Synapses… passing along important information

1. See how much you know about action potentials. As a team try to line these events up in the correct order.

3. Synapses… passing along important information http://www.youtube.com/watch?v=70DyJwwFnkU

4. What is it? • Synapse- the space where a neuron communicates with another neuron, a muscle, or a gland • Where the electrical activity in one neuron effects the excitability of another

5. What was a gap junction? In what body system did we talk about them?

6. 2 types of synapses… • 1. Electrical • plasma membranes of the presynaptic and postsynaptic cells are joined by a gap junction • Electrical impulse passes from cell to cell very quickly • In cardiac and smooth muscle  NOT our focus!

7. 2. Chemical- no physical connection between cells; need a messenger neurotransmitters • Sent neurotransmitter/message can: • generate an action potential/response from the receiving cell (excitatory synapse) • prevent the receiving cell from generating an AP/showing a response (inhibitory synapse)

8. How does a synapse work? • If I told you muscles are “activated” the same way resting neurons are excited, then what must be present during a synapse to make the muscle move? • Can these things (that will make muscles move) enter and exit the cell freely? Explain why or why not. • How will the neuron send a message to the receiving muscle cell? • Based on all of the answers to the above questions begin to formulate a theory about how neurons talk to muscle cells and tell them to move. *THEORY:

9. Model it… • Using the materials you have been given design a sensible model that shows how a neuron can make a muscle move. Feel free to manipulate the materials as needed. Keep your answers to the previous questions in mind. • Identify what each material represents • White cell: • Red/pink cell: • Pipecleaner: • Pony beads: • Beans:

10. Now… • Merge with another group and explain your models • Discuss that aspects of the model are plausible and which may need some refinement and see if you can create a better working model. • This final idea from the group duet will be shared with the class.

11. http://www.youtube.com/watch?v=HXx9qlJetSU

12. Events of a Chemical Synapse • An AP stimulates the release of synaptic vessicles (contain neurotransmitters) • Vessicles bind w/ the terminal axon membrane  exocytosis • Released NTs bind to receptor proteins on the plasma membrane of the post-synaptic cell • Excitatory response  yes AP fired/receiving cell shows response • Inhibitory response  no AP fired/receiving cell not stimulated • Neurotransmitters don’t last for long b/c they are either • inactivated by enzymes • taken back up by the axon terminal  reuptake http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__transmission_across_a_synapse.html

13. What do you know? • Get into your small groups from yesterday • In a type 1 list the steps that occur, from start to finish, that allow a neuron to talk to a muscle • NOW swap papers with another group, read their list of events and comment on anything that seems incorrect • Meet up with the group that has your paper and discuss the criticisms • Any questions?

14. Synaptic Integration • *** 1 synapse is not usually enough to cause activation but there are thousands of synapses occurring some happen close enough that their effects can add together to cause activation http://www.youtube.com/watch?v=HXx9qlJetSU

15. Neuron-Muscle Communication 1. Ach (Aceytlcholine) • is released from the nerve • Both Na and K channels open simultaneously • way more Na comes in than K goes out  net increase in charge • 10,000 ions cross in first millisecond • Causes muscle to respond to stimulus • - Removed from synaptic cleft VERY FAST by an enzyme called acetylcholinesterase • Sarin inhibits this enzyme  how? • Nerve gas in Japanese terrorist attacks http://www.youtube.com/watch?v=ra2HeSjo82c (start 6:08)

16. Neuron-Neuron Communication 1. GABA • Major inhibitory NT in brain • actually inhibits the signal and causes the cell to go further from the threshold (Opens Cl- channels) • Valium increases GABA levels by increasing release of GABA • Taken to relieve anxiety, muscle spasms, and seizures

17. Neuron-Neuron Communication 2. Dopamine • Involved in emotional behavior and motor control • Lack of dopamine causes Parkinsons (characterized by excessive shaking) • Amphetamines stimulate dopamine receptors  why they’re addictive • When we are rewarded, feel good there are inc levels of dopamine

18. Neuron-Neuron Communication 3. Serotonin • Serotonin involved in control of sleep and emotion • Lack of serotonin one cause of depression • Many antidepressants block the reuptake of serotonin so effectiveness in increased  more positive feelings 4. Endorphins • Example of a NEUROMODULATOR – which have slower, longer effects on pre- or post- synaptic cells. • Blocks perception of pain and evokes a feeling of well-being • Runner’s High  lets you push yourself… sometimes too far