Physiology Flashcards
(120 cards)
1
Q
what is osmolarity
A
concentration of osmotically active particles present in a solution
2
Q
what are the units of osmolarity
A
osmol/l or mosmol/L (for body fluids as weaker)
3
Q
how can you calculate osmolarity
A
the molar concentration of the solution x
the number of osmotically active particles present
e.g. 150mM NaCL = 2 x 150m = 300 mosmol/l
4
Q
what is the units for osmolality
A
osmol/kg
5
Q
what is tonicity
A
the effect ta solution has on cell volume
6
Q
what is a isotonic solution
A
a solution that causes no change in cell volume, there is no net movement of water
7
Q
what is a hypotonic solution
A
solution that causes an increase in cell volume, water moves into cell by osmosis, more water initially outside of the cell
(more water)
8
Q
what is a hypertonic solution
A
causes a decrease in cell volume, cell loses fluid as initially less water in external environment
(less water, concentrated salt solution)
9
Q
what can happen if a cell expands with water too much
A
lysis
10
Q
what is hydrostatic pressure
A
pressure created by fluid- high hydrostatic will push water into lower hydrostatic pressures
11
Q
what osmolarity are isotonic solutions usually
A
300 mosmol/l
less than 300= hypotonic
more than 300= hypertonic
12
Q
what other that osmolarity affects tonicity
A
the permeability of the membrane (ability of solute to cross the cell membrane)
e.g. 300 mM or urea will be hypotonic as RBC have transporters for this and leave more water outside the cell
300 mM of sucrose is isotonic as RBC membrane not permeable to this
13
Q
what is the osmolairty of plasma and extracellular fluid
A
300 mosmol/l
14
Q
do male or females have more body water
A
males
15
Q
what are the 2 main compartments of total blody water
A
intracellular fluid (67%) extracellular fluid (33%)
16
Q
what makes up extracellular fluid
A
plasma (20%) (liquid component of blood)
interstitial fluid (80%)
lymph (negligible) and transcellular fluid (negligible)
17
Q
what makes up transcellular fluid
A
CFS and pleural fluid
18
Q
how can you measure body fluid
A
tracers can show the distribution volume (allow it to equilibrate with body water then take sample and measure its concentration)
TBW- 3H2O
ECF- inulin
plasma- labelled albumin
(dose/ sample concentration= volume of distribution)
19
Q
what are the fluid inputs
A
fluid intake
food intake
metabolism
20
Q
what are the fluid outputs
A
insensible loss (not controllable) (skin diffusion, lung exhalation) sensible loss (controllable) (sweat, faeces, urine)
21
Q
what is water imbalance mainfested as
A
changes in body fluid osmolarity
22
Q
what is the normal rate of urine production
A
1ml/min
23
Q
what does a change in plasma volume affect
A
arterial BP
24
Q
what happens to lung water loss when its cold
A
increases
25
can you completely turn off urine production
no as some waste products can only be excreted in solution
26
what is the ionic composition of ECF
high Na+
high Cl-
high bicarbonate (HCO3-)
27
what is the ionic composition of ICF
high potassium
high Mg2+
negatively charged proteins
28
what fluids have similar ionic composition
plasma and intersitial fluid
29
what is the ionic composition of plasma
high Na+
| high Cl+
30
what separates ECF and ICF
plasma membrane
31
are the osmotic concentrations of ECF and ICF the same/ different
identical- 300 mosmol/l
32
what is fluid shift
movement of water betweem the ICF and ECF in response to an osmotic gradient
33
what would happen if the osmotic concentration of the ECF increases
ECF would become hypertonic meaning water would be lost from the ICF
34
what would happen if the osmotic concentration of the ECF decreases
ECF is now hypotonic so water would go into the ICF
35
what happens to the volumes of ICF and ECF when there is a loss or gain of NaCl in the ECF
(Na excluded from)
ECF NaCl gain= ECF increased, ICF decreases (water leaves)
ECF NaCl loss= ECF decreased, ICF increased (ECF hypotonic)
36
what are the challenges to fluid homeostasis
gain or loss of water- changes fluid osmolarity
gain or loss of NaCl- ^same
gain or loss of isotonic fluid (e.g. saline= 0.9% NaCl)
no change in osmolarity but change in ECF volume ONLY
37
what alters composition and volume of the ECF
kidneys
38
why is regulation of ECF volume important
for long term regulation of blood pressure
39
what is electrolyte balance
when rate of gain= rate of loss
40
why is electrolyte imbalance important
concentrations can affect water balance (via changes in omsolarity)
concentrations can affect cell function
41
