1. The Brain and All Neurons Part 1

2. Neurons- or Nerve Cells
There are many different types– but all have the same principles
Neural impulses can travel from 2 – 200 or more miles/hour

3. Parts the Neuron

5. How does a neuron fire? It is an electro-chemical process
Electrical inside
Chemical outside

6. Key Concepts
The Neuron is polarized when it is ready to fire. We also call this 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.
See, the tank is filled with water.

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. Action Potential
A neuron fires an impulse when it receives a signal from sensory receptors.
They may be stimulated by pressure, heat, or light, or by chemical messages from neighboring neurons.
The impulse, called the action potential, is the brief electrical charge that travels down the axon.

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. Wanna hear it from someone else?

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

16. How Neurons Communicate

17. 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.

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)
We can become addicted to endorphin secreting activities

25. Why Acupuncture?

27. Agonists and Antagonists

28. Cocaine blocks dopamine reuptake sites

29. 3 Different Types of Neurons
Sensory neuron- send information from the body’s tissues and sensory organs inward to the brain and spinal cord, which process information. (We have a few million)
Inter-neurons- enable internal communication within the central nervous system (Billions and Billions)
Motor neurons- sends instructions to the body’s tissues (A few million)