Download Inhibitory postsynaptic potential

Figure 2.6 Synapses (Part 1)
Postsynaptic potentials
• Postsynaptic potentials are brief changes in the
resting potential at a synapse
– Excitatory postsynaptic potential (EPSP) – produces a
small local depolarization, pushing the cell closer to
threshold
– Inhibitory postsynaptic potential (IPSP) – produces a
small hyperpolarization, pushing the cell further away from
threshold
• EPSP can result from sodium ions (Na+) entering
the cell, making the inside more negative.
• IPSP can result from chloride ions (Cl-) entering
the cell, making the inside more negative.
Fig 3.9 Recording Postsynaptic Potentials
Figure 3.10 Integration of Excitatory and Inhibitory Inputs
Spatial and Temporal summation
• Spatial summation
– summing of Postsynaptic potentials arriving at different
parts of the cell.
• Temporal summation
– summing of Postsynaptic potentials that arrive at
different times
• The integration of EPSPs and IPSPs
– at the axon hillock
– Determines if an action potential will occur
Figure 3.11 Spatial Versus Temporal Summation (Part 2)
A segment of pyramidal cell dendrite from stratum radiatum
(CA1) with thin, stubby, and mushroom-shaped spines from
rat hippocampus. Found at Synapse Web
http://synapses.clm.utexas.edu/anatomy/compare/compare.st
m
The Brain: The Connections May Be the Key
Discover Magazine By Carl Zimmer,| Tuesday, March 20,
2012
http://discovermagazine.com/2012/apr/07-brain-connectionsmay-be-key/
3-D reconstruction of part of three neurons, generated from a stack of images of the mouse cortex.
R. Schalek, B. Kasthuri, K. Hayworth, J. Tapia, J. Lichtman/Harvard and D. Berger, S. Seung/MIT
Spatial and Temporal Summation
• You Tube video animations
– Neuron Synapse: EPSP and IPSP
– Neural Communication: EPSP and IPSP
EM of synapses on cell body
Figure 2.3 Variety in the
Form of Nerve Cells
Figure 2.15 Layers of the Cerebral Cortex
Gross Electrical Activity of the Human Brain
• An electroencephalogram (EEG) is a recording of
brain potentials, or brain waves.
– patterns of activity from large areas of the brain
• measure electrical activity from more than 100,000 neurons
• Used in both clinical and experimental settings
– study sleep states
– processing in auditory circuit “event-related potentials”
(ERP)
– seizure disorders
Fig 3.16a EEG recording
Epilepsy
• Characterized by a synchronization of electrical activity
during seizure as described as epileptiform
– Grand mal – (Tonic-clonic)
• abnormal activity throughout the brain
• movements are tonic and clonic contractions
• Seizure is followed by confusion and sleep.
– Petit mal seizure – (Absence)
• seizure activity for 5 to 15 seconds
• No unusual muscle activity
• Events during seizure are not remembered.
– Complex partial seizures
• do not involve entire brain
• Wide variety of symptoms
• Aura – unusual sensation that may precede a seizure
• Causes of Epilepsy
– Head injury from trauma, stroke, tumors or infection
– Developmental: anatomical, channelopathy
– Abnormal levels of ions “Na” or blood glucose
Figure 3.20 Discharge Patterns during Seizures
Basic mechanisms of epilepsy
• Mechanisms in chronically epileptic tissue
– Increased synaptic connectivity
• mossy fiber sprouting
– Channelopathies (see Box 3.1)
• potassium channels are weakened
• sodium channels are more persistent
• weak GABA receptor activation
– alterations in expression of receptors
Event-related potentials (ERPs)
Large potential shifts caused by discrete stimuli.
flash of light or clicking sound
Auditory-evoked brainstem potentials are
generated in the brainstem, far from the
recording site and can be used to detect
hearing impairment.
Figure 3.21 Event-Related
Potentials
Emotional Processing, P50 Sensory Gating,
and Social Functioning in Bipolar Disorder
• Sensory gating
– Is filtering out redundant or unnecessary stimuli
– is modified by emotional processing
– Can be measured with event-related potentials using the paired-click
paradigm
• Individuals with bipolar disorder
– emotional processing can be either to high or to low
• Test emotional processing effects on sensory gating
– in individuals with bipolar disorder
– Present either a disgusting facial expression or a neutral faces
• Bipolar Disorder causes impaired filtering of auditory
information when paired with an emotionally salient image
“disgusting facial expression”