The document discusses how bioelectricity arises in excitable tissues like nerves. The resting potential of neurons is maintained by the sodium-potassium pump, which pumps sodium ions out and potassium ions into neurons. When the membrane is stimulated, voltage-gated sodium channels open, causing sodium to rush in and depolarize the membrane. This generates an action potential that propagates along the axon. At synapses, an action potential causes neurotransmitter release, which can excite or inhibit the next neuron.

1. BIOELECTRICITY AND EXCITABLE TISSUE THE ORIGIN OF BIOELECTRICITY AND HOW NERVES WORK www.freelivedoctor.com

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4. BIOELECTRICITY THE ORIGIN OF THE MEMBRANE POTENTIAL www.freelivedoctor.com

6. IONS MOVE WITH THEIR HYDRATION SHELLS - + - + Hydration Shells - + - + - + - + - + - + - + - + - + www.freelivedoctor.com Na + - + - + Cl - - + - + - + - + - + - + - + - + - + - + - + - + - +

7. ELECTRONEUTRAL DIFFUSSION HIGH SALT CONCEMTRATION LOW SALT CONCEMTRATION BARRIER SEPARATES THE TWO SOLUTIONS www.freelivedoctor.com + - + - + - + - + - + - + - + -

8. ELECTRONEUTRAL DIFFUSSION + - CHARGE SEPARATION = ELECTRICAL POTENTIAL www.freelivedoctor.com HIGH SALT CONCEMTRATION LOW SALT CONCEMTRATION + - BARRIER REMOVED + - + - + - + - + - + - + -

9. ELECTRICAL POTENTIAL=CHARGE SEPARATION In water, without a membrane hydrated Chloride is smaller than hydrated Sodium, therefore faster: Cl - Na + The resulting separation of charge is called an ELECTRICAL POTENTIAL + - www.freelivedoctor.com

10. THE MEMBRANE POTENTIAL M E M B R A N E Extracellular Fluid Intracellular Fluid Na + K + Sodium channel is less open causing sodium to be slower Potassium channel is more open causing potassium to be faster + - MEMRANE POTENTIAL (ABOUT 90 -120 mv) www.freelivedoctor.com

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14. ACTIVE TRANSPORT ADP ATP www.freelivedoctor.com

17. THE NERVE CELL CELL BODY DENDRITES AXON AXON HILLOCK AXON TERMINALS www.freelivedoctor.com

19. EQUILIBRIUM POTENTIALS FOR IONS FOR EACH CONCENTRATION DIFFERENCE ACROSS THE MEMBRANE THERE IS AN ELECTRIC POTENTIAL DIFFERENCE WHICH WILL PRODUCE EQUILIBRIUM. AT EQUILIBRIUM NO NET ION FLOW OCCURS www.freelivedoctor.com

20. THE EQUILIBRIUM MEMBRANE POTENTIAL FOR POTASSIUM IS -90 mV + - CONCENTRATION POTENTIAL K + K + IN www.freelivedoctor.com

21. THE EQUILIBRIUM MEMBRANE POTENTIAL FOR SODIUM IS + 60 mV Na + Na + + - CONCENTRATION POTENTIAL IN OUT www.freelivedoctor.com

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28. PROPAGATION OF THE ACTION POTENTIAL +++++ -------- --------------------- +++++++++++++ AXON MEMBRANE INSIDE OUTSIDE ACTION POTENTIAL DEPOLARIZING CURRENT www.freelivedoctor.com

29. PROPAGATION OF THE ACTION POTENTIAL +++++ -------- --------------------- +++++++++++++ AXON MEMBRANE INSIDE OUTSIDE ACTION POTENTIAL DEPOLARIZING CURRENT www.freelivedoctor.com

30. PROPAGATION OF THE ACTION POTENTIAL --+++ ++------ +++------------------ ---++++++++++ AXON MEMBRANE INSIDE OUTSIDE ACTION POTENTIAL DEPOLARIZING CURRENT www.freelivedoctor.com

31. PROPAGATION OF THE ACTION POTENTIAL -------- +++++ ++++++------- -----------++++ AXON MEMBRANE INSIDE OUTSIDE ACTION POTENTIAL DEPOLARIZING CURRENT www.freelivedoctor.com

32. SALTATORY CONDUCTION +++++ -------- -------- +++++ AXON MEMBRANE INSIDE OUTSIDE ACTION POTENTIAL DEPOLARIZING CURRENT MYELIN NODE OF RANVIER NODE OF RANVIER www.freelivedoctor.com

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36. THE SYNAPSE SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ••• ••• INCOMING ACTION POTENTIAL CALCIUM CHANNEL ION CHANNEL RECEPTOR ENZYME www.freelivedoctor.com

37. THE SYNAPSE SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ••• ••• INCOMING ACTION POTENTIAL CALCIUM CHANNEL ION CHANNEL RECEPTOR ENZYME www.freelivedoctor.com

38. THE SYNAPSE SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ••• ••• INCOMING ACTION POTENTIAL CALCIUM CHANNEL ION CHANNEL RECEPTOR ENZYME www.freelivedoctor.com

39. THE SYNAPSE SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ••• ••• CALCIUM CHANNEL ION CHANNEL RECEPTOR ENZYME www.freelivedoctor.com

40. THE SYNAPSE SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ••• ••• CALCIUM CHANNEL ION CHANNEL RECEPTOR ENZYME ••• www.freelivedoctor.com

41. THE SYNAPSE SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ••• ••• CALCIUM CHANNEL ION CHANNEL RECEPTOR ENZYME www.freelivedoctor.com

42. THE SYNAPSE SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ••• ••• CALCIUM CHANNEL ION CHANNEL RECEPTOR ENZYME www.freelivedoctor.com

43. POSTSYNAPTIC POTENTIALS RESTING POTENTIAL EPSP TIME www.freelivedoctor.com IPSP

44. TEMPORAL SUMMATION TIME TOO FAR APART IN TIME: NO SUMMATION www.freelivedoctor.com

45. TEMPORAL SUMMATION TIME CLOSER IN TIME: SUMMATION BUT BELOW THRESHOLD THRESHOLD www.freelivedoctor.com

46. TEMPORAL SUMMATION TIME STILL CLOSER IN TIME: ABOVE THRESHOLD THRESHOLD www.freelivedoctor.com

47. SPATIAL SUMMATION TIME SIMULTANEOUS INPUT FROM TWO SYNAPSES: ABOVE THRESHOLD THRESHOLD www.freelivedoctor.com

48. EPSP-IPSP CANCELLATION www.freelivedoctor.com