1. Biological Psychology and Neurotransmission
Module 9
Biological Psychology and Neurotransmission

2. Neurons- or Nerve Cells
The most basic building block of the nervous system

3. Parts of the Neuron Figure 9.2 A motor neuron
David G. Myers: Myers’ Psychology for AP®, Second Edition Copyright © 2014 by Worth Publishers

4. Nodes of Ranvier

5. How does a neuron fire?
Neurons generate electricity from chemical events
Ions (electrically charged atoms) are exchanged
Electrical inside
Chemical outside

6. Key Concepts
The Neuron is polarized when it is ready to fire, also known as resting potential.
As a neuron’s membrane depolarizes the sodium/potassium pumps open and action potential occurs.
When the neuron hyperpolarizes, it is returning to its polarized state. This is known as the refractory period.

7. Resting Potential
The Neuron is ready to fire– as the toilet is ready to flush.

8. Resting Potential
At rest the cell is polarized with an interior negative charge of -70 mv.
There is about 10X more sodium (Na+) outside and 20 X more potassium (K+) inside.

9. Figure 9.3 Action potential
David G. Myers: Myers’ Psychology for AP®, Second Edition Copyright © 2014 by Worth Publishers

10. Action Potential
When a neuron becomes stimulated, the area of the membrane at the point of stimulation becomes more permeable to Na+ (it is depolarized).
This depolarization voltage activates the Na+ gates to open. Na+ rushes inside the cell.
At the same time the K+ gates, which were partially open allowing K+ to pass freely all along, open wider and K+ rushes out.
This rapid exchange of ions reverses the electrical gradient because the influx of positive ions cancels out the negative interior causing the valence to reach zero.
Then the influx of Na+ takes the interior to a slightly more positive state (+20 mv).

11. Sodium Potassium Pump

12. Refractory Period Remedial Chemistry Kids…
Advanced Chemistry Kids…
This hyper-polarization (known as the refractory period) is only momentary as the rapid out flux of K+ returns the interior to a negative state.
The sodium/potassium pump is also working to re-establish the resting potential. In other words the out flux of K+ combined with the action of the sodium/potassium pump restores the electrical and concentration gradients. Within milliseconds the polarity is re- established and the neuron is once again ready to fire.
Remedial Chemistry Kids…
The refractory period-- brief period after 1 millisecond action potential when the neuron is resistant to re-excitation after an action potential. Permeability to sodium ions is low and to potassium ions is higher than normal.
Below 50 IQ…
The toilet tank is filling

13. Summary

14. The All-or None Response
The neuron fires or it does not- but there is NO part way firing.
Like a gun

15. How Neurons Communicate
Figure 9.4 How neurons communicate
David G. Myers: Myers’ Psychology for AP®, Second Edition Copyright © 2014 by Worth Publishers

16. Neurotransmitters
Neurotransmitters are chemical messengers that are released from the vesicles in the axon terminal of the pre-synaptic cell to hook up to a receptor on the dendrite of the postsynaptic cell.
Neurotransmitters are like keys which fit into the receptor lock.
The receptor will recognize only one type of neurotransmitter.
When a neurotransmitter is received by a receptor it either excites (depolarizes) or inhibits (hyperpolarizes) the postsynaptic cell.

17. Figure 9.5 Neurotransmitter pathways
Each of the brain’s differing chemical messengers has designated pathways where it operates, as shown here for serotonin and dopamine (Carter, 1998).
Figure 9.5 Neurotransmitter pathways
David G. Myers: Myers’ Psychology for AP®, Second Edition Copyright © 2014 by Worth Publishers

19. Norepinephrine
Helps control alertness, arousal, sleeping, dreaming, emotions, and learning. It also can elevate mood and relieve depression
Too much… mania
Not enough… depressed moods, lethargy
How does Wellbutrin, Cymbalta, and Effexor work? It blocks norepinephrine reuptake

20. Acetylcholine
Triggers muscle contraction, stimulates the excretion of some hormones, and plays a vital role in learning and memory
Too much… may cause muscle spasms
Not enough… may cause paralysis
Lack of ACH has been linked to Alzheimer’s disease.

21. Botulin and Botox

22. Dopamine
influences mood, involved in controlling movement and posture, learning, attention, involved in storing memories
Too much… May cause Schizophrenia (over-stimulation of arousal producer)
Too little… associated with Parkinson’s Disease which is caused by the deterioration of neurons that manufacture most if the brain’s dopamine

23. Serotonin
Promotes feelings of well being, regulates mood, emotions, anxiety, libido, aggression, sleep, body temperature, appetite, and thinking abilities
Too much…seizures, fever, comas
Too little…Linked to Depression

24. Endorphins
Natural painkillers, play an important role in control of pain and emotions (anxiety, fear, tension, pleasure)
Too much...feel no pain
Too little...feel everything
We can become addicted to endorphin secreting activities

25. Why Acupuncture?

26. Table 9.1 Some Neurotransmitters and Their Functions
David G. Myers: Myers’ Psychology for AP®, Second Edition Copyright © 2014 by Worth Publishers

27. Agonists and Antagonists

28. Figure 9.6 Agonists and antagonists
Curare blocks ACh
Curare poisoning paralyzes its victims by blocking ACh receptors involved in muscle movements. Morphine mimics endorphin actions. Which is an agonist, and which is an antagonist? (Art adapted from Higgins & George, 2007.)
ANSWER: Morphine is an agonist; curare is an antagonist.
Figure 9.6 Agonists and antagonists
David G. Myers: Myers’ Psychology for AP®, Second Edition Copyright © 2014 by Worth Publishers

29. Cocaine blocks dopamine reuptake sites