LEC EXAM #2 CHP 7 Flashcards
3 types of excitable cells:
- neurons
- muscles (skeletal, smooth, and heart)
- secretory cells (pituitary, insulin producing cells of the pancreas)
How is the electrochemical gradient “established”?
Na/K ATPase pump
How is the RMP “maintained”?
- Na/K ATP ase pump
- Na leak channels
- K leak channels
What contributes to resting membrane potential?
- Electrochemical gradients (charge + concentration)
- amount of leak channels present for each ion
Has the most leak channels:
K+
What are the 4 phases for excitable cells?
- RMP (-70 mv)
- depolarization -> threshold (-55 mv)-> action potential
- repolarization
- hyperpolarization-> back to RMP
Na/K ATPase pump pumps:
3 Na+ out and 2 K+ in per ATP
Conc. of K+ inside/outside:
Inside: 150
Outside: 5
Conc. of Na+ inside/outside:
Inside: 15
Outside: 150
K+ wants to go:
Outside
Na+ wants to go:
Inside
Why does the RMP never reach -90 mv?
Due to the Na/K ATPase pump
K+ equilibrium:
-90 mv
What resets RMP?
Na v.g.c. pump + leak channels
Which voltage gated channel is used during depolarization?
Na+ v.g.c.
Which voltage gated channel closes and which is used during repolarization?
Na+ v.g.c closes
K+ v.g.c opens
Na equilibrium:
+60
Na+ voltage gated channel phases:
Open, inactive, closed
In Na v.g.c, if you don’t hit threshold of ___, you don’t get:
-55 mv
an action potential
T or F
Once an AP has been generated, the amplitude of the depolarization wave will be the same for all action potentials generated:
True
V.G.C won’t pop open if _______, once reset to _____ is when you will get a stimulus and it’ll respond
inactive
closed
Repolarization makes the inside more:
Negative
2 types of refractory periods:
- Absolute
- Relative
Absolute refractory period:
Na+ v.g.c. are inactive-> no AP possible
Depolarization makes the inside more:
Positive
Low potassium affects:
Coordination and skeletal muscles
Relative refractory period:
Some Na+ v.g.c. closed and some inactive-> can have an AP with a stimulus greater than -55 mv
What happens if you block K+ v.g.c.?
Makes depolarization last longer
Develops when there is a charge difference:
Electrical gradient
Develops when there is a concentration of ion difference:
Chemical gradient
Ions tend to move from an area of ____ conc. to an area of ___ conc.
High to low
What measures the inside of the cell?
RMP
The presence of ____ ______ in the cytosol adds to the negativity of the cytosolic side of the membrane:
Anionic proteins (A-)
AP operate on:
an all-or-none principle
Once Na v.g.c. become inactive…
K+ v.g.c. open
Propagation down a nerve axon occurs in ____ direction because Na v.g.c. are inactive for a certain length of time:
one
Purpose of lidocaine and tetracaine:
Blocks Na v.g.c. so there is no depolarization
The hyperpolarization phase of the action potential is due to:
the prolonged opening of the K+ v.g.c.
In the nervous system, the strength of the stimulus is coded into:
The frequency of the action potentials generated
Which area of the neuron generate signals that open the voltage-gated channels in the first part of the axon, thus causing an action potential?
Dendrites and cell body
The fastest conduction of an action potential would occur in an axon with which of the following characteristics?
Large diameter and myelinated
A cation is a:
Positively charged ion
