Term
| What are the five main functions of the neuron? |
|
Definition
- communication system
- regulatory and control of body functions
- sensory
- memory
- carries responses from the brain
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Term
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Definition
| the state where membrane potential is not 0 mV |
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Term
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Definition
| a change in the membrane potential that makes the membrane less polarized (less negative) than at resting potential (for ex, going from -70 mV to -50 mV) |
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Term
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Definition
| the membrane returns to its resting potential |
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Term
| What is hyperpolarization? |
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Definition
| a change in the membrane potential that makes the membrane more polarized than at resting potential (for ex, goes from -70 mV to -80 mV) |
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Term
| List the order of what happens to the membrane potential during an action potential. |
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Definition
| depolarization, repolarization, hyperpolarization, and resting potential (basic polarization) |
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Term
| What is the resting potential of most membranes? |
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Definition
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Term
| What part of a nerve cell makes up the input zone? |
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Definition
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Term
| What part of the a nerve cell is the triggering zone? |
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Definition
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Term
| What part of the nerve cell is the conducting zone? |
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Definition
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Term
| What part of a nerve cell makes up the output zone? |
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Definition
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Term
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Definition
| It is what insulates the axon of nerve cells. |
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Term
| What is myelin made up of? |
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Definition
| It is made up of lipids. It is actually a thick layer of lipid cells that are wrapped around the axon. |
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Term
| Is the entire axon myelinated? Explain. |
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Definition
| no, there are little gaps between each section of myelination called nodes of ranvier. |
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Term
| How much space is there between each node of ranvier? |
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Definition
|
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Term
| What are the cells called that make up myelination of nerves in the peripheral nervous system? |
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Definition
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Term
| What are the cells called that make up the myelin of nerve cells in the central nervous system? |
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Definition
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Term
| What are the two main functions of dendrites? |
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Definition
| to recieve sensory input and initiate an action potential when stimulated |
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Term
| What makes up the cell body of a nerve cell? |
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Definition
| nucleus, cytoplasm, and organelles |
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Term
| Is an axon aferent or efferent? |
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Definition
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Term
| An axon conducts _________ to a ________ or ________. |
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Definition
| action potential, synapse, muscle fiber |
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Term
| What are the two main functions of myelin? |
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Definition
| to insulate and speed up transmission of an action potential |
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Term
| Are all nerves myelinated? |
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Definition
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Term
| What structural components speed up transmission of an action potential? Explain. |
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Definition
| size and myelination; the greater the diameter of the axon, the faster an action potential will travel |
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Term
| How fast can nerve cells with fast transmission transmit an action potential? |
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Definition
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Term
| How fast can nerve cells with a slow transmission transmit an action potential? |
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Definition
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Term
| A _______ is where an action potential is passed to another nerve cell using __________ which affect the next cell starting a second action potential. |
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Definition
| synapse, neurotransmitters |
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Term
| What are voltage gated channels? Give an example. |
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Definition
| They are channels that open and close in response to changes in membrane potential (Na+, K+ channels) |
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Term
| What are chemically gated channels? Give an example. |
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Definition
| They are channels that change allosterically in response to the binding of specific chemical messengers with a mmebrane receptor. (serotonin receptor) |
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Term
| What are mechanically gated channels? Give an example. |
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Definition
| They are chemicals that respond to stretching or other chemical deformation (your stomach stretches when you eat) |
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Term
| What produces and action potential? |
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Definition
| Changes in ion movement through ion channels across the plasma membrane |
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Term
| What is a graded potential? |
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Definition
| It is a local change in membrane potential that occurs in varying grades or degrees. |
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Term
| The stronger the trigger the (smaller/larger) the resulting graded potential. |
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Definition
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Term
| What happens during an graded potential? |
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Definition
- At first, the entire membrane is at resting potential.
- Then a triggering event opens the ion channels, most commonly permitting net Na+ entry.
- The inward movement of the Na+ depolarizes the membrane, producing a graded potential.
- This current then flows between the active and adjacent inactive areas (across the membrane, not through the membrane.
- This depolarization spreads by local current flow to adjacent inactive areas, away from the point of origin.
