1. History of Biological Bases
Phrenology – Studying bumps on the skull
Franz Gall
Biological Psychology
Study of links between biological and psychological processes.
Genetic, Neural, Hormonal effects on behavior

2. The Nervous System
It starts with an individual nerve cell called a NEURON.
Neurons and what they do

3. Neurons – What are they?
Long, thin cells of a nerve tissues along which messages travel to and from the brain
They are the building block of the nervous system
Everyday millions of neurons are firing and sending signals to the brain
The brain is made up of approximately ________ neurons.
100 billion

4. Structure of a Neuron

5. Structure of a Neuron – Dendrites

6. Dendritic Growth Receive inputs from neighboring neurons
If threshold (level of stimulation required to trigger a neural impulse) is reached the AXON will generate an output
Dendritic growth allows for more connections to other neurons
New connections are basis for learning
Studies show people with higher education have more dendritic connections than someone that is a high school dropout.
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 similarly 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 spread it to other parts of the neuron.

7. Structure of a Neuron – Soma
nucleus

8. 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
All neurons have an outer membrane, cell body and mitochondria (Bernstein p61)
Interesting facts:
Our brains account for 2% of our body weight but use 20% of our oxygen (sokoloff 1981)
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.
Module 3 garber edits

9. Structure of a Neuron – Axon

10. Axon Where all the action is
Action Potential takes place – electrical charge is sent down the axon.
One axon per cell, 2 distinct parts
tube-like structure
branches at end (axon terminals) that branch out to dendrites of other cells
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).
Myelnated about 224 mph (biopsych text 69) 100 meters/sec
Unmylenated 1 meter/sec

11. Structure of a Neuron – Myelin Sheath

12. Myelin Sheath White fatty casing on axon
Acts as an electrical insulator
When present, increases the speed of neural signals - like a paved highway
If this degenerates (dirt road), you have multiple sclerosis and can’t control your muscles.
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.

13. Structure of a Neuron – Axon Terminals

14. Axon Terminal
When the electrical signal reaches the axon terminal, the information is converted into a chemical signal known as a neurotransmitter.
The axon terminal then sends the chemical signal into the dendrite of the next neuron
Neurotransmitters are chemicals that enable neurons to “talk” to one another

15. Synapse
“Spatial junctions” where impulses are chemically transmitted from neuron to another
Axon terminals contain small storage sacs called synaptic vesicles
Sending
Neuron
Synapse
Axon
Terminal
Synapse was coined by Lord Sherrington ( ) who inferred it through behavioral experiments. Cajal ( ) described the synapse based on his anatomical studies of the brain.
This tiny gap is called the synaptic gap or cleft.
Less than 1 millionth of an inch
vesicles contain neurotransmitter molecules

16. Neuroscience and Behavior
Reuptake
Neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake.
This process applies the brakes on neurotransmitter action.

17. Neurotransmitters
A chemical messenger that travels across the synapse from one neuron to the next
Can influence whether the second neuron will generate an action potential or not (excite or inhibit)
When released by the sending neuron, neuro-transmitters travel across the synapse and bind to receptor sites on the receiving neuron

18. Neurons – magnified view
Neuron recap

19. Axon B. Dendrites C. Neurotransmitters D. Sodium ions
E. Synapse F. Myelin Sheath G. Terminal Buttons
Chemical messengers called neurotransmitters enter receptor sites on the dendrites and cell body. This causes the cell membrane to open up and sodium ions to flow in. When there is enough of a positive charge, the neuron reaches threshold, and the first section of the axon opens up and sodium ions flow in. This exchange of sodium ions happens down the length of the axon and is the process is sped up by the myelin sheath. When the signal reaches the terminal branches at the end of the axon, neurotransmitters flow out into the empty space called the synapse.
The first click will highlight the first blank. Students click in with their answers. The next click will remove the highlighted box to reveal the correct answer below. 19