Potentials Flashcards
Do all neurons and all cells have a resting membrane potential?
a) yes
b) only neurons
c) only other cells
d) neither
yes
True or False: Neurons can rapidly change their resting membrane potential in a positive direction.
True
Neurons are highly excitable like ________ cells
Voluntary Muscle
What is required to keep opposite charges separated across a membrane?
Energy
What happens when energy is liberated?
Charges move towards one another
Do opposite charges attract?
Yes
When does the system have potential energy?
When opposite charges are seperated
What does it mean when a membrane is polarized?
Negative on the inside and positive on the outside
What is voltage?
A measure of potential energy generate by separated charge
How is voltage measured?
Between two points in volts (V) or millivolts (mV)
Define potential difference or potential
The charge difference across the plasma membrane
What results in a higher voltage?
Greater charge difference between points
What is current?
The flow of electrical charge (ions) between two points
Can be used to do work
What is the flow of current dependent on?
Voltage and resistance
What is resistance?
It hinders current
What is a substance with high electrical resistance called?
Insulator
What is a substance with low electrical resistance called?
Conductor
What are the two main types of ion channels?
Leakage (nongated)
Gated
Which types of channels are always open?
Leakage (nongated)
How do gated channels work?
Part of the protein changes shape to open/close the channel
What are the three main gated channels?
Chemically gated
Voltage-gated
mechanically gated
What is the role of membrane ion channels?
Large proteins (channels) that selectively let ions through the membrane
What passes through k+ ion channels?
k+ ion
Which channel will only open with the binding of a specific chemical? Name one chemical that might bind to it.
Chemically gated (ligand-gated)
Neurotransmitter
Which channels open and close in response to changes in membrane potential?
Voltage-gated ion channels
Which channels open and close in response to physical deformation of receptors such as sensory receptors?
Mechanically gated channels
What is the electrochemical gradient
The combination of the electrical and chemical gradient
ion flow create an electrical current + voltage changes across membrane
What factors are important to cell voltage?
the difference in ion concentration inside and outside the cell + conductance (permeability) for that ion across the membrane
One cannot work without the other
What causes the resting membrane potential to change?
Change in [] of ions across membrane
Change in membrane permeability to ions
What types of signals do changes in membrane potential cause?
Graded potentials- Incoming signals over short distances
Action potentials- Long distance signals of axons
What is the purpose of changes in the membrane potential?
Used to create signals to receive, integrate, and send information
What is depolarization?
decrease in membrane potential (moves toward zero and above)
Inside of the membrane less negative then the resting membrane potential
Does depolarization decrease the probability of impulses occurring?
No- It increases the probability of producing impulses
What is hyperpolarization?
Increase in membrane potential (away from 0)
Increase of membrane becomes more negative than resting membrane potential
Does hyperpolarization increase or decrease the probability of producing impulses
decrease
Describe Graded potentials in detail
Short-lived changes in membrane potential that are triggered by a stimulus that opens gated ion channels
What are graded potentials names according to?
Location and function
What are the types of graded potentials? What are there differences?
Receptor/generator potential- graded potentials in receptors of sensory neurons
Postsynaptic potential- Neurons graded potential at a synapse
True or false: In graded potentials, a stronger stimulus results in more voltage changes and farther current flows?
True
True or false: In graded potentials, the current flows for a long time without decaying?
False- The current flows but dissipates quickly and decays because the current is lost through “leaky” plasma membrane and voltage is decremental
What is the principal way that neurons send signals?
Action Potentials
Where do action potentials occur?
Muscle cells and axons of neurons
True or false: Action potentials decay over long distances?
False- Action potentials do not decay over long distances because it is constantly being regenerated
graded potentials do
What is another term for an action potential?
Nerve impulse
How are action potentials generated?
Na+ influx causes depolarizations down the length of the axon
Why does the action potential move in one direction down the axon?
Absolute refractory period
What is the difference between the relative and absolute refractory period?
The relative refractory period can be overcome by a strong enough stimulus while the absolute refractory will not respond to any stimulus no matter how strong
What is a refractory period? How does it occur?
The time in which a neuron cannot trigger another AP
This occurs because the voltage-gated Na+ channels are open so the neuron cannot respond to another stimulus
Which refractory period enforces one-way transmission of nerve impulses and ensures that each action potential is an all-or-none event?
Absolute
What is happening during the absolute refractory period on a biological basis?
The time from the opening of Na+ channels until resetting of the channels
What comes first, the absolute or relative refractory period?
Absolute, then refractory
What is happening on a biological basis during the relative refractory period?
Most Na+ channels have returned to their resting state
Some K+ channels are still open
Repolarization is occurring
How does the CNS tell the difference between a weak stimulus and a strong one?
Frequency of impulses- Aps received per second
Higher frequency means stronger stimulus
True or false: The intensity of the stimulus increases the strength of the action potential?
False- Only the frequency of APs has an effect on the strength of the action potential
What are the subdivisions of postsynaptic potentials?
Excitatory (EPSP)
Inhibitory (IPSP)
What are the differences between excitatory postsynaptic potentials and inhibitory postsynaptic potentials?
EPSP-
Trying to generate an AP by depolarizing the membrane and moving the membrane potential toward the threshold
Opens channels that allow simultaneous fluxes in Na+ and K+
Moves toward 0 mV
IPSP-
Trying to move the membrane away from the threshold by hyperpolarizing
Opens K+ or Cl- channels
Moves toward - 90 mV
What are the similarities between EPSPs and IPSPs?
Their gates are both opened by chemicals ex. neurotransmitters
The refractory period is absent
The summations are present; temporal or spatial
Conduction distance is the same
Voltage independent; Occurs when NT is no longer present
