Chapter 7 Flashcards
Contrast a graded response with an action potential.
Graded response is proportional to stimulus intensity and is degraded over a distance. Action potential is all or none once a depolarization surpasses threshold.
What are the Na+ and K+ currents dependent on?
Time and Voltage dependent
How does a macroscopic current become generated?
Through the summation of many single ion channels that generate current when ions enter or leave the cell
What is beneficial about the Hodgkin-Huxley model?
Predicts macroscopic currents and the shape of the action potential
What generates the rapid depolarization phase of an action potential?
Opening of Na+ channels that allows Na+ ions to enter the axon/cell.
How can you block the Na+ channels (voltage-dependent)?
Neurotoxins or anesthetics
Can Ca2+ participate in action potentials?
Yes, it is an ion with a positive charge! So it functions in electrical and chemical coupling mechanisms. Responsible for action potentials in cardiomyocytes.
What are the different types of Ca2+ channels? (5)
L-type, T-type, P/Q-type, N-type, and R-type
How are the different types of Ca2+ channels characterized?
Through their kinetic properties and their sensitivity to inhibitors
What determines the resting potential?
K+ channels
What else do K+ channels participate in besides the resting membrane potential?
The frequence of action potentials and their termination (refractory phase)
What is the Kv family of K+ channels responsible for?
The delayed outward rectifying current as well as the transient A-type current
What are the Kir K+ channels responsible for?
They mediate inward rectifying K+ currents
What are K2P channels responsible for?
Detecting stress
What participates in the propagation of electrical signals in neurons?
Local current loops
Why are axons wrapped in myelin?
To improve the efficiency and speed to which an electrical current can propagate through the axon.
What determines the velocity of an electrical signal?
The cable properties of the membrane and cytoplasm of the cell
Which part of the action potential is called the “overshoot”?
The part that is above 0 mV
Can the shape of an action potential be changed in some cells?
Yes, by hormonal modulation
What is the time constant of a depolarization equal to?
t = RC
t = time constant
R = Resistance
C = Capacitance
What is electrotonic conduction?
The decay that is seen with a depolarization/hyperpolarization that degrades over a distance from the stimulus site. (Graded potentials only).
Does the action potential propogate at constant velocity or is there an acceleration/deceleration? What is a direct result of this?
Constant velocity. This causes the time delay between the stimulus and the peak of the action potential to increase linearly with distance from the stimulus site.
What 2 variables are responsible for excitation and how are they related to each other?
Duration of stimulus and stimulus intensity. The larger the product of the two variables, the more likely you will get excitation (they are inversely related).
TEA blocks?
Potassium channels
TTX blocks?
Sodium channels