what creates 90% of the ECF's osmotic concentration
sodium salts (as this is mainly present in the ECF is a major determinant of ECF volume)
42
what follows sodium
water
43
what affects sodium reabsorbtion in the kidneys
aldosterone
44
what is a key role of potassium
establishing membrane potential
45
is potassium intracellular or extracellular
intracellular
46
what can fluctuations in the concentration of plasma potassium cause
muscle weakness, paralysis, cardiac arrhythmias, cardiac arrest
47
where do you lose salt
sweat and faeces 0.5 g
| urine 10 g
48
what is salt imbalance manifested as
changes in extracellular fluid volume
49
what are the functions of the kidneys
```
water and salt balance
maintain plasma volume and osmolarity
acid base balance
excretion of metabolic waste and exogenous compounds
secretion of renin and erythopoietin
conversion of vit D into clcitriol
```
50
what is the active form of vit D and its role
calcitriol- calcium absorption in the GI tract
51
what controls the conversion of vit d to calcitriol
parathryoid hormone
52
when is erythropoietin release
when hypoxic- stimulates RBC production
53
what muscles line the ureters
smooth muscles- peristaltic action to push urine down to baldder- colicky pain
54
does the urine get modified when it enters the ureter
no- same as when leaves bladder
55
what is the 'appearance' of the inside of the kidney
cortex is granular
| medulla is striated
56
what is the functional unit of the kidney
the nephron
57
what are the functions of the nephron
```
filtration
reabsorption (move things back into the blood)
secretion (move from blood into tubular fluid)
```
58
what makes up the wall of the nephrons
single layer of epithelial cells
59
describe the blood supply of a cortical nephron (80% of the nephrons)
renal artery- afferent artery- glomerulus- efferent arteriole- pertibular capillary (meshwork closely related to the tubular component of nephron)- venules- renal vein
60
what supplies the tubular nephron and secretes/ recieves reabsorbed particles
peritublar capillaries
61
where does the collect duct start and end
starts in cortex, goes through medulla connecting with proximal tubules, ends in renal pelvis
62
what is the fluid in the nephron called
tubular fluid (still being modified- when it enters collecting duct=urine)
63
what are the parts of the nephron
bowmans capsule- proximal tubule- descending then ascending limb of loop of henle- distal tubule- collecting duct
64
describe the blood supply of a juxtamedullary nephron
single capillary (vasa recta) which follows the route taken by the loop of henle
65
which type of nephron has a bigger loop of henle
juxtamedullary
66
what creates the striated appearance of the medulla
the loops of henle ad the collecting ducts (as arranged in a radial fashion)
67
does the afferent or efferent artery have a bigger diameter
afferent bigger- maintains pressure
68
what muscles line the afferent arterioles
smooth- contraction reduces the amount of blood that flows into the glomerulus
69
what makes up the glomerular membrane
capillary endothelium
basal lamina
podocytes
70
what are the roles of the juxtaglomerular aparatus
macula densa cells are salt sensitive- monitor salt in tubular fluid
granular cells produce and secrete renin
71
what is urine
modified filtrate of blood
72
what are the renal processes
glomerular filtration
| tubular reabsorption and secretion
73
how much of plasma that enters the glomerulus is filtered
20%
74
what does rate of excretion=
rate of filtration + rate of secretion - rate of reabsorption
75
what does rate of filtration =
concentration of X in plasma x GFR
76
what is a healthy GFR
125 ml/min
77
what does rate of excretion =
concentration of x in urine x volume of urine produced
78
what does rate of reabsorption =
rate of of filtration of X - rate of excretion of X
79
what does rate of secretion =
rate of excretion of X - rate of filtration of X
80
what must have happened if rate of filtration > rate of excretion
net reabsorbtion
81
what are the filtration barriers
```
Glomerular Capillary Endothelium (barrier to RBC)
Basement Membrane (basal lamina) (plasma protein barrier)
Slit processes of podocytes (plasma protein barrier)
(Glomerular epithelium)
```
82
what makes up the basement membrane
collagen and glycoprotein
83
why cant plasma proteins cross the basement membrane
as plasma proteins are negatively and so too is the basement membrane
84
should RBC get through into the lumen on bowens capsule
no- if RBCs in urine then something is wrong
85
what forces make up the net filtration pressure
