HOW THE NERVOUS SYSTEM FUNCTIONS! By Brad Zeller SIMPLE EDITION

The Nervous System  The nervous system is one of many systems used within our bodies  This system is one of the most intricately organized aggregate of matter on the face of this planet  Its unique ability to send and receive specific signals from specific parts of the body using nerve cells, chemicals, and electrical impulses is simply amazing

Different Pathways  Afferent nerves – (sensory nerves) are nerves that carry information about the external environment to the brain and spinal cord  Efferent nerves – (motor nerves) are the nerves which do the opposite and carry information out of the brain and spinal cords to regions of the body where work can be done  Most of the information will move through and be processed by neural networks, which integrate sensory input and motor output

The Main Divisions  The central nervous system (CNS) is made up of the brain and spinal cord  More than 99% of all nerves cells in our body are located here  The peripheral nervous system (PNS) is the network of nerves which connects the brain and spinal cord to the rest of the body

Subdivisions of the PNS  1) The somatic nervous system consist of the sensory nerves, whose function is to convey information from the skin and muscles to the CNS that report pain or temperature, and also contains motor nerves, which tell muscles what to do  2) The autonomic nervous system takes messages to and from the body’s internal organs (processes like breathing, heart rate, and digestion)

Subdivisions of the Autonomic Nervous System  1) The sympathetic nervous system is the system that arouses the body to mobilize it for action  System that gives you the “fight or flight” reaction  Also involved in stress  2) The parasympathetic nervous system calms the body

The Cellular Level  In each system a lot of work is being done at a much smaller scale where the nerve cells, chemicals, and electrical impulses work together to send messages at a rate of 330 miles per hour  Because of these speeds, information can travel from the brain to your hands (or vice versa) within a matter of milliseconds!

The Two Main Types of Cells Associated  Neurons – nerve cells from the nervous system that handle the information processing function  The typical human brain contains above 100 BILLION neurons!  ALSO, the average neuron is a complex structure with as many as 10,000 physical connections with other cells!  This explains how a message can be sent so friggin fast!  Glial cells – cells in the nervous system that provide support, nutrients, and other functions and keep neurons running smoothly

Specialized Cell Structure!  As every cell does a neuron has a cell body. The cell body contains the nucleus, which directs the manufacture of substances that the neuron needs for growth and maintenance.  There are also dendrites. Dendrites are treelike fibers that project from a neuron. They will receive information and direct it toward the nucleus of the cell.  Having numerous dendrites helps increase the surface area so when a signal is sent out, more neurons will be able to receive it.

Specialized Cell Structure!  Another portion called the axon carries information away from the neuron to other neurons  Axons are extremely thin, but can run extreme distances as well. In fact, some axons extend 3 feet in length!  Encasing and insulating most axons is a myelin sheath, which consist of a layer of cells containing fat.

Terminal Button Specialized Cell Structure! Different Cell Synapses Vesicle Dendrites Cell Body Nucleus Myelin Sheath around Axon Axon Axon Terminals

The Neural Impulse  The way these neurons send information from one to another is through brief electrical impulses  Each neuron will send the impulse to the next through the axon electrically because the membrane of an axon is very unique  Each axon has thousands of tiny gates that can open making the membrane semi permeable  These gates are known as ion channels

The Neural Impulse  The ion channels will open and close allowing ions to pass in and out of the cell  When a cell is resting (not transmitting information) the ion channels are closed creating a slight negative charge. Outside the cell, the charge is positive making the resting neuron become what is known as polarized.  The resting potential (the stable, negative charge of an inactive neuron) has a potential between -60 and -75 millivolts, meaning each cell maintains the potential for about 75,000 volts of electricity!

The Neural Impulse  So because opposite charges attract the ions inside and outside the cell will rush to each other when given the chance  So when the impulses run down the neuron by opening and closing ion channels, this allows the ions to flow in and out  As certain ions move in and out of the neuron, the neuron becomes positively charged making it depolarized. Once negative ions rush back in the neuron will return to a negative charge.  Then the same process occurs as the next group of channels flips open briefly

Synaptic Transmission  As the impulse goes all the way down the axon, it will eventually reach what is known as a synapses. These are small gaps between neurons, which are referred to as synaptic gaps.  Before an impulse can cross a synaptic gap, it must be converted into a chemical signal  Each axon branches out into numerous fibers that end in a structure called terminal buttons  Within each terminal button are chemical substances known as neurotransmitters

Synaptic Transmission  Neurotransmitters will carry the information across the synaptic gap to the next neuron to continue the transmission of the message  The neurotransmitters will flood the synaptic gap when the impulse reaches them. Their movement is random allowing some of them to bump into receptor sites of the next neuron (they can be interpreted as a lock and key).  There are several neurotransmitters in our body and all have major effects on behavior

Common Neurotransmitters  Acetylcholine – involved in action of muscles, learning, and memory  GABA – keeps neurons from firing  Norepinephrine – stress stimulates the release of norepinephrine  Dopamine – helps to control voluntary movement and affects sleep, mood, attention, learning, and reward recognition  Serotonin – involved in regulation of sleep, mood, attention, and learning  Endorphins – shields the body from pain and elevates feelings of pleasure  Oxytocin – plays an important role in the experience of love and social bonding

In Conclusion…  …all of these mechanisms work together within our nervous system so that we are able to live our lives happily.  They help to keep us safe and sense danger, and at the same time allows us to feel the special feeling of love.  The nervous system is just another magnificent portion of our body that all of us need in order to live our long, happy lives!

Works Cited  Pictures  science-of-simulation-mirror-neurons/ science-of-simulation-mirror-neurons/  ard.php?az=view_all&address=222x ard.php?az=view_all&address=222x51167   A bunch of clip arts from Microsoft Powerpoint  Information  All from the book: Experience Psychology by Laura A. King. (all info was between pages 40-49)