Download Understanding-the.. - Windsor C

Understanding the Neuron
2 Internal Messaging Systems
1. Nervous System- fast
acting- messages travel
through neurons (nerve cells)
2. Endocrine System- slower
acting- messages travel
through hormones
3 Types of Neurons
1. Sensory- afferent- receives
messages from sense organs
2. Motor- efferent- sends
messages to other parts of
the body
3. Inter- communicates between
sensory and motor neurons
How Neurons Work
• Dendrites receive messages
• Pass info to SOMA; prioritizes
messages to send to AXON
How a neural message is “Fired”
• Resting potential: resting axon has a – charge
• Action potential: when excited, pores open
and + ions flow through axon “firing” an
electrical pathway to the terminal button
– Increase in + ions is called depolarization
– the # of ions necessary for “firing” is called
the threshold
• Once the process starts, it cannot stop: All-ornone principle.
• After neuron has “fired” there is a period of time
where it cannot “fire” again. This is called the
refractory period.
Synaptic Transmission
• The end of the axon = terminal button
• When electric pulse reaches TB, it converts to a
chemical message which can cross the synapse =
(space between neurons)
– This is called a synaptic transmission
Neurotransmitters
• Chemicals that
can take a
message across
the synaptic gap
• Until electric
pulses to terminal
button, NTs are
“stored” in a sac
held in the TB
called a synaptic
vesicle
• Like a lock and key,
specific
neurotransmitters are
designed to “fit” specific
receptors.
• NTs are broken down
and recycled to be
reused
• Through reuptake,
recycled NTs are sucked
back into synaptic
vesicles, resulting in a
more muted message
***Memorize table 3.1 on
page 76***
Plasticity
• Refers to neural ability to change,
create new and strengthen
existing connections
–Means recovery is possible
when brain is damaged
• Especially effective in children
Glial Cells
• Support neurons by holding
them together and providing
structural support
• Form myelin sheath (fatty
insulation) around axonsimportant b/c it protects the
neurons while electrically
charged!