Term
| what can cross the lipid bilayer |
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Definition
| Gases, small uncharged molecules |
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Term
| water channels that lets water cross the barrier |
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Definition
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Term
| describe an aquaporin's transmembrane structure |
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Definition
| 6 full transmembrane proteins and a couple half way- the cluster of 6 transmembrane domains per aquaporin subunit. |
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Term
| describe the aquaporin's channels |
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Definition
| There are 4 subunits per aquaporin and each subunit forms a water channel to allow the passage of water across the membrane. So you end up with 4 channels |
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Term
| how fast do ion transport channels go |
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Definition
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Term
| this type of transporter requires a specific protein but nothing else |
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Definition
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Term
| this type of transporter requires a specific transporter, transports against the concentration gradient and is coupled to ATP hydrolysis |
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Definition
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Term
| this type of transporter requires a specific protein, transports against teh concentration gradient and a cotransporter ion that moves down its concentration granient |
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Definition
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Term
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Definition
| atp hydrolysis by phosphorylation causing a conformational change |
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Term
| P-class pumps include Na/K pumps. How many Na/K do they pump? |
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Definition
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Term
| the Na/K and Ca pumps are called P-pumps for this reason |
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Definition
| the transport protein is phosphorylated |
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Term
| what direction do Ca pumps pump Ca? |
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Definition
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Term
| how much Na inside the cell vs out |
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Definition
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Term
| how many K ions inside the cell vs out |
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Definition
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Term
| how much Ca inside the cell vs out |
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Definition
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Term
| how many subunits in ion channel proteins |
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Definition
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Term
| how many subunits in aquaporin proteins |
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Definition
| 4 subunits making 4 channels |
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Term
| Na and K are surrounded by |
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Definition
| a hydration shell of water |
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Term
| as Na and K pass through the ion channel the hydration shell is replaced with this |
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Definition
| by carbonyl oxygen molecules |
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Term
| how does the ion channel regulate which ions go through it? |
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Definition
| the channel has an outer selectivity filter that uses size and charge specificity to select a particular ion |
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Term
| membrane potentials are always expressed as |
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Definition
| the inside relative to the outside |
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Term
| membrane resting potential can be as low as |
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Definition
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Term
| at rest the cell is permeable to ------- and impermeable to --------- |
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Definition
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Term
| what is responsible for the negative charge |
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Definition
| is mostly in the form of protein and phosphate |
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Term
| at rest what are the states of the K and Na channels |
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Definition
| K is open and Na is closed |
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Term
| eventually excess negative charge results in an inside-negative voltage gradient that opposes further diffusion. This is termed the |
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Definition
| equilibrium potential for K+ |
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Term
| about what is the ENa+ for sodium |
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Definition
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Term
| very few ions actually have to move across the phospholipid bilayer for this reason |
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Definition
| the phospholipid bilayer is effective in separating charges membrane |
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Term
| how do heart pacemaker cells maintain a higher resting potential than other cells (-60mV) |
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Definition
| by being more permeable to Na |
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Term
| by being impermeable to ions the cell becomes a--------- |
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Definition
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Term
| this allows a voltage difference to be rapidly established with very little change in cellular K+ so a membrane can quickly establish a resting potential |
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Definition
| Charge stored by the membrane |
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Term
| if the cell depolarizes/repolarizes several times a second what changes will be seen in the concentration of Na and K |
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Definition
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Term
| predicted from balance between concentration and voltage gradients. About -90 mV for K+, +60 mV for Na+ |
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Definition
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Term
| a function of the relative permeability for K+ vs Na+. For some cells resting potential may be -60 mV, for others it may be -90 mV. |
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Definition
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Term
| ionic events that produce the resting potential. Resting potential may vary according to different stimuli. |
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Definition
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Term
| an event that results in the membrane potential becoming less negative, most often an increase in Na+ permeability |
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Definition
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Term
