1. How do the different parts of our body COMMUNICATE?
ANSWER: via the endocrine and nervous systems

2. Why is it important for us to understand how cellular
communication works?

3. The Nervous System: Parts & Pieces

4. Two cell types in the NS: 10% Neurons & 90% Glial Cells
A “typical” motor neuron is multipolar
Cell body (soma) is the “life hub” mediates cell metabolism, growth, division, contains DNA
Axons are specialized to send information to other neurons
Dendrites are specialized to receive information from other cells

5. A “typical” sensory neuron is unipolar or bipolar

6. Most neurons in the brain are interneurons
Most interneurons don’t need an axon… WHY?

7. Communication between neurons: Step 1: the neuron at rest (polarized)
Inside is more negative than outside
Outside has more
Sodium (+) and
Cholride (-) 
lipid molecules
Ion channels
Inside has more
Potassium (+) and anions (-) 

8. What keeps the cell at -70 mV when at rest?
Concentration gradient
ions move from an area of high to low concentration
2. Electrical gradient
ions with the same sign (polarity) repel each other
ions with the opposite sign attract each other

9. Step 2: the neuron’s membrane potential begins to depolarize (inside becomes less negative)
If neighboring cells stimulate our neuron, sodium (+) will rush into
the cell, making it less and less negative.
If it reaches approximately -55mV, our neuron will fire
That is, it will generate an action potential.

10. Step 3: the neuron’s membrane potential begins to repolarize (inside starts to become negative)
Eventually, the cell reaches its positive peak, causing sodium gates
to close and potassium (+) gates to open… K+ rushes out, returning
the cell to - ive
Oops! Too far! No
worries, the Na – K
pump will bring us
back to normal 

11. Step 4: action potentials sweep down the axon
The first action potential begins at the AXON HILLOCK
This creates a dominos effect of action potentials which end
at the axon terminals

12. The dominos effect

13. Step 5: neurotransmitters are released
When the action potential reaches the terminal button, NT’s are released

14. Step 6: NT’s cross the synapse and bind to receptors on the post-synaptic cell

15. ____ synaptic
Pre
____ synaptic
Post

16. The NT will general either an IPSP or EPSP
Once NT’s bind to receptors on the postsynaptic cell, what then?
The NT will general either an IPSP or EPSP
IPSP’s make the cell more negative, decreasing the prob
that the cell will fire
EPSP’s make the cell less negative, increasing the prob
PSP’s are “local potentials” which are distinct from
action potentials

17. Local potentials vs. action potentials
Analogous to a gentle nudge vs. a explosive push
Local potentials Action potential
Decremental
Graded
Initiated in dendrite or soma
Non-decremental
All-or-none
Initiated at axon hillock

18. From local potential to action potential
Once an IPSP or EPSP is generated, it travels to the axon hillock
One IPSP or one EPSP is not enough to generate an action potential
But, at any given time, MANY IPSP’s and EPSP’s are being generated
The axon hillock “adds up” all the PSP’s… if the sum is ≥ -55mV …

19. How can local potentials have more “umph”?
Temporal summation & Spatial summation

20. What determines the firing rate for a cell?
Absolute Refractory Period
Immediately after the AP,
the cell cannot fire
How does the neuron code the intensity of the EPSP?
Relative Refractory Period
This occurs after the
absolute refractory period
Only a large EPSP can get the
cell to fire

21. Terminating synaptic activity
Enzyme degradation
Re-uptake

22. Regulating synaptic activityX C I T A O N
INHIBI T I O N
Agonists
Antagonists

23. What about Glial Cells in the nervous system?

24. What Gial cells do They are the glue that hold neurons in place
They increase speed of conduction of the neural impulse
Local potentials travel faster down
The axon than action potentials
Between schwann cells are gaps
“Nodes of Ranvier”
AP’s occur at the nodes, local
Potentials occur under the myelin
Saltatory conduction

25. What Gial cells do continued…
Glial cells provide energy to neurons
They remove cellular debris
They contribute to the development & maintenance of
connections between neurons
6. During fetal development,
they help guide neurons to
their destination

26. NEUROTRANSMITTERS

27. The major players