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NERVE IMPULSE TRANSMISSION  nerve cells are like no other cell in the body because they possess an electrical charge  the axon of a neuron has a cell.

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Presentation on theme: "NERVE IMPULSE TRANSMISSION  nerve cells are like no other cell in the body because they possess an electrical charge  the axon of a neuron has a cell."— Presentation transcript:

1 NERVE IMPULSE TRANSMISSION  nerve cells are like no other cell in the body because they possess an electrical charge  the axon of a neuron has a cell membrane that is semipermeable

2  imbedded in the membrane are specialized proteins called ION PUMPS that produce an unequal concentration of charged particles between the cell and its fluid extracellular environment

3 RESTING MEMBRANE POTENTIAL (Polarized RESTING MEMBRANE POTENTIAL (Polarized)  this refers to the charge of an axon that is waiting for a nerve impulse (resting)  Na + and K + ions are found both outside and inside the neuron

4  there is a higher concentration of Na + in the extracellular environment than inside  K + is more highly concentrated inside than out

5  a SODIUM POTASSIUM PUMP, in the membrane, is used to actively transport 3 Na + out of the axon for every 2 K + it moves in; this creates a charge of -70mV

6 ACTION POTENTIAL  an action potential is the name for the transmission of an electro- chemical stimulus through a nerve  in order for an action potential to occur the stimulus has to be strong enough, this is referred to as THRESHOLD LEVEL

7  there are two stages to an action potential:  Depolarization and Repolarization

8 DEPOLARIZATION:  when the neuron is stimulated, its membrane becomes more permeable to Na + ions, and impermeable to K +, so Na + ions move into the neuron by diffusion and K + ions are not able to move out.

9  this creates a reversal of charge in the neuron called depolarization, now the neuron is more positive than its surroundings (+40mV)

10 REPOLARIZATION:  is the return of the neuron to its resting state.  Na + channels close so Na + can no longer move into the neuron  K + rushes out of the axon and into the extracellular fluid by diffusion

11  The Sodium Potassium Ion pump then begins functioning; it pumps 3 Na + ions out of the neuron and 2K + ions into the neuron, returning the cell to its polarized condition (-70 mV)

12  depolarization and repolarization must be complete before a neuron can transmit another stimulus; this is called the REFRACTORY PERIOD

13  a neuron transmits the electrical impulse in wavelike fashion, once a region of the axon becomes depolarized adjacent regions will also become depolarized.

14  once a neuron’s threshold level has been reached it will respond totally, if it is not reached the neuron will not respond = ALL OR NONE RESPONSE

15  neurons in your body have different threshold levels allowing for different intensities of response.  the more neurons that reach threshold levels the more intense the response.

16 w The more rapidly impulses are sent, the more intense the response as well

17 Graphing an Action Potential ChargemV Restingpotential Depolarization Repolariztion Restingpotential Time(us) + 40 - 70 0


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