9: Communication via Neurons Flashcards
Module 2, Lesson 3
The transmission of nerve impulses is based on ____ across the plasma membrane.
Electrical potential
The inside of a neuron’s plasma membrane is more ____ than the outside.
Negative
The electrical potential across the plasma membrane is created by…
Maipulating concentrations of ions inside the membrane
List two major types of ion channels.
- Leakage
- Gated
____ ion channels are always open.
Leakage
____ ion channels open in response to a stimulus.
Gated
The ____ is a gated ion channel critical in maintaining concentration differences across the membrane.
Sodium-potassium pump
Sodium-potassium pumps use ____ to transport ions.
Active transport
A sodium-potassium pump simultaneously transports ____ into the cell and ____ out of the cell.
2 K ions ; 3 Na ions
As the sodium ions leave the cell, the transport protein ____ to bring potassium ions into the cell.
Dephosphorylates
The concentration of potassium ions is higher ____ the cell.
Inside
The concentration of sodium ions is higher ____ the cell.
Outside
The neuron’s plasma membrane has many ____ and ____, which maintain membrane potential.
Sodium-potassium pumps and potassium channels
The ____ found in a neuron’s plasma membrane are leaky.
Potassium channels
Inside the neuron, there are many ____ and ____ – large molecules that remain inside the cell.
Negatively-charged proteins and amino acids
Which three factors combine to create a buildup of charge difference across the cell membrane?
- Sodium-potassium pumps
- Leaky potassium channels
- Negatively charged molecules
____ is the normal charge difference across the cell membrane.
Resting membrane potential
The average magnitude of resting membrane potential is…
-70 mV
Membranes are very sensitive to ____, which can disrupt resting potential.
Stimuli
____ are small, continuous changes in membrane potential.
Graded potentials
____ occurs when membrane potential becomes less negative/more positive.
Depolarization
Which two factors can affect the magnitude of a graded potential?
- Strength of the stimulus
- Amount of ligand available
____ occurs when membrane potential becomes more negative.
Hyperpolarization
When open, gated channels allow ions to enter and leave the cell, which…
Changes membrane potential
List the two major types of gated ion channels.
- Chemically gated
- Voltage gated
____ ion channels are opened when a molecule binds to its receptor.
Chemically gated
____ ion channels open in response to changes in membrane potential.
Voltage-gated
The opening of voltage gated ion channels results in…
Action potentials
____ are short-lived disruptions in membrane potential that move along the axon.
Action potentials
The magnitude of depolarizing graded potential necessary to produce an action potential is called…
Threshold potential
In many mammals, threshold potential is about…
-55 mV
Which two ion channels are directly involved in action potentials?
- Voltage-gated Na channels
- Voltage-gated K channels
The voltage-gated ____ ion channel has two gates.
Sodium
List the two gates in a sodium ion channel.
- Activation gate
- Inactivation gate
____ are triggered by the opening and closing of Na and K voltage-gated ion channels.
Action potentials
List the four phases of an action potential.
- Resting
- Rising/depolarization
- Peak
- Falling/repolarization
During the resting phase…
- The sodium channel’s activation gate is closed and its inactivation gate is open
- The potassium channel is closed
When a graded potential reaches threshold…
The sodium activation gate opens
During the ____ phase, a rapid influx of sodium occurs due to concentration amd voltage gradients.
Rising/depolarization
What happens at the top of the activation potential curve?
- The sodium inactivation gate closes
- The potassium gate opens
During the falling/repolarization phase, repolarization occurs because…
The potassium gates are open
True or false:
The potassium gates close faster than the sodium gates.
False
The excess movement of potassium out of the neuron causes a temporary…
Undershoot / refractory period
During the ____, membrane potential is lower than resting potential.
Refractory period
After the falling/repolarization phase, ____ restore ion concentrations to their resting states.
Na-K pumps
Once resting potential is restored, what happens to the sodium gates?
The activation gate closes and the inactivation gate opens
True or false:
Action potentials are “all or none” events - you cannot have a partial action potential.
True
If threshold is reached or exceeded, then…
An action potential will be generated
If threshold is not reached, then…
No action potential will be generated
True or false:
Two action potentials can add together or interfere with each other.
False
After sodium channels fire, they remain inactive until…
The inactivation gate reopens
During the ____, no additional action potentials can occur.
Absolute refractory period
During the ____, only a very strong stimulus can cause an action potential to occur.
Relative refractory period
True or false:
The production of action potentials is passive (does not require energy).
True
Action potentials are initiated at the ____, located at the base of the axon.
Axon hillock
____ describes the movement of an action potential down an axon.
Propagation
In an unmyelinated axon, the influx of Na ions during an action potential causes…
An action potential to be triggered in an adjacent section of membrane
True or false:
Propagation can occur in all directions.
