1. Inter-workings of the Brain
The Neuron
Inter-workings of the Brain

2. Drill #22
Draw the neuron.
Label it correctly with the following parts:
Soma
Dendrites
Axon
Myelin Sheath
Terminal Buttons
Write the function of each of the parts

3. Neural Impulse
NEURAL IMPULSES are complex electrochemical reactions involving IONS – electrically charged atoms that flow back and forth across the cell membrane
Positively charged ions – sodium & potassium
Negatively charged ions - chloride
Positively & negatively charged ions DO NOT travel at the same rate
This leads to a slightly higher concentration of negatively charged ions inside the cell

4. Resting vs. Action Potential Alan Hodgkin & Andrew Huxley
Resting Potential
when a neuron is at its stable, negative charge
When it is inactive
Action Potential
A very brief shift in a neuron’s electrical charge that travels along an axon – a voltage spike occurs
This occurs when channels open up, briefly allowing positively charged sodium ions to rush in

5. Absolute Refractory Period & The All or None Law
The minimum amount of time after an action potential during which another action potential CANNOT begin
All or None Law
Think of a Neuron like a gun – you cannot half-fire a gun
Either the neuron fires, or it doesn’t
Action potentials are all the same size – weaker stimuli do not produce smaller action potentials
**Neurons can convey information about the strength of a stimulus by varying the rate at which they fire**

6. The Synapse Where neurons meet
Synaptic Cleft – an infinitely small gap between the terminal buttons of one neuron & the cell membrane of another neuron
Signals have to jump this gap to communicate
Presynaptic Neuron
Sends the signal
Postsynaptic Neuron
Receives the signal

7. NeuroTransmitters
Chemicals that transmit information from one neuron to another – fundamental to behavior & play a key role in everything from muscle movement to mood and mental health

8. Common Neurotransmitters & Their Functions
Acetylcholine (can be stimulated by nicotine)
Activates motor neurons controlling skeletal muscles
Regulates attention, arousal, and memory
Dopamine (Cocaine & amphetamines elevate Dopamine activity)
Control of voluntary movement & pleasurable emotion
Overactivity is associated with Schizophrenia
Norepinephrine (Cocaine & amphetamines elevate NE levels)
Modulation of mood & arousal
Serotonin (Prozac & antidepressants affect Serotonin levels)
Regulation of sleep, eating & aggression
Abnormal levels contribute to depression & OCD
GABA (Valium & anti-anxiety drugs work at GABA synapses)
Seem to produce only inhibitory postsynaptic potentials
Regulation of anxiety in humans & plays a role in seizures
Endorphins (resemble opiate drugs in structure & effects)
Pain relief & pleasurable emotions

9. Receiving Signals Postsynaptic Potentials (PSP) Excitatory PSP
Voltage change at the receptor site on a postsynaptic cell membrane
DO NOT follow the All or None Law
Vary in size and increase or decrease probability of a neural impulse
Excitatory PSP
A positive voltage shift that increases likelihood that the postsynaptic neuron will fire action potentials
Inhibitory PSP
A negative voltage shift that decreases the likelihood that the postsynaptic neuron will fire action potentials

10. The Reuptake Process
A process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane