Ex Cells Flashcards
1
Q
types of Excitable cells
A
Neurons
Sensory Cells
Most muscle cells
2
Q
why are cells called excitable
A
Physiologic function relay critically on electrical events in their plasma membrane
3
Q
what is an electrical event
A
A mechanism of cell-to-cell (intercellular) communication
4
Q
speed of electrical events
A
Very rapid
5
Q
what do electrical events allow
A
Precise timing of signals between cells
complex patterns of communication between cells
6
Q
what do electrical events serve as a mechanism for
A
sensing environmental changes
triggering intracelular events
7
Q
how can electrical events trigger intracellular events
A
rapid intracellular changes
accumulations over time (memory and learning)
8
Q
the 3 physical components used for cell excitations
A
ECF
ICF
membrane
9
Q
composition of the ECF
A
primarily ions, proteins, and other molecules
high NaCl
10
Q
what is the ECF ionic concentration like
A
Similar to plasma in ionic composiition
11
Q
Composiition of the ICF
A
ions
more proteins and other molecules
12
Q
PRedoninant salt of the ICF
A
KCl
13
Q
what allow cells to communicate
A
Inside and outside of cells are very different
14
Q
what is the membrane composed of
A
phospholipid bilayer and proteins
equal amounts of protein and lipid with a small amount of carbs
15
Q
what is premeability a characteristic of
A
The cell membrane
16
Q
what is the permeability of a membrane to an ion
A
an index of the ability of the ion to cross the membrane
17
Q
how does permeability affect cell excitation
A
Changes in permeability that are ion-specific and exquisitely timed
18
Q
SImple diffusion
A
random diffusion down and electrical or concentration gradient
19
Q
how well do non-polar molecules difuse
A
rapid through the membrane b/c it ids 50% lipids
20
Q
how do ionspass the membrane
A
through channels which are proteins of several units with are ion-specific (generally)
21
Q
What is flux
A
the amount of a substance cross a surface per unit of time
22
Q
what way does diffusion occur between 2 compartments
A
Bi-direction
23
Q
Net flux
A
difference between the 2 unidirection fluxes
24
Q
what is something at diffusion equilibrium
A
when net flux equals 0
25
what is mediated transport
when something passes through the membrane but not directly
26
two types of mediated transport
Facilitaetd diffusion
| active transport
27
energy need of facilitated diffusion
no energy
28
how does facilitated diffusion occur
membrane proteins serves as a carrier to translocate a molecule across the membrane
29
what types of molcules tend to use facilitated diffusion
large polar molecules
30
benifiti of facilitated diffusion
makes it hard for certain molecules to leave the cell
31
how does active transport work
molecule/ion bound to transporter in membrane using enegy to move up its concentration/electrical gradient
32
other name for active transporter
pumps
33
energy can affect what in active tranport
affinity of transporter for the ligant on one side of the membrane more than on the other side
rate of transporter conformational change
34
what happens in primary active-transport model
energy from hydrolgysis of ATP
transporter becomes phosphorylated changes affinity for solute (ligand)
increases transport rate
35
what happens in secondary active transport
uses energy in concetration gradient across membrane
| transporter has 2 binding sites
36
steps in mediated transport
Ligand binds to transporter
transporter undergoes conformational change
ligand released on other side of membrane
37
factors that determine rate of flux
number of transporters in membrane
extrent of transporter saturation (transporter affinity,ligant concentration)
rate of transporter conformational change
38
types of channels
ligand-sensitive
voltage-sensitive
mechanosensitive
39
what is osmosis
Bulk flow of water acrosss a membrane
40
how does water diffuse
down its concentration gradient via aquaporins
41
osmolarity
the total solute concentration in a solution
42
osmolarity of ECF
300 mOsm
43
Isotonic
300 mOsm on Non-penetrating solutes in the ECF resulting in no change in cell volume
44
