1. 31.2 The Central Nervous System
Lesson Overview
31.2 The Central Nervous System

2. THINK ABOUT IT
The nervous system contains billions of neurons, each capable of carrying impulses and sending messages.
What keeps them from sending impulses everywhere and acting like an unruly mob? Is there a source of order in this complex system, a central place where information is processed, decisions are made, and order is enforced?

3. Types of Neurons
Neurons can be classified into three types according to the direction in which an impulse travels.
Sensory neurons carry impulses from the sense organs, such as the eyes and ears, to the spinal cord and brain.
Motor neurons carry impulses from the brain and the spinal cord to muscles and glands.
Interneurons process information from sensory neurons and then send commands to other interneurons or motor neurons.

4. Structure of Neurons
The largest part of a typical neuron is its cell body, which contains the nucleus and much of the cytoplasm.

5. Structure of Neurons
Spreading out from the cell body are short, branched extensions called dendrites.

6. Structure of Neurons
Dendrites receive impulses from other neurons and carry impulses to the cell body.

7. Structure of Neurons
The long fiber that carries impulses away from the cell body is the axon.

8. Structure of Neurons
An axon ends in a series of small swellings called axon terminals.

9. The Synapse
At the end of the neuron, the impulse reaches an axon terminal, which may pass the impulse along to another cell. A motor neuron, for example, may pass impulses to a muscle cell, causing the muscle cell to contract.
The point at which a neuron transfers an impulse to another cell is called a synapse.
A space, called the synaptic cleft, separates the axon terminal from the adjacent cell.

10. The Brain and Spinal Cord
Where does processing of information occur in the nervous system?

11. The Brain and Spinal Cord
Where does processing of information occur in the nervous system?
Each of the major areas of the brain—the cerebrum, cerebellum, and brain stem— is responsible for processing and relaying information.
The spinal cord is the main communication link between the brain and the rest of the body.
This makes up the CENTRAL NERVOUS SYSTEM

12. Cerebrum The largest region of the human brain is the cerebrum.
The cerebrum is responsible for the voluntary, or conscious, activities of the body. It is also the site of intelligence, learning, and judgment.

13. Cerebellum The second largest region of the brain is the cerebellum.
Information about muscle and joint position, as well as other sensory inputs, is sent to the cerebellum.

14. Brain Stem The brain stem connects the brain and spinal cord.
The brain stem includes three regions— the midbrain, the pons, and the medulla oblongata. Each of these regions regulates the flow of information between the brain and the rest of the body.
Functions such as regulation of blood pressure, heart rate, breathing, and swallowing are controlled by the brain stem. The brain stem keeps the body functioning even when you have lost consciousness due to sleep or injury.

15. PERIPHERAL NERVOUS SYSTEM: nerves branched off the spinal cord and brain.

16. Nervous System
Function: Recognizes and coordinates changes in internal and external environments.
Control center of the body.
Invertebrate Organs
Nerve nets, ganglia, nerve rings
Vertebrate Organs
Main organs
Brain
Spinal cord
Peripheral nerves
Think about this…
Describe internal and external conditions that an organism would respond to?
Which organs allow you to respond?
How does the body perceive or “know” what is occurring?

17. Nervous System: Response to the environment
All animals respond to their environment through specialized cells called nerve cells (neurons).
In most animals nerve cells hook together to form the nervous system.
Nervous systems can range from fairly simple to extremely complex.
The arrangement of nerve cells from phylum to phylum can be dramatically different.

18. Figure 29–12 Invertebrate Nervous Systems
Section 29-2
Arthropod
Brain
Ganglia
Ganglia
Brain
Nerve Cells
Think about this…
Cnidarian
Flatworm
Which nervous system seems to be the simplest? Why?
Mollusk
What is “Ganglia” ? How does it differ from a brain?
Hint: You will need to look this up

19. The Human Brain: Control center of the Nervous System
Figure 35-9 The Brain
Section 35-3
Pons
Pituitary gland
Hypothalamus
Cerebrum
Medulla oblongata
Spinal cord
Cerebellum
Pineal gland
Thalamus
Discuss the brains function in sensory perception and action control.
Brain stem

20. Human Nerve Cell: Messenger of the nervous system
Discuss how nerve cells line up, how impulses are sent throughout the body.
Think about this…
What role does the neuron (nerve cell) play in response to a stimulus?

21. Craniate Brains (con’t)
Figure 15.15: Dorsal view of craniate brains (book figure 16.14).

22. Fish Cerebrum Primitive sensory Motor area
Pallium- dorsal area
Motor area
Subpallium- ventral area
Globus pallidus (Striatum)
Figure 15.16: Globus pallidus of fish; left cerebral hemisphere (book figure 16.25).

23. Amphibian Cerebrum Similar pallium and globus pallidus
Split left and right hemispheres
Figure 15.17: Globus pallidus of amphibian; left cerebral hemisphere (book figure 16.25).

24. Reptile Cerebrum Cerebrum is huge compared to amphibians
Increase of lateral walls
Pushes into lateral ventricle
Dorsal ventricular ridge forms
Receives visual, auditory, and sensory stimuli
Figure 15.18: Globus pallidus of reptile and bird; left cerebral hemisphere (book figure 16.25).

25. Bird Cerebrum Similar to reptiles Avian ridge (hyperstiatum)
Stratum of neurons that capped ridge
Processes visual information
Important to instinctive stereotypic behavior
Migration and courtship

26. Mammal Cerebrum Lateral ventricles extremely expanded
Neocortex
Higher mental facilities
Grooves (sulci)
Folds (gyrae)
Figure 15.19: Neocortex of mammalian brain.

27. Mammal Cerebrum (con’t)
Figure 15.20: Ventral view of human brain (book figure 16.17).