Term
| What are the two kinds of potential change? |
|
Definition
1) Graded potentials
2) Action potentials |
|
|
Term
| __________ __________ serve as short-distance signals whereas __________ __________ serve as long-distance signals. |
|
Definition
1) Graded potentials
2) Action potentials |
|
|
Term
| How do local disturbances in membrane potential occur? |
|
Definition
| 1) Occur when neuron is stimulated by chemicals, light, heat, or mechanical disturbance |
|
|
Term
| What are the steps that take place for local potentials? |
|
Definition
1) Depolarization is a positive shift in potential due to opening of gated Na+ channels
2) Na+ diffuses for a short distance inside membrane producing a change in voltage called local potential |
|
|
Term
| What differences does a local potential possesses in contrast to an action potential? |
|
Definition
1) Are graded (vary in magnitude with stimulus strength)
2) Are decremental (get weaker the farther they are spread)
3) Are reversible as K+ diffuses out of the cell
4) Can be either excitatory or inhibitory (hyperpolarize) |
|
|
Term
| What does it mean for a potential to be graded? |
|
Definition
| 1) Potential varies in magnitude with stimulus strength |
|
|
Term
| What does it mean for a potential to be decremental? |
|
Definition
| 1) Potential gets weaker the farther they are spread |
|
|
Term
| __________ is a decrease in potential which causes the membrane to be less negative. |
|
Definition
|
|
Term
| What is depolarization? What are its effects on the membrane? |
|
Definition
1) Decrease in potential
2) Causes the membrane to be less negative |
|
|
Term
| __________ is a return to the resting potential after depolarization. |
|
Definition
|
|
Term
|
Definition
| 1) Return to resting potential after depolarization |
|
|
Term
| __________ is an increase in potential that causes the membrane to be more negative. |
|
Definition
|
|
Term
| What is hyperpolarization? What are its effects on the membrane? |
|
Definition
1) Increase in potential
2) Causes the membrane to be more negative |
|
|
Term
| What are three characteristics of graded potentials? |
|
Definition
1) Stimulus induced (delta Vm)
2) Transmitter or sensory
3) Channels open or close |
|
|
Term
| In graded potentials, a stronger stimulus produces a __________ Vm. |
|
Definition
|
|
Term
| True or False: In graded potentials, a weaker stimulus produces a larger Vm. |
|
Definition
| 1) FALSE: In graded potentials, a STRONGER stimulus produces a larger Vm. |
|
|
Term
| What are the effects of an Na+ influx on graded potentials? Of a Cl- influx? |
|
Definition
1) Na+ influx causes depolarization
2) Cl- influx causes hyperpolarization |
|
|
Term
| In graded potentials, Vm is greatest at __________ site ans smaller at __________ sites. |
|
Definition
|
|
Term
| Where is the Vm the greatest in graded potentials? Where is it smaller? |
|
Definition
1) Stimulation site
2) At distant sites |
|
|
Term
In graded potentials, above the __________ depolarization occurs, causing __________ __________ __________ channels to open at the __________ __________.
