1. The Nervous System

2. Review: What makes up the Nervous System?
The brain
Spinal cord
Nerves
2 types of cells:
neurons: send and receive signals
glial cells: protect, support, and insulate neurons

4. Review: What are the two types of neurons?
Sensory neurons
What do sensory neurons do?
Cells that monitor stimuli and send signals to the spinal cord or brain.
Motor neurons
What do motor neurons do?
Cells that carry impulses from the brain or spinal cord to muscles, glands, or other neurons

5. Let’s take a closer look at a neuron.
Dendrites-branchlike structures on the cell body that receive the signal
Cell body-Central part of the neuron that contains the cell nucleus
Axon-rod-like extension off of cell body which conducts signal through neuron
On your diagram, label dendrite, cell body, cell nucleus, and axon.

6. A Neuron
Glial cell

7. How are neurons organized?
Each neuron connects to 100’s of thousands of other neurons.

8. How is a signal sent?
First, a stimulus happens. A stimulus is any incoming information that causes a response.
The signal moves from the
stimulus dendrites cell body  axon  another neuron.
Sensory neurons detect the stimulus, and begin to send an electrical signal that passes through several neurons.
The signal then starts all over in another neuron.

10. Is it that easy?
No.
When the signal gets to the end of a neuron, it comes to a synapse, or a small space between the neurons.

11. What happens at the synapse?
In order to transmit the signal from one neuron to another across the synapse, the neuron releases a chemical called a neurotransmitter. Neurotransmitters act as chemical messengers from one neuron to another.

13. Neurotransmitters and Disease
Dopamine is a neurotransmitter related to muscular function
Serotonin is a neurotransmitter that is associated with “happy” nerve signals

14. Once a signal is sent through the neurons, where does it go?
It is usually sent to the brain, processed, and then another signal is sent through the motor neurons to induce movement or give a response.

15. Think about when you touch a hot object.
You withdraw your hand without having to think at all.
Your brain processes it later.
This quick response to a stimulus that does not require a trip to the brain is called a reflex arc.

16. The brain is not involved in a reflex arc.
Look at the picture describe where the signal is sent and how it is returned.

17. Ms. Plecki’s Biology Class Proudly Presents….
A Biodrama on
The Nervous System

18. Study your notes for 3 minutes.

19. Motor Neurons
Left hand= dendrite
Body= cell body
Right hand= axon

20. http://teachhealthk-12. uthscsa