Chapter 2_The neuron Science

The Structure of a Neuron
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How neurons communicate
Neurons communicate by means of an electrical signal called the Action Potential （动作电位） , which is based on movements of ions (离子) between the outside and inside of the cell
K+ Na+ ClOutside of Cell
Cell Membrane at rest
K+ Na+ ClInside of Cell
Potassium (K+) can pass through to equalize its concentration Sodium and Chlorine cannot pass through Result - inside is negative relative to outside
A-
- 70 mv
[pəˈtæsiəm]

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Resting Potential 静息电位
At rest the inside of the cell is at -70 millivolts 毫伏
With inputs to dendrites inside becomes more positive if resting potential rises above threshold, an action potential starts to travel from cell body down the axon 14
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Neurotransmitters
Normal Function:
Dopamine
Serotonin 5-羟色胺
Regulates sleep and dreaming, mood, pain, aggression, appetite and sexual behavior
The brain on the left with an abundance of red is the healthy, active brain.
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Do Blind People See in Their Dreams?
People born without the ability to see report no visual imagery in their dreams, but they do experience a heightening of taste, touch and smell.
People going blind before age 5 rarely experience visual imagery in their dreams. But those who lose their vision after age 5 often continue to see in their dreams, though the frequency and clarity diminish over time.
CNS： central nervous system
Motor neurons (carry messages from CNS toward muscles and glands) Interneurons (carry messages between nerve cellsefractory period (不应期)

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Neurotransmitters
Chemical messengers that relay neural messages across the synapse
Dopamine Serotonin Acetylcholine Endorphins
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Chapter 2 Neuroscience and Behavior
Neurons
The Nervous System The Brain Session Work
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Neurons 神经元


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Neurotransmitters
Normal Function:
Dopamine Serotonin Acetylcholine
乙酰胆碱
Primary transmitter used by neurons carrying messages from CNS; involved in some kinds of learning and memory

Repolarization follows
After depolarization potassium (K+) moves out restoring the inside to a negative voltage. This is called repolarization



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Types of Neurons
Sensory neurons (carry messages from sense receptors towards the CNS)
Carlsson was awarded the 2000 Nobel Prize in Physiology or Medicine for showing that dopamine is not just a precursor of norepinephrine (noradrenaline) and epinephrine (adrenaline), but a neurotransmitter as well.
Human Brain, a Miracle!
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As we look at side-by-side PET scans of a person who has never used cocaine compared with a cocaine addict, can you tell which brain is more active and healthy? Take a guess.
1. Types of Neurons 2. The structure of the neuron 3. How neurons fire


4. Where neurons meet: Synapse 突触 5. Neurotransmitters 神经递质
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Depolarization (去极化)
AP opens cell membrane to allow sodium (NA+) in
Inside of cell rapidly becomes more positive than outside This depolarization travels down the axon as leading edge 15 of the AP
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Neurotransmitters
Dopamine 多巴胺 Serotonin Acetylcholine
Normal Function:
Produces sensations of pleasure and reward; used by CNS neurons in voluntary movement

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多巴胺(Dopamine) (C6H3(OH)2-CH2-CH2-NH2)
In 1957 Carlsson demonstrated that dopamine was a neurotransmitter in the brain.
He is also known for his work on dopamine’s effects in Parkinson's disease.
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Ion concentrations
Outside of Cell
potassium ion K+
Na+
Cl-
Cell Membrane in resting state
sodium ion
K+
Na+
Cl-
A-
Inside of Cell
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The Cell Membrane is Semi-Permeable
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Finally, Hyperpolarization
Repolarization leads to a voltage below the resting potential, called hyperpolarization
Now neuron cannot produce a new action potential
Problems with Imbalance:
Endorphins
Schizophrenia 精神分裂症 more dopamine, Parkinson’s disease
Substances that Affect:
Cocaine, amphetamines, Ritalin, alcohol The 2000 Nobel Prize in Physiology or Medicine