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Term
| What is the purpose of a graded potential? |
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Definition
| to influence action potentials |
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Term
| What happens to graded potentials as they travel away from the point of origin? Why? |
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Definition
| they die out; this happens because current is lost across the cell membrane as charge crrying ions leak out through open channels |
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Term
| Graded potentials can initiate _________. |
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Definition
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|
Term
| What is an action potential? |
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Definition
| It is a brief, rapid, large change in membrane potential. |
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Term
| About how much does the membrane potential have to change in order to produce an action potential? |
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Definition
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Term
| During an action potential, the membrane potential transiently _______. |
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Definition
|
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Term
| What causes an action potential? |
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Definition
| marked changes in membrane permeability and ion movement |
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Term
| What type of channels play a major role in action potentials? |
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Definition
| voltage gated Na+ and K+ channels |
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Term
| Does the sodium/ potassium pump do active transport or passive transport? |
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Definition
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Term
| For every ___ sodium that the sodium/ potassium pump transports, it transport ____ potassium. |
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Definition
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Term
| The imbalance between sodium and potassium concentrations produces an _____________. |
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Definition
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Term
| What are some examples of stimuli that can trigger an action potential? |
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Definition
- sound waves
- electrical field change in the vicinity of the ion channel
- action of chemical messenger on receptor
- spontaneous change of potential caused by inherent imbalancesin the leak-pump cycle
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Term
| How is it that action potentials are not decremental like graded potentials? |
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Definition
| they use a positive feedback system to send the action potential down the whole length of the axon |
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Term
| What is threshhold potential? |
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Definition
| It is the level of polarization that the membrane must reach in order to initiate an action potential |
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Term
| What are the steps that lead to an action potential? |
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Definition
- At first, the membrane is at resting potential and both the Na+ and K+ channels are closed (Na+ is capable of opening)
- At the theshold (50 mV), the Na_ activation gate opens and the sodium potential rises.
- Na+ rushes into the cell, causing an explosive depolarization to 30 mV
- At the peak of the action potential, the Na+ inactivation gate closes and sodium potential falls, ending net movement of Na+ into the cell. At the same time the K+ activation gate opens and K+ potential rises
- K+ leaves the cell, causing repolarization to resting potential
- On return to resting potential, Na+ activation gate closes and the inactivation gate opens, resetting the channel to respond to another depolarizaing trigger event
- Further outward movement of K+ leads to hyperpolarization
- K+ activation gate closes and the membrane returns to resting potential
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Term
| What is the threshold potential for most memebranes? |
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Definition
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|
Term
| At what membrane potential does the action potential reach its peak after depolarization? |
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Definition
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Term
| At what memebrane potential do the K+ channels open? |
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Definition
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Term
| At what membrane potential does the Na+ activation gate close and the inactivation gate close? |
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Definition
| -70 mV (resting potential) |
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Term
| What reestablishes the electrochemical gradient after a resting potential? |
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Definition
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Term
| If the Na+/ K+ pump is slow to restore the original concentration gradient, why is another action potential able to be triggered before this gradient is reestablished? |
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Definition
| because there is still a concentration gradient; compared to what does not move across the membrane, there are alot more Na + and K+ ions that do not move across the membrane so the concentration gradient still exists and it only needs to be completely reestablished every once in awhile |
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Term
| What is a refractory period? |
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Definition
| It is a period in which another action potential can't be initiated by normal events in a region that has just undergone an action potential |
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Term
| What is an absolute refractory period? |
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Definition
| It is a period in which a recently activated patch of membrane is completely refractory |
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Term
| During which stages of polarization does an absolute refractory period take place? |
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Definition
| during depolarization and repolarization |
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Term
| What causes an absolute refractory period? |
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Definition
| It happens because during depolarization and repolarization, the Na+ channel is not in its resting conformation so it has not closed/ closed properly yet. |
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Term
| What is a relative refractory period? |
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Definition
| It is a period in which a second action potential can be produced only by a triggering event that is much stringer than usual. |
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Term
| At what stage of polarization does a relative refractory period take place? |
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Definition
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|
Term
| What causes a relative refractory period to take place? |
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Definition
| The K+ channel has not yet closed so the membrane is hyperpolarized and any triggering event must over come this hyperpolarization to reach the action threshold |
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Term
| Once action potential are initiated, they are conducted over the ______________. |
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Definition
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Term
| What does the action potential ensure? |
|
Definition
