Term
| During signaling, the membrane potential does not stay constant at the RMP but changes briefly, these brief changes are known as |
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Definition
|
|
Term
| How do you measure an action potential? |
|
Definition
| with an electrode fabricated in the lab and then penetrate the cell and measure compared to outside of the cell which is zero. Follow membrane depolarization as they happen |
|
|
Term
| What are the general features of an AP? |
|
Definition
1) Threshold
2) Depolarization
3) Overshoot
4) Repolarization
5) Afterpotential
6) Resting Potential |
|
|
Term
| What are the major players in the AP? |
|
Definition
Voltage gated Na+ channel
Voltage gated K+ channel |
|
|
Term
| The Na channel can assume, how many conformations? |
|
Definition
|
|
Term
| For the Na channel, what is transient above threshold depolarization? |
|
Definition
|
|
Term
| For the Na channel, what is the steady subthreshold depolarization, RMP to t.p. called? |
|
Definition
| Slow inactivation- important for modulating neurons |
|
|
Term
| At rest the K+ voltage-dependent channel is? |
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Definition
|
|
Term
| When a Na+ or K+ channel opens, which DIRECTION will the ions flow? |
|
Definition
The DIRECTION depends on the energy difference
between Em and the equilibrium potential for each ion. |
|
|
Term
| the energy difference between Em and the equilibrium potential for each ion, this difference is called? |
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Definition
|
|
Term
| Ion movement during AP can be measured either as... |
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Definition
|
|
Term
| After an AP, what restores the ion gradients? |
|
Definition
|
|
Term
| What is the period where the cell can not fire, since the Na+ channels have not returned to their resting state from the the inactive state? |
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Definition
|
|
Term
| What are the two stage of the refractory period? |
|
Definition
ARP-no stimulus can cause an action potential
RRP- an action potential can occur since enough Na+ channels are ready to go, but Resting potential hasn't occurred yet |
|
|
Term
| What is the ability or readiness of a nerve or muscle to fire an AP? |
|
Definition
|
|
Term
| How do cells modulate their RMP to respond to different conditions? |
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Definition
Typically, by having resting K+ channels whose activity
is regulated by cellular metabolites, hormones or neurotransmitters.
This alters PNa/PK ratio which in turn alters the RMP |
|
|
Term
| A cell with a LESS negative RMP is... |
|
Definition
| Less likely to fire an AP |
|
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Term
| A cell with a MORE negative RMP is... |
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Definition
| MORE likely to fire an AP |
|
|
Term
| Sodium channels can only open from the? |
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Definition
|
|
Term
|
Definition
| DEpolarizing, same direction as Na+ entry |
|
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Term
| In the heart ventricle, ___a____ influx starts the depolarization and ___b___ influx keeps it going |
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Definition
|
|
Term
| Some cells also use, what to REPOLARIZE the AP? |
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Definition
|
|
Term
| Cl- ion s move _____ the cell for repolarization |
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Definition
|
|
Term
| How is an AP initiated on the cell membrane? |
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Definition
| A local depolarization brings one area of membrane to TP |
|
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Term
| On avg, the RMP of a nerve membrane is more depolarized (-70mV) than the RMP of skeletal muscle (-90mV)? Which cell is better positioned to modulate excitability? |
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Definition
| Nerve- it can move up or down, the muscle can't move much lower so it is ready to respond |
|
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Term
| THREE ways a depolarization can spread along a membrane from the site of stimulus |
|
Definition
-Passive Spread (NO Na+ channels)-fast
-Active Propagation (Na+ channels)- faster
-Saltatory Conduction (Na+ channels, myelin)- fastest |
|
|
Term