Hypotonic
less than 300mOsm of non-penetrating solutes in the ECF resulting in cell swelling
45
Hypertonic
greater than 300 mOsm of non-penetrating solutes in the ECF resulting in cell shrinking
46
difference in toniciity and osmoloarity
Toniciity is only non-penetrating
| Osmolarity is non-penetating and penetrating
47
ligand sensitive channels
channel that binds to ligand to open
48
voltage-sensitive channel
changes by predominating charge diference
49
Mechanosensitve channels
bases on the mechanics of the envirnoment
50
Endocytosis
Engulfment of fluid and particles from the ECF
51
pinocytosis
Engulfment of small particles with or without a small volume of ECF
52
what does Pinocytosis
all cell types
53
phagocytosis
engulfment of large particels or cellular debris
54
what does phagocytosis
Special cells called phagocytes (usually at sites of tissue damage)
55
what is exocytosis
export of material from a cell (reverse of endocytosis)
56
what does Exocytosis lead to
replaces membrane patches internalixed through endocytosis
| releases stuff from inside the cell
57
what is a lotinside the cell
K
Ca
Organic
w
58
what is a lot outside the cell
Na
| Cl
59
where is most of the Ca inside the cell
bound or sequestered (free Ca is very low)
60
Voltage of a cell
Electrical charge difference between the inside and outside of a cell
61
why must the plasma membrane have resistance
because the voltage of a resting cell is steady
62
what happens when the resistance of the membrane changes
Ions cross the membrane leading to a curent
63
Ohm's Law
V=IR
64
what is Conductance
The reciprocal of resitnace
65
Nernst equation
E= (58/z)log([X1]/[X2])
| z=valence
66
what does the Nernst equation give
the hypothetical equilibtrium potention of a single ionic species
67
what is the equalibrium potention of a single ionic species
the votlage across a cell membrane that exactly balances the forces in the concetration gradient of a permeable ion
68
do diffusion potentials always stay the same
Can be transient, but also can be maintained at a steady level over time
69
what causes the transient property of diffusion potentials
due to asymmetric ion flow of one or many ions between 2 compartments
70
K and Na in and outside the cell
K higher inside
| Na higher outside
71
what ion is the membrane permiable
most permeable to K
72
ratio of the permiability of K and Na
pK/PNa=60
73
membrane potention
-70 mV
74
what hold K inside
the charge (more negative inside) the cell
75
what does K do to create a diffusion potential
K ions move down their concentration gradient leading to the development of a diffusion potential
76
when is equilibrium found within the cell
when the force in the concentration gradient of K ions to move out of the cell is balanced by opposing force in electrical gradient
77
what does the equilibrium do to the cell
keeps K ions inside the cell
78
what is the equilibrium potental of K
about -100mV (close to the resting membrane potential of a cell)
79
why is the resting membrane potential different than that of the equalibrium potential of K
other ions must contribute to the resting potental
80
how does Na diffuse
Down its concetration gradient and electrical gradient
81
diffuse of Na leads to what
| of equilibrium potential
a resting membrane potential slightly lower than Equilibium of K
82
is the resting membrane potential steady of transient
Steady
83
does instaneous movement of ions cause the resting membrane potential
Not due to the instantaneous movement (due to the fact that ions have moved across the membrane)
84
what keeps the resting membrane potential from decreasing (keeps homeostasis)
the Na/K ATPase pump moving K ions in and Na ions out
85
depolarization
towrds 0 mV
86
repolarization
toward resting potential
87
Hyperpolarization
increase in membrane potential (more negative)
88
how does Na/K ATPase pump do work
hydrolyzes ATP to do work(active transport)
89
what would happen if Na/K ATPase were to go away
resting membrane potential would go back to 0mV
90
Homeostasis
mechanism that have, as their goal, the maintenance of the body's internal environment.
