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a b c Need to think about this question 2 ways 1. within neurons – 2. between neurons-

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Presentation on theme: "a b c Need to think about this question 2 ways 1. within neurons – 2. between neurons-"— Presentation transcript:

1

2 a b c

3 Need to think about this question 2 ways

4 1. within neurons – 2. between neurons-

5 Neuron receiving info Information traveling down neuron

6 within neurons – electrically between neurons – chemically Synapse – space between neurons

7 developed Golgi Stain first determined space between neurons synapse

8 the resting state the active state neuron is firing action potential the refractory state

9 giant squid axon

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12 inside of the axon has a slightly negative charge relative to outside the axon called the membrane potential usually around -70mV

13 inside of the axon has a slightly negative charge relative to outside the axon called the membrane potential why?

14 action potential or spike

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16 see depolarization (change from negative inside neuron to more positive)

17 action potential or spike

18 see depolarization (change from negative inside neuron to more positive) threshold – if a great enough depolarization occurs, an action potential will occur action potential – very quick – milliseconds Other terms – spike, firing, generating an AP

19 action potential or spike

20 Hyperpolarization return to negative this is the refractory or recovery period

21 action potential or spike

22 All axons and cells have a membrane thin lipid (fat) bilayer The membranes have channels (to allow ions in or out) Ions – molecules with a charge These channels can be open or shut

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24 Ions flowing across the membrane causes the changes in the potential Ions are molecules that contain a positive or negative charge anion – negative charge cation – positive charge

25 Na+ sodium HIGHER CONCENTRATION OUTSIDE THE AXON Cl- chloride HIGHER CONCENTRATION OUTSIDE AXON K+potassium higher concentration inside the axon A- anions -large (-) molecules with a negative charge (stuck inside the axon)

26 INSIDE AXON (intracellular) OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ Na+ and Cl- are in higher concentration in the extracellular fluid Cl- Neuron at Rest Na+ Cl- A-

27 INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ A- K+ and negative anions are in higher concentration in the intracellular or inside the axon Cl- K+ Cl- K+ Neuron at Rest K+ A- Na+ Cl- K+

28 concentration gradient – ions diffuse from higher concentration to lower concentration

29 example of concentration forces

30 Na+ K+ Cl- What would each ion do if the ion channel opened based on the concentration gradient?

31 concentration gradient – ions diffuse from higher concentration to lower concentration electrical gradient - opposite charges attract so ions are attracted to an environment that has a charge that is opposite of the charge they carry!

32 example of electrostatic forces

33 Na+ K+ Cl- What would each ion do if the ion channel opened based on electrostatic forces ?

34 INSIDE AXON (intracellular) OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ Na+ and Cl- are in higher concentration in the extracellular fluid Cl- Axon depolarizing Na+ Cl- A-

35 opening of Na+ channels and influx of Na+ ions

36 lidocaine, novocaine, cocaine TTX – tetrototoxin Sagitoxin- red tides

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38 Na+ K+ Cl- Concentration Gradient Electrical Gradient after the AP (+ intracellular)

39 INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ A- K+ and negative anions are in higher concentration in the intracellular or inside the axon Cl- K+ Cl- K+ Neuron at Rest K+ A- Na+ Cl- K+

40 Sodium-potassium pump – active force that exchanges 3 Na+ inside for 2 K+ outside

41 INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ A- K+ and negative anions are in higher concentration in the intracellular or inside the axon Cl- K+ Cl- K+ After the action potential K+ A- Na+ Cl- K+ Na+

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43 myelin sheath (80% fat and 20% protein) produced by glia

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45 nodes of ranvier

46 myelin sheath (80% fat and 20% protein) produced by glia nodes of ranvier

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48 myelin sheath (80% fat and 20% protein) produced by glia nodes of ranvier saltatory conduction (200 ft/sec)

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52 speed, efficiency of neurotransmission

53 disease: Multiple Sclerosis progressive, autoimmune disease onset ~ 20 years of age early symptoms: motor symptoms, such as weakness, leg dragging, stiffness, a tendency to drop things, a feeling of heaviness, clumsiness,

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55 What about communication between neurons?


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