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Terms in this set (51)
What is the only type of cell that can communicate signals across long distances?
What part of the neuron is responsible for receiving signals?
Cell body with dendrites
What part of the neuron integrates all the signals?
Transmission of signal in the neuron takes place in which part?
The information is transmitted to target cell through which part of the neuron?
What are 3 factors that contribute to membrane potential?
(1) Distribution of ions across the membrane (2) Relative permeability of ions (3) Charges of the ions
What type of transporter maintains the membrane potential?
Describe what happens when there is an incoming signal at the dendrite/cell body
(1) Membrane bound receptor binds neurotransmitter (2) Receptor transduce chemical signal into electrical signal (3) This changes ion permeability and causes changes in membrane potential
Opening of Na+ ________________ (depolarizes/hyperpolarizes) the membrane
Opening of K+ ____________________ (depolarizes/hyperpolarizes) the membrane
How does a stimulus affect the amplitude of a graded potential?
The amplitude of the graded potential directly reflects the strength of the incoming stimulus.
Explain the notion of "conduction with decrement" in graded potentials
Magnitude of graded potential decreases with increasing distance from open channel
What are 3 reasons for why there is decrement in graded potentials?
(1) Leakage of charged ions across the membrane (2) Electrical resistance of cytoplasm (3) Electrical properties of the membrane
How can action potentials be triggered?
The graded potential must reach threshold potential
What is sub-threshold potential? Will this initiate an action potential
It is depolarization below threshold. It will not initiate an action potential
What is a supra-threshold potential? Will this initiate an action potential?
Potentials that are larger than required to trigger an action potential. This will initiate an action potential
True or false. Many graded potentials can be generated simultaneously or close together.
True. This is because there are many receptor sites and many types of receptors on dendrites
When Na+ and Ca2+ channels are open, is this depolarization or hyperpolarization graded potential?
When K+ and Cl- channels are open, is this depolarization or hyperpolarization graded potential?
Define spatial summation
Graded potentials from different sites influence the net change
Is depolarization excitatory or inhibitory?
Is hyperpolarization excitatory or inhibitory?
Define temporal summation
Graded potentials that occur at slightly different times influence net change
In temporal summation, what must happen for there to be a net change?
The second graded potential must be triggered before the first one decays, or else they won't get added up and there won't be an action potential
True or false. Temporal or spatial summation at the axon hillock can trigger an action potential when a threshold potential is achieved
What are the 4 main characteristics of action potentials?
(1) They are triggered by net graded potential at the axon hillock (2) They do not degrade over time or distance (3) They travel long distances along membrane (4) They are all-or-none
What is the zone in a neuron where an action potential gets triggered?
True or false. Graded potentials are all-or-none
False. Action potentials are all-or-none
True or false. Action potentials degrade over time/distance
False. Graded potentials do
True or false. Action potentials travel long distances along membrane
What is the Hodkins cycle?
A POSITIVE FEEDBACK drives the propagation the the action potential. Influx of Na+ causes local depolarization which makes more Na+ channels open and causes more depolarization
What happens to the K+ and Na+ channels if there is a suprathreshold?
Both Na+ and K+ channels open. Na+ channels open faster than K+ channels, and they also close faster. Because K+ channels close more slowly, as they are closing they cause hyperpolarization
What is the role of K+ ions in action potentials?
When K+ channels open there is repolarization -> hyperpolarization
True or false. At the end of the action potential, some Na+ has moved out of the cell and some K+ has moved in.
False. Some Na+ has moved in and some K+ has moved out
Describe an action potential involving both Na+ and K+
(1) Na+ channels open fast -> depolarization (2) K+ channels open more slowly -> repolarization (3) Na+ channels close (4) K+ channels close more slowly
True or false. A single action potential is enough to have an effect on ion concentrations inside and outside of the cell
False. We need several action potentials one after the other
After repeated action potentials, what restores the concentration gradient?
What are the 3 phases of an action potential
(1) Depolarization (2) Repolarization (3) Hyperpolarization
What is the absolute refractory period
The period where the cell is incapable of generating a new AP
What is the relative refractory period
The period where the cell is capable of generating a new AP, but it is just more difficult
True or false. The difference in the time it takes for the activation of voltage gated Na+ channels and voltage gated K+ channels to open is the reason depolarization occurs before repolarization.
In action potential, why does depolarization occur before repolarization?
The difference in the time it takes for the activation of voltage gated Na+ channels and voltage gated K+ channels to open is the reason depolarization occurs before repolarization
True or false. Na+/K+ ATPase plays an important role in restoring ion gradients following repeated action potentials.
True or false. All action potentials are the same magnitude.
True. They are all-or-none
Why are action potentials said to be self propagating
An action potential triggers the next action potential in adjacent areas of membrane without degradation. It spreads electronically
What are the 3 resistors in an axon?
(1) Extracellular fluid Re (2) Membrane Rm (3) Intracellular fluid Ri
What is the length constant of neurons
Distance over which membrane potential will decrease to 37% (1/e) of its original value
What are the variables affecting length constant
(1) Resistance of cell membrane (Rm) (2) Resistance of intracellular fluid (Ri) (3) Resistance of extracellular fluid (Ro)
What is the formula to calculate length constant based on Rm and Ri.
Square root of (Rm/Ri)
True or false. Length constant is largest when rm is high and ri is low
What is the time constant
The time required for the membrane capacitor to be charged: time constant
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