Transcript Your Nervous System

Your Nervous System
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Lorenzo’s Oil Discussion
Explore
Quick Communications
 Neuron Models
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Explain
Nervous System
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Four Major Parts of the Nervous System
Neurons
Nerves
Brain
Spinal Cord
Two Major Nervous System
Central Nervous System
 Peripheral Nervous System
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Nerves and Neurons are found in both and
this is where we will begin
Neuron
”Nerve Cell”
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Functional Unit of Nervous System
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Cell Body – center part of the cell containing the
nucleus
Dendrites
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3.
Carries messages toward the cell body.
Fingerlike projections
Axon
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Carries messages away from the cell body.
Elongated extension of the cell body
End of the axon is divided into fingerlike projections called
axon terminals.
Neuron Model
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To check for understanding you will need
to construct a neuron model that contains
dendrites, a cell body (soma), axon, and
axon terminals.
Types of Neurons
Sensory Neurons – picks up the stimuli
(nerve impulse) and carries it to the spinal
cord and brain.
 Interneurons- Found within the brain and
spinal cord. Relays the message between
the sensory neurons and the motor
neurons.
 Motor Neurons – transfers impulses away
from the brain to the spinal cord
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How Neurons Work
1.
Reception
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2.
Transmission
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Information is sorted and interpreted
Transmission
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5.
Sensory neurons transmit the touch message
Data Interpretation
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4.
Receptors in the skin sense stimuli
Motor Neurons transmit a response message to a
muscle
Response
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Muscles are activated causing a response
Impulse Transmission
Start with a RESTING neuron – one NOT
transmitting an impulse
 Plasma membrane controls [ ] of ions
inside the cell
 Na+ and K+ on both sides of membrane
 Na+ Higher Conc Outside
 K+ Higher Conc Inside
 Remember Na+/K+ ATPase Pump
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Sodium Potassium Pump
How an Impulse Travels
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Stimulus excites a neuron
Na+ channels open, Na+
build up inside
Inside more + that outside
Change in charge
(depolarization)
Membrane immediately
behind depolarization returns
to RESTING STATE
RESTING STATE – inside
negative, outside positive
1. Resting State
A neuron is not conducting an impulse
 The K+ concentration is much higher
inside the cell than out
 The Na+ concentration is much higher
outside the cell than in
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2. Depolarization
A nerve cell is stimulated
 Membrane becomes permeable to Na+ for
an instant and they quickly move into the
cell
 The inner surface of the cell membrane is
now more positively charged then the
outside.
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3. Repolarization
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When the cell membrane becomes
depolarized, K+ automatically leaves the
cell until the cell is back to its resting state.
4. The Impulse Travels
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“Wave” of depolarization – transmission of an
impulse along length of axon
All or None Principle – must reach a threshold
level or the impulse dies
Covered by a white covering called a myelin
sheath (Schwann Cells), an insulator
Myelin sheath causes the ion exchange to occur
only at the nodes which speeds up the process
For a short time after depolarization; the neuron
cannot be stimulated
5. Transmission Across a Synapse
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Neurons do not actually touch. This gap
between the two cells is call a SYNAPSE
Impulses are carried across a synapse by
chemical messengers called
neurotransmitters.
Approximately 30 different neurotransmitters;
do one of two things:
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Stimulate the action potential in a second cell
Inhibit the action potential in the next cell
6. Refractory Period
The period of time it takes a neuron to
return to its resting potential after being
stimulated
 A neuron cannot be stimulated during this
period
 This period of time is about 0.0004 of a
second
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Elaboration
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Neurotransmission:
Nifty Neurons and Muscle Messages
Evaluation
Parts of Nervous System
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List the Four Major Parts of the
Nervous System
Neurons
Nerves
Brain
Spinal Cord