Excitable Cells Flashcards
1
Q
3 electrical events
A
cell to cell communication (intercellular)
sensing environmental changes
triggering intracellular events
2
Q
extracellular fluid composition
A
ions, proteins, HIGH NaCl
3
Q
Intracellular fluid composition
A
ions, lots of proteins, HIGH KCl
4
Q
what allows cells to communicate with each other?
A
major difference between inside and outside of cell (Na outside, K inside)
5
Q
3 major parts of cell excitation
A
extracellular fluid
intracellular fluid
cell membrane
6
Q
types of movements that occur across cell membrane
A
Simple Diffusion mediated transport osmosis endocytosis exocytosis
7
Q
simple diffusion
A
random diffusion, down a concentration gradient.
8
Q
what kind of molecules can simply diffuse?
A
organic molecules or ions.
9
Q
organic molecules that can simple diffuse
A
non polar organic because solubility in lipid is high. membrane 50% lipid composition
10
Q
ion simple diffusion uses what
A
ion channels, which are proteins themselves, several subunits generally and ion-specific (K channels).
11
Q
examples of non polar substances are
A
O2, CO2, fatty acids, steroid hormones
12
Q
Amount of substance crossing a suface per unit time is termed what
A
flux
13
Q
diffusion equilibrium
A
flux=0
14
Q
diffusion between a substance between two compartments is always ______
A
bi-directional
15
Q
mediated transport
A
ligand binds to a transporter in the membrane, transporter undergoes a conformational change and ligand is released on the other side of the membrane
16
Q
two types of mediated transport
A
facilitated diffusion
active transport
17
Q
facilitated diffusion and example
A
NO energy. glucose, large and polar molecules
18
Q
active transport
A
requires energy, moves up concentration/electrical gradient
19
Q
active transport also called what
A
pumps
20
Q
energy can affect what in active transport
A
- affinity of the transporter for the ligand on one side of the membrane more than on the other side
- rate of transporter conformational change
21
Q
primary active transport and example
A
uses metabolic energy to transport molecules. uses ATP, most called ATPases. Na/K pump best example
22
Q
secondary active transport and example
A
different source of energy, NO direct coupling of ATP, uses electrochemical potential difference created by pumping ions out of the cell is used, TWO binding sites. Amino Acids use Na concentration gradient
23
Q
3 factors determine the rate of flux
A
- number of transporters
- extent of transporter saturation, which, in turn is affected by
a. transporter affinity
b. ligand concentration - rate of transporter conformational change
24
Q
types of channels
A
ligand sensitive (chemical) voltage sensitive (voltage) mechanosensitive- atria of heart
25
osmosis
bulk flow of water across membrane, lead to cell swelling/shrinkage
26
how does water cross membranes
channels called aquaporins
27
osmolarity
total solute concentration in a solution. 1 osmol= 1 mole of solute
28
1 mole of NaCl = ___ osmoles
2
29
osmolarity of extracellular fluid =
300 mOsm.
30
isotonic
= 300 mOsm. of non-penetrating solutes - no change in cell volume
31
hypotonic
< 300 mOsm. of non-penetrating solutes - cell swells
32
hypertonic
> 300 mOsm. of non-penetrating solutes - cell shrinks
33
isoosmotic
= 300 mOsm. of non-penetrating plus penetrating solutes
34
hypoosmotic
< 300 mOsm of non-penetrating plus penetrating solutes
35
hyperosmotic
> 300 mOsm. of non-penetrating plus penetrating solutes
36
what kinds of cells can pinocytosis? phagocytosis?
all cells can pinocytosis, specialized cells called phagocytes use phagocytosis
37
intra/extracellular K
intra- 124
| extra- 2.25
38
intra/extracellular of Na
intra- 10.4
| extra- 109
39
intra/extracellular of Cl
intra- 1.5
| extra- 77.5
40
intra/extracellular of Ca
intra- 4.9* most is bound or sequestered
| extra- 2.1
41
intra/extracellular of organic anions
intra- 74
| extra- 13
42
Ohm's law
V = IR
43
in a cell....voltage is, resistance is, and current is...
```
V = charge difference between inside and outside of cell
R = membrane
I = ion movement, in to out, out to in.
```
44
Conductance (G) =
reciprocal of resistance G = I/V
45
conductance and resistance are ____ related to each other and are _____ properties
inversely, membrane
46
Nernst equation
E = (58/z) log10 [X1]/[X2]
| z is the valance of the ion
47
nernest equation yields what
equilibrium potential (equilibrium voltage) - of a single ionic species, is the voltage across a cell membrane that exactly balances the force in the concentration gradient of a permeable ion
48
log10 of .1 =
-1
49
log10 of 1 =
0
50
log10 of 10 =
1
51
log10 of 100 =
2
52
what is due to asymmetric ion flow and can disappear over time?
diffusion potentials
53
resting membrane potentials
membrane of a resting cell is most permeable to K. K ions diffuse across a typical cell membrane 60 times more readily than do Na ions
54
which ion is higher concentration inside the cell?
