The Nervous System

1. The Nervous System Lesson 5: Standard 9b. Students know how the nervous system mediates communication between different parts of the body and the body’s interactions with the environment. Standard 9d. Students know the functions of the nervous system and the role of neurons in transmitting electrochemical impulses.

2. The Nervous System • Consists of the brain, spinal cord, and peripheral nerves • Controls and coordinates functions throughout the body and responds to internal and external stimuli • Helps maintain homeostasis in the body through feedbackloops

3. The Central Nervous System (CNS) • Consists of the brain and spinal cord • Both the brain and spinal cord are wrapped in a membrane called the meninges • Meningitis is caused by a bacterial infection that causes the meninges to swell. It can be fatal. There IS a vaccine for meningitis. • Between the meninges and the CNS, there is a liquid called cerebrospinalfluid that cushions the CNS and acts as a shock absorber. It also allows for the exchange of nutrients and waste between the brain and the blood.

4. The Brain • The place nerve impulses flow to and originate from • The cerebrum is the largest area of the brain and is the site of learning, intelligence, and judgment. It is divided into two hemispheres that are connected by a band of tissue called the corpus callosum. • The cerebellumis the second largest region of the brain. It is responsible for coordinating and balancing the body’s movements • The brain stem is below the cerebellum. It connects the brain to the spinal cord. It consists of the pons and the medulla oblongata. It regulates the flow of information from the brain to the rest of the body. Blood pressure, heart rate, and breathing are controlled by the brain stem. • The thalamus & hypothalamus are found between the brain stem and the spinal cord. They receive messages from the body and recognize hunger, thirst, anger, fatigue, and body temperature.

5. The Spinal Cord • The spinal cord is like a telephone wire – it is the main communication link between the brain and the body. • it transmits nerveimpulses from brain to body • The spinalnerves branch out, connecting to the rest of the body. This is where the chicken pox virus, varicella-zoster, likes to hide out and be dormant after an infection. If you had the chicken pox as a child, you might get shingles as an adult. • some reflexes are processed in the spinal cord

6. The Peripheral Nervous System • Consists of all of the nerves that are not part of the brain and spinal cord • The sensory division transmits nerve impulses from sense organs to the CNS • The motor division transmits impulses from CNS to muscles or glands • The motor division is further divided into the somatic and autonomic nervous systems. • The somatic nervous system regulates voluntary movements • The autonomic nervous system regulates involuntary movements

7. Neurons • Neurons are the specialized cells of the nervous system • Most neurons have an axon, cell body, and dendrites • Neurons transmit information via electricalimpulses

8. Neurons (continued) • The cell body is the largest part of the neuron. This is where the nucleus and most of the cytoplasm is. • The dendrites are short branches that carry impulses from the environment or from other neurons toward the cell body • The axon is a long fiber that carries impulses away from the cell body. It is covered in a fatty myelin sheath that insulates and protects it.

9. Types of Neurons • Motor neurons carry impulses from the brain and spinal cord to the muscles and glands • Sensory neurons carry impulses from the sense organstothe spinal cord and brain • Interneurons connect sensory and motor neurons and transmit impulses between them.

10. Nerve Impulses During the video, answer the questions in your notes.

11. The Synapse • At the end of a neuron, there is an axon terminal. Usually, the neuron makes contact with another cell here. This is where impulses are transmitted from one neuron to the next. • The synapse is the place where a neuron can transmit its impulse to another cell • The terminals contain tiny sacs of neurotransmitters, chemicals that are used to transmit an impulse across a synapse to another cell