The Nervous System

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

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

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.

A Neuron

Glial cell

How are neurons organized?

• Each neuron connects to 100’s of thousands of other neurons.

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.

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.

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.

Neurotransmitters and Disease

• Dopamine is a neurotransmitter related to muscular function

• Serotonin is a neurotransmitter that is associated with “happy” nerve signals

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.

• 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.

The brain is not involved in a reflex arc.

Look at the picture describe where the signal is sent and how it is returned.

Ms. Plecki’s Biology Class Proudly Presents….

A BIODRAMA ONTHE NERVOUS SYSTEM

Study your notes for 3 minutes.

Motor Neurons

• Left hand= dendrite• Body= cell body• Right hand= axon

• http://teachhealthk-12.uthscsa.edu/curriculum/brain/pa03pdf/0301E-Wires.pdf