The Nervous System:The Basic Structure

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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

PART TYPE OF PROTECTION

Brain Skull & sheathing

Spinal cord Vertebrae

Peripheral nerves sheathing

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

dendritesAxon 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