1. 13.1 Overview of the nervous system
Nervous system – Allows for communication between cells through sensory input, integration of data and motor output
2 cell types: neurons and neuroglia

2. Expanding on neurons 3 types of neurons: Neuron structure:
13.1 Overview of the nervous system
Expanding on neurons
3 types of neurons:
Sensory – takes impulses from sensory receptor to CNS
Interneurons – receive information in the CNS and send it to a motor neuron
Motor – takes impulses from the CNS to an effector (i.e. gland or muscle fiber)
Neuron structure:
Cell body – main cell where organelles and nuclei reside
Dendrite – many, short extensions that carry impulses to a cell body
Axon (nerve fiber) – single, long extension that carries impulses away from the cell body

3. 13.1 Overview of the nervous system
Types of neurons

4. 13.1 Overview of the nervous system
The myelin sheath
A lipid covering on long axons that acts to increase the speed of nerve impulse conduction, insulation and regeneration in the PNS
Schwann cells – neuroglia that make up the myelin sheath in the PNS
Nodes of Ranvier – gaps between myelination on the axons
Saltatory conduction – conduction of the nerve impulse from node to node

5. 13.1 Overview of the nervous system
Neuron structure

6. The nerve impulse: resting potential (RP)
13.1 Overview of the nervous system
The nerve impulse: resting potential (RP)
Resting potential – when the axon is not conducting a nerve impulse
More positive ions outside than inside the membrane
There is a negative charge of -65mV inside the axon
More Na+ outside than inside
More K+ inside than outside

7. Threshold Stimulus
Membrane must be made more permeable to sodium ions.
Once a threshold permeability is reached, the entire impulse begins
“All or None Principle”

8. The nerve impulse: action potential
13.1 Overview of the nervous system
The nerve impulse: action potential
Action potential – rapid change in the axon membrane that allows a nerve impulse to occur
Sodium gates open letting Na+ in
Depolarization occurs
Interior of axon loses negative charge (+40mV)
Potassium gates open letting K+ out
Repolarization occurs
Interior of axon regains negative charge (-65mV)
Wave of depolarization/repolarization travels down the axon
Resting potential is restored by moving potassium inside and sodium outside. Another action potential can be transmitted until the entire resting potential is restored. (Refractory Period)

9. The nerve impulse: action potential
13.1 Overview of the nervous system
The nerve impulse: action potential

10. Plumbing Analogy A toilet flushing can be described in these steps:
Tank above bowl is full of water
Lever is pushed until flush initiates
Water rushes into the bowl and flushes waste into sewer
Tank above bowl fills with water
Toilet can not flush again until tank is full.

11. Summary
In your notes, Write a summary describing how the propagation of an action potential works like the flushing of a toilet. Include all 5 steps!

12. 13.1 Overview of the nervous system
The synapse
A small gap between the sending neuron (presynaptic membrane) and the receiving neuron (postsynaptic membrane)
Transmission is accomplished across this gap by a neurotransmitter (e.g. ACh, dopamine and serotonin)
Neurotransmitters are stored in synaptic vesicles in the axon terminals

13. Close up look at your synapse (The Gray Matter)
AXON
What is this in the membrane?
The synapse - where the action happens
Transport protein
The next cell’s plasma membrane

14. How does the Synapse carry the signal?
1. impulse travels down the axon (The White Matter)
Vesicles with neurotransmitters move toward the membrane
Neurotransmitters are released and diffuse toward the next cell’s plasma membrane
4. The chemicals open up the transport proteins and allow the signal to pass to the next cell

15. The synapse carries a signal from cell to cell1 3 4 2

16. How many synapses are in one neuron?
1,000 to 10,000!!

17. 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.
NIH Publication No

18. See it in action!