1. Aim: How do neurons transmit impulses?

2. The Nervous System Nerve cells that carry messages throughout the body. Allow for cell to cell communication REGULATION of body processes. REGULATION is the control and coordination of activities (maintain homeostasis)

3. Parts of the NERVOUS SYSTEM Central N.S. Peripheral N.S. Spinal CordBrain The body’s main information processing center. All of the nervous tissue outside the CNS. sends info to and from the Central nervous system

4. Nerve Impulse The electrical signal transmitted through the nervous system The electrical signal transmitted through the nervous system Nerve – a bundle of neurons. Nerve – a bundle of neurons. Neuron – nerve cell that transports impulses from one place to another in the body. Neuron – nerve cell that transports impulses from one place to another in the body.

5. Structure of a Neuron Dendrites- receive signals and carry them toward the neuron’s cell body. Axon- carries electrical signals away from the cell body and toward other cells. Nerve (many neurons) Direction of Impulse

6. Structure of a Neuron Myelin Sheath- made of fat and insulates the axon. Increases the speed that electrical signals are transmitted. Nodes- uninsulated part of the axon. Electrical signal jumps from node to node. Terminal Branches- end of axon, transmits signal to the next neuron.

7. NEURON FACTS Average number of neurons in the human brain= 100 billion Average number of neurons in an octopus brain= 300 billion Rate of neuron growth during development of a fetus (in the womb)= 250,000 neurons/minute Longest axon of a neuron= around 15 feet (Found in the Giraffe and runs from toe to neck) Velocity of a signal transmitted through a neuron= 150 meters per second.

8. Chain Reaction Stimulus - change in internal or external environment (ex. sound, odor) Receptor - specialized structures to receive stimulus (ex. ear, nose, mouth, eyes, and skin…5 senses) Effectors – specialized to produce a response ( a muscle or gland) Response - the physical movement made in response to the stimulus or the secretion of a hormone from a gland.

9. For Example What happens when you touch a hot surface like an iron? Burn Hot Iron (Stimulus)Pain Receptors in your hand (Receptor) CNS PNSMuscles in your hand (Effector) Move your hand away (Response)

10. How does a nerve signal travel? 1) Na + /K + Pump- pumps out 3 Na + and pumps in 2 K +. 2)This leaves a net positive charge on the outside and a net negative charge on the inside. This state is known as Resting Potential. 3)If a neuron is stimulated enough, Na+ Channels open and Na+ will rush in (diffusion) and cause a temporary positive charge on the inside of the neuron. This active state is known as Depolarization!

11. How does a nerve signal travel? ** Keep in mind, that a neuron will only fire if the stimulus is strong enough to depolarize the membrane to a certain level called the Threshold. This strong depolarization, is the start of the nerve signal called the Action Potential. 4)This will set off a chain Reaction of action potentials across the neuron.

12. How does a nerve signal travel? 5)After the signal is transmitted, K + Channels will open and K+ will diffuse out of the neuron and this will help restore the Resting Potential.