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Chapter 6B
Objectives
18
Physiology
Undergraduate 2
02/08/2011

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Term
Potential
Definition
voltage difference between 2 parts
Term
Polarize
Definition
outside and inside of cell have a different net charge
Term
Depolarize
Definition
potential becomes less negative than resting potential
Term
Repolarize
Definition
when membrane that has been depolarized returns toward resting value
Term
Hyperpolarize
Definition
when potential is more negative than resting levels
Term
What kinds of cells have membrane potentials?
Definition
Electrogenic pumps create concentration gradients and thus membrane potentials (nerve cells have membrane potentials)
Term
Two gating mechanisms which alter the permeability of neural and muscle membranes to specific ions?
Definition
Mechanically gated channels: membrane ion channel that is opened or closed by deformation or stretch of the plasma membrane.

Voltage gated channels: cell membrane ion channel opened or closed by changes in the membrane potential
Term
Permeability of cell sodium, potassium, and chloride
Definition
Sodium is .04, potassium is 1, chloride is .04
Term
Action potential
Definition
electrical signal propagated by nerve and muscle cells
Term
How is ATP generated and what determines its size?
Definition
An all-or-none depolarization of membrane polarity and has a threshold refractory period and is conducted without decrement.

Changes in membrane permeability allow sodium and potassium to move down concentration gradient. Begins with a depolarizing stimulus, which opens some voltage gated sodium channels and further entry of more sodium ends to depolarization.
Term
Repolarization of a neuron occur
Definition
Sodium permeability aburptly declines because cycle of positive feedback is broken by blocking sodium channels. Depolarized state opens voltage gated potassium channels. Potassium flux out of cell rapidly repolarizes membrane to resting value.
Term
Cell's equilibrium potential
Definition
voltage difference across a membrane that produces a flux of a given ion species that is equal but opposite to the flux due to the concentration gradient of the same ion species.
Term
Absolute refractory period
Definition
time during which an excitable membrane cannot generate an action potential in response to any stiumlus (sodium channel is already open or proceeded to inactivated)
Term
Relative refractory period
Definition
time during which excitable membrane will produce action potential but only to a stimulus of great strength than usual threshold strength
Term
How does a threshold stiumulus change as the relative refractory period progresses
Definition
Stimulus has to be greater than usual but as relative refractory period goes on, it doesnt have to be as great
Term
What ion channel changes are responsible for the changes in threshold stimulus
Definition
Voltage gated sodium channels: some have returned to resting state potassium channels are open
Term
What portion of the neuron are voltage gated ion channels found
Definition
There are none on dendrites, some on soma, lots on axons
Term
What portions of the neuron are transmitter gated ion channels found
Definition
any portion where receptor is present
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