1. Do Now: 3 Types of Nerve Cells
Glue in your notebook on the next blank page!

2. Do Now: 3 Types of Nerve Cells

3. Levels of Organization

4. Whiteboard Activity Opinion Question
What is an ELECTROLYTE?
You have 3 minutes to talk to your lab group and then be ready to share out.

6. What is an ELECTROLYTE? DO NOT WRITE…DISCUSSION ONLY
All salts are electrolytes!
Substances that conduct an electrical current in a solution
A salt is an organic compound found in the body in the form of minerals
Calcium and phosphorus, found in teeth and bones
Dissolved minerals found in urine
Sodium and potassium ions used for nerve impulses in the brain
Iron, found in hemoglobin, in the blood cells (this is what makes it red in color)

7. Notes: How Neurons Communicate
Glue this picture on the next blank page

8. Why is this impulse called an ACTION POTENTIAL?
Voltage = measures the difference in concentration of charges.
The positives are the “hole” you leave behind when you move an electron.
Original experiments on giant squid neurons!

9. Important Chemistry Vocabulary
anions (negative)
more concentrated IN THE CELL
cations (positive)
more concentrated in the extracellular fluid
(OUTSIDE THE CELLS)
channel leaks K+ K+
Na+ K+
Cl-
aa- + – K+

10. Transmission of a Nerve Signal
Neuron communicate similar to dominoes
Once the 1st protein channel on the cell membrane opens…the rest open up in succession
(one after the other) all or nothing response
a “wave” travels along neuron
Then…protein channels need to be re-set so neuron can react again

11. How does a nerve impulse travel? STEP 1 and 2
Step 1 - Stimulus: nerve is stimulated (ACTIVATED)
Protein channels open on the cell membrane
Step 2 - Na+ ions diffuse into cell
charges reverse
positive inside; negative outside
The 1st domino goes down! – +
Na+

12. How does a nerve impulse travel? STEP 3
STEP 3 - Wave: nerve impulse travels down neuron
change in charge opens the protein channels “wave” moves down neuron =
action potential
Gate + –
channel closed
channel open
The rest of the dominoes fall! – +
Na+
wave 

13. How does a nerve impulse travel? STEP 4
STEP 4 - Re-set: 2nd wave travels down neuron
K+ protein channels open
K+ ions diffuse out of cell
charges reverse back
negative inside; positive outside
Set dominoes back up quickly! + –
Na+ K+
wave 
Opening gates in succession =
- same strength
- same speed
- same duration

14. Checking For Understanding
1. What are the 4 steps of nerve impulse travel? Write a paragraph or bullet points or draw a flow chart.

15. Myelin sheath Axon coated with Schwann cells insulates axon
speeds signal
signal hops from node to node
signal
direction
myelin sheath

16. Multiple Sclerosis action potential saltatory conduction Na+ myelin +–
axon + + + + –
Na+
Multiple Sclerosis
immune system (T cells) attack myelin sheath
loss of signal

17. What happens at the end of the axon?
Impulse has to jump the synapse!
junction between neurons
has to jump quickly from one cell to next
How does the wave jump the gap?
Synapse

18. Chemical synapse Events at synapse
action potential depolarizes membrane
opens Ca++ channels
neurotransmitter vesicles fuse with membrane
release neurotransmitter to synapse  diffusion
neurotransmitter binds with protein receptor
ion-gated channels open
neurotransmitter degraded or reabsorbed
axon terminal
action potential
synaptic vesicles
synapse
Ca++
Calcium is a very important ion throughout your body. It will come up again and again involved in many processes.
neurotransmitter acetylcholine (ACh)
receptor protein
muscle cell (fiber)
We switched…
from an electrical signal
to a chemical signal

19. Nerve impulse in next neuronK+
Post-synaptic neuron
triggers nerve impulse in next nerve cell
chemical signal opens ion-gated channels
Na+ diffuses into cell
K+ diffuses out of cell
switch back to voltage-gated channel K+
Na+
ion channel
binding site
ACh
Here we go again! – +
Na+

20. Neurotransmitters Acetylcholine
transmit signal to skeletal muscle
Epinephrine (adrenaline) & norepinephrine
fight-or-flight response
Dopamine
widespread in brain
affects sleep, mood, attention & learning
lack of dopamine in brain associated with Parkinson’s disease
excessive dopamine linked to schizophrenia
Serotonin
Nerves communicate with one another and with muscle cells by using neurotransmitters. These are small molecules that are released from the nerve cell and rapidly diffuse to neighboring cells, stimulating a response once they arrive. Many different neurotransmitters are used for different jobs:
glutamate excites nerves into action;
GABA inhibits the passing of information;
dopamine and serotonin are involved in the subtle messages of thought and cognition.
The main job of the neurotransmitter acetylcholine is to carry the signal from nerve cells to muscle cells. When a motor nerve cell gets the proper signal from the nervous system, it releases acetylcholine into its synapses with muscle cells. There, acetylcholine opens receptors on the muscle cells, triggering the process of contraction. Of course, once the message is passed, the neurotransmitter must be destroyed, otherwise later signals would get mixed up in a jumble of obsolete neurotransmitter molecules. The cleanup of old acetylcholine is the job of the enzyme acetylcholinesterase.

21. Checking For Understanding
2. How does the transmission of an action potential from neuron to neuron represent a set of dominoes falling down?
Write a paragraph or bullet points or draw a flow chart.

22. Human Action Potential
Everyone in your group should have at least 1 poster. (everyone participates)
Objective: Stand up and stand on the line (tape on the floor) to assemble 2 human neuron.
The order of the posters should demonstrate the change in electrical charges and movement of ions (charged particles) down the neuron.

23. Exit Slip Work on your own. Open note.
When you finish your paragraph…
Peer grade - choose a lab group member to read your paragraph and provide feedback.
Turn in your exit slip into the exit slip tray