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Physiology III > Lecture 17: Cortical Electrical Recordings > Flashcards

Lecture 17: Cortical Electrical Recordings Flashcards

1
Q

What is idiopathic epilepsy

A

Seizures as a result of an unknown cause

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2
Q

What is primary epilepsy

A

Genetic

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3
Q

What is symptomatic epilepsy

A

Known, underlying cause: developmental, degenerative, inflammatory, infectious, neoplastic, and traumatic

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4
Q

What is reactive epilepsy

A

Metabolic, nutritional or toxic cause

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5
Q

What is reflex epilepsy

A

Sensory stimuli triggers an episode

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6
Q

What is a seizure

A

Physical findings and/or changes in behavior that result from abnormal electrical activity in the brain. May include motor, sensory, autonomic or psychic effects

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7
Q

What is epilepsy

A

Abnormal activity in the cerebral cortex that results in a seizure. A epileptic seizure is a clinical sign of an abnormal forebrain disorder

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8
Q

What is status epilepticus

A

A seizure that lasts for 5 minutes or longer or multiple seizures within a 5 minute period

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9
Q

What are cluster seizures

A

Increased frequency of seizures within a few days or 2 seizures within 24 hours

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10
Q

What are the three phases of a seizure

A
  1. Pro-dromal
  2. Citrus
  3. Post-ictal
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11
Q

What is the prodromal phase

A

Pre-octal period, abnormal behavior that may occur hours before ictus

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12
Q

What is ictus

A

Seizure lasting 1-2 minutes, characterized by the loss of consciousness and alteration of muscle tone, repetitive movements

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13
Q

What is “aura”

A

Onset of ictus

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14
Q

What is the post-octal period

A

Return to normal or altered behavior, recovery period

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15
Q

What do EEG’s measure

A

Collective electrical activity neurons in the cortex

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16
Q

What layer of the cortex is made of glia cells and dendrites of neurons in lower layers

A

Layer 1

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17
Q

What layers of the cortex contain Stellate cells that receive afferents from brainstem; pyramidal cells send axons to other parts of the cortex

A

Layers 2-6

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18
Q

What layer receives thalamic inputs

A

Layer 4

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19
Q

What layer is the motor efferent neurons to the spinal cord

A

Layer 5

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20
Q

What layer of the cortex has projections to basal ganglia and thalamus

A

Layer 6

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21
Q

What are the major cell types in the cortex

A
  1. Pyramidal neurons- Long distance excitatory
  2. Stellate neurons- local excitatory and inhibitory
  3. Glial cells
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22
Q

What are focal seizures

A

Partial, originates in a localized portion of the cortex=seizure focus

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23
Q

What is a generalized seizure

A

Involves both hemispheres of the brain, originates in the thalamus with abnormal activity in thalamocortical circuit

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24
Q

What is a secondary generalized seizure

A

When a focal seizure starts locally and spