Lesson Overview

1. Lesson Overview 31.1 The Neuron

2. Functions of the Nervous System

3. Functions of the Nervous System • Peripheral nervous system= (made up of nerves and supporting cells) collects information about the body’s external and internal environment. • Also delivers instruction from brainto the appropriate part of the body.

4. Functions of the Nervous System • Central nervous system (brain and spinal cord) processes information and creates a response • Draw CNS in the space below:

5. Neurons • Messages carried by the nervous system are electrical signals called impulses. • Nervous system impulses are transmitted by cells called neurons. • Recall on page 1 of your notes that Neurons are the cells that carry nerve impulses and glial cells surround and protect neurons

6. Types of Neurons • Neurons are classified according to the direction in which an impulse travels: • Sensory neurons = carry impulses from sense organs (eyes and ears) to spinal cord and brain. • Motor neurons = carry impulses from brain and the spinal cord to muscles and glands. • Interneurons = process information from sensory neurons and then send commands to motor neurons.

7. Structure of Neurons • Cell body = contains the nucleus and much of the cytoplasm • Dendrites= receive impulses from other neurons and carry impulses to the cell body. • Axon= carries impulses away from the cell body • Neurons may have dozens of dendrites, but usually they have only one axon.

8. Structure of Neurons • Axon terminals = series of small swellings at the end of the axon • Myelin sheath = an insulating membrane that surrounds the axon and speeds up impulses • The myelin sheath has many gaps, called nodes, where the axon membrane is exposedand where impulses travel slower.

9. Label the picture:

10. The Nerve Impulse • An impulse begins when a neuron is stimulated by another neuron or by the environment. • A neuron remains in its resting state until it receives a stimulus to its dendrites large enough to start a nerve impulse from the cell body • Once it begins, the impulse travels quickly down the axon away from the cell body toward the axon terminals.

11. The Synapse • At the end of the neuron, the impulse reaches an axon terminal where a synapse is created to cross the synaptic cleft • Synapse = the point at which a neuron transfers an impulse to another cell • Synaptic cleft = the space that separates the axon terminal from the adjacent cell.

12. The Synapse • The axon terminal at a synapse contains tiny vesicles filled with neurotransmitters. • Neurotransmitters= chemicals that transmit an impulse across a synapse to another cell.

13. Review: steps of synapse transmission • Impulse arrives at the synapse from the axon terminals • Neurotransmitters are released from the axon • Neurotransmitters diffuse across the synaptic cleft and bind to receptors on the dendrites of the receiving cell • This binding stimulates a new impulse begins in the second cell.

14. Draw the nerve synapse: neurotransmitters axon terminal Axon of first cell impulse New impulse in dendrite of second cell