The Neuron & Action Potential

1. The Neuron & Action Potential The basic building block of our nervous system and how it sends messages.

2. What do you think of the brain series we are watching? • It is interesting • I learned something new • It is ok • I haven’t been paying attention

3. Do you think taking risks can be addictive? • Absolutely…it can provide the same rush as mind altering substances • Possibly, but it is not the same as drug/alcohol addiction • No…you either choose to do or not to do certain things

4. What chemical is closely associated with the high people feel when engaging in “risk” behavior? • Estrogen • Testosterone • Dopamine • Serotonin

5. Roughly how many people are “psychopaths”? • 1 in 10 • 1 in 100 • 1 in 1,000 • 1 in 10,000

6. What is the KEY characteristic all psychopaths share? • Lack of remorse • Unintelligent • Good Natured • Moody

7. Which statement is TRUE of the psychopathic brain? • 17% larger amygdala • 17% smaller amygdala • Small frontal lobes • No amygdala

8. Cell Body & Nucleus

9. The Cell Body Contains the cell’s nucleus • round, centrally located structure • contains DNA • no role in neural signaling (Not involved in sending or receiving messages)

10. What part of Clive Wearing’s brain was damaged? • Hypothalamus • Cerebellum • Hippocampus • Amygdala

11. What is one function of the hippocampus? • Sleep • Aggression • Digestion • Memory

12. Farmers in England are required by law to provide their pigs with? • Meatballs • Bacon • TV • Toys

13. Dendrites

14. Dendrites • Information collectors or receivers • Receive inputs or signals from neighboring neurons • Inputs may number in thousands • If enough inputs the cell’s AXON may generate an electrical output

15. Dendritic Growth • Dendritic growth allows for more connections to other neurons • New connections are basis for learning • Studies show people with higher education have more dendritic connections than someone that is a high school dropout.

16. Which part of the neuron plays no role in neural signaling? • Dendrite • Axon • Cell Body • Myelin

17. Which of the following states is considered the biggest “couch potato” state in the country this year? • Mississippi • Oklahoma • Georgia • Tennessee

18. Axon Axon

19. Axon • Where all the action is • Action Potential takes place – electrical charge is sent down the axon. • One axon per cell, 2 distinct parts • tube-like structure • branches at end (axon terminals) that branch out to dendrites of other cells

20. Which of the following receives messages from other neurons? • Axon • Cell Body • Dendrite • Nucleus

21. Myelin Sheath & Nodes of Ranvier

22. Myelin Sheath • White fatty casing on axon • Acts as an electrical insulator • When present, increases the speed of neural signals - like a paved highway • If this degenerates (dirt road), you have multiple sclerosis and can’t control your muscles.

23. Axon Terminal or Buttons Axon Terminals

24. Axon Terminal or Buttons • This is where the electrical impulse triggers synaptic transmission (release of neurotransmitters) to the dendrites of a receiving neuron. • Neurotransmitters are chemicals that enable neurons to “talk” to one another

25. Synapse or Synaptic Gap • The Synapse is the tiny space between neurons • The dendrites of one neuron do not touch the axon buttons of another

26. Which of the following is true of neurons? • Neurons generate electrical impulses. • The axon isn’t involved in sending messages • Neurons do touch one another • None of the above 20

27. Action Potential How neurons send an electrical message

28. How Neurons Communicate • Neurons communicate by means of an electrical signal called the Action Potential • Action Potentials are based on movements of ions between the outside and inside of the axon • When an Action Potential occurs, a molecular message is sent to neighboring neurons • Action Potential is an All or Nothing Process

29. Steps to Action Potential

30. Step 1: Threshold is Reached • Axon at Resting Potential - fluid inside the axon is mostly negatively (protein) charged with positive on the outside (sodium) • An impulse is triggered in the neuron’s dendrite when stimulated by pressure, heat, light or a chemical messenger from another neuron (stimulus threshold). • This minimal level of stimulation that causes the axon to fire is called Stimulus Threshold

31. Step 2: Action Potential Begins • When neuron fires, its axon membrane is selectively permeable. • Gates in the axon called ion channels open allowing positive sodium ions to enter the axon while potassium ions leave giving it a brief positive electrical charge the axon • The brief positive charge is action potential.

32. Step 3: Refractory Period • As the next gates open allowing positive sodium ions in, the previous gates close and begin to pump the positively charged sodium ions out of the axon and potassium ions back inside. • This step is called the refractory period and the axon cannot fire again until it returns to resting state • The entire process is like falling dominoes all the way down the axon except these dominoes can set themselves back up as soon as they fall over. • Why do you think the axon has to set itself back to a resting state so quickly (3 milliseconds)? • So the neuron can fire again and send another message immediately after the last one.

33. Action Potential Within a Neuron

37. DAILY DOUBLE

38. How can a toilet represent Action Potential? • Full Toilet – Resting Potential • Push Flush Lever – Threshold Stimulus triggering Action Potential. • Toilet Refilling/Can’t Flush – Repolarization/Refractory Period • Sewer Pipes – One-way communication like action potential only goes from dendrite end to axon terminal end.