This elicits an action potential. |
|
Definition
1) Threshold
2) Voltage-gated sodium
3) Axon hillcock |
|
|
Term
| How do action potentials occur in graded potentials? |
|
Definition
1) Stimulus causes Vm to rise about the threshold
2) Depolarization occurs, causing voltage-gated sodium channels to open at the axon hillock
3) Elicits action potential |
|
|
Term
| Where are the trigger zones for graded potentials? |
|
Definition
1) Axon hillock
2) Initial segment of axon |
|
|
Term
| If a stimuli is inhibitory it causes a __________ effect. |
|
Definition
|
|
Term
| What is the difference between a sub threshold potential and a supra threshold potential? |
|
Definition
1) At a sub threshold potential, a graded potential starts above threshold at its initiation point, but decreases in strength as it travels through the cell body. At the trigger zone it is blow threshold and therefore does not initiate an action potential
2) At a supra threshold potential, a stronger stimulus at the same point on the cell body creates a graded potential that is still above threshold by the time it reaches the trigger zone, so an action potential results |
|
|
Term
| Action potentials have __________ Vm. |
|
Definition
|
|
Term
| Action potentials are generated in __________ cells such as __________ and __________ cells. |
|
Definition
1) Excitable
2) Neurons
3) Muscle |
|
|
Term
| What cells in the human body are excitable? |
|
Definition
1) Neurons
2) Muscle cells |
|
|
Term
| Action potentials function as a __________. |
|
Definition
|
|
Term
| In neurons, action potentials are generated at the __________ __________ and __________ to the axon terminal; they are responsible for the release of __________. |
|
Definition
1) Axon hillock
2) Propagate
3) Neurotransmitter |
|
|
Term
| Where are action potential generated in neurons? What do they release as an outcome of their production? |
|
Definition
1) At the axon hillock (they then propagate to the axon terminal)
2) Neurotransmitters |
|
|
Term
| True or False: There is a more dramatic change in membranes where a high density of voltage-gated channels occur |
|
Definition
|
|
Term
| What is the threshold potential in action potentials? |
|
Definition
|
|
Term
| What occurs when the membrane reaches the threshold potential? |
|
Definition
| 1) Voltage-gated Na+ channels open and Na+ enters for depolarization |
|
|
Term
| What occurs when the membrane potential surpasses 0 mV? |
|
Definition
| 1) The Na+ channels close |
|
|
Term
| What is the peak mV level for membrane potentials? |
|
Definition
|
|
Term
| What occurs when the membrane potential reaches the peak mV level? |
|
Definition
| 1) K+ gates fully open (K+ leaves); this produces repolarization |
|
|
Term
| What is the result of repolarization in the membrane potential? |
|
Definition
| 1) Negative overshoot produces hyperpolarization |
|
|
Term
| What ion enters during depolarization? During repolarization? |
|
Definition
|
|
Term
At what mV level do voltage-gated Na+ channels open? When do they close?
When do K+ gates open? When do they close? |
|
Definition
1) Voltage-gated Na+ channels open at the threshold (-55mV) and close at 0mV
2) K+ gates open at the peak mV (+35mV) and close at the conclusion of repolarization |
|
|
Term
| What are the three phases of an action potential? |
|
Definition
1) Deploarization
2) Repolarization
3) Hyperpolarization |
|
|
Term
| Explain the steps that occur for an ion to move across the cell membrane during an action potential. |
|
Definition
1) Sudden increase in Na+ permeability
2) Na+ enters cell down electrochemical gradient
3) Influx causes depolarization of membrane potential (electrical signal produced)
4) The action potential is terminated when the Na+ inactivation gate closes |
|
|
Term
| Action potentials in most __________ cells initiate when a __________ __________ on a cell reaches the __________ in which voltage-gated __________ channels open, greatly increasing __________ conductance. |
|
Definition
1) Excitable
2) Local potential
3) Threshold
4) Na+
5) Na+ |
|
|
Term
| When do action potentials in most excitable cells initiate? |
|
Definition
| 1) When a local potential on a cell reaches the threshold at which voltage-gated Na+ channels open greatly increasing Na+ conductance |
|
|
Term
| Na+ channels in axons have __________ gates. |
|
Definition
|
|
Term
| How many gates do Na+ channels in axons have? |
|
Definition
|
|
Term
| What are the two gates of axon Na+ channels? |
|
Definition
1) Activation gate
2) Inactivation gate |
|
|
Term
| Na+ entry in an action potential is based on what? When do the gates which allow Na+ to enter in close? |
|
Definition
1) Na+ entry is based on positive feedback loop and needs intervention to stop
