Download Part 2 - glenbrook s hs

• Cell body – nucleus and other organelles
• Dendrites – branched, short and receive
incoming messages from other cells or the
environment
• Axon – long, single fiber, conducts signal
toward another neuron or effector
• Supporting cells – protect, insulate and
reinforce neurons
• Myelin sheath – chain
of beadlike supporting
cells
• Nodes of Ranvier –
spaces in myelin, only
points where the impulse
can be transmitted
– Signals can travel
>150 m/sec (330
mi/hr)
• Synaptic knob – relays
signals to another neuron
or effector
Motor Neuron
• Resting Potential –
voltage (potential
difference) across the
plasma membrane of a
resting neuron
– Negative charge inside,
positive charge outside
• Stimulus – anything that
causes a nerve signal to
start
• Action potential – selfpropagating change in the
voltage across the plasma
membrane
How an impulse move
through a neuron
1. Resting potential – negative on
inside / positive on the outside
2. Stimulus allows a few positive
ions to enter neuron.
•
•
3.
4.
If strong enough stimulus then
action potential
Threshold potential – minimum
change in membrane’s voltage to
reach action potential
Inside becomes positive and
outside becomes negative
Membrane returns to resting
potential by allowing positive
ions to diffuse back outside
neuron
•
The action potential must be
propagated (travel along the neuron)
Propagation
• Starts near the cell body and moves
toward the axon terminals
1. In the 1st section of the neuron positive
ions diffuse inward to generate an
action potential
2. The 1st section allows positive
ions to diffuse out of the
neuron and prevents more
positive ions from entering
3. 1st section then returns to
resting potential