Transcript Communications in the Nervous System

Communications in the Nervous
System
Blueprint was general idea
Now the details
Objectives- THE STUDENT WILL:
• Analyze Parts of the Neuron
• create an illustration of a Neuron
• Summarize the importance of nerves for the
PERIFRIAL NERVOUS SYSTEM
• Explain how neurons communicate
Nervous system components
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Neurons (nerve cells) make up part of N.S
Neurons brain’s communication specialist
100 billion or more in brain
Held in place by Glia (GLEE-uh)
Glial cells- Greek for glue
90% of brain is Glia cells
Glia cells cont.
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Neurons with nutrients
Insulate them
Provide protections from toxins
Remove debris when neurons die
Give go ahead to tell neurons to start talking
Diagram of Neuron
Glia=Glue
Structure of the Neuron
• 3 main parts: Dendrites, Cell body, Axon
• Dendrites- Greek for Little tree; antennas with
communication with nerve cells
• Cell body- shaped like a pyramid or sphere,
decides if neuron FIRES OR NOT, biochemical
machinery
• Axon- Greek for axel, transmits messages away
from the cell body to other neurons, muscles and
glands. Can split and divide into branches= axon
terminals
chapter 4
Structure of a neuron
Dendrites
Receive information from other neurons
and transmit toward the cell body
Cell body
Keeps the neuron alive and determines
whether it will fire
Axon
Extending fiber that conducts impulses
away from the cell body and transmits
to other cells.
Another neuron
More Neuron Structure
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Myelin sheath- Cover for the axons, fatty
Constrictions in the M.S. called nodes
Divide into segments so look like sausage
M.S. also keep signals from adjacent cells out
Myelin sheath
• Also CAN SPEED UP Conduction of Neural
impulses
• OR like in multiple sclerosis, loss of Myelin
causes erratic nerve signals, leading to loss of
sensation, weakening, paralysis, lack of
communication, vision weak
Myelin Sheath
Peripheral Nervous System OB #3
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Fibers of individual neurons (axons, dendrites)
Collect and bundle together called Nerves
Like lines in a telephone cable
Human body has 43 pairs of Peripheral nerves
Nerves Cont.
• Left/right side of body
• Most enter or leave spinal cord
• However; 12 pairs in the head, Cranial
nerves, connect to the brain.
• SO Senses : Smell, taste
Stem Cell Controversy
• 1990 Mammals can produce CNS cells after
infancy
• Human brain and body organs have such cells
• Called stem cells
• In animal studies, Can reproduce if exercise,
die if stress or nicotine
• Controversy; Scientist use aborted fetuses and
test tube embryos
chapter 4
Neurons in the news
Neural regeneration
The ability of neurons to grow
back after injury or damage
Stem cells
Immature cells that renew
themselves and have the
potential to develop into
mature cells
How Neurons Communicate
• Separated by synaptic cleft, neurons don’t
touch
• Axon terminal and one neuron almost touch
• Synaptic cleft + axon terminal+ covering
membrane= synapse
chapter 4
How neurons
communicate
Axon terminals release
neurotransmitter.
Neurotransmitter enters
synapse.
Neurotransmitter binds
to receptors that it fits.
Synapse
This is how NEURONS TALK
• Action potential- When a nerve cell is
stimulated, creates electrical voltage.
• Like fuse on firecracker
• Neurotransmitter- neural impulse reaches
axon terminal, must reach across synaptic
cleft, synaptic vessels, reach axon terminal=
release a few thousand neurotransmitters
• Excitatory (good) inhibitory (neg)
chapter 4
Action potential
A brief change in electrical voltage that
occurs between the inside and outside of an
axon when a neuron is stimulated.
chapter 4
Neurotransmitter
Chemical released by a transmitting
neuron at the synapse and capable
of affecting the activity of a
receiving neuron
Neurotransmitter crossing a synapse
Summary
• Parts of Neuron
• How do they communicate?