2) Voltage-gated Na+ channels close in response to a delay in depolarization |
|
|
Term
| Na+ entry is based on a __________ __________ __________ and requires intervention to stop. |
|
Definition
| 1) Positive feedback loop |
|
|
Term
| Na+ __________ __________ close due to delayed response to __________. |
|
Definition
1) Inactivation gates
2) Depolarization |
|
|
Term
| What are the steps in which the Na+ activation / inactivation gates open and close? |
|
Definition
1) At the resting membrane potential, the activation gate closes the channel
2) With the activation gate open, Na+ enters the cell
3) During repolarization caused by K+ leaving the cell, the two gates reset to their original positions
4) Depolarizing stimulus arrives at the channel
5) Inactivation gate closes and Na+ entry stops |
|
|
Term
| During depolarization, __________-__________ __________ __________ open. |
|
Definition
| 1) Voltage-gated Na+ channels |
|
|
Term
| What occurs during depolarization? |
|
Definition
| 1) Voltage-gated Na+ channels open |
|
|
Term
| What are the steps of the positive feedback cycle which causes depolarization to occur during an action potential? |
|
Definition
1) Some Na+ channels open, causing an Na+ influx
2) The Na+ influx causes depolarization
3) Depolarization causes more Na+ channels to open |
|
|
Term
| Do Na+ channels open fast or slow? What about K+ channels? |
|
Definition
1) Na+ channels open fast
2) K+ channels open slow |
|
|
Term
| True or False: Na+ channels become inactive after a short delay. |
|
Definition
|
|
Term
| Are K+ channels open when Na+ channels are open? |
|
Definition
|
|
Term
| When do K+ channels finally open? |
|
Definition
| 1) When Na+ inactivating channels are open |
|
|
Term
| Which channels (Na+ or K+) close as a result of membrane repolarization? |
|
Definition
|
|
Term
| The __________ increase in conductance for Na+ is associated with the __________ phase of the action potential, whereas the __________ increase in conductance for K+ is associated with __________ of the membrane and after __________ . |
|
Definition
1) Fast
2) Rising (depolarization)
3) Slow
4) Depolarization
5) Hyperpolarization |
|
|
Term
| What factors are responsible for causing repolarization to occur in an action potential? |
|
Definition
1) Delayed closing of voltage-sensitive Na+ channels (inactivation)
2) Delayed opening of voltage-sensitive K+ channels (delayed rectifier K+ channel) |
|
|
Term
| What factors are responsible for causing hyperpolarization to occur in an action potential? |
|
Definition
| 1) A large number of open, delayed, rectified K+ channels |
|
|
Term
| What factors are responsible for causing recovery to occur in an action potential? |
|
Definition
1) K+ channels close
2) Na+ channel inactivation gates reopen |
|
|
Term
| What are the two principle of action potentials? |
|
Definition
1) All or None Principle
2) The Refractory Period Principle |
|
|
Term
| The __________ __________ __________ principle states that action potential occur in an all or none fashion depending on the strength of the stimulus. |
|
Definition
|
|
Term
| The __________ __________ principle states that the refractory period is responsible for setting up the limit on the frequency of action potentials, and that only a small patch of membrane can experience refractory periods at a time. |
|
Definition
|
|
Term
| What is the all or none Principle? |
|
Definition
| 1) States that action potentials occur in an all or none fashion depending on stimulus strength |
|
|
Term
| What is the refractory period principle? |
|
Definition
1) States that the refractory period must set the limit on the frequency of action potentials
2) Refractory period can only occur to a small patch of membrane at a time (for quick recovery) |
|
|
Term
| The all or none principle states that __________ the threshold delta V depends on stimulus __________ whereas __________ the threshold delta V does not. |
|
Definition
1) Below
2) Strength
3) Above |
|
|
Term
| The __________ __________ __________ states that during repolarization, Na+ channels are inactivated and that another action potential cannot be generated. |
|
Definition
| 1) Absolute refractory period |
|
|
Term
| What is the absolute refractory period? What does it ensure? |
|
Definition
1) The absolute refractory period is the time during repolarization in which Na+ channels are inactivated and thus another action potential cannot be generated
2) One-way propagation of action potentials in an axon |
|
|
Term
| The __________ __________ __________ states that during hyperpolarization some Na+ channels can be re-activated and that a second action potential can be generated only by a suprathreshold stimulus |
|
Definition
| 1) Relative refractory period |