| In PASSIVE CONDUCTION, AMPLITUDE of the depolarization ____________ with distance along the axon |
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Definition
|
|
Term
| What type of conduction occurs in the synapse and cell body? |
|
Definition
|
|
Term
| What type of AP occurs in the Axon hillock and axon? |
|
Definition
|
|
Term
| What is a fatty white substance (essentially layers of membrane) produced by glial cells? |
|
Definition
|
|
Term
| When you separate charges, you... |
|
Definition
|
|
Term
| The amount of energy stored is measured in? |
|
Definition
|
|
Term
| What are the two gradients across cell membranes? |
|
Definition
-concentration gradient- generated by the Na/K pump
-electrical gradient- results from separation of charges |
|
|
Term
| The concentration and electrical gradient are called? At equilibrium, these two gradients are __________. |
|
Definition
-Electrochemical gradient
-EQUAL |
|
|
Term
| In terms of K+, at equilibrium there is what two things? |
|
Definition
| K+ gradient and opposite electrical gradient |
|
|
Term
| How do many cells signal each other? |
|
Definition
| with changes in membrane potentials |
|
|
Term
| During signaling, the membrane potential does not stay constant at the RMP but changes briefly. These brief changes are called? |
|
Definition
|
|
Term
| Starting at resting potential, tell me the order of events in an AP? |
|
Definition
1) Resting Potential
2) Signal - that reaches threshold or beyond
3) Depolarization
4) Overshoot
5) Repolarization
6) Afterpotential
7) Resting Potential |
|
|
Term
| What are the two major players in in the Action Potential? |
|
Definition
-Voltage-gated Na+ Channel
-Voltage-gated K+ Channel |
|
|
Term
| What are the three conformations of the Voltage-gated Na+ channel? |
|
Definition
1) resting (closed)
2) inactive (closed)
3) Active (open) |
|
|
Term
| Na channels can only open from which state? |
|
Definition
|
|
Term
| Which pathway for the Voltage-gated Na+ channel has a transient above threshold depolarization? |
|
Definition
|
|
Term
| Which pathway for the Voltage-gated Na+ channel has a steady subthreshold depolarization, RMP to t.p.? |
|
Definition
|
|
Term
| For the fast pathway of the VGNC, return to resting state from inactive state in? |
|
Definition
|
|
Term
| In the Slow pathway for the VGNC: resting to inactive conformation without opening in___________, and depolarization in range ___________________? |
|
Definition
- 10-50 ms
- -90 to -50 mV |
|
|
Term
| The Voltage-gated K+ channel, is it the same or a different protein form the resting K+ channel? |
|
Definition
| different- it has a resting and an active state |
|
|
Term
| When a Na+ or K+ channel opens, which DIRECTION will the ions flow? |
|
Definition
| The DIRECTION depends on the energy difference between Em and the equilibrium potential for each ion |
|
|
Term
The DIRECTION depends on the energy difference
between Em and the equilibrium potential for each ion. This difference is called the... |
|
Definition
|
|
Term
| What are two ways to measure ION MOVEMENTS? |
|
Definition
-Current (coulombs per sec per cm2)
- Flux (moles per sec per cm2) |
|
|
Term
| After an AP, what restores the ion gradients? |
|
Definition
|
|
Term
| The amount of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following excitation? |
|
Definition
|
|
Term
| What is the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied? |
|
Definition
| Absolute Refractory Period |
|
|
Term
| What is the interval immediately following during which initiation of a second action potential is inhibited but not impossible? |
|
Definition
| Relative Refractory Period |
|
|
Term
| What can be modulated for longer times by changing the RMP? |
|
Definition
|
|
Term
| What is the ability or readiness of a nerve or muscle to fire an AP? |
|
Definition
|
|
Term
| Long-term changes in excitability are modulated by changes in the? |
|
Definition
|
|
Term
| When the RMP depolarizes (movement up on graph), is the cell less or more excitable? |
|
Definition
|
|
Term
| When the RMP hyperpolarizes (movement down on graph), is the cell less or more excitable? |
|
Definition
|
|
Term
| A cell with a LESS negative RMP is _____ likely to fire an AP |
|
Definition
|
|
Term
| A cell with a MORE negative RMP is ______ likely to fire an AP |
|
Definition
|
|
Term
| How do cells modulate their RMP to respond to different conditions? |
|
Definition
Typically, by having resting K+ channels whose activity
is regulated by cellular metabolites, hormones or neurotransmitters.
