The Nervous System 2003-2004 *

Overview Central Nervous System (CNS) Peripheral Nervous System (PNS) The Nervous System controls and coordinates all the functions of the body. The Nervous System consists of two main sub-divisions: Central Nervous System (CNS) Peripheral Nervous System (PNS) The Peripheral Nervous System is divided into two sub-divisions: Somatic- voluntary Autonomic- involuntary 2003-2004 *

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Structure and Function of the Neuron Neuron is the scientific name for a Nerve Cell. Neurons consist of 3 basic structures: Cyton, or cell body. Dendrites- receive messages, impulses, and send them to the cell body. Axons- send messages away from the cell body. Nerve impulses travel from one neuron to another across synapses, or spaces in between the cells. The “jumping across” the synapse is facilitated (helped) by chemicals called Neurotransmitters. 2003-2004 *

Parts of the Neuron Dendrites – Branched parts of a neuron that receive impulses from other neurons. Cyton- Contains cytoplasm and the nucleus. Impulses pass through here to the axon. Axon- Single long fiber that carries impulses away from the cell body. A Neuron 2003-2004 *

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Synapse Junction between nerve cells 1st cell releases chemical to trigger next cell where drugs affect nervous system synapse 2003-2004

Types of Neurons Neurons can also be classified by the direction that they send information: ･Sensory (or afferent) neurons: send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system. ･Motor (or efferent) neurons: send information AWAY from the central nervous system to muscles or glands. ･Interneurons: send information BETWEEN sensory neurons and motor neurons. Most interneurons are located in the central nervous system. 2003-2004 *

Reflexes Stimulus- a change in the environment. Response/Reaction- how the body reacts to a stimulus. Reflex Arc- the pathway that an impulse follows to illicit a response to a stimulus. 2003-2004 *

Parts of the Central Nervous System Brain Spinal cord 2003-2004

The Brain Coordinates body activities Made up of approximately 100 billion neurons Uses 20% of bodies oxygen and energy Divided into three major parts- the Cerebrum the Cerebellum the Brain Stem (Medulla Oblongata, Pons) 2003-2004

Cerebrum Largest part of the brain Thinking Memory is stored Movements are controlled Impulses from the senses are interpreted. 2003-2004

Myelin Sheath signal direction Axon coated with insulation made of myelin cells (Fatty, protein substance) speeds signal 330 mph vs. 11 mph myelin coating Multiple Sclerosis immune system (T cells) attacks myelin coating loss of signal 2003-2004 *

Gray Matter vs. White Matter Gray Matter – Absence of myelin in masses of neurons accounts for the gray matter of the brain – Cerebral Cortex White Matter - Myelinated neurons gives neurons a white appearance – inner layer of cerebrum

Cerebrum specialization Regions specialized for different functions Lobes frontal speech, control of emotions temporal smell, hearing occipital vision parietal speech, taste reading frontal parietal occipital temporal 2003-2004 *

Cerebellum Responsible for the coordination of muscles and is the center of balance 2003-2004 *

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Medulla Center of heart beat, respiration, and other involuntary actions 2003-2004 *

Other Structures inside the Brain Thalamus – receives messages from sensory receptors; relays information to proper regions of cerebrum Hypothalamus - Regulates hunger, thirst, fatigue, anger, etc… Control of pituitary for endocrine function

The Spinal Cord Extension of the brain stem Bundles of neurons that carry impulses from all parts of the body to the brain and from the brain to all parts of your body 2003-2004

The Peripheral Nervous System Your brain and spinal cord are connected to the rest of your body by the peripheral nervous system. The PNS is made up of 12 pairs of nerves from your brain called cranial nerves, and 31 pairs from your spinal cord called spinal nerves. Spinal nerves are made up of bundles of sensory and motor neurons bound together by connective tissue. For this reason, a single spinal nerve can have impulses going to and from the brain at the same time. Some nerves contain only sensory neurons, and some contain only motor neurons, but most nerves contain both types of neurons. Somatic and Autonomic Systems The peripheral nervous system has two major divisions. The somatic system controls voluntary actions. It is made up of the cranial and spinal nerves that go from the central nervous system to your skeletal muscles. The autonomic system controls involuntary actions-those not under conscious control-such as your heart rate, breathing, digestion, and glandular functions. These two divisions, along with the central nervous system, make up your body's nervous system.                                                                                                                                                                                                                                                                             Research Visit the Glencoe Science Web site at tx.science.glencoe.com for more information about the nervous system. Make a brochure outlining recent medical advances. 2003-2004