1. The Nervous System
Chapter 5
Section 1

2. Objectives
Describe the basic structure of a neuron and how impulses move across a synapse.
Compare the central and peripheral nervous systems.
Explain how drugs affect the body.

3. Responding to Stimuli Stimulus
Any internal or external change that brings about a response.
Your body adjusts to changing stimuli with the help of the nervous system.
The regulation of steady, life maintaining conditions inside an organism, despite changes in the environment is called homeostasis.

4. Nerve Cells Neurons The basic functioning units of the nervous system.
Made up of
Cell body
Dendrites
Receive messages from other neurons and send them to the cell body
Axons
Carry messages away from the cell body.

6. Types of Nerve Cells Sensory Neurons Motor Neurons
Receive information and send impulses to the brain or spinal cord.
Motor Neurons
Interneuron’s relay impulses to motor neurons.
Motor neurons then conduct impulses from the brain and spinal cord to muscles and glands throughout the body.

7. Sensory Neuron
Interneuron's
Motor Neurons

8. Facts Neurons do not touch one another.
An impulse crosses a small space called a synapse.
When a nerve impulse reaches the end of an axon, the axon releases a chemical.
The chemical flows across the synapse and stimulates the impulse in the dendrite of the next neuron.
Impulses only move in one direction.

9. The Path of an Impulse

10. Central Nervous System
Made up of the brain and the spinal cord.
Peripheral Nervous System
Made up of all of the nerves outside of the central nervous system.
Connects the brain and spinal cord to other body parts.

11. Central Nervous System
Brain
Coordinates all body activities
100 billion neurons
Cerebrum
Largest part of the brain
Thinking takes place
Movements are controlled
Memories are stored
Cerebellum
Stimuli from the eyes and ears and from muscles and tendons are interpreted here.
Help maintain balance
Coordinate voluntary muscle movements

12. Central Nervous System
Brain Stem
Extends from the cerebrum and connects the brain to the spinal cord.
Midbrain
Provide pathways connecting various parts of the brain to each other.
Pons
Same as above
medulla
Controls involuntary actions such as heartbeat

13. Spinal Cord
This is an extension of the brain stem
About the width of the human thumb
About 43 cm

14. Peripheral Nervous System
Somatic
Controls voluntary actions
Cranial and spinal nerves that go from the CNS to the skeletal muscles.
Autonomic
Controls involuntary actions

15. Reflexes Spinal Pain Cord Withdrawal Reflex
Is a involuntary, automatic response to a stimulus.
Spinal
Cord
Pain
Interneuron
Impulse
Withdrawal
Reflex
Motor Neuron
Reflex responses are controlled in the spinal cord not the brain

16. How do Drugs Affect the Nervous System?
Alcohol
Absorbed directly into the stomach and small intestine into the circulatory system.
Disrupts the functions of cells
Depressant
Caffeine
Stimulant
Can increase heart rate, cause insomnia

17. Alzeimer’s