmotic fluid with filtrate
43
what is reabsorbed in the proximal tubule?
sugars
amino acids
phosphate
sulphate
lactate
44
what is secreted in the proximal tubule?
H
hippurates
neurotransmitters
bile pigments
uric acid
drugs
toxins
45
what is primary active transport?
energy is directly required to operate the carrier and move the substance against its concentration gradient
46
what is secondary active transport?
the carrier molecule is transported coupled to the concentration gradient of an ion (usually Na)
47
what is facilitated diffusion?
passive carrier-mediated transport of a substance down its concentration gradient
48
where are sodium ions reabsorbed?
all areas of the nephron except the descending loop of henle
49
what drives Na reabsorption in the proximal tubule?
the basolateral Na-k ATPase
50
what drives Cl reabsorption?
Na reabsorption
51
what is the function of the loop of henle?
generates a cortico medullary solute concentration gradient which enables the formation of a hypertonic urine
52
what is counter current flow?
opposing flow in the two limbs of the loop of henle
53
what are the features of the ascending limb of henle?
Na and Cl are being reabsorbed
relatively impermeable to water
54
what is the feature of the descending limb of henle?
does not reabsorb NaCl and is highly permeable to water
55
which drugs block the triple co transporter in the thick ascending loop of henle?
loop diuretics
56
what are the features of the countercurrent exchange?
vasa recta runs alongside the long loop of henle of juxtamedullary nephrons
capillary blood equilibrates with interstitial fluid across the "leaky" endothelium
blood osmolality rises as it dips down the medulla (water loss, solute gained)
blood osmolality falls as it rises back up into the cortex (water gained, solute lost)
57
true or false- all tubules empty into collecting ducts?
true
58
what affect does ADH have on water?
increases reabsorption
59
what affect does aldosterone have?
increase Na reabsorption
decrease H/K secretion
60
what affect does atrial natriuretic hormone have?
decreases Na reabsorption
61
what affect does PTH have?
increases Ca reabsorption
decreases PO4 reabsorption
62
what has a low permeability to water and urea?
the distal tubule
63
where is urea concentrated?
in the tubular fluid
64
what happens in the early distal tubule?
Na-K-2Cl transport (NaCl reabsorption)
65
what happens in the late distal tubule?
Ca reabsorption
H secretion
Na reabsorption
K reabsorption
66
what are the features of the late collecting duct?
a low ion permeability
permeability to water (and urea) influenced by ADH
67
where is ADH secreted from?
the posterior pituitary
68
what happens when we are dehydrated?
ADH secretion is increased (leading to a high water permeability and a highly concentrated urine)
69
what happens to the collecting duct in the presence of minimal ADH concentration?
impermeable to water so therefore there is no water reabsorption
70
what are the symptoms of diabetes insipidus?
large volumes of dilute urine
constant thirst
71
how is diabetes insipidus treated?
ADH replacement
(demsopressin)
72
what is aldosterone?
a steroid hormone secreted by the adrenal cortex
73
when is ADH secreted?
in response to rising K concentration or falling Na conc in the blood
also secreted after activation of the renin-angiotensin system
74
what does aldosterone do?
it stimulates Na reabsorption and K secretion
75
what is the affect of an increase in K concentration as a result of aldosterone?
directly stimulates the adrenal cortex
76
what increases production of aldosterone?
angiotensin II
77
what does angiotensin II do?
increase thirst
increase vasopressin
increase arteriolar vasoconstriction
78
what can trigger the release of renin?
reduced pressure in afferent arteriole
macula densa cells sense the amount of NaCl in the distal tubule
increased sympathetic activity
79
what can abnormal increases in the RAA system cause?
hypertension
80
what is responsible for the fluid retention associated with congestive HF?
RAA system
81
how is fluid retention associated with HF treated?
low salt diet
loop diuretics
82
what does ANP promote?
excretion of Na and diuresis, decreasing plasma volume
lowers BP
83
what affect does an increase in H ion conc have on pH?
reduces pH
84
what affect can acidosis have on the nervous system?
depresses CNS
85
what affect can alkalosis have on the nervous system?
overexcitability of the peripheral nervous system and the CNS
86
where does H ions come from?
carbonic acid formation
inorganic acids produced during breakdown of nutrients
organic acids resulting from metabolism
87
what is bodily pH equal to?
concentration of kidneys divided by lungs
88
what is the rate of HCO3 filtration?
GFR x conc of HCO3
(4320mmol/day filtered by the kidneys)
89
what is the result of H ion secretion by the tubule?
drives reabsorption of HCO3
forms acid phosphate
forms ammonium ion
90
what is the purpose of excreting TA and NH4 simultaneously?
it rids the body's acid load and regenerates buffer zones (alkalinizes the body)
91
what is the normal acid base balance in the body?
plasma pH close to 7.4 (7.35-7.45)
conc of HCO3 close to 25 mmol/l
arterial PCO2 close to 40mmHg
92
which condition can cause respiratory acidosis?
chronic bronchitis
chronic emphysema
airway restriction
chest injuries
respiratory depression
93
what is the definition of uncompensated respiratory acidosis?
pH<7.35 and PCO2>45mmHg
94
how does the renal system compensate for respiratory acidosis?
H secretion is stimulated
all filtered HCO3 is reabsorbed
H continues to be secreted and generates titratable acid and NH4
acid is excreted and new HCO3 is added to the blood
95
what is respiratory alkalosis?
the excessive removal of CO2 by the body
96
what are some causes of respiratory alkalosis?
low PO2 at altitude (hypoxia)
hyperventilation
97
how does the renal system compensate for respiratory alkalosis?
H secretion is insufficient to reabsorb HCO3
HCO3 is excreted and the urine is alkaline
no TA and NH4 are formed so no new HCO3 is generated
98
what are some causes of metabolic acidosis?
ingestion of acids
excessive metabolic production of H (eg lactic acidosis during exercise or ketoacidosis)
excessive loss of base from the body (eg diarrhoea)
99
how does the renal system correct metabolic acidosis?
filtered HCO3 is very low and readily absorbed
H secretion continues and produces TA and NH4 to generate more new HCO3
the acid load is excreted (urine is acidic) and the conc of HCO3 is absorbed
ventilation can then be normalised
100
what are some causes of metabolic alkalosis?
vomiting
ingestion of alkali
aldosterone hypersecretion
101
how does the renal system compensate for metabolic alkalosis?
not all the filtered HCO3 is reabsorbed
no TA or NH4 is generated
HCO3 is excreted
conc of HCO3 falls backwards towards normal
