1. Nerve Cells
The Neuron

2. Fun facts about neurons
Most specialized cell in animals
Longest cell:
blue whale neuron
10-30 meters
giraffe axon
5 meters
human neuron
1-2 meters
Nervous system allows for 1 millisecond response time

3. 3 parts of a Neuron
Dendrite – branched end that extends out from the cell, provides a large surface area to receive nervous information
Cell Body – control center, regular cell organelles (nucleus etc)
Axon – long thin fiber, extends out from cell body, carries action potential from cell body
-ending are called synaptic terminals

4. Nervous system cells Neuron Structure and function a nerve cell
signal
direction
dendrites
cell body
Structure and function
many entry points for signal
one path out
transmits signal
axon
signal direction
synapse
dendrite  cell body  axon

5. 3 Types of Neurons Motor – connects to a muscle or gland
Sensory – receives a stimulus
Interneuron – connects the above 2

6. Myelin Sheath
-Myelin Sheath covers some axons

7. Myelin Sheath
-Formed by a type of neuroglia called Schwann cells

8. Myelin Sheath
-Schwann cells contain a lipid called myelin in cell membrane
-Schwann cells wrap around axon many times
Nodes of Ranvier- gaps between Myelin sheaths

9. Reflex
Rapid, predictable, and involuntary responses to stimuli

10. Reflex arc
Direct nervous message from a sensory neuron to inter-neuron to a motor neuron to an effector (a muscle or a gland)
Video

12. Reflex Arc A motor, sensory and inter neuron form a reflex arc
Begins with a stimulus causing an impulse in the sensory receptors of a sensory neuron.
The impulse then continues on through the dendrite, cell body and axon of a sensory neuron (DCA).

13. The impulse passes to the interneuron, passing through dendrite, cell body and axon (DCA).
The impulse passes onto the motor neuron, passing through the dendrite, cell body, and axon (DCA).
This causes a response in an effector (a muscle or a gland)

14. Reflex Arc

15. Reflex Arc

16. Nerves Combination of nerve cell fibers
Sensory dendrites and motor axons

17. Summary Neuron Types
Sensory Neuron Interneuron Motor Structure
Long dendrite
Short axon
Short dendrite
Long axon
Function
Conduct impulse to cord
Interconnect sensory neurons with motor neurons
Conduct impulse to effector (muscle/ gland)
Location
Cell body/ dendrite outside spinal cord
Cell body- dorsal root
Entirely within CNS
Cell body/ dendrites in spinal cord
Axon outside spinal cord

18. Synapses/ synaptic gap
Synapse- region of close proximity
Synaptic gap- Space between a neuron (axon terminal) and the next cell
The next cell could be another neuron or an effector (muscle/ gland)
Space between must be bridged by neurotransmitters
More on neurotransmission and nerve impulses tomorrow!

19. Synapse