|
|
Term
| Which refractory period prevents another action potential from occurring through inactivation of Na+ channels? |
|
Definition
|
|
Term
| Which refractory period insures one-way propagation of action potentials in an axon? |
|
Definition
|
|
Term
| Which refractory period allows some Na+ channels to be re-activated during hyperpolariation? |
|
Definition
|
|
Term
| Which refractory period allows a second action potential to be generated only in the presence of a suprathreshold stimulus? |
|
Definition
|
|
Term
| Which refractory period occurs during repolarization? |
|
Definition
|
|
Term
| Which refractory period occurs during hyperpolarization? |
|
Definition
|
|
Term
| Where does an action potential begin? |
|
Definition
|
|
Term
| What occurs in an action potential when K+ moves out? |
|
Definition
| 1) Brief hyperpolarization |
|
|
Term
| When during an action potential do voltage-gated Na+ channels open? |
|
Definition
|
|
Term
| What are the steps for the conduction of a graded potential? |
|
Definition
1) A graded potential above the threshold reaches the trigger zone
2) Voltage-gated Na+ channels open and Na+ enters the axon
3) Positive charge flows into adjacent sections of the axon by local current flow
4) Local current flow from the active region causes new sections of the membrane to depolarize
5) The refractory period prevents backward conduction. Loss of K+ from the cytoplasm repolarizes the membrane |
|
|
Term
| What are the steps for the conduction of an action potential? |
|
Definition
1) In the RESTING POTENTIAL, all voltage gated channels are closed
2) A stimulus opens some Na+ channels; the Na+ influx achieves the THRESHOLD potential with additional Na+ gates opeening.
3) Na+ continues to enter the cell, causing explosive DEPOLARIZATION to +30mV, which generates the rising phase of the action potential
4) At peak of action potential, Na+ inactivation gate closes, ending net movement of Na+ into the cell. At the same time, K+ activation gates open and K+ concentration rises
5) K+ leaves the cell, causing its REPOLARIZATION to resting potential, which generates the falling phased of the action potential
6) On return to the resting potential, Na+ activation gate closes and inactivation gate opens, resetting channel to respond to another depolarizing trigger event
7) Further outward movement of K+ through still-open K+ channel briefly HYPERPOLARIZES membrane, which generates after hyperpolarization
8) K+ activation gate closes, and membrane returns to resting potential |
|
|
Term
If an axon were to be related to an electrical circuit, how would the following terms be defined?
-Potential difference
-Current
-Resistance
-Conductance
-Capacitance |
|
Definition
1) Potential difference - Charge difference
2) Current - Flow of charge
3) Resistance - Resistance to current flow
4) Conductance - Ease of current flow inverse of resistance)
5) Capacitance - Build up of charge on each side of a layer of insulation |
|
|
Term
| What are the twp types of propagation found in action potentials? |
|
Definition
1) Contiguous conduction
2) Saltatory conduction |
|
|
Term
| __________ __________ is conduction in unmyelinated fibers in which an action potential spreads along every portion of the membrane |
|
Definition
|
|
Term
| What is contiguous conduction? |
|
Definition
| 1) Conduction in unmyelinated fibers in which an action potential spreads along every portion of the membrane |
|
|
Term
| __________ __________ is rapid conduction in myelinated fibers in which an impulse jumps over sections of the fiber covered with insulating myelin. |
|
Definition
|
|
Term
| What is saltatory conduction? |
|
Definition
| 1) Rapid conduction in myelinated fibers in which an impulse jumps over sections of the fiber covered with insulating myelin |
|
|
Term
| Which conduction is in unmyelinated fibers? |
|
Definition
|
|
Term
| Which conduction involves action potentials spreading along every portion of the membrane? |
|
Definition
|
|
Term
| Which conduction is in myelinated fibers? |
|
Definition
|
|
Term
| Which conduction involves impulses jumping over sections of the fiber covered with insulating myelin? |
|
Definition
|
|
Term
| __________ produce myelin sheath in the CNS and __________ __________ produce myelin sheath in the PNS. |
|
Definition
1) Oligodendrocytes
2) Schwann cells |
|
|
Term
| What are two factors that can increase propagation speed? |
|
Definition
1) Mylein sheath
2) Larger axon diameter |
|
|
Term
| __________ is proportional to the square root of the diameter. |
|
Definition
|
|
Term
Increases in axon __________ increase velocity, largely because the longitudinal resistance of a larger axon is __________, so local circuits can spread further.
