1. The Nervous System – synaptic transmission
Chapter 9

2. I. Introduction
The Nervous and Endocrine Systems together perform communication. Communication makes possible control; control makes possible integration; integration makes possible homeostasis; homeostasis makes possible survival; survival makes it possible to populate.

3. II. Nervous System
-consists of brain, spinal cord, and nerves

4. A. Organization of NS
1. Divided according to relative position (central and peripheral)
a. Central Nervous System (CNS)- brain and spinal cord
b. Peripheral Nervous System (PNS) – nerves outside of CNS (in the periphery)

5. 2. Divided according to “one way streets”
a. Afferent pathway – (incoming) the information going to the brain from the sensory tissues
b. Efferent pathway – (outgoing) the information leaving the brain to the muscles

6. 3. Divided according to the types of organs the innervate
a. Somatic Nervous System
i. Somatic Motor Division – carries information to the skeletal muscles
ii. Somatic Sensory Division – provides feedback from the muscles
b. Autonomic Nervous System (governs itself)
i. Sympathetic – prepares the body for fight or flight response. Increased heart rate, decreased peristalsis, contraction of errector pili, increased sweat.
ii. Parasympathetic – coordinates the body’s normal resting activities. Sometimes called the rest and repair.

7. B. Anatomy 1. Neurons (nerve cells) a. Cell body (soma)
b. One or more dendrites – Greek word meaning “trees” – receive the stimuli
c. One axon – conducts impulses away; can be a meter long. Developing NS in baby – think about the progression of the head control, neck control, lumbar control, sitting, standing, walking, etc. This is because neurons migrate downward… so until the baby has leg control it is useless to try to potty train because the neuronal pathway is not developed.

8. 2. Synapses 3. Nerves a. Gap between two communicating neurons
b. The neuron before the gap is called the presynaptic neuron.
c. The neuron following the synapse is called the postsynaptic neuron.
3. Nerves
a. Bundles of nerve fibers

9. C. Repair
- mature neurons are incapable of cell division, therefore damage to nervous tissue is usually permanent.
1. PNS – repair can be made if damage is not too extensive
2. CNS – repair is unlikely (paraplegic – arms affected, quadriplegic or tetraplegic – arms and legs affected)

11. D. Nerve Impulses
1. Presynaptic neuron receives the information that is needed to fire
2. Neurotransmitter is released from the presynaptic neuron into the synaptic cleft.
3. Receptors on the postsynaptic neuron take the neurotransmitter and fire

12. 4. The process continues from neuron to neuron
5. Speed of transmission
a. Fast – close to 300 mph
b. Slow – a little more than 1 mph

13. E. Neurotransmitters
The compounds by which neurons talk to each other.
Will be either excitatory or inhibitory. Which one a neurotransmitter is depends on the receptor, not the neurotransmitter.

14. 1. Serotonin – involved in moods, sleep, emotions - inhibitory
2. Epinephrine (adrenaline) – both inhibits and excitatory
3. Dopamine – mostly inhibitory, involved in emotions, moods, regulating motor control
4. Acetylcholine – is inhibitory in the cardiac muscle, yet excitatory in the skeletal muscles.

15. Major Neurotransmitters in the Body
Role in the Body
Acetylcholine
A neurotransmitter used by the spinal cord neurons to control muscles and by many neurons in the brain to regulate memory. In most instances, acetylcholine is excitatory.
Dopamine
The neurotransmitter that produces feelings of pleasure when released by the brain reward system. Dopamine has multiple functions depending on where in the brain it acts. It is usually inhibitory.
GABA
(gamma-aminobutyric acid)
The major inhibitory neurotransmitter in the brain.
Glutamate
The most common excitatory neurotransmitter in the brain.
Glycine
A neurotransmitter used mainly by neurons in the spinal cord. It probably always acts as an inhibitory neurotransmitter.
Norepinephrine
Norepinephrine acts as a neurotransmitter and a hormone. In the peripheral nervous system, it is part of the flight-or-flight response. In the brain, it acts as a neurotransmitter regulating normal brain processes. Norepinephrine is usually excitatory, but is inhibitory in a few brain areas.
Serotonin
A neurotransmitter involved in many functions including mood, appetite, and sensory perception. In the spinal cord, serotonin is inhibitory in pain pathways.