| undirectional propagation of the action potential |
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Term
| If action potentials spread in a similar way to graded potentials where it is sent in both directions away from the origin, why don't action potentials get sent backwards? |
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Definition
| because the previous active area is in its refractory period |
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Term
| Action potentials occur in an ____________ fashion. |
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Definition
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Term
| The strenght of the stimulus is coded by ________________. |
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Definition
| the frequency of action potentials |
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Term
| What are the two main purposes of myelination? |
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Definition
| It increases the speed of conduction of an action potential and it conserves energy. |
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Term
| At the peak of an action potential, sodium potential (increases/decreases) and potassium potential (increases/decreases). |
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Definition
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|
Term
| What causes depolarization? |
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Definition
|
|
Term
| What causes repolarization? |
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Definition
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|
Term
| Why is a refractory period so important with regards to the cardiac muscle? |
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Definition
| it keeps the heart from remaining contracted |
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Term
| What triggers a graded potential? |
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Definition
| a specific stimulus or the binding of a neurotransmitter with a receptor on the postsynaptic membrane |
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Term
| What triggers and action potential? |
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Definition
| the passive spread of depolarization from an adjacent area undergoing a graded or action potential |
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Term
| What kind of ion movement creates a graded potential? |
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Definition
| the net movement of Na+, K+, Ca 2+, and Cl- across the plasma membrane |
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Term
| What ion moveemnt produces an action potential? |
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Definition
| sequential movement of Na+ into and K+ out of the cell through voltage-gated channels |
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Term
| How is the magnitude of a triggering event coded with a graded potential? |
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Definition
| it varies with the magnitude of the triggering event |
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Term
| How id the magnitude of a triggering event coded with an action potential? |
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Definition
| all-or-none membrane response; magnitude of triggering event is coded in frequency rather than amplitude of action potentials |
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Term
| What is the duration of a graded potential? |
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Definition
| it varies with the duration of the triggering event |
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|
Term
| What is the duration of an action potential? |
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Definition
| it is always constant in the same neuron |
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Term
| What is the magnitude of potential change with distance from the initial site in a graded potential? |
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Definition
| decremental conduction; magnitude diminishes with distance from the initiation site |
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Term
| What is the magnitude of potential change with distance from the initial site in a action potential? |
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Definition
| it is propagated throughout the membrane in undiminishing fashion; self-regenerated in neighboring inactive areas of the membrane through positive feedback |
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Term
| What kind of refractory period does a graded potential have? |
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Definition
| none; it has no refractory period |
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|
Term
| What kind of refractory period does an action potential have? |
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Definition
|
|
Term
| What kind of summation does a graded potential have? |
|
Definition
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|
Term
| What kind of summation does a action potential have? |
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Definition
| none; it has no summation |
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Term
| What kind of membrane potential can a graded potential have? |
|
Definition
| depolarization or repolarization |
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|
Term
| What kind of potential change can an action potential have? |
|
Definition
| always depolarization and reversal of charges |
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Term
| Where do graded potetnials occur? |
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Definition
| in specialized regions of the membrane designed to respond to the triggering event |
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|
Term
| Where do action potentials take place? |
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Definition
| in regions of the membrane with a sufficient number of voltage gated Na+ channels |
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|
Term
|
Definition
| a junction across which a nerve impulse from an axon terminal to a neuron, muscle cell, or gland |
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Term
| What type od synapses are there? |
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Definition
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Term
| What are electrical synapses? |
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Definition
| it is a synapse in which an electrical signal is passed directly through a gap junction |
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Term
| Is an electrical synapse fast or slow? |
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Definition
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Term
| What are three examples of cells with electrical synapses? |
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Definition
| retinal neurons, smooth muscle, and cardiac muscle |
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Term
| Electrical synapses are (indirect/direct). Chemical synapses are (indirect/direct). |
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Definition
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Term
| Chemical synapses convert action potentials into _________ which are exocytosed into the __________. |
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Definition
| neurotransmitters, synaptic gap |
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Term
| Are chemical synapses fast or slow? |
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Definition
|
|
Term
| What are neurotransmitters? |
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Definition
| chemical messengers that are passed from a presynaptic neuron to a postsynaptic cell (neuron/ muscle/ gland) |
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Term
| Neurotransmitters are ________ from the neuron and ________ to the target. |
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Definition
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Term
| What are two advantages of chemical synapses? |
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Definition