__________ reduces membrane capacitance and hence reduces the amount of __________ required to effect a particular membrane potential change which again means the currents can spread further. These effects are __________ so the fastest velocities are achieved in __________ __________ axons. |
|
Definition
1) Diameter
2) Lower
3) Myelination
4) Current
5) Additive
6) Large myleinated |
|
|
Term
| How does increases in axon diameter increase velocity? |
|
Definition
| 1) Increases in axon diameter lower the longitudinal resistance of a larger axon, allowing local circuits to spread further. |
|
|
Term
| The __________ __________ __________ help to increase action potential conductance and velocity. |
|
Definition
|
|
Term
| Nodes of Ranvier increase action potential conduction velocity __________ fold. |
|
Definition
|
|
Term
| Schwann cells hold small __________ __________ in grooves on their surface with only one membrane wrapping. |
|
Definition
|
|
Term
| Conduction speed depends on what two factors? |
|
Definition
1) Axon diameter
2) Membrane resistance |
|
|
Term
| The __________ the axon diameter the __________ the conduction speed will be. |
|
Definition
|
|
Term
| High resistance of __________ __________ reduces leakage of current flow between __________ and __________. |
|
Definition
1) Myelin sheath
2) Axon
3) ECF |
|
|
Term
| Speed of signal transmission along nerve fibers depends on __________ of fiber and presence of __________. |
|
Definition
|
|
Term
__________ nerve signals supply the stomach and dilate pupils
__________ nerve signals supply skeletal muscle and transport sensory signals for vision and balance. |
|
Definition
|
|
Term
| __________ occurs when the body's own immune cells attack the nervous system. |
|
Definition
|
|
Term
| __________ __________ is an autoimmune disease possibly triggered by a virus in genetically susceptible individuals. |
|
Definition
|
|
Term
| True or False: MS is more common in women than men. |
|
Definition
|
|
Term
|
Definition
1) Visual disturbances
2) Muscle weakness
3) Loss of muscular control
4) Urinary incontinence
5) Eventual paralysis |
|
|
Term
| __________ __________ occurs when the body lacks hexosaminidase A, a protein that helps break down a chemical found in nerve tissue called gangliosides. |
|
Definition
|
|
Term
__________ ions are needed to close sodium channels during the generation of action potentials.
Low levels result in repeated transmissions of __________ __________ and __________ __________. |
|
Definition
1) Ca2+
2) Action potentials
3) Muscle spasms |
|
|
Term
| __________, __________, and __________ all block nerve impulses by reducing membrane permeability to ions, mainly Na+ |
|
Definition
1) Alcohol
2) Sedatives
3) Anesthetics |
|
|
Term
| What are a few examples of neuromodulators? |
|
Definition
1) Catecholamine
2) Dopamine
3) Norepinephrine
4) Epinephrine
5) Indolamine
6) Serotonin |
|
|
Term
| The __________ __________ is a complex network of neurons that form the rapid control system of the body. |
|
Definition
|
|
Term
| __________ __________ of the nervous system include consciousness, intelligence, and emotion. |
|
Definition
|
|
Term
| The efferent neurons include __________ __________ __________ which control skeletal muscles, and __________ __________ which control smooth and cardiac muscles, glands, and some adipose tissue. |
|
Definition
1) Somatic motor neurons
2) Autonomic neurons |
|
|
Term
| Material is transported between the cell body and axon terminal by __________ __________. |
|
Definition
|
|
Term
| __________ __________ __________ that can develop into new neurons and glia are found in the ependymal layer as well as in other parts of the nervous system. |
|
Definition
|
|
Term
| The __________ __________ describes the membrane potential of a cell that is permeable to only one ion. |
|
Definition
|
|
Term
| Membrane potential is influenced by the __________ __________ of ions across the membrane and by the __________ of the membrane to those ions. |
|
Definition
|
|
Term
| The permeability of a cell to ions changes when ion channels in the membrane __________ and __________. |
|