K
55
which ion is higher concentration outside the cell?
Na
56
are rest what way to Na and K ions diffuse
K diffuse out of the cell
| Na diffuse into the cell
57
resting membrane potential number
- 90 mV
Equilibrium potential of K is -100 mV, the difference comes from the small amount of Na coming into the cell. this number is steady, so this diffusion potential is not transient.
58
depolarization (or hypopolarization)
change in membrane potential towards 0mV
59
repolarization
change in membrane potential towards negative voltage direction
60
hyperpolarization
change in membrane potential, becoming more negative from the resting value (i.e. > -90)
61
Sodium Potasium Pump
ATPase pump. maintains concentration gradient for Na and K. 3 Na out for 2K in. without this pump the potential would slowly go to 0 mV. example of homeostasis
62
does it take a large or small number of ions to cause a change in membrane potential?
very small number, relative intra and extracellular concentrations remain the same.
63
large and very rapid changes in membrane potential
action potentials.
64
most common places of action potentials
neurons and muscle cells
65
action potentials _____ over a distance of the cell membrane
propagated
66
examples of stimuli
light, temperature, and sources of pain.
67
stimuli process
---> change in ion permeability (increased Na) ---> membrane depoloarizes
68
where is the first change in membrane potential associated with the stimulus
dendrites, then cell body
69
first place the AP developes
initial segment, then travels down the axon.
70
step 1 of AP
increase in membrane permeability to Na ions
71
step 2 of AP
Na ions travel down concentration and electrical gradients through Na channels. carry + charge with them
72
step 3 of AP
membrane potential moves closer to 0 mV
73
step 4 of AP
if potential threshold is reached additional Na channels open (they are voltage-gated)
74
step 5 of AP
even more Na enters the cell, positive feedback cycle, all part of rising phase.
75
step 6 of AP
membrane potential very rapidly moves towards O mV then to 40 mV.
76
step 7 of AP
K channels open. K ions move from inside to outside. mem. potential reverses direction, falling phase. Na channels close as well (repolarization)
77
step 8 of AP
hyperpolarization. (after polarization phase)
78
time line of events
depolarization and repolarization in 1 ms
| after polarization > 10 ms
79
latent period
between AP's. where neuron can't depolarize
80
equilibrium potential for Na is what
58 mV, the peak of the AP approaches this.
81
peak of AP approaches what, the end of the depolarization phase is close to what
peak approaches equilibrium potential for Na (58)
| end of repole. approaches equilibrium potential of K
82
sub threshold stimulus, threshold stimulus, spurathreshold stimulus
sub- stimuli isn't strong enough
just sufficient
stimulus is greater than threshold stimulus
83
all action potentials are ____-or-_____
all or nothing
84
graded potentials
amplitudes are graded with the strength of the stimulus. weak stimuli that are sub threshold and not propagated.
85
absolute refractory period
brief period after the AP when a second threshold stimulus or supra threshold cannot elicit a second AP.
86
relative refractory period
when a supra threshold can elicit another AP but a threshold stimulus still cannot. even longer time
87
refractory periods impose what
limits on the frequency at which cells can fire AP, important in heart.
88
neural adaptation
is a change over time in the responsiveness of the sensory system to a constant stimulus. hand on table, sense table at first but then slowly stop sensing it.
89
accommodation
transition from closed state to the open state of the channels is dependent on the rate of stimulus change.
90
adaptation is a property of the ____ and it is due to accommodation of ion _____
neuron
| channels
91
stimulus parameters
1. intensity
2. duration
3. rate of change
4. frequency
92
Rhenobase
magnitude of the least intense stimulus that can elicit a response
93
utilization time
duration required to elicit a response by a stimulus with a rhenobase magnitude
94
chronaxie
duration required to elicit a response for a stimulus that has a magnitude that is twice the rhenobase magnitude.
95
electronic currents (local currents)
passive currents, do NOT propagate, can generate AP though. "Electrotonic potentials represent changes to the neuron's membrane potential that do not lead to the generation of new current by action potentials" small neurons, in longer axons local currents initiate action potentials
96
salutatory conduction
AP's skip along the axon from node of ranvier to another node.
97
A alpha function diameter velocity
motor, proprioception
12-20 micrometers
70-120 m/s
98
A beta function diameter and velocity
touch, pressure
5-12 micrometers
30-70 m/s
99
A gamma function diameter and velocity
muscle spindles
3-6 micrometers
15-30 m/s
100
A delta function diameter and velocity
pain, cold, touch
2-5 micrometers
12-30 m/s
101
B fiber function, diameter, and velocity
preganglionic autonomic
<3 micrometers
3-15 m/s
102
C dorsal root
pain, temp, mechanoreceptors, reflexes
.4-1.2 micrometers
.5-2 m/s
103
C sympathetic
postganglionic, sympathetic
.3-1.3 micrometers
.7-2.3 m/s