False
Na channels are inactive during the refractory period which means action potentials can only propagate in one direction
In a myelinated axon, action potentials are only generated at…
Nodes of Ranvier
An action potential at one node of Ranvier serves as the ____ for the next.
Depolarization stimulus
____ occurs in myelinated axons when depolarization spreads beneath the myelin between nodes.
Saltatory conduction
In a myelinated axon, action potentials appear to…
Jump from one node to the next
Axons with a larger diameter conduct action potentials ____ than smaller axons.
Faster
The combination of ____ and ____ produces the fastest-travelling action potentials.
Myelination and large diameter
Once an action potential reaches the end of an axon, it must be…
Communicated to an adjacent neuron or effector
The intracellular gap junctions between neurons are called…
Synapses
The ____ neuron transmits the action potential to the synapse.
Presynaptic
The ____ neuron receives the action potential from the synapse.
Postsynaptic
List the two main types of synapses in animals.
- Electrical
- Chemical
____ use gap junctions to directly transmit action potentials between cells.
Electrical synapses
_____ synapses are the predominant type of synapse found in vertebrates.
Chemical
The small space between the pre- and postsynaptic cells in chemical synapses is called the…
Synaptic cleft
The presynaptic cell contains ____ that contain neurotransmitters.
Synaptic vesicles
____ are chemical ligands that carry messages across the synapse.
Neurotransmitters
When an action potential reaches the end of an axon, it triggers the opening of…
Voltage-gated calcium ion channels
The opening of voltage-gated calcium ion channels triggers events that result in…
The fusion of synaptic vesicles with the plasma membrane
Neurotransmitters are released into the synaptic cleft via…
Exocytosis
Neurotransmitters bind to ____ on the plasma membrane of the postsynaptic cell.
Chemically gated receptor proteins
As the ____ of action potentials increases, the number of neurotransmitters released will also increase.
Frequency
An increased frequency of action potentials will result in the production of more ____ on the postsynaptic neuron.
Graded potentials
In order to terminate an existing signal, neurotransmitters must be…
Removed from the synaptic cleft
List two mechanisms by which neurotransmitters may be removed from the synaptic cleft.
- Re-uptake by the presynaptic neuron
- Enzymatic digestion
List eight major neurotransmitters.
- Acetylcholine
- Glutamate
- Glycine
- GABA
- Epinephrine
- Norepinephrine
- Dopamine
- Serotonin
____ is an excitatory neuotransmitter found in neuromuscular junctions.
Acetylcholine
Glutamate is an ____ neurotransmitter.
Excitatory
Glycine is an ____ neurotransmitter.
Inhibitory
GABA is an ____ neurotransmitter.
Inhibitory
Glutamate, glycine, and GABA are neurotransmitters that are also…
Amino acids
Epinephrine, norepinephrine, dopamine, and serotonin are neurotransmitters that are also…
Biogenic amines
____ is a neurotransmitter involved in hormone release and the fight-or-flight response.
Epinephrine
____ is a neurotransmitter involved in the sympathetic nervous system and the fight-or-flight response.
Norepinephrine
____ is a neurotransmitter released in areas of the brain controlling body movements.
Dopamine
____ is a neurotransmitter that helps regulate sleep and emotional states.
Serotonin
When ____ neurotransmitters bind to a chemically-gated channel, they produce an EPSP.
Excitatory
An ____ occurs when an influx on ions results in depolarization of the plasma membrane.
Excitatory post-synaptic potential
(EPSP)
When an ____ neurotransmitter binds to a chemically-gated channel, it results in an IPSP.
Inhibitory
An ____ occurs when an influx on ions results in hyperpolarization of the plasma membrane.
Inhibitory post-synaptic potential
(IPSP)
____ is the process by which IPSPs and EPSPs interact with each other in the cell body.
Synaptic integration
____ occurs when a large number of presynaptic dendrites produce graded potentials simultaneously.
Spatial summation
True or false:
The result of spatial summation is always an EPSP.
False
Either an EPSP or an IPSP can result.
____ occurs when a single presynaptic dendrite produces repeated EPSPs.
Temporal summation
When temporal summation occurs, the EPSPs must be…
Close enough in time to be summed
____ refers to a loss of sensitivity in neurons.
Habituation
Habituation occurs when cells are exposed to a constant stimulus that produces a…
Chemical signal
In response to high levels of neurotransmitters, some nerve cells will…
Reduce the number of receptors
Habituation means that if a drug produces neurotransmitter effects, then over time…
More of the drug is needed to achieve the same effect
____ increases the amount of dopamine in the synapse and the length of time that dopamine is present.
Cocaine
Cocaine works by….
Binding to transporter proteins and preventing re-uptake of dopamine
____ binds directly to acetylcholine receptors on postsynaptic neurons.
Nicotine
