Transcript Neurons - DocuShare

Neurons
AP Psych p.51-58
Question?
 Repeat the definition of psychology.
 The science of behavior and mental processes.
 What mental process is done without the brain or the
nervous system?
 Our brain is like a computer and how it is binary, meaning it
is either on or off. Neurons are the same way.
Neurons
 Neurons = Nerve Cells.
 Sensory Neurons carry messages from the bodies sensory
organs and tissues inward to the brain and spinal cord.
 Inbound
 Motor Neurons carry outgoing messages from the brain and
spinal cord to the muscles and glands.
 Outbound
 Interneuron's are neurons that process information in the brain.
Parts of the Neuron: Dendrite
 Dendrite
 Branching extensions of a neuron that receive messages. (Then
sends it to the cell body, which is the cell’s life support center)
Dendrite
Cell Body or
Soma
Parts of the Neuron: Axon
 Axon
 The extension of the Neuron that passes messages to other
neurons, muscles, or glands.
 May be short or long and if axons are longer it takes more time
for the brain to send a signal (Circle example)
Dendrite
Axon
Cell Body or Soma
Parts of the Neuron: Myelin Sheath
 Myelin Sheath
 A layer of fatty tissue that may encase some axons of neurons (not all)
 Helps to speed up neural transmissions (up to 200 miles an hour)
 If I am driving across Nebraska do I want to go fast?
 If I am driving across Rhode Island do I want to go fast?
 Myelin continues to develop up to about age 25. (correlations with
judgements and self control)
Dendrite
Axon
Cell Body or Soma
Myelin Sheath
Parts of the Neuron: Terminal
Branches
 Terminal Branches
 Branch like connections at the end of the axon that forms
connections with other cells.
 Passes the message to other neurons or cells.
Dendrite
Terminal Branches
Axon
Cell Body/ Soma
Myelin Sheath
Resting Potential
 Resting Potential is the axon's electrical state during the
period between action potentials. The fluid inside the axon
membrane is electrically negative compared to the fluid
outside the axon.
 Like a phone its charged and ready to go 
 Here the axon is selectively permeable because it is not letting
the positive ions into the axon.
Action Potential
 A brief electrical charge that travels down an axon.
 Triggered by a chemical reaction. Positive ions are rushing into
the negatively charged axon and moving down the axon toward
the terminal branches. We call this depolarization.
Refractory Period (Recovery Time)
 The time after the action potential (depolarization) when the
axon is sending the positively charged ions back outside of
the axon.
 An action potential can not fire again until the refractory
period is over and the axon is back at the resting potential.
Neuron Signals and Absolute Threshold
 Neurons can receive two types of signals.
 Excitatory Signals tell the neuron to go
 Inhibitory Signals tell the neuron to stop
 If the excitatory signals minus the inhibitory signals exceeds a
minimum intensity or THRESHOLD, then the combined
signals trigger an action potential.
 Threshold = the level of stimulation required to trigger a neural
impulse.
 ALL OR NOTHING RESPONSE
 It either fires or it does not fire…like a gun.
Squid Video
 http://news.discovery.com/animals/videos/animals-
dancing-zombie-squid-explained.htm
 This Discovery online uses two different YouTube hits to
explain why post-mortem activity can still occur in a dead
organism. Creepy, fascinating, ethical, unethical and more.
 What do you think?
 How does this relate to neurons?
How do Neurons Communicate?
 Synapse
 The meeting point between the terminal branches of one
neuron and the dendrite or cell body of another neuron.
 They do not touch each other there is a tiny gap called the
synaptic gap.
Neurotransmitters!
 When the action potential reaches the terminal branches, it
triggers the release of chemicals called neurotransmitters
into the synapse.
 These neurotransmitters then cross the synaptic gap binds to
the dendrite of the new neuron at receptor sites.
 If there are any neurotransmitters left in the synaptic gap the
neuron that sent them will reabsorbed them back into the
neuron.
 Lets look at the diagram on the next page
Drugs and Neurotransmitters
 Drugs and other chemicals can boost or block
neurotransmitters.
 We call the boosting drugs or chemicals agonist
 We call the blocking drugs or chemicals antagonist
Neurotransmitters and what they
do to us!
 Endorphins
 Pain control and pleasure
 Runners High
 Morphine - Agonist
Neurotransmitters and what they
do
to
us!
 Acetylcholine (Ach)
 Enabled muscle action (makes our muscles
contract) and has something to do with
learning and memory.
 Ach the the neurotransmitter found at every
synapse between a motor neuron and a
muscle.
 Curare (drug) - on the tip of a blow
dart causes paralysis
 An Antagonist because it blocks the Ach
 Black Widow spider venom – produces
convulsions
 An agonist because it boosts ach
Neurotransmitters and what they
 Dopamine
do to us!
 Does a lot – pleasure and addiction or
mood…cravings
 When present in very high levels it is
associated with schizophrenia
 Low amounts of dopamine in other areas
of the brain is associated with Parkinson’s
Neurotransmitters and what they
do to us!
 Serotonin
 Mood, hunger, sleep, and arousal
 Depression is correlated with low serotonin
 Prozac –Agonist (boost serotonin)
 SSRI (Selective serotonin reuptake inhibitor) - a
shield that blocks the reuptake of serotonin
 takes 6–8 weeks for the drug to begin reaching its full potential
Neurotransmitters and what they
do to us!
 GABA
 Always Inhibitory – primary NT for keeping your brain
under control, usually associated with anxiety
 Undersupply linked to seizures.
 Alcohol – agonist
Neurotransmitters and what they
do to us!
 Glutamate
 Excitatory NT
 Can cause overstimulation of the brain, producing migraines
or seizures.
 Alcohol – antagonist
Mouse Party
 http://learn.genetics.utah.edu/content/addiction/drugs/m
ouse.html