1. Homeostasis and Transport Flashcards
circulation
moves fluids and gases
diffusion of fluid (homeostasis)
to interstitial space
into and out of cell
diffusion of gas (homeostasis)
from extracellular fluid
into and out of cell
diffusion of ions/molecules
from high to low concentration gradient
transport
movement of ions/molecules through channels or transporters into and out of cells
pumping of ions/molecules against a concentration gradient
4 regulations of homeostasis
regulation of blood gases
regulation of [ion]/H2O
regulation of BP
regulation of hormones
homeostasis
tendency of an organism or a cell to regulate its internal conditions usually by a system of feedback controls regardless of outside conditions
to stabilize health and functioning
positive feedback loop
causes a self-amplifying cycle
physiological change leads to an even greater change in the same direction
negative feedback loop
process in which the body senses a change and activates mechanisms to reverse that change
[Na+] extracellular
142 mEq/L
[Na+] intracellular
10 mEq/L
Na+ flows
OUT –> IN
[K+] extracellular
4 mEq/L
[K+] intracellular
140 mEq/L
K+ flows
IN –> OUT
[Ca++] extracellular
2.4 mEq/L
[Ca++] intracellular
0.0001 mEq/L
[Ca++] flows
OUT –> IN
[Cl-] extracellular
103 mEq/L
[Cl-] intracellular
4 mEq/L
Cl- flows
OUT –> IN
[HCO3-] extracellular
28 mEq/L
[HCO3-] intracellular
10 mEq/L
HCO3- flows
OUT -> IN
[Glucose] extracellular
90 mg/dl
[Glucose] intracellular
0-20 mg/dl
Glucose flows
OUT –> IN
[Proteins] extracellular
2 g/dl
5 mEq/L
[Proteins] intracellular
16 g/dL
40 mEq/L
Proteins flow
IN –> OUT
passive transport
no energy needed
flow [high] -> [low]
(down conc gradient)
active transport
need energy
against conc gradient
[low] -> [high]
factors that alter diffusion rate
membrane permeability
concentration difference
electrochemical potential
pressure
membrane permeability
(P)
membranes are semipermeable
P=0 : not perm
P = 10: low perm
p = 1000: high perm
concentration difference
(chemical force)
if there is a difference in concentration in 2 regions, there will be a tendency to flow from high to low
electrical potential
(electrical force)
if there is difference in electrical potential in 2 regions, there will be a tendency to flow from high to low
pressure
tendency to flow from area of high p to low p
explain how O2 diffuses between alveoli and capillary blood flow
low PO2 inside capillary
high PO2 in alveoli
O2 diffuses from alveoli into capillary blood flow
explain how CO2 diffuses between alveoli and capillary blood flow
low PCO2 inside alveoli
high PCO2 inside blood
CO2 diffuses from capillary blood flow to alveoli
what determines simple diffusion
conc difference
electrical difference
permeability (open channels)
channels
cellular membrane proteins
types of channel gates
voltage
ligand
voltage-gate ion channel
opne and close by membrane potential
ligand-gate ion channel
conformational change induced by binding molecule opens/closes channel
how many gates for voltage-gated Na+ channel
2 gates
type of gates for voltage-gated Na+ channel
activation gate
inactivation gate
activation gate location
outside cell
inactivation gate location
inside cell
how do ion channels filter?
selectively filter by size
channel pore size is similar to target ion size
how many states for VG Na+ channels
3 states
types of states for VG Na+ channels
resting - no Na+ move
activation - Na+ into cell
inactivation - no Na+ move
resting membrane potential (VG Na+)
-70mV
activation membrane potential (VG Na+)
> = -55 mV
inactivation membrane potential (VG Na+)
-56 mV to -69 mV
speed of Na+ channel open/close
1 ms
what type of currents are VG Na+?
inward
how many gates for VG K+ channels?
1 gate
how many states for VG K+ channels?
2 statest
types of states for VG K+ channel?
resting - no K+ move
slow activation - K+ move out of cell
resting membrane potential (VG K+)
-70 mV
slow activation membrane potential (VG K+)
> =-69 mV
what type of currents are VG K+?
outward
hyperpolarization
change in membrane potential to make it more (-)
decrease mem potential
depolarization
change in membrane potential to make it less (-)
increase membrane potential
ligand gated ion channel
open in response to ligand binding to receptor
channels open longer than ion(?)
