The Nervous SystemChapter 8

The Nervous SystemThe system of cells, tissues, and organs that

regulates the body’s response to internal and external stimuli.

The Nervous SystemYour nervous system is responsible for

Maintaining consciousnessLearning and remembering new thingsCoordinating what you sense or feel

Nervous SystemCentral Nervous System (CNS)

Brain and Spinal CordPeripheral Nervous System (PNS)

All the nerves that branch out to the body

Autonomic Nervous System (ANS)Involuntary Functions

NeuronsNeurons are cells that make up nervous

tissue.Neurons transmit nerve messages.

This image is copyright Dennis Kunkel at www.DennisKunkel.com

Neurons

Axon endings(synaptic terminals)

NucleusAxon

Dendrites

Cell Body

Nerve impulses go only one way

Nerve ImpulseSelf propagating wave of electrical

disturbance Sodium (Na+) ions racing inward

Inside + Outside -

Keeps going down the membrane of the axonThe myelin sheath helps make it go faster

Hold Hands and Circle Up!

The SynapseGap between adjacent neuronsSynaptic knob, synaptic cleft, and the plasma

membrane

NeurotransmittersChemicals that move from the synaptic knob

to the synaptic cleft. Ex: acetycholine, norepinepherine, dopamine,

serotonin - play a role in sleep, motor functions, mood, and pleasure recognition

Neurons: 3 typesSensory neuron-

go towards the spinal cord and brain, also referred to as afferent neurons

Motor neuron- go away from the brain and spinal cord to the

muscle and glands, also referred to as efferent neurons

Interneuron- conduct between sensory and motor neurons

(central or connecting neurons), also known as associative neurons

Glia CellsGlia- special type of

supporting cellsHold functioning

neurons together and protect them

Vary in size and shape

Glia Cells: 3 types

Astrocytes look like stars;

attach to neurons and to small blood vessels. Form the blood-brain barrier.

Microglia act as

microbe-eating scavengers

Oligodendrocyte help hold

nerve fibers together and also produce the fatty myelin sheath (in CNS only)

NervesGroups of peripheral nerve fibers bundled

together like the strands of a cable.

NervesAxons are wrapped by a fibrous connective

tissue called the endoneurium. Groups of these wrapped axons are called fascicles.

Each fascicle is surrounded by a thin, fibrous perineurium and a tough, fibrous sheath called the epineurium covers the whole nerve.

NervesWhite matter – nerves that have a myelin

sheath covering them (axons)Gray matter – tissue composed of cell bodies,

dendrites, and unmyelinated axons

Reflex ArcsPathway a message takes to cause a reflex 1. Sensory neurons directly to motor neurons

Ex: “knee jerk”

Reflex Arcs

2. Sensory neurons to interneurons to motor neurons

Ex: withdrawal reflex