1. Neurons

2. Neurons)
Cells of the nervous system, called nerve cells or neurons, are specialized to carry "messages" through an electrochemical process.
The human brain has approximately 100 billion neurons.

3. Dendrites of another neuron
Neurons
Cell Body
Dendrites
Axon
Myelin Sheath
Dendrites of another neuron
Axon of another neuron

4. Structure – Explanation
Dendrites – branching neuron structures that receive neural impulses from other neurons and convey impulses toward the cell body
Cell Body – the part of the neuron that contains the cell nucleus, as well as other structures that help the neuron carry out it functions
Axon – a long, tubelike structure that conveys impulses away from the neuron’s cell body toward other neurons or to muscles or glands
Myelin – a layer of fatty insulation wrapped around the axon of some neurons, which increases the rate at which nerve impulses travel along the axon

5. Neural Anatomy and communication
Synapse
junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron
tiny gap at this junction is called the synaptic gap or cleft

6. Specific Parts: The Neuron Structure
Figure 2.6 from:
Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.
Source:

7. Relay Race Action Potential starts at dendrite Through cell body
Down Axon
Axon Terminals
How does it get to the next cell’s dendrites?
Neurons don’t touch
Synapse = millionth inch gap
In synapse = vesicles w/ neurotransmitters
Chemical messengers that transmit info

8. Communication Impulse releases neurotransmitter from vesicles
Neurotransmitter enters synaptic gap
Neurotransmitter binds to receptors on the receiving neuron
Figure 2.7 from:
Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.
Source:

9. Terminal buttons release the neurotransmitters into the synapse.
Neurotransmitters float across the space to the dendrites of the next neuron in line.

10. Neurotransmitters
chemical messengers that traverse the synaptic gaps between neurons
when released by the sending neuron,
neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse
Drugs work by imitating or blocking the action of natural neurotransmitters

11. More neurotransmitters
Receptor binding movie

12. Absolute Threshold
An individual neuron will react to stimulation only if the level of stimulation reaches a certain trigger point.
Absolute threshold refers to the minimum amount of stimulation necessary to cause a neuron to “fire” a signal.

13. All-or-Nothing Principle
A neuron will either send a signal or not.
No such thing as a 27% strength signal.
YES or NO no such thing as “maybe”
ON or OFF no such thing as a partial signal

14. ACTION POTENTIAL The neuron signal is called the “action potential”
When a neuron has “fired” the action potential shoots through the axon, it takes time to reset and get ready to go again.
This is called
the refractory
period.

15. RESTING POTENTIAL When a neuron is not sending a signal, it is at rest
This is different than refractory period because when a neuron is at resting potential it is waiting to fire NOT unable to fire