The Nervous System Chapter 8
Jan 17, 2016
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