1. Neurons and Synapses Types of Neurons Sensory Motor Interneurons
Key words: Types of neurons; sensory neurons; motor neurons; interneurons; afferent nerves; efferent nerves

2. Sensory Neurons
INPUT From sensory organs to the brain and spinal cord.
Brain
Drawing shows a somatosensory neuron
Vision, hearing, taste and smell nerves are cranial, not spinal
Sensory
Neuron
Spinal
Cord
Key words: sensory neurons; afferent nerves; types of neurons

3. Motor Neurons
OUTPUT From the brain and spinal cord To the muscles and glands.
Spinal
Cord
Brain
Sensory
Neuron
Motor
Key words: Motor neurons; efferent nerves; types of neurons

4. Interneurons
Interneurons carry information between other neurons only found in the brain and spinal cord.
Spinal
Cord
Brain
Sensory
Neuron
Motor
Key words: interneurons; types of neurons

5. Structures of a neuron
Key words: Neuron; sructures of neurons

6. The cell body Contains the cell’s Nucleus
Round, centrally located structure
Contains DNA
Controls protein manufacturing
Directs metabolism
No role in neural signaling
Key words: Cell body; soma; cell nucleus
Interesting facts:
The DNA in the nucleus of the cell has lost its ability to divide. therefore, when a neuron dies,for the most part, the adult brain cannot simply grow new neurons. (Note there are a few exceptions to this rule.)
The relative inability to grow new neurons leads to two interesting questions:
Q1: How do brain tumors (cancer) occur?
A: Unlike neurons, glial cells can divide and grow new cells throughout one's lifetime. Most brain tumors are limited to glial cells, not neurons.
Q2: If a person cannot grow new neurons, how does the brain change in order to accomodate new learning?
A: One mechanism by which the brain adapts to help you learn new information involves the structure on the next slide: the dendrites.

7. Dendrites Information collectors
Receive inputs from neighboring neurons
Inputs may number in thousands
If enough inputs the cell’s AXON may generate an output
Key words: dendrite
Interesting facts:
- The word DENDRITE comes from the Greek word for tree. This may serve as a useful analogy in discussing the dendrites for several reasons:
1. The dendrites branch repeatedly from the cell body (to increase the surface area of the cell to better allow the cell to receive incoming information). These radiations from the cell body are often referred to as a dendritic tree.
2. In terms of function, the dendrites function similiarly to the roots of a tree. Just as the roots take water and other nutrients from the soil and carry them to other parts of the tree, the dendrites collect information and and spread it to other parts of the neuron.

8. Dendritic Growth Mature neurons generally can’t divide
But new dendrites can grow
Provides room for more connections to other neurons
New connections are basis for learning
Key words: dendrite
Interesting facts:
- The word DENDRITE comes from the Greek word for tree. This may serve as a useful analogy in discussing the dendrites for several reasons:
1. The dendrites branch repeatedly from the cell body (to increase the surface area of the cell to better allow the cell to receive incoming information). These radiations from the cell body are often referred to as a dendritic tree.
2. In terms of function, the dendrites function similiarly to the roots of a tree. Just as the roots take water and other nutrients from the soil and carry them to other parts of the tree, the dendrites collect information and and spread it to other parts of the neuron.

9. Axon The cell’s output structure One axon per cell, 2 distinct parts
tubelike structure branches at end that connect to dendrites of other cells
Key words: axon; action potentials
Interesting facts:
- The diameter of an axon may vary from approximately 1mm-20mm.
- An axon may travel long distances to reach it's destination (longest axon is approximately 3 feet in humans and 10 feet in giraffes).

10. Myelin sheath White fatty casing on axon
Acts as an electrical insulator
Not present on all cells
When present increases the speed of neural signals down the axon.
Myelin Sheath
Key words: myelin sheath; action potentials; axon
Interesting facts:
- The myelin sheath is NOT a part of the axon. The myelin sheath is actually formed of glial cells (oligodendricytes and Schwann cells) that wrap around the axon.
- You may have often heard the brain referred to as either white matter or gray matter. The myelin sheath appears white in nature. Hence, the term white matter refers to areas of the brain that are myelinated. Gray matter refers to areas of the brain that are unmyelinated.
- When you accidentally cut yourself, you often visually notice that you've cut yourself before you actually feel any pain from the cut. The reason for this is that visual information uses myelinated axons; whereas, pain information uses unmyelinated axons.
- The loss of myelin is a significant factor in the disease multiple sclerosis (MS). When myelin is lost, the high-speed transmission of information is slowed down or blocked completely, which could lead the person with the inability to walk, write or speak.

