3.1 lecture

Chapter 3.1
The Neuron

Wednesday, September 12, 12 1

Biological Psychology and Neuroscience
-concerned with the links between biology and
behavior


Agenda

 3.1: The Neuron
– Neurons
– Action potentials
– Synaptic communication
 3.2: The Brain
 3.3: Methods of Brain Research
 3.4: Nervous System and Endocrine
System


Phrenology ≠ Neuroscience
 Franz Gall
 Germany
 Early 1800’s
 bumps =
mental
abilities
 37 traits



 Systems: A group of interacting, interrelated, or
interdependent elements forming a complex whole.

 Biological, Psychological, Social

 What is the smallest level of analysis?

 What is the smallest level of analysis?

 Biological.

 We will examine how at this level “we” take in

Glial cells
 Help neurons
function properly
– Dispose waste
– Create myelin
– Help neurons
communicate

 “Mommy cells”


Neuron = Nerve Cell
-receives, processes, and
transmits information

Nodes of Ranvier


Form follows function.

 Get into a 4 groups. Make a cafeteria
line.
 Create a system of communication
within the group that does not use
sound or vision to convey a number.
– Touching is OK.
 Create a system of communication
between groups using these.
 One catch: You cannot cross the gap.
 The goal:
 We’re going to play silent telephone
islands.
 I’m going to give a number to a
group and see if we can get that
number to the last student in line.


How do these nerve cells
exchange information?
 Electrochemically.
– Between neurons, a signal travels chemically.
– Within the neuron, a signal travels
“electrically.”
 There is no “beginning” but we will start
with this question.
 Where do neurons get the energy to
communicate?


 Let’s start at the “beginning” with
resting potential.


 Resting potential:

Fragrance in a balloon demonstration to represent the building of resting potential by the Na-K pumps.

 Resting potential:
– Generated by Sodium-Potassium pumps on neuron
membrane.
– Ratio of
2 Positively charged K+ atoms inside
 3 Positively charged Na+ atoms outside

– Outside the neuron, it is positively charged
– Inside the neuron, it is negatively charged (-70
mV)
 In other words,
 the neuron is polarized.


After resting potential

Depolarization --> Threshold (sometimes)


Threshold analogy
 The cell body and axon hillock are like
a water gun, clown’s mouth, and a
balloon.
 In other words, it’s an adding machine.
 Only when there is enough
depolarization (Na+ ions) in the cell
body and thus axon hillock, do we
reach threshold.


After Threshold

 We reach the “touching in our
islands”
 The action potential.


Action Potential parts

Nodes of Ranvier


Form follows function.

 Action potential:
– Positive Na atoms rush in and trigger a domino
effect down the axon. The region inside becomes
slightly positively charged.
 Inother words, the cell becomes
depolarized.
 And guess what? It’s like dominoes.
Once it starts, it can’t be stopped.
– This is called the all-or-none principle.


Don’t forget the
Nodes of Ranvier


After the action potential
Refractory period:
– A period of time when
the neuron must
become polarized again
– In other words…
– The Na-K pumps make
Na+ ions go back
outside the neuron to
re-establish resting
potential.

*1000 times/second

Next slide is about the chemical communication Prefeace by bringing back idea of electrochemical communication.

Remember: communication is
electroCHEMICAL.
• Neurons are NOT physically joined together.
• Therefore how do they pass a signal across a
physical space known as a synapse?


 The word "synapse" comes from Greek: "syn" meaning "together"
and "haptein" meaning "to clasp."

“You are your synapses.”
-Joseph Le Doux


Neurotransmitters (NT)
– Exocytosis triggered by action potential
– Released from the axon terminal buds.
– NT’s cross synapse via diffusion.
– Connect to correct receptor-channels on
dendrites of next neuron.
– Unlock channels at the receiving site allowing
Na+ ions into the receiving neuron.


Which brings us to...

 Depolarization --> Threshold


Two Categories of Neurotransmitters (NT)

Excitatory: allow ____________into the neuron to
depolarize the cell.
 ACh (acetylcholine): excitatory NT

Inhibitory: allow __________ into the neuron to prevent
ﬁring
 GABA: inhibitory NT – keeps brain calmed down and not ﬁring out of
control


NT’s are
“expensive” to make.
So neurons recycle,
i.e. REUPTAKE.


DRUGS
 Every chemical that affects behavior works at
the synapse
 They act like…
 Neurotransmitters (NT’s)
– Agonist: drug that mimics an NT’s effects.
 They are similar enough the NT to open receptor channel.
 They can block the reuptake of the NT in the synapse.
– Antagonist:
 They can block receptor site.


Agonist or Antagonist?

 Curare:
– Stops ACh from ﬁtting into receptor sites (used by
natives on poison darts)
 Botox aka Botulin
– Blocks the release of Ach from the sending neurons
(paralysis)
 Black Widow venom:
– Is similar to Ach and activates receptor sites
(seizures and convulsions)
!



 Dopamine (NT):
 Excessive levels in the brain associated
with schizophrenia
 Low levels associated with Parkinson’s

– Thorazine used for Schizophrenia
 Because it _____ dopamine
– L-Dopa used for Parkinsons
– Because it _______ dopamine



 Endorphins: natural pain killing NT
– Toughens the membrane of
neurotransmitter sacs preventing them
from breaking
 Pain signal is stopped

 Morphine, Heroin, and other opiates


Seratonin (NT)

– Low levels associated with depression
– Administer Prozac – prevents reuptake
 It is a _____________.


With so many NTs, are some found only
in certain places?

How do they affect mood, memories,
and mental abilities?

Can we boost or diminish these effects
through drugs or diet?


Certain pathway uses 1 or 2 NT’s and
that NT has a particular effect on a
behavior and emotion.


If you can teach it, you know it.

Go to Catlink and ﬁnd our homework
assignment under Day 2 this week: “Explaining
the Neuron.”


3.1 lecture

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