G protein coupled receports
TBD???
slide 18
facilitated diffusion
down conc gradient
need carrier protein
1 carrier protein per molecule
conformational change to protein
facilitated diffusion Vmax determining factors
[carrier molecules]
rate of movement of carrier molecules across channel
Vmax
max rate of diffusion
active transport
movement of molecules against conc gradient
requires energy
requires carrier protein
primary active transport
energy source is ATP breakdown
active transport examples
Na+/K+ pump
Ca2+ pump
H+ pump
secondary active transport
uses energy of one solute moving with the conc gradient to move another substance against conc gradient
will be paired with primary active transport
cotransport
(symport)
both ions move in the same direction
one down its gradient
one against its gradient
contransport examples
Na/Amino acid
Na/Phosphate (NaPi)
SGLT (Na Glucose co transporter)
Anion Exchanger 1
(AE1)
antiporter
ions move in separate directions
one uphill
one downhill
AE1 Chloride Shift
(Respiring Tissues)
HCO3- moves against gradient: IN -> OUT
Cl- moves down gradient: OUT -> IN
AE1 Chloride Shift
(Lungs)
HCO3- moves down gradient: OUT -> IN
Cl- moves against gradient: IN -> OUT
AE1 Chloride shift transport type
secondary active transport
counter transport
uses a gradient of one molecule to move another against the concentration gradient but in the opposite direction
counter transport examples
ATP-dependent Ca++ pump
Na+/Ca++ exchanger
Na+/K+-ATPase pump
how does water move across a cell membrane
aquaporin
(AQP)
how many subtypes of aquaporin
14
AQP 0 - 13
how do solvents move across semi-permeable membrane
from area of [high solvent] to [low solvent] across semipermeable membrane
osmotic pressure
pressure required to maintain an equilibrium with no net movement of solvent
semi-permeable membrane
water can pass
ions cannot pass
movement determine by molar concentration of solute
how does water move across semi-permeable mebrane
from low to high
molarity
moles of solute per liter of solution
osmolarity
osmoles (Osm) of solute per liter of solution
how many osmoles of solute particles does 1 mole of NaCl produce in water?
2 osmoles
Na = 1
Cl = 1
1+1 = 2
osmotic pressure
minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane
osmotic pressure is determine by the _______ not the _______.
osmotic pressure is determined by the number of particles, not the size.
1 M Glucose
1 Osm/L Glucose
1 M NaCl
2 Osm/L NaCl solution
1 M CaCl2
3 Osm/L CaCl2 solution
osmolarity of normal body fluid
280-310 mOsm/L
hypertonic solution
water leaves cell
shrivel
A solution will be hypertonic to a cell/body fluids
its solute concentration is higher than that inside the cell.
hypotonic solution
water enters cell
lyse
A solution will be hypotonic to a cell/body fluids
its solute concentration is lower than that inside the cell
isotonic solution
same [solute] compared to inside cell
no overall change
ECF (extracellular fluid) osmolarity
280-310 mOsm/L
0.9% NaCl osmolarity
308 mOsm/L
3% NaCl osmolarity
1026 mOsm/L
crystalliods
aqueous mineral solutions
semi-permeable
colloids
large molecular weight
mostly impermeably
increase oncotic pressure
Ex. Albumin
resting membrane potential
(RMP)
difference in electrical potential between the interior and the exterior of a biological cell membrane at rest
graded potential
(GP)
changes in membrane potential that vary in size
types of graded potentials
synaptic
end plate
receptor
pacemaker
slow-wave
action potential
(AP)
occurs when the membrane potential rapidly rises and falls in excitable cells
types of excitable cells
neurons
muscle cells
cardiac cells
endocrine cells
What ion influences the RMP?
K+
(some Na+, some Cl-)
((but mostly K+))
why is RMP negative?
more cations (+) are leaving the cell than entering
RMP determinators
[ion] differences
ion permeabilities (channels)
Na+/K+ pump
anions (-) inside cell
how do we calculate RMP
Nernst Eq
Simplified Nernst Equation
E = (61/Z)*Log([ion o]/[ioni])
picure of eq here?