Definition
|
|
Term
| Gated ion channels in neurons open or close in response to __________ or __________ signals or in response to __________ of the cell membrane; they also close to inactivation. |
|
Definition
1) Chemical
2) Mechanical
3) Depolarization |
|
|
Term
| The wave of depolarization that moves through a cell is known as __________ __________ __________. |
|
Definition
|
|
Term
| Action potentials begin in the __________ __________ if a single graded potential or the sum of multiple graded potentials exceeds the __________ voltage. |
|
Definition
1) Trigger zone
2) Threshold |
|
|
Term
| __________ graded potentials make a neuron more likely to fire an action potential; __________ graded potentials make a neuron less likely to fir an action potential. |
|
Definition
1) Depolarizing
2) Hyperpolarizing |
|
|
Term
| The voltage-gated Na+ channels of the axon have a fast __________ __________ and a slower __________ __________. |
|
Definition
1) Activation gate
2) Inactivation gate |
|
|
Term
| During the __________ __________ __________, a higher-than-normal graded potential is required to trigger an action potential. |
|
Definition
| 1) Relative refractory period |
|
|
Term
The myelin sheath around an axon speeds up conduction by increasing __________ __________ and decreasing current __________.
__________-diameter axons conduct action potentials faster than __________-diameter axons do. |
|
Definition
1) Membrane resistance
2) Leakage
3) Larger
4) Smaller |
|
|
Term
| The apparent jumping of action potential from node to node is called __________ __________. |
|
Definition
|
|
Term
| Changes in blood K+ concentration affect __________ membrane potential and the conduction of __________ __________. |
|
Definition
1) Resting
2) Action potentials |
|
|
Term
| In __________ __________ an electrical signal passes directly from the cytoplasm of one cell to another through gap junctions. |
|
Definition
|
|
Term
| __________ __________ use neurotransmitters to carry information from one cell to the next, with the neurotransmitter diffusing across the __________ __________ to bind with receptors on target cells. |
|
Definition
1) Chemical synapses
2) Synaptic cleft |
|
|
Term
| Neurotransmitter receptors are either __________-__________ __________ __________ (ionotropic receptors) or __________ __________-__________ __________ (metabotropic receptors). |
|
Definition
1) Ligand-gated ion channels
2) Metabotropic receptors |
|
|
Term
| What are three ways in which neurotransmitter action is rapidly terminated? |
|
Definition
1) Reuptake into cells
2) Diffusion away from the synapse
3) Enzymatic breakdown |
|
|
Term
| When a presynaptic neuron synapses on a larger number of postsynaptic neurons, the pattern is known as __________. |
|
Definition
|
|
Term
| When several presynaptic neurons provide input to a smaller number of postsynaptic neurons, the pattern is known as __________. |
|
Definition
|
|
Term
| Synaptic transmission can be modified in response to activity at the synapse, a process known as __________ __________. |
|
Definition
|
|
Term
G protein-coupled receptors either create __________ __________ __________ or modify cell metabolism.
Ion channels create __________ __________ __________. |
|
Definition
1) Slow synaptic potentials
2) Fast synaptic potentials |
|
|
Term
| The summation of simultaneous graded potentials from different neurons is known as __________ __________. |
|
Definition
|
|
Term
| The summation of graded potentials that closely follow each other sequentially is called the __________ __________. |
|
Definition
|
|
Term
| __________ __________ of an axon terminal allows selective modulation of collaterals and their targets. |
|
Definition
| 1) Presynaptic modulation |
|
|
Term
| __________ __________ occurs when a modulatory neuron synapses on a postsynaptic cell body or dendrites. |
|
Definition
| 1) Postsynaptic modulation |
|
|
Term
| __________-__________ __________ and __________-__________ __________ are mechanisms by which neurons change the strength of their synaptic connections. |
|
Definition
1) Long-term potentiation
2) Long-term depression |
|
|