glomerular capillary blood pressure (largest: 55mmHg)
bowmans capsule oncotic pressure (0 as no plasma proteins in bowens)
bowmans capsule hydrostatic pressure (fluid within capsule- opposes net filtration)
capillary oncotic pressure (plasma proteins within lumen pull water back into capillaries opposing net filtration)
86
is filtration active or passive
passive- driven by net filtration pressure
87
how can glomerulae capillary pressure remain constant across the capillary
as efferent diameter smaller than afferent
88
what is the usual net filtration pressure
10mm Hg
89
what are starling forces
the balance of hydrostatic pressure and osmotic (oncotic) pressures
90
what is GFR
rate a which protein free plasma is filtered from the glomeruli into bowmans per unit time
= Kf (filtration coefficient- how permeable the glomerular membrane is) x net filtration pressure
91
what is the major determinant of GFR
glomerular capillary fluid pressure
92
what is the extrinsic control of GFR
sympathetic control via baroreceptor reflex
93
what is the intrinsic control of GFR
autoregulation:
myogenic
tubuloglomerular feedback mechanism
94
how does arterial blood flow affect GFR
if increases causes increased net filtration pressure, increasing GFR (opposite applies)
vasoconstriction of smooth muscles of afferent arterioles decreases blood supply to glomerulus, decreasing GFR
vasodilation of afferent ateriole increases blood flow, increasing GFR
95
how is GFR controlled by changes in arterial blood pressure
```
e.g
fall in blood volume
decreased ABP
detected by aortic and carotid sinus baroreceptors
increased sympathetic activity
arteriolar vasoconstriction
decreased glomerular blood flow
decreased GFR
decreased urine volume
helps compensate for lack of blood
```
96
what allows the GFR to remain fairly constant despite MABG
autoregulation- intrinsic control
| myogenic and tubuloglomerular feedback
97
what is myogenic intrinsic control
if vascular smooth muscle is stretched (increased ABP) then it contracts constricting the arteriole
aims to maintain constant blood flow to the kidneys
98
what is tubuloglomerular feedback
involves the juxtaglomerular apparatus (macula densa cells- release vasoactive substances)
if GFR rises more NaCl flows through the tubule leading to the constriction of afferent arterioles
this decreases blood flow and decreases GFR
99
what senses the NaCl content of the tubular fluid
macula densa cells in the juxtaglomerular apparatus
100
what cause cause increased bowmans capsule fluid pressure
e.g. kidney stone, blockage in drainage
101
what cause cause increased capillary oncotic pressure
diarrhoea (losing water but not plasma proteins)
102
what cause cause decreased capillary oncotic pressure
severe burns (losing plasma proteins but not water)
103
what can decrease the filtration coefficient
a decrease in the surface area available for filtration
104
what is plasma clearance
a measure of how efficiently the kidneys can clean the blood of a substance
= the volume of plasma completely cleared of a substance per minute (each substance has specific plasma clearance value)
105
how do you calculate clearance of a subance
rate of excretion of X / plasma concentration of X
= [X]urine x Vurine / [X] plasma
106
what substance does plasma clearance = GFR
inulin (rate of excretion matches rate of filtration)
107
is inulin secreted or reabsorbed
no
108
what can be used instead of inulin
creatinine
109
what is the down side to creatinine
undergoes small amount of tubular secretion
110
name a substance that is completely reabsorbed and not secreted
glucose
| clearance= 0
111
name a substance where clearance less than GFR
urea- as is partly reabsorbed and not secreted
112
name a substance where clearance is more than GFR
H+ as is secreted but not reabsorbed
113
what has happened when clearance
substance is reabsorbed
114
what has happened when clearance = GFR
substance is neither reabsorbed or secreted
115
what has happened when clearance > GFR
substance is secreted into tubule
116
what can be used to calculate renal plasma flow
para-amino hippuric acid (is freely filtered at glomerulus and secreted into tubule- is not reabsorbed (completely cleared from plasma)
117
what is a normal renal plasma flow
650 ml/min
118
what should a GFR marker be
freely filtered
| not secreted or reabsorbed
119
what should a RPF marker be
filtered and completely secreted
120
what is filtration fraction
the fraction of plasma flowing through the glomeruli that is filtered into the tubules
GFR/ renal plasma flow
