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physics)principle #1) what is potential energy?
- separation of positive and negative charges
- *results in voltage
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physics)principle #1) what is kinetic energy?
- allows the separated charges to move freely
- *flow is called Amps
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physics)principle #1) What is resistance?
the force which slows down current flow
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physics)principle #1) what is an insulator?
substance which inhibits current flow
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physics)principle #1) what is conductor?
promotes current flow
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physics)principle #1) what is the formula of Ohm's law?
Current= Voltage/resistance
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Physics applied to living systems) what is the current?
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Physics applied to living systems) example of potential enrgy creation?
charge separation
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Physics applied to living systems) example of insulator?
plasma membrane
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Physics applied to living systems) example of conductors
- channels
- *integral transmembrane proteins
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channels) What are passive channels?
- they are always open and allow specific ions to flow through them
- *leaking
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channels) what are active gated channels?
only open when stimulated
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channels) 2 types of active gate channels?
chemical and voltage
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channels)(active) how do chemical gated channels open?
- by chemical stimulus
- *ligand binds to the receptor then it opnes
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channels)(active) How do voltage gated channels open?
by change in potential energy
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which 2 factors does current flow depend on?
-electrical charge movement
-chemical diffusion
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factors that current flow depend on- what is electrical charge movement
ions that are charged will move toward an area that contains an opposite charge
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factors that current flow depend on- chemical diffusion
diffuse from an area of high concentration to low concentration
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what 2 forces are known are electrochemical gradient?
-chemical diffusion
-electrical charge movement
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resting membrane potential) definition
created by unequal concentrations of ions of both charges that exist in a narrow band around each side (cytoplasmic and extracellular) of the plasma membrane
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what is referred to as charge separation?
- polarization of the membrane
- *basis of all electrical conductivity of cells
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Is the cell electrically neutral?
yes
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generation and maintenance of RMP) polarization
- specific ions separate themselves at different concentrations immediately around the membrane
- *CL, K, NA are allowed to move in back and forth
- *A isnt
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generation and maintenance of RMP) what 2 things generate the concentration difference?
-NA/K ATPase pump
-passive K and NA channesl
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generation and maintenance of RMP) what is the NA/K ATPase pump method?
- it pumps 3 NA out and 2 K are pumped into the cell simultaneously.
- *antiport example
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generation and maintenance of RMP) what 3 things does the NA/K ATPase pump do?
-pumping creates equilibrium from being reaches
- -maintain unequal distirbution of ions
- *because more positives are coming out then bringing in, this creates a negative environment inside
-electro-chemical gradient
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generation and maintenance of RMP) what do the passive channels of K and NA allow?
allows K to move out and NA to move in
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generation and maintenance of RMP) why does K move out?
K is already pumped in by the NA/K pump therefore it wants to move along the concentration gradient
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generation and maintenance of RMP) passive channels- which ion has more channels? K or NA?
K
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which 2 cell types change their membrane potential?
nerve and muscle
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Can other cells other than muscle of nerve alter their membrane potential?
no, they maintain a constant resting memebrane potential throughout life
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what is a polarized cell
- is a cell with a charge that is separated across
- *-70MV
- **resting potential cell
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what is a depolarized cell? (3)
-not polarized
-charges have been allowed to flow
-potential enrgy is 0 MV
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what is hyperpolarized cell?
- more polarized than the resting potential
- *potential energy is greater
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what is repolarized?
return polarity to baseline
**return from hyperpolarized state> decrease potential energy, return from depolarized state> increase potential energy
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what are the 2 mechanisms that change the plasma membrane potential?
-graded potential
-action potential
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how do graded potential and action potential differ?
in amount of ions that move and type of membrane channel which opens
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characteristics of chemically gated (2)
- -few ions cross the membrane
- *more than resting potential though
- -small and limited graded potential
- *small spark and it is limited
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characteristics of voltage gated (2)
-many ions cross the membrane
- -large and all or none
- *large spark and if it sparks it goes throughout the membrane.
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graded potentials) what channels do cells capable of conducting graded potentials have?
chemically gated channels
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graded potentials) what happens when the gates are opened? (3)
-few ions go across
-often only one type of ion
-area of membrane that changes potential is relatively small
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graded potentials) what 2 states can graded potentials create?
depolarized and hyperpolarized
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graded potentials) when positive charges neutralize negative interior, what occurs?
depolarization
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graded potentials) when positive charges leave interior of the cell, what occurs?
hyperpolarization
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action potentials) what type of channels do cells contain the ones that are capable of creating action potentials?
voltage-gated channels
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action potentials) are the voltage channels specific for an ion or broad?
specific
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how are action potentials usually initiated by?
graded potentials at a different area of the membrane
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4 phases of AP) Resting phase
-closed gated channels
- -Resting membrane potential exists
- * there are ion movements but not on these chemical or voltage channels
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4 phases of AP) Action phase:Depolarization (3)
-hemically gated channels open
-NA enters which depolarizes membrane which
-causes NA voltage gated channels to open
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4 phases of AP) active phase: repolarization
-NA channels close
-chemically gated channels have already closed
- -K voltage channels open
- *these will not open unless it senese a large positive gradint on the interior side of membrane
- *K will leave the cell along the electrochemical gradient
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4 phases of AP) Active phase: Hyperpolarization
- -K channels stay open awhile
- *goes into negative bc the K channels allow K to keep moving out
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what restores the membrane to be ready for the next Action potential?
NA/K ATPase pump
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where do Action potential travel along the membrane?
where there are voltage gated channels
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whats action potential threshold?
- must have enough stimulus to open the voltage gated channels
- *sometimes the graded potential did not reach the threshold to create AP
- **occurs frequently
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Once voltage gated channels open...
AP goes through the length of membrane, no exceptions
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what are refractory periods?
- period where all ions need to be returned to baseline lcoations
- *sodium out and K in
- **NA/K pump does this
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2 types of refractory periods
-absolute
-relative
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refractory periods) Absolute (2)
-incapable of stimulus response, an AP
- -happens immediately after
- *ions are on the wrong side of baseline locations
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refractory periods) Relative (2)
-large stimulus can generate an action potential
-na/k pump has had chance to sort of sort through all the ions but only a big spark can create an AP
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