This alters PNa/PK ratio which in turn alters the RMP |
|
|
Term
| Ca2+ entry is ________, same direction as Na+ entry |
|
Definition
|
|
Term
| What depolarizes the SA node of the heart? |
|
Definition
| Entry of Ca2+ only, no sodium channels in the SA node |
|
|
Term
| In the heart ventricle, ____ influx starts the depolarization and ____ influx keeps it going. |
|
Definition
|
|
Term
| What can help repolarize the AP in some cells? |
|
Definition
|
|
Term
| Does Cl- move into or out of the cell, when it helps repolarize the membrane? |
|
Definition
|
|
Term
| How is an AP initiated on the cell membrane? |
|
Definition
A local depolarization brings one area of the membrane to TP
examples include...
-Post synaptic potentials
-end plate potentials
-pacemaker potentials |
|
|
Term
IF an ion channel is OPEN and there is a
concentration gradient for the permeant ion,
WILL ION CURRENT FLOW? |
|
Definition
NO, if Em is at the Equilibrium potential for the ion
YES, if Em is away from the Equilibrium potential |
|
|
Term
| What are the three ways a depolarization can spread along a membrane from the site of stimulus? |
|
Definition
-Passive spread- No NA+ channels
- Active Propagation- Na+ channels
- Saltatory Propagation- Na+ channels, myelin |
|
|
Term
| In PASSIVE CONDUCTION, AMPLITUDE of the depolarization IN or DE creases with distance along the axon? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| Myelin reduces signal loss by acting as an... |
|
Definition
|
|
Term
| Myelin speeds conduction velocity by increasing... |
|
Definition
| the effective thickness of the membrane |
|
|
Term
| Myelin is found on what part of the axon? |
|
Definition
|
|
Term
When the Na+ enters, it is normally attracted...
but myelin has what effect? |
|
Definition
| to the negative charges outside the cell, but myelin means that it moves quickly to the next internode where it can make a connection with the outside |
|
|
Term
| What is the diameter (um) and conduction velocity (m/s) in a large myelinated axon? |
|
Definition
|
|
Term
| What is the diameter (um) and conduction velocity (m/s) in a small myelinated axon? |
|
Definition
|
|
Term
| What is the diameter (um) and conduction velocity (m/s) in a small unmyelinated afferent nerve? |
|
Definition
|
|
Term
| What is the diameter (um) and conduction velocity (m/s) in a mammalian muscle fiber? |
|
Definition
|
|
Term
| What do Beta cells in the pancreas use to trigger insulin secretion? |
|
Definition
|
|
Term
| What happens in Beta cells when blood glucose rises? |
|
Definition
1) K+ channels go from open to closed state (ATP binding causes it to close)
2)The cell depolarizes from a higher Na/K ratio
3)membrane reaches potential for Ca2+ channels to open
4)APs are fired in a bursting pattern for 5s
5) Ca2+ entry from the burst causes the secretion of insulin to happen |
|
|
Term
| In Type 2 diabets, what is targeted to help have more insulin secreted? |
|
Definition
| Some drugs target KATP receptor, causing it to close for more insulin to be secreted |
|
|
Term
| What is mutated in some forms of Type II diabetes? |
|
Definition
|
|
Term
What is is a rare disorder. Normally, type II diabetes has a late onset. These children were found to have a mutation in the Katp channel which prevents it from closing in response to elevated [ATP]i
Gain-of-function mutations in the genes encoding the Kir6.2 (pore forming subunit) and SUR1 subunits of this channel cause neonatal diabetes.