| They operate in only one direction and they allow for various kinds of signaling events other than simply triggering action potentials in the target |
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Term
| How does a neuron to neuron synapse work? |
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Definition
- an action potential is propagated to the terminal of the presynaptic neuron
- Ca 2+ enters the synaptic knob
- neurotransmitter is released into the synaptic cleft by exocytosis
- neurotransmitter binds to the receptor on the postsynaptic neuron
- Specific ion channels open in the subsynaptic membrane
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Term
| What causes the calcium channels to open and let calcium into the axon terminal? |
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Definition
| a change in membrane potential from -70 mV to 30 mV |
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Term
| Almost all nerve cells in our body produce __________ and __________. |
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Definition
| norepinephrine, acetylcholine |
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Term
| Neurotransmitters can be either _________ or _________. |
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Definition
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|
Term
| What happens with a excitatory syanpse? |
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Definition
| A relatively large amount of Na+ enters the cell compared to K+ inducing a small depolarization (excitory postsynaptic potential) |
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Term
| What happens with a inhibitory synapse? |
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Definition
| It induces either Cl- influx or K+ efflux, inducing a small hyperpolarization (inhibitory postsynaptic potential) |
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Term
| Can fast synapses be both excitatory and inhibitory? |
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Definition
| no, they are always either one or the other |
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Term
| Do axon terminals release many neurotransmitters? What is an exception? |
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Definition
| no, axon terminals usually only release one neurotransmitter. An exception is GABA |
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Term
| Do all neurotransmitters induce inhibition and excitatation? |
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Definition
| no, some always induce excitation while other always induce inhibition |
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Term
| In what three ways are neurotransmitters quickly removed from the synaptic cleft? |
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Definition
- they diffuse away from the synaptic cleft
- they are inactivated by specific enzymes
- or they are take bakc into the axon terminals for reuse (reuptake)
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|
Term
| How do neurotransmitters in slow synapses function? |
|
Definition
| through a second messenger system |
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Term
| Second messenger systems take ________ and last ________. |
|
Definition
|
|
Term
|
Definition
| It is a neurotransmitter that links electrical signals in motor neurons with electrical signals in skeletal muscles |
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|
Term
| Acetylcholine mainly functions in ___________ synapses. |
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Definition
|
|
Term
| How many axon terminals are there per muscle cell? |
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Definition
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|
Term
| What are the steps in conduction at a neuromuscular synapse? |
|
Definition
- action potential in motor neuron is propagated to axon terminal
- this triggers opening of Ca 2+ channels which comes into the axon terminals
- Ca 2+ triggers the release of acetylcholine by exocytosis
- acetylcholine diffuses across the synapse and binds with receptors on the motor end plate of the muscle cell membrane
- this leads to the opening of cation channels, causing a large influx of Na+ campared to smaller K+ efflux
- this results in an end plate potential where local current flows from depolarized regions to adjacent inactive regions
- this current flow opens voltage gated Na+ channesl in the adjacent membrane
- this reduces the potential to threshold which initiates an action potential
- acetylcholine is destroyed by acetylcholinesterase, allowing relaxation of the muscle
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|
Term
| What is the grand postsynaptic potential (GPSP)? |
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Definition
| it is a composite of all the EPSPs and IPSPs occuring at approximately the same time |
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|
Term
| What does the GPSP depend on? |
|
Definition
| the sum of all the activities of presynaptic inputs |
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|
Term
| What are the two kinds of synaptic integration? |
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Definition
| temporal and spatial summation |
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Term
| If an excitatory presynaptic input is stimulated a second time after the first one has died off, what happens? |
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Definition
| the second EPSP will be of the same magnitude |
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Term
| If an excitatory presynaptic input is stimulated a second time before the first one has died off, what happens? |
|
Definition
| the second one will add to the first one resulting in temporal summation, which may bring the potential to threshold |
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Term
| If two EPSPs are initiated by simultaneous activation of two or more excitatory presynaptic inputs, what happens? |
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Definition
| the two action potentials add to each other, causing spatial summation which may reach the threshold potential |
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Term
| What happens if a excitatory and inhibitory presynaptic input are activated simultaneously? |
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Definition
| the postsynaptic potential does not change because they cancel each other out |
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|
Term
| Why are action potentials initiated at the axon hillock? |
|
Definition
| because it has the lowest threshold because there is a much greater density of Na+ channels |
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|
Term
| Explain how presynaptic inhibition works? |
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Definition
| A, an excitatory synaptic ending is innervated by inhibitory terminal B. Stimulation of A produces a EPSP but stimulation of B simultaneously inhibits A by producing a IPSP. |
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|
Term
| What is the purpose of presynaptic inhibition? |
|
Definition
| it selectively depresses activity in one terminal without supressing any other excitatory input to the cell body (postsynaptic neuron) and without interfering with other excitatory presynaptic inputs |
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|
Term
|
Definition
| they are larger molecules made up of anywhere fro 2 to 40 amino acids |
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|
Term
| Neuropeptides mainly function as ___________. |
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Definition
|
|
Term
| What are neuromodulators? |
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Definition
| chemical messengers the do not cause the formation of EPSPs and IPSPs but rather bring about long term changes that subtly modulate-- depress or enhance-- the action of the synapse |
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|
Term
| Neurons are linked to eachother through _________ and __________ to form complex _______________. |
|
Definition
| convergence, divergence, neural pathways |
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