16. Drugs Interfere with Neurotransmission
Drugs can affect synapses at a variety of sites and in a variety of ways, including:
Increasing number of impulses
Release NT from vesicles with or without
impulses
Block reuptake or block receptors
Produce more or less NT
Prevent vesicles from releasing NT

17. Three Drugs (of many) which affect Neurotransmission
Methamphetamine
Nicotine
Alcohol
seattlepi.nwsource.com/ methamphetamines/
science.howstuffworks.com/ alcohol.htm

18. Methamphetamine alters Dopamine transmission in two ways:
1. Enters dopamine vesicles in axon terminal causing release of NT
2. Blocks dopamine transporters from pumping dopamine back into the transmitting neuron
seattlepi.nwsource.com/ methamphetamines/
NIH Publication No

19. Result: More dopamine in the Synaptic Cleft
This causes neurons to fire more often than normal resulting in a euphoric feeling.

20. Problems……
After the drug wears off, dopamine levels drop, and the user “crashes”. The euphoric feeling will not return until the user takes more methamphetamine
Long-term use of methamphetamine causes dopamine axons to wither and die.
Note that cocaine also blocks dopamine transporters, thus it works in a similar manner.

21. What about Nicotine?
Similar to methamphetamine and cocaine, nicotine increases dopamine release in a synapse.
However, the mechanism is slightly different.
Nicotine binds to receptors on the presynaptic neuron.

22. Nicotine binds to the presynaptic receptors exciting the neuron to fire more action potentials causing an increase in dopamine release.
Nicotine also affects neurons by increasing the number of synaptic vesicles releasing dopamine.

23. How does alcohol affect synapses?
Alcohol has multiple effects on neurons. It alters neuron membranes, ion channels, enzymes, and receptors.
It binds directly to receptors for acetylcholine, serotonin, and gamma aminobutyric acid (GABA), and glutamate.
We will focus on GABA and its receptor.

24. GABA and the GABA Receptor
GABA is a neurotransmitter that has an inhibitory effect on neurons.
When GABA attaches to its receptor on the postsynaptic membrane, it allows Cl- ions to pass into the neuron.
This hyperpolarizes the postsynaptic neuron to inhibit transmission of an impulse.

25. Alcohol and the GABA Receptor
When alcohol enters the brain, it binds to GABA receptors and amplifies the hyperpolarization effect of GABA.
The neuron activity is further diminished
This accounts for some
of the sedative affects
of alcohol
science.howstuffworks.com/ alcohol.htm

26. The Adolescent Brain and Alcohol
The brain goes through dynamic change during adolescence, and alcohol can seriously damage long- and short-term growth processes.
Frontal lobe development and the refinement of pathways and connections continue until age 16, and a high rate of energy is used as the brain matures until age 20.
Damage from alcohol at this time can be long-term and irreversible.

27. The Adolescent Brain (cont.)
In addition, short-term or moderate drinking impairs learning and memory far more in youth than adults.
Adolescents need only drink half as much as adults to suffer the same negative effects.

28. Drugs That Influence Neurotransmitters
Change in Neurotransmission
Effect on Neurotransmitter release or availability
Drug that acts this way
increase the number of impulses
increased neurotransmitter release
nicotine, alcohol, opiates
release neurotransmitter from vesicles with or without impulses
increased neurotransmitter release
amphetamines
methamphetamines
release more neurotransmitter in response to an impulse
nicotine
block reuptake
more neurotransmitter present in synaptic cleft
cocaine
amphetamine
produce less neurotransmitter
less neurotransmitter in synaptic cleft
probably does not work this way
prevent vesicles from releasing neurotransmitter
less neurotransmitter released
No drug example
block receptor with another molecule
no change in the amount of neurotransmitter released, or neurotransmitter cannot bind to its receptor neuron
LSD
caffeine

29. Faces of Meth

33. Antidepressants and Anesthetics
III. Medications
Antidepressants and Anesthetics

34. A. Antidepressants Usually used to inhibit the uptake of serotonin
Common drug used: Prozac

35. B. Anesthetics
Substances administered to reduce or eliminate the sensation of pain by blocking the initiation or conduction of nerve impulses