| Return to the resting potential after a depolarization |
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Definition
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Term
| an event that results in the membrane potential becoming more negative, most often an increase in K+ permeability –or- an increase in Cl- permeability. |
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Definition
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Term
| a function of the number of channels for a particular ion and the probability they are open. Measured as conductance (Siemens = 1/resistance |
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Definition
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Term
| sensations from the anterolateral system |
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Definition
1. Pain
2. Thermal sensations, including both warmth and cold sensations
3. Crude touch and pressure sensations capable only of crude localizing ability on the surface of the body
4. Tickle and itch sensations
5. Sexual sensations |
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Term
| Mechanosensitive Channels are opened by |
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Definition
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Term
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Definition
| have ion channels that open when the membrane is deformed and allow Na+ to enter, depolarizing the receptor membrane |
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Term
| Above threshold, a greater stimulus is translated into a |
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Definition
| greater frequency of action potentials |
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Term
| Action potentials are of equal magnitude (all-or- none). It is the ----------that conveys intensity. |
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Definition
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Term
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Definition
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Term
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Definition
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Term
| what change takes place to cause the depolarization of the cell |
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Definition
| the cell membrane becomes more permeable to Na |
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Term
| what is it called when the membrane potential becomes patrially positive? |
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Definition
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Term
| The fourth transmembrane helix in each group has this to cause the pore to open when the membrane becomes charged |
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Definition
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Term
| Voltage gated channels have this in transmembrane regions that can control the opening of the channel |
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Definition
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Term
| how does the ball and chain block voltage gated channels? |
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Definition
| the ball moves into the channel when it is closed, blocking Na from entering the cell |
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Term
| The charge displaced from a node of Ranvier during an action potential displaces this |
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Definition
| + charge electrotonically to the next node |
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Term
| what is the purpose for the refractory period? |
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Definition
| to allow the charge to travel in only one direction |
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Term
| if you artificially stimulate an axon in the middle the impulse will be sent in this direction |
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Definition
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Term
| If you artificially stimulate an axon in the middle region,why would an action potential be conducted in both directions, towards and away from the cell body, |
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Definition
| because the refractory state is only produced in the newly closed channels. |
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Term
| length constant” refers to the drop in voltage between nodes. The greater the length constant, the |
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Definition
| smaller the drop so the distance between nodes is greater, giving a faster conduction velocity |
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Term
| type I or alpha mylinated fiber size and speed |
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Definition
| large fibers- 10-20um, 100-120 m/s |
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Term
| type II or beta and gamma size and speed |
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Definition
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Term
| non-mylineated fiber size and speed |
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Definition
| smallest and very slow- 1-2m/s |
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Term
| how do local anesthetics work |
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Definition
| Local anesthetics block voltage-gated channels so that nerve impulse conduction is blocked |
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Term
| where do local anesthetics preform there actions |
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Definition
| at the cytosolic side of the membrane |
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Term
| how does lidocaine react to a acidic or neutral pH? |
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Definition
| In acidic –neutral media the quaternary amino group accepts a proton and becomes positively charged |
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Term
| how does lidocaine react to an alkaline environment? |
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Definition
| alkaline media the proton dissociates, the molecule has a neutral charge and is more permeable across cell membranes |
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Term
| once inside the cell what happens to the lidocaine and how is this beneficial? |
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Definition
| the lower pH protonates the anesthetic, giving it a positive charge which keeps it inside the cell for a longer period of time |
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Term
| The pKa for lidocaine is 7.9. At that pH what % of the lidocaine will be in the uncharged form? |
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Definition
| half of the lidocaine will be in the charged and half in the uncharged state. |
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Term
| at physiological pH (7.4) how much lidocaine is in the uncharged form? |
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Definition
| the charged form is 3 x that of the neutral form |
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Term
| in inflamed tissue the pH may be much lower. how much charged form of lidocaine will be present? |
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Definition
| as much as 10X more charged than uncharged- very little free to move into the cell so it goes really slow |
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Term
| with epinephrine how much lidocaine is uncharged and free to move into the cytoplasm? |
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Definition
| 1 uncharged/10,000 charged |
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