The Nervous System: The Basic Structure 6-1

From “Running and ME: A Love Story” by Joan Nesbit, 1999 It’s almost like running is this great friend we both share…Anyway, that’s what I’d like to talk to you about…running as a friend, a companion, a lover even…in other words, the relationship of running. “WHAT!?” many of you will be saying, “I thought that I was going to learn how to improve my 10k time.” Go read Runner’s World for that. You see, I don’t view running as what I DO or who I AM, but as this thing, this force, that changes me over time….

The Nervous System Controls: – emotions – movements – thinking – behavior

The Nervous System Parts: – central nervous system (CNS) brain & spinal cord – peripheral nervous system (PNS) Smaller parts/branches of the nerves that go to the parts of the body

Nervous System Protection All parts have protection PARTTYPE OF PROTECTION BrainSkull & sheathing Spinal cordVertebrae Peripheral nervessheathing

Neurons long, thin cells of nerve tissue on which messages travel to and from the brain

Parts of a Neuron Cell body – Has the nucleus – Produces energy needed for the neuron to work Dendrites – Short, thin fibers that stick out from the cell – Receive impulses, or messages, from other neurons and send them to the cell body Axon – Can be very short, or several feet long – Long fiber that carries the impulses away from the cell body to the dendrites of another neuron

Neuron Parts cont… Myelin sheath – Insulates and protects the axon for some neurons – Speeds the transmission of impulses Axon terminals – Branch out at the end of the axon

nucleus dendrites Axon terminals Cell body axon Myelin sheath

Neuron Connection Synapse – The gap that happens between individual nerve cells Impulses/messages are transmitted across the synapse to another neuron Neurotransmitters – The chemicals released by neurons – Determines the rate at which other neurons fire

dendrite

Neurotransmitters Excite – make the neuron transmit Inhibit – make the neuron stop transmitting

Neuron Activity Neurons are either ON or OFF Neuron tracks: – Ascending – go up Carry messages to the brain – Descending – go down Carry messages from the brain to the body

Types of Neurons Afferent neurons – Sensory neurons – Send messages from the organs (including eye, nose, ear, skin) Efferent neurons – Motor neurons – Send signals from the brain to the glands and muscles Interneurons – Carry impulses between neurons in the body

Types of Activities Voluntary – Lifting your hand – Running – Turning your head Involuntary – Heartbeat – Blood pressure – Size of the pupils

What systems control what? Somatic Nervous System (SNS) – Part of peripheral nervous system – Controls voluntary actions Autonomic Nervous System (ANS) – Controls involuntary actions

Autonomic Nervous System (ANS) Parts: Sympathetic – Prepares the body to deal with emergencies or hard labor – Speeds up the heart to get oxygen and other nutrients to the body – Controls how much blood goes to different parts of the body – Increases blood pressure – Suspends/stops some activities (ex: digestion) Parasympathetic – Saves energy – Helps the body recover from hard work – Reduces the heart rate & blood pressure