Synaptic Transmission (a.k.a. how neurons communicate)

Synaptic Transmission(a.k.a. how neurons communicate) (4R)

Reminder: • The Nervous System is a very complicated collection of cells known as neurons. • quick check: do you remember the main parts of a neuron?? No peeking! Dendrites 1 Axon terminals 5 4 Cell body 2 Axon 3

Reminder: • Neurons receive information through branch-like structures called dendrites. • As neurons grow, their dendrites reach out and “make contact”* with the axons of adjacent neurons. * There is no physical contact between neurons!!!

The Synapse: • There is no physical contact between the axon terminal of one neuron and the dendrite(s) of another. • Instead, between the axon and the dendrites is a space or gap, which is called the synapse. Fun Fact: The average neuron has 1,000+ synapses with other neurons. neurotransmitter = NT

Thinking Cap • How fast do you think synaptic transmission happens? Why do you think that? (hint: try to pick a number! Miles per hour work for units ;) • Do you think all neurons transmit at the same speed? Why / why not?

Synaptic Transmission • 1. A chemical change occurs that creates an electrical impulse down the axon • 2. These NT float across the synapse and connect like a “lock-and-key” with receptors on the dendrites of the receiving neuron.

Synaptic Transmission (cont.) NOTE: It is the presence of the NT (chemical) 'keys' opening the receptor 'locks' on the surface of the dendrites of the 2nd neuron that excites or inhibits the 2nd neuron into activating or not. ***it is NOT an electrical signal that “jumps” the synapse***

https://www.youtube.com/watch?v=WhowH0kb7n0 Figure 48.12 A chemical synapse Don’t be a’scared! No need to draw any of this!

Thinking Cap • Neurotoxins from marine snails like the cone snail (see below) are some of the deadliest in the world. • Why do you think that is? (hint: think evolution) • What part of their prey’s body do you think the venom targets to kill it fastest? • Do you think we could ever use this venom for the good of humanity? Explain...

The Neurotransmitters • There are many different chemicals in the brain that function as neurotransmitters, but a small handful do most of the work. dopamine Acetylcholine Serotonin GABA Endorphins EPI

Thinking Cap • Have you ever heard the term “happy pills” to describe drugs prescribed for mood-regulation (specifically for depression)? Why do you think people call them that?

Types of NTs • Inhibitory NTs: prevent neurons from talking to one another • Example: GABA = nature’s Valium • Excitatory NTs: encourage neurons to talk to one another • Example: Epinephrine (a.k.a. adrenaline) = fight-or-flight response

Neuron Communication:with your partner, you should be able to identify the parts of the neuron AND the type of signal present at each part! Hint: the signal can be electrical or chemical 1. 2. ________ signal 3. ____________signal 4. 5. (blue dots) ____________signal

Drugs Interfere with Neurotransmission • Drugs can affect synapses in a variety of ways (excite or inhibit), including: • Increasing number of impulses • Release NT from vesicles with or without impulses • Block reuptake or block receptors • Produce more or less NT* • Prevent vesicles from releasing NT

“This is your brain on drugs”

Alcohol is an inhibitor / depressant • Using the picture below and what we just talked about, explain what an inhibitor might be… https://www.youtube.com/watch?v=vkpz7xFTWJo

Alcohol • IncreasesGABA (inhibitor) • causes sluggish movements and slurred speech • Decreasesglutamate (excitatory) • causes the physiological slowdown • Increases dopamine (both excitatory & inhibitory) in the brain's reward center • Causes the feeling of pleasure that occurs when someone takes a drink. Cerebellum* = affected ‘the most!’

Let the data do the talkin’ Summarize the reaction times of both Drivers at both speeds, comparing baseline reactions to alcohol impaired, reading a text, and texting reaction times: (Source: Car and Driver. June 25, 2009) Note: “Baseline” represents reaction times under normal driving conditions.

Something to think about... • “But the [reaction times] don't tell the whole story. • Looking at Driver I’s slowest reaction time at 35 mph, he traveled an extra 21 feet (more than a car length) before hitting the brakes while reading a text and went 16 feet longer while texting. • While reading a text and driving at 35 mph, Driver II’s average baseline reaction time of 0.57 second nearly tripled, to 1.44 seconds. While texting, his response time was 1.36 seconds. These figures correspond to an extra 45 and 41 feet, respectively, before hitting the brakes.” (Car and Driver, June 25, 2009)

Let the data do the talkin’ Should the laws for texting while driving be as severe as the laws for driving under the influence of alcohol? Use evidence (data!) to support your position. (Source: Car and Driver. June 25, 2009) Note: “Baseline” represents reaction times under normal driving conditions.

Synaptic Transmission (a.k.a. how neurons communicate)