11. How neurons communicate
Neurons communicate by means of an electrical signal called the Action Potential
Action Potentials are based on movements of ions between the outside and inside of the cell
When an Action Potential occurs a molecular message is sent to neighboring neurons

12. Cell Membrane in resting state
Ion concentrations
Cell Membrane in resting state K+
Na+
Cl- A-
Outside of Cell
Inside of Cell
Key words: ion concentrations; cell membrane; intracellular fluid; extracellular fluid; Na+; Cl-; K+
Slide ten represents a schematic of the typical concentrations of the intracellular and extracellular fluids. There are large concentrations of sodium and chloride ions concentrations of on the outside of the cell (relative to inside the cell). There are large concentrations of potassium ions and protein molecules on the insde of the cell (relative to concentrations on the outside of the cell).

13. The Cell Membrane is Semi-Permeable
Cell Membrane at rest
Na+
Cl- K+ A-
Outside of Cell
Inside of Cell
Potassium (K+) can pass through to equalize its concentration
Sodium and Chlorine cannot pass through
Result - inside is negative relative to outside
- 70 mv
Key words: Cell membrane; semi-permeable; K+; Na+; Cl-
The cell membrane is semi-permeable. That is, when the neuron is at rest, the cell membrane allows some ions (K+) to pass freely through the cell membrane, whereas other ions (such as Na+ and Cl-) cannot.
Hit enter once and K+ ions will slowly pass through the cell membrane.
After K+ animation is finished, hit enter again and animation showing that Na+ and l- ions cannot pass through the membrane will occur.

14. Resting Potential At rest the inside of the cell is at -70 microvolts
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
Figure shows resting axon being approached by an AP

15. Depolarization ahead of AP
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 of the AP

16. Repolarization follows
After depolarization potassium (K+) moves out restoring the inside to a negative voltage
This is called repolarization
The rapid depolarization and repolarization produce a pattern called a spike discharge

17. Finally, Hyperpolarization
Repolarization leads to a voltage below the resting potential, called hyperpolarization
Now neuron cannot produce a new action potential
This is the refractory period

18. Neuron to Neuron
Axons branch out and end near dendrites of neighboring cells
Axon terminals are the tips of the axon’s branches
A gap separates the axon terminals from dendrites
Gap is the Synapse
Cell
Body
Dendrite
Axon
Key words: axon terminal .

19. Synapse
Sending
Neuron
Synapse
Axon
Terminal
axon terminals contain small storage sacs called synaptic vesicles
key words: axon terminal; synaptic vesicles; neurotransmitters
vesicles contain neurotransmitter molecules

20. Neurotransmitter Release
Action Potential causes vesicle to open
Neurotransmitter released into synapse
Locks onto receptor molecule in postsynaptic membrane

21. Locks and Keys Neurotransmitter molecules have specific shapes
Receptor molecules have binding sites
When NT binds to receptor, ions enter
positive ions (NA+ ) depolarize the neuron
negative ions (CL-) hyperpolarize

22. Some Drugs work on receptors
Some drugs are shaped like neurotransmitters
Antagonists : fit the receptor but poorly and block the NT
e.g. beta blockers
Agonists : fit receptor well and act like the NT
e.g. nicotine.

23. Glial cells function

24. Metabolism and Synthesis in a Neuron

25. Neuronal Differentiation

26. In the developing brain, a neuron depends on molecular signals from other cells, such as astrocytes, to determine its shape and location, the kind of transmitter it produces, and to which other neurons it will connect. These freshly born cells establish neural circuits - or information pathways connecting neuron to neuron - that will be in place throughout adulthood.