The mutations increase the OPEN time of the channel pore, thereby indirectly producing a marked decrease in the ability of ATP to close the channel. |
|
Definition
| Type 2 Diabetes of Infancy |
|
|
Term
| What is a treatment for Type 2 Diabetes of Infancy and how does it work? |
|
Definition
Sulfonylurea drug
This drug directly targets the SUR subunit of the Katp channel and causes the channel to CLOSE. |
|
|
Term
| What disease is characteristic of a muscle contracting normally, but not being able to relax? |
|
Definition
|
|
Term
| What EMG is found in a person with Myotonia Congenita? |
|
Definition
|
|
Term
| What ) is a disease of action potential generation in skeletal muscle caused by mutations in the muscle Cl channel? |
|
Definition
| Myotonia Congenita (Thomsens Disease) |
|
|
Term
| What normally flows with K current to repolarize the membrane? |
|
Definition
|
|
Term
| What happens with a person with Myotonia Congenita? |
|
Definition
1)AP repolarization is slowed when chloride channels are absent
-2)this prolongs repolarization, allows time for some Na channels to recover from inactivation
these Na channels can re-open, when Vm is near threshold
result: probability of firing extra APs |
|
|
Term
| What is the genetic basis of MC (Myotonia Congenita)? |
|
Definition
MC is caused by a mutation in the gene coding for the skeletal muscle Cl
channel. The Cl channel is a large membrane protein with 12 membraning spanning helices (drawn as cylinders in a linear sequence), which assemble to form a central pore. The mutation in MC results in glutamate being substituted for glycine at amino acid 230. Mutant Cl channels cannot conduct Cl- ions. |
|
|
Term
| What is a mutation in voltage-dependent sodium channel? |
|
Definition
| HYPERKALEMIC PERIODIC PARALYSIS (HYPP) |
|
|
Term
| What is a disease of action potential generation in skeletal muscle resulting from an abnormal Na channel? |
|
Definition
| HYPERKALEMIC PERIODIC PARALYSIS (HYPP) |
|
|
Term
| Tell me more about HYPERKALEMIC PERIODIC PARALYSIS (HYPP)? |
|
Definition
| It HYPP is a dominantly inherited disorder of skeletal muscle. Affected individuals experience brief, mild but frequent attacks of muscle weakness. Weakness often develops following a period of rest after exercise and can be provoked by oral K+ loading. During these attacks serum [K+] may rise to 6.0 - 7.0 mM. Some individuals may exhibit signs of muscle membrane hyperexcitability, in the form of clinical and electrical myotonia (repetitive firing). |
|
|
Term
| What happens in HYPP in terms of sodium channels? |
|
Definition
They are even more sluggish in getting to the inactive state, so have residual sodium current , that can drive an AP
-eventually have accumulation of sodium channels in inactive state and this is when the periodic paralysis occurs |
|
|
Term
| What syndrome is due to an immune response to foreign antigens (such as infectious agents produced by campylobacter or influenza virus) that is mistargeted at host nerve tissues instead? The targets of such immune attack are thought to be gangliosides, compounds naturally present in large quantities in human nerve tissues. The end result of such autoimmune attack on the peripheral nerves is damage to the myelin, the fatty insulating layer of the nerve, and a nerve conduction block, leading to a muscle paralysis |
|
Definition
| Guillain–Barré syndrome |
|
|
Term
What general class of disease is this...
When the myelin sheath is damaged, propagation of nerve signals is disrupted and a variety of neurological disorders can result. |
|
Definition
| Disorders of myelination, or demyelinating diseases and can be caused by a number of different factors including genetic, autoimmune or viral disease. |
|
|
Term
|
Definition
|
|
Term
| When saltatory conduction is slowed and/or blocked, a plethora of clinical symptoms arise, including... |
|
Definition
| Aberrant vision, lack of motor control, and eventually paralysis |
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|