Log 100
2
Log 10
1
Log 1
0
Log 0.1
-1
Log 0.01
-2
Equilibrium potential
(Eion)
electrical potential difference that balances an ionic concentration gradient
Na+ Eion
+70 mV
(60-70mV)
K+ Eion
-95 mV
(-90 - -95 mV)
Ca++ Eion
+134 mV
(120-135 mV)
Cl- Eion
-86 mV
(-65 - -88 mV)
Goldman Equation
equilibrium potential for multiple ions
Should not need to use
depolarizing graded potential
stimulus that causes the cell to be less negatively charged compared to ECF
RMP increase
hyperpolarizing graded potential
stimulus that causes the cell to be more negatively charged compared to ECF
RMF decrease
Synaptic potentials are what type of potential
graded potential
synaptic potential sequence
AP reaches axon terminal
Depolarizes membrane
VG Ca++ channel open
Ca++ flow in
Synaptic vesicles release
neurotransmitters
NeuroT binds to
receptors
(+) ions flow in
are synaptic potentials depolarizing or hyperpolarizing?
depolarizing
(+) ions flow in which will cause potential to be less negatively charged
excitatory postsynaptic potential
(EPSP)
closer to threshold of action potential
typically triggered by glutaminergic (CNS) and cholinergic (PNS) presynaptic neurons
NueroT binding opens cation (+) channels
(permeable to Na+ Ca++)
inhibitory postsynaptic potential
(IPSP)
most often evoked by GABA or glycine-ergic presynaptic neurons
NeuroT binding opens Cl- channels
How do EPSP and IPSP compare pre-synapse?
they are similar
How to EPSP and IPSP compare post-synapse?
EPSP is closer to AP threshold
IPSP is further from AP threshold
where does the AP generate?
axon hillock
spike initiation zone
Steps of AP
resting
threshold
depolarization
repolarization
hyperpolarization
resting stage
RMP
determined by K+ leak channels
threshold level
EPSPs: Na+ IN
(ligand gated channels)
IPSPs: K+ OUT
EPSP > IPSP
depolarization
VG Na+»_space; VG K+
VG Na+ channels open
Na+ rushes in
lesser K+ channels open
K+ slowly moves out
repolarization
VG K+»_space; VG Na+
more VG K+ open
K+ moves out
Na+ channels start to close
hyperpolarization
VG K+ channels remain open after the potential reaches resting level
conductance
how many ions rush into cell during certain time
open/close durations of Na+ and K+ VG channels
VG Na+: quick
VG K+: slow
how is an AP triggered in a neuron?
a strong stimulus creates a graded potential that is above the threshold by the time it reaches the trigger zone (axon hillock) so an AP results
summation of graded potentials
summation of all EPSPs and IPSPs will determine if AP occurs
types of summations
spatial
temporal
how does AP move down an axon?
depolarization of the axon at one point causes VG Na+ channels to open ahead, facilitating flow down
Myelin
schwann cells (PNS)
oligodendrocytes (CNS)
multiple sclerosis (MS)
autoimmune disease affecting the oligodendrocytes (CNS)
slows down AP transduction resulting in muscle weakeness and other symptoms
myelinated conduction rate
100 m/s
unmyelinated conduction rate
0.25 m/s
why does the AP not move ‘backward’?
Na+ channels have a refractory period where they cannot re-open during
diffusion due to charge will occur toward the open Na+ channels
absolute refractory period
inactivation gate of Na+ channel closed
(above resting potential)
relative refractory period
need a stronger stimulus to initiate response
(below resting potential)
(hyperpolarized)
graded potential overview
- stimulus does not reach threshold
- stimulus causes local change in mem pot
- dies over short distance
- can be summated
- does not obey all or none
action potential overview
- stimulus reaches threshold -> AP
- stimulus causes depolarization to threshold level
- propagated
- can not be summated
- obeys all or none law
action potential shape/amplitude
always the same because they either happen or they dont
either an AP is triggered or it is not triggered
AP will always manifest the same way if threshold levels are met
Na+/K+ Pump
(Na+/K+ ATPase)
-establish ion gradients
-helps set RMP
-creates some (-)
potential
-determine excitability of
nerve/muscle (fatigue)
-control cell volume
