1. Neurons and Neurotransmitters

2. Spinal cord
Transmits messages from the brain to the other areas of the body.
Efferent – away from the brain out to the body
Produces muscle action
Afferent – from the periphery to the brain
Relays information from the sensory organs
Extends down from the base of the brain stem. Disorders of the spinal cord include poliomyelitis, paraplegia, and quadriplegia. Poliomyelitis is a viral disease that attacks the spinal nerves and destroys the cell bodies of the motor neurons. This means that impulses cannot be carried from the spinal cord to the body. Consequences may be difficulty walking, can be as severe as paralysis. Paraplegia is paralysis of the lower extremities of the body and occurs when the lower portion of the spinal cord is damaged. Quadriplegia is paralysis of all four limbs and the trunk of the body. It occurs when the upper portion of the spinal cord is severed. When the spinal cord is severed, impulses can’t travel from the brain to the periphery or back to the brain from the periphery. The person usualy looses bladder and bowel control.

3. Facts About Neurons
There are about 1000 billion Each can be connected to over 10s of 1000s of other neurons

4. What they do
Sensory Neurons – take info from the world Inter neurons make the connection between motor and sensory neurons – they do the thinking makes the connection between sensation and action Motor neurons - dictate to the muscles

5. All or Nothing
Neurons either fire or not. Sensation and action are graded by number of neurons triggered and/or frequency

6. The GAP
Between each neural dendrite and axon there is a tiny space (about 1/10,000th of a mm). This gap is called a synapse.

7. Its a Chemical Thing
When a neuron fires the axon shoots chemicals through the synapse and they affect the dendrites. These chemicals are called neurotransmitters.

8. Neurotransmitters are contained within a structure called the presynaptic membrane. Once released neurotransmitter molecules are picked up by receptors - structures that appear on cellular surfaces that pick up molecules that fit into them like a "lock and key"

9. Receptors are located in postsynaptic membrane of another nearby neuron. Once the neurotransmitter is picked up by receptors in the postsynaptic membrane, the molecule is internalized in the neuron and the impulse continues.

10. Each neurotransmitter binds only to specific receptors on the postsynaptic membrane.
There are a number of types of receptors for different neurotransmitters.
This binding eventually brings about a change in the electrical state of the postsynaptic cell either exciting or inhibiting it.

11. Action of neurotransmitter can be decreased or neutralized by:
Glial cells which remove neurotransmitters from the synaptic cleft
reuptake, where the chemical is taken back to the axon that released it
blocking, whereby the flow by substances that attach to specific receptors is blocked

12. For Example:
The release of various neurotransmitters can excite or inhibit neurons. This means the understanding of neurotransmitters is very important to pharmaceuticals.

13. Pharmaceuticals
Drugs developed to treat illnesses related to neurotransmitters are either Agonists or Antagonists. There are currently at least 50 identified neurotransmitters. Agonists – increase the effects of a neurotransmitter, makes more of it, or stops the minimizing of it Antagonist – slows down neurotransmitters either because they destroy or inhibit production, or they “paste over” dendrites so that neurotransmitters cannot connect

14. Specific Neurotransmitters
Acetylcholine Acetylcholine is linked with learning and memory formation A lack of acetylcholine in the brain is thought to be partly responsible for the symptoms of Alzheimer's disease. * See study by Martinez and Kesner, 1991, on lab mice

15. Dopamine Dopamine is concentrated in very specific groups of neurons collectively called the basal ganglia. A decreased brain dopamine concentration is a contributing factor in Parkinson’s disease. Increased amounts have other effects.

16. Serotonin In addition to mood control, serotonin has been linked with a wide variety of functions, including the regulation of sleep, pain perception, body temperature, blood pressure and hormonal activity. * See study by Kasamatsu and Hirai, 1999, on zen meditation

17. SSRIs????? Selective Serotonin Reuptake Inhibitors
Used to regulate depression (Prozac, Zoloft, Paxil)
High levels = bliss, happiness, hallucinations
Low levels =sleep disruption, depression, fatigue, anxiety

18. Other Drugs?
Heroin = mimics endorphins by binding to endorphin receptors
Morphine = stimulates endorphin production
Cocaine = Increases dopamine production (blocks reuptake)
Marijuana = THC blocks reuptake and normal functioning of anandamide, dopamine and serotonin (neurotransmitters)

19. How neurotransmitters impact behaviour?