1. NEURONS
Bio 12

2. Wouldn’t that be great! 
Joke of the day:
Wouldn’t that be great! 

3. Review: Neuron
Neurons: cells that conduct nerve impulses. They function electrically to create thought and action in our bodies
Three types of neurons:
Sensory neurons
Interneurons
Motor neurons

4. Parts of a neuron:
Label diagram together 

5. Parts of a neuron: Cell body
controls the metabolism and growth of the cell
contains the nucleus.
Dendrites
projections of cytoplasm which receive electrochemical messages from the axons of other nerve cells. They conduct impulses towards the cell body.

6. Parts of a neuron:
Axon
extension of the cytoplasm which carries nerve impulses away from the cell body towards other neurons, glands or muscles (away from the cell body)
the end of the axon is subdivided into many filaments, forming the end brush
transmit impulses away from the cell body

7. Parts of a neuron cont’d:
Myelin sheath:
this is the extra covering along the axon of a neuron because they require the insulation to work properly.
it is a glistening white coat of a fatty protein which also provides nourishment to the axon.
Axons that have a myelin sheath are said to be myelinated.
Schwann cells:
these are special Glial cells that surround the axon and form the myelin sheath.

8. Parts of a neuron: Nodes (Nodes of Ranvier):
the areas between the sections of myelin sheath along an axon.
nerve impulses jump from one node to another which speeds up the movement of the nerve impulses.

9. Message flow in a nerve cell:
Dendrites
Cell body
axon
effector (muscle or gland)
dendrites etc of next neuron

10. Synapse
There is a microscopic gap between the terminal end of the axon and the membrane of another neuron or effector cell.
Nerve impulses must cross this gap as part of the transmission of the impulse.
The synapse must be bridged by a chemical called a neurotransmitter.

11. Reflex Arc
Reflexes are involuntary and often unconscious, they are fast because they do not go through the brain.
The reflex arc is the simplest nerve pathway, which occurs without brain coordination.

12. Video clips Synapse: http://www.youtube.com/watch?v=FR4S1BqdFG4
Arc Reflex:

13. To do:
Arc Reflex WS
Page 417
Questions 1-5
Arc Reflex Lab Activity