the nervous system and neurons is this even possible? why or why not?
TRANSCRIPT
The Nervous System and
Neurons
Is this even possible? Why or why not?
• Network of connected cells, tissue, and organs
• Controls thoughts, movement, life processes
• Quick responses– Ex: Sunny day pupils
shrinking
Nervous System
CNS and PNS
• AKA: Highly specialized nerve cells– Transfer electrical impulses to/from the brain
• 4 Main Parts1) Cell body: contains nucleus and organelles2) Dendrites: branches that receive messages from neighboring cells3) Axon: extension that carries messages away from the cell body4) Axon Terminal: End of neuron
Neurons
Three Types of Neurons:
1) Sensory– Detect stimuli and
transmit signals to/from the brain
– Detect sense (sight, smell, sound, taste, touch)
2) Interneuron– Located in the brain– Receive signals from the sensory neurons
Three Types of Neurons:
3) Motor– Pass messages to other tissue– Ex: Nerve attached to muscle
• Muscle reacts by contracting and stretching
Three Types of Neurons:
Resting Potential
• Defined: Neuron at rest• Neuron Exterior is positive in
charge – Due to abundance of Na+
outside
• Neuron Interior is negative– Due to abundance of
proteins and…– Some K+ inside the cell
K+
K+K+
K+K+
K+
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K+
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Interior
Action Potential• Defined: The electrical
impulse that is triggered & moves quickly down an axon
• Generating the Impulse– Na channels in the
membrane open and allow Na+ to diffuse into the cell
– Area becomes positively charged (impulse)
• After the Impulse– K channels open to allow K+
to exit the cell– Area returns to negative
charge• Process continues down the
axon
impulse
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impulseimpulse impulse
Cleaning Up the Mess
• Who?– Na/K pump
• What?– Na is pumped back out of
the cell…– K is pumped back into the
cell• When?
– After the impulse has passed
• Where?– Located in cell membrane
• Why?– To restore the initial charge
inside & outside the cell• How?
– Active transport (REQUIRES ATP)
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Synapse• Defined: Gap between
neurons• Problem: Impulse cannot
cross the gap• Solution: Neurotransmitter
proteins are sent from one neuron to another
• Steps:1) Impulse reaches axon
terminal (end)2) Vesicle releases
neurotransmitters, which attach to receptors on neighbor
3) Channels open on dendrite of neighboring cell…new impulse created
Neuro
transm
itter
pro
tein
s
Impulse reaches the axon terminal
Vesicle exits the cell and dissolves
Terminal end of one cell
Dendrite of another cell
Na
impulseK
NaNa
impulse
impulseK K
impulse
Neurotransmitters diffuse across the synapse and attach to receptors of a neighboring neuron
Neurotransmitters cause Na channels to open… creating new impulse
Terminal end of one cell
Dendrite of another cell
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K Kimpulse
impulse
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K
Feet
Brain
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impulse
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neurotransmitters
neurotransmitters
neurotransmitters
neurotransmitters
and causes MOVEMENT!
Impulses eventually reach the muscles…
1. What is the function of the nervous system?2. List the 4 main parts and describe the purpose of the 4 main parts of
a neuron.3. The nervous system is divided into 2 parts. What are they and what
do they include?4. Describe the internal and external environment of a neuron in resting
potential. How is resting potential reached?5. What is a synapse and why is it a problem for neurons?6. To what part of the nervous system do motor neurons, interneurons,
and sensory neurons belong?7. When an impulse is within a neuron it is electrical. When the signal
moves to the next neuron it is _________________. What is the specific name for this?
8. Describe how an action potential moves down a neuron.
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