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Lecture 4

EXSC 224 Lecture Notes - Lecture 4: Axon Hillock, Muscarine, Endorphins

5 pages50 viewsFall 2016

Department
Exercise Science
Course Code
EXSC 224
Professor
Thompson
Lecture
4

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Postsynaptic Potentials
Graded potentials
Strength determined by:
Amount of neurotransmitter released
Time the neurotransmitter is in the area
Types of postsynaptic potentials (graded potentials)
1. EPSP - excitatory postsynaptic potentials
Depolarizing stimulus - membrane potential rises toward 0
2. IPSP - inhibitory postsynaptic potentials
Opposite - hyperpolarization
Reduce in membrane potential
EPSPs - Excitatory
ALWAYS depolarizing, goes toward 0
Kind of signal that leads to action potential if large enough
Neurotransmitter binds to and opens chemically gated channels that allow simultaneous
flow of Na and K+ in opposite directions
Na+ influx is greater than than K+ efflux, causing a net depolarization
EPSP helps trigger AP at axon hillock if EPSP is of threshold strength and opens the
voltage-gated channels
IPSPs - Inhibitory
ALWAYS hyperpolarizing, makes it more negative
Make it more difficult to excite a neuron
Neurotransmitter binds to and opens channels for K+ or Cl-
Causes a hyperpolarization (the inner surface of membrane becomes more negative)
Reduces the postsynaptic neuron’s ability to produce an action potential
ADD and ADHD - associated with inactive regions of the brain
This region of the brain inhibits other regions of the brain, making it difficult to
focus
Stimulant (riddalin) excites this region of the brain
Integration: summation
A - no summation
Nothing happens
If the stimuli are not adequately close together, in time, there is NO SUMMATION
Summation means EFFECT
B - temporal summation
Presynaptic neuron fires twice, close in time
1st signal has depolarization but doesnt quite reach threshold
Since next stimuli happens quick enough, it reaches threshold and causes an
action potential
2 events have an additive effect and cause a summation
2nd stimulus is usually the same as the first
Temporal = time
C - spatial summation
Two different excitatory potential
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If both fire approximately at the same time, we will have a summation - a larger
change in MP than if either one fired indepenantly
Two different neurons each firing at the same time
D - spatial summation, 1 EPSP and 1 IPSP
If both fire at the same time, the net result is 0
Additive - requires at least 2 neurons
No summation - can be just 1 neuron
Neurotransmitters and neuromodulators
Look at ppt
Almost all signaling molecules bind to a receptor
Few exceptions can bypass the receptor - dont need to know them
**KNOW THESE**
1. Acetylcholine (Ach)
Most abundant
Nervous system - skeletal muscle
Binds to 2 different kinds of receptors - nicotinic (excitatory) & muscarinic
(excitatory OR inhibitory)
Nicotine & Muscarine
Secreted by presynaptic neuron
Excitatory or inhibitory
Receptor on post synaptic neuron determines if the signal is excitatory or
inhibitory
Don’t worry about ‘sites where secreted’ or ‘comments”
2. Biogenic Amines - Just look at table 11.3…
All are derivatives of the amino acid Tyrosine
Low levels of norepinephrine, dopamine, and serotonin in the brain are
associated with depression
Dopamine - pleasure the ‘feel good neurotransmitter’
● Orgasm
Serotonin - most associated with depression
Histamine - not as important, don’t look at it
3. Amino acids
Some amino acids serve as neurotransmitters
^^ that’s all you need to know on the exam
Don’t need to know these specifics
4. Peptides
Endorphins block pain
● Opioid
ONLY need to know about endorphins and maybe a little CCK
■ CCK
Released by the gut
Involved in regulating appetite (satiety factor)
5. Purines
■ ATP
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