CSB332H1 Study Guide - Winter 2018, Comprehensive Midterm Notes - Neuron, Wireless Access Point, Protein
12 Oct 2018
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CSB332H1
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Lecture 1(b): Synapse Overview
Complicated Stress Response…
• Basal release of glucocorticoids varies in a diurnal pattern
o High release during the day | low release while asleep
• Adrenal steroids can have multiple effects because of complexities in signaling
o Direct/in-direct genomic effects | non-genomic effects
Cumulative Effects of Stress:
a) Acutely (hours):
o Low to moderate physiological levels of adrenal steroids enhance synaptic function
and certain types of memory
b) Chronically (days-weeks):
o High levels of corticosterone mediate adaptive plasticity involving:
§ Spine synapse turnover, dendritic shrinkage
o Adult brains are continuously producing new neurons at the level of the dentate gyrus
§ With chronic stress, levels of neurogenesis decrease dramatically
o An individual with chronic stress is more vulnerable if they experience a sudden insult
(seizure, stroke, head trauma); such as irreversible hippocampal damage
Electrical Signaling:
• Neurons encode information by the flow of ions into and out of neurons which is a form of
electrical signaling
o Flow of ions (carrying a charge) that cause on/off signals on neurons
ð Ions are separated by the cell membrane:
o Ions are only capable of passing the cell membrane when ion channels are opened
§ Passage of ions generate an electrical signal or electron current that can be
recorded using electrophysiology
Phospholipid Bilayer:
• Phospholipid bilayer is not homogenous and is impermeable
to ions
o Regions of the bilayer (yellow) is enriched for
specific lipids, proteins and cholesterol than
anywhere else known as lipid rafts
§ Lipid rafts have multiple functions:
• Cluster signaling molecules in 1 place
• Specific molecules only found in
those regions (i.e. Flotillin, Caveolin)
ð Enrichment of: cholesterol, flotillin, caveolin
(caveolin are explicitly found in caveoli pits)
find more resources at oneclass.com
find more resources at oneclass.com
Methyl-Beta-Cyclodextran (MBCD):
• MBCD applied to a living neuron in culture will infiltrate into the plasma membrane removing
the lipid rafts
o Lipid rafts play an incredible role in the differentiation of neurons and
neurodegeneration
Components in a Lipid Raft:
• Enrichment of: cholesterol, GPCR, flotillin, caveolin
o Adding MBCD will negatively affect the
function of GPCR
Neurodegenerative Theory:
• Amyloid precursor protein (APP) is another molecule found to be enriched in lipid rafts
o Hallmark feature of Alzheimer’s disease is the toxic molecule amyloid beta (A
b
)
ð APP is assumed to help in synaptic functioning and other purposes however it has the capacity
to generate the toxic protein, amyloid beta
o Beta amyloid converting enzyme (BACE1)
functions to convert APP into A
b
• A
b
will accumulate to form clumps in the lipid rafts
and interact with neuronal GPCR to negatively
affect synaptic and receptor function
Why Do We Need Lipid Rafts?
• Physiological reason - consists of GPCR
Resting Membrane Potential (Vm):
• Phospholipid bilayer is impermeable to ions
o Ions can only cross the membrane:
§ Passively through channels
§ Actively through pumps
• Separation of ions across a cell membrane = cell has a resting membrane potential (Vm)
o Neurons have a negative Vm (-30 to -100mV)
§ Inside of the cell is more negative than the outside
• Electrical signals are generated by changes in the Vm
o Depolarization => making the inside of the cell less negative
§ transport negative ions outside | transport positive ions inside
o Hyperpolarization => making the inside of the cell more negative
§ transport negative ions inside | transport positive ions outside
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Cumulative effects of stress: acutely (hours), low to moderate physiological levels of adrenal steroids enhance synaptic function and certain types of memory, chronically (days-weeks), high levels of corticosterone mediate adaptive plasticity involving: Spine synapse turnover, dendritic shrinkage: adult brains are continuously producing new neurons at the level of the dentate gyrus. With chronic stress, levels of neurogenesis decrease dramatically: an individual with chronic stress is more vulnerable if they experience a sudden insult (seizure, stroke, head trauma); such as irreversible hippocampal damage. Electrical signaling: neurons encode information by the flow of ions into and out of neurons which is a form of electrical signaling, flow of ions (carrying a charge) that cause on/off signals on neurons. Ions are separated by the cell membrane: ions are only capable of passing the cell membrane when ion channels are opened. Passage of ions generate an electrical signal or electron current that can be recorded using electrophysiology.