maintaining parameters of the internal environment at constant values
91
eq potential of K
-101 mV
92
eq potential of Na
+59 mV
93
eq potential of Cl
-99 mV
94
Action potential
A large transient change in membrane potential
95
4 parts of the neuron
Dendrites
Cell body
Axon
Axon terminal
96
stimulus leads to what in neuron
Depolarizaes membrane (dendrites)
Depolarizes cell body
AP first develops at initial segment
AP propagates along axon
97
where is the initial segment
where the axon meets the cell body
98
where the AP begins
Initial segnment
99
is the AP transient or steady
transient
100
steps of an AP
1 increased in the membrane permeability to Na ions
2 Na ions enter via channels driven by electrical and concentration gradients
3 membrane potential moves closer to 0 mV (depolarizes)
4 if depolarization reaches threshold, more Na votlage gated channels open
5 Na enters cells in a positive feed back cycle leading to the rising phase of an AP
6 eventually reaches +40mV
7 K chanells open and K leaves the cell
8 membrane potential abruptly reverses direction and returns in the falling phase of an AP
9 overshoot - hyperpolarization
101
what kind of channels allow Na ions to enter during an AP
Voltage regulated Na-channels
102
what is the movemeent of K driven by in an AP
concentration gradient and initiallly by electical gradient
103
why does Na channels close (Na Inactivation
Close during falling phase baecause voltage regulated channels now experience a negative change
104
length of depolarization and repolarization
1 ms
105
after polarization phase
10 ms
106
Do a lot of ions need to move to cause a great change in the membrane potential
no, only a few number of ions
107
Latnet period
Very brief period between applying stmulus and beginning of depolarization during rising phase of an AP
108
what occures during the latent phase
Channels are opening
109
what does the peak of an AP approach
the ENa( about 58 mV)
110
why does the Peak of an AP approach ENa
because the permiability of Na is very high during the rising phase of an AP
evnetually almost reaches where its ionic gradient is in eq with membrane potential
111
what does the end of the repolarization phase come close to
EK
112
why does the repolarization phase come close to Ek
becuase the permiability of K is high and crosses the membrane freely until its ionic gradient is in equilibium with membrane potential
113
when a stimulus is insufficient to take membrane to threshold
Subthreshold stimulus
114
when a stimultus is just sufficient to take membrane to threshold
Threshold stimulus
115
when a stimulus is greater than a threshold stimulus
Suprathreshold stimulus
116
where are subthreshold stimulus's found
Confined to the immediate region of the membrane
117
small depolarization or hyperpolarizations that do not move along the membrane
Local responses
118
what are graded/local responses proportional to
Stimulus strenght
119
absolute refractor period
Brief period when a second threshold stimulus of suprathreshold stimulus cannot elicit a second AP
120
Relative refractory period
for a longer period after a AP suprathreshold stimulus can get an AP but threshold cannot
121
what does Tetrodotoxin do
Binds to sodium channels and blocks sodium influx
122
adaption
where 2 waves of depolarization can be applied to a cell at different rates of ramping and lead to different responses (square wave gives and AP and ramp does not)
123
what causes adpation
property of channels called accommodation
124
stimulus strength duration curve relates
less intense stimuli need more time to ilicit a response
125
Rheobase
Magnitude of least intense stimulus that can elicit a response
126
Utilization time
Duration required to elicit a response by a stimulus with a rheobase magnitude
127
Chronaxie
duration required to elicit response for a stimulus that has a magnitude that is twice the rheobase magnitude
128
use of chronaxie
compare excitability of different cells
129
what shape of stimuli do you need to get an AP
square wave
130
what kind of current are electrotonic currents
passive currents (do not propagate)
131
what happens if Electrotonic current are sufficient in magnitude
lead to an AP
132
flow in stimulating electrodes
current flows from anode through the neuron to the cathode
133
what does the cathode do
Causes cations to move toward it in both the ECF and inside the cells
the cations inside cell membrane are trapped in the membrane and depolarize the membane
134
what does the anode do
Anode attracts anions
135
layers of Schwann cell membrane
Myelin
136
roll of myelin
electrical insulation do allow AP to travel faster and farther due to the AP skipping along the axon
137
are large diameter axons faster or slower conducting
larger have higher velocities
138
Recording the AP of a periferal nerve far and close
far: gives multiple AP due to different speeds
close: one large AP due to all the AP stacking up on each other
139
where do AP occur in saltatory conduction
in the nodes of ranvier
