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Flashcards in Neurophysiology (scavma) Deck (25):
1

Neurons

Functional units of the nervous system

2

Primary function of nervous system

To receive information form the environment and act on this information

3

Signal information pathway through nervous system

Environment- sensory receptor- receptor (generator) potential- CNS- action potentials- output, muscle contraction

4

CNS signal information

Action potential reaches CNS

then have synaptic transmission, post synaptic potentials, integration and action potentials which then leave

5

Sensory transduction

Physical or chemical signal from environment is changed to an electrical signal known as receptor potential or generator potential which can lead to a potential

6

Transient electrical signals

Generator potentials, Postsynaptic potentials also and action potentials

Convey info within and between the cells of the nervous system , all result in brief membrane changes

7

Membrane potential

Exchange of ions across the membrane is responsible for this potential and bioelectrical activity of the neuron

8

Extracellular Na and Cl

Higher than intracellular and reverse for K, higher intracellular

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Electrical Potential

Difference between intracellular and extracellular fluid compartments

Intracellular is negative vs extracellular= membrane potential

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Depolarizing

Towards 0 and extracellular potential

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Hyperpolarization

More negative

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Resting potential

Resting, steady state

Excess of + along outside of membrane and - along inside

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3 influential factors in ion movement

Concentration gradient, voltage gradient, membrane permeability

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Voltage gradients

For Na and K are inside because cell is negative

For Cl is outwards because attracted by outside +

15

Net flux

Movement of ions across a membrane dependent on both the forces or gradients acting on that ion and permeability of the cell membrane to that ion

Flux= Pion x driving force

16

Anions

Driving force is large but permeability is zero so no net flux

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At rest permeability

More permeable to K and Cl vs. Na

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Steady state transfer

3 Na in for every 2 K out

To offset passive movement cells like neurons have developed ATP dependent ion pumps which transport 3 Na out for every 2 in

So in steady state no net transfer

19

Electrochemical potential gradient

Sum of 2 passive forces, concentration gradient of ion and voltage of electrical gradient

At rest this should be zero

20

Potassium equilibrium potential

Membrane potential at which inward electrical flux is counterbalanced by outward diffusional flux

NERNST equation: Ek= RT/zF lnKo/Ki

At body temp: 61mVlog Ko/Ki

21

Driving potential

Difference between the membrane potential and the Nernst potential for an ion is called this

Resting potential -equilibrium potential

22

Change to relative permeability

When this changes for various ions this is the basis for electrical signals used by the nervous system for information processing

23

Membrane potential in resting condition

Determined primarily by the K+ gradient

So that at body temp resting potential can be determined

If ratio of K and Na permeability changes this is what happens with electrical signal

24

Na-K pump

In most excitable cells the active effluent of Na and active influx of K are coupled because move simultaneously

Phosphate bond of ATP provides energy

Mediated by enzyme which hydrolyzes ATP and activated by an increase in intracellular Na or extracellular K : Na, K activated ATPase

25

Energy for transport

To transport Na and K against electrochemical gradients is 20% excess of energy capacity of neuron