Transcript Biological Psychology CH 3

Chapter 3:
Neural Communication
A Resting Neuron

If a neuron is not active receiving or transmitting
information, it maintains a resting potential

The cell keeps this negative charge by:
1.
Only allowing certain ions (charged particles)
the cell membrane
2.
And by actively pumping other ions out of the
cell = sodium-potassium pump.
Concentration Gradient
vs.
Electrical Gradient
1.
Concentration gradient is the difference in
the AMOUNT of a given ion on either side of
the membrane.
2.
Electrical gradient describes the difference in
the CHARGE on either side of the
membrane.
Picture of Both Gradients
1
2
The Key Players: Sodium (Na+) and Potassium (K+)
1.
Na+ really wants into the cell because of both the
concentration and electrical gradients
2.
K+ wants into the cell because of the electrical
gradient, but wants out of the cell because of the
concentration gradient
What purpose does the resting
potential serve?
Action Potential

Three simple concepts:

Rapid depolarization

Short-lived hyperpolarization

Role of the threshold of excitation
How does the AP happen?
•
Back to the ions!
And what happens next?
•
How does the cell get itself back to rest?
All or Nothing

The AP is not a graded response
Refractory Period

This is a short period of time following an AP
where the cell cannot be made to fire again.
Where does the AP start?

It begins at the axon hillock and moves down the length of
the axon
How does it keep moving?

Role of the refractory period

Contribution of Myelin
Not just electrical…
Sherrington made several important observations
about nervous control of muscles:

1.
Muscular reflexes are slower than the speed of the
AP
2.
Summation
3.
Synchrony of contraction & relaxation
Proving Sherrington Right

Leowi confirmed Sherrington’s
suspicions about chemical
communication in 1920
 Frog heart experiment
Chemical Events
What happens in the neuron in order for
neurotransmission to take place?

1.
Neurotransmitters are made in the cell
2.
When the AP reaches the terminals…
Then What?

The “hook-up”

After the transmitter has its fun with the
receptor, it:
•
It is degraded in the synapse
or
•
It is taken back up into the cell and broken
down there
or
•
It is taken back into the cell and reused
Post-Synaptic Activity

1.
2.
There are two ways a neurotransmitter
effects the post-synaptic cell
Ionotropic
Metabotropic
 The end result is a change in the resting
potential of the post-synaptic neuron!!
Types of Neurotransmitters
1.
2.
3.
4.
5.
Amino acids
Peptides
Acetylcholine
Monoamines
Gases
Drug Effects at the Synapse
Agonists vs. Antagonists
Affinity & Efficacy
Next Time: Chapter 7 –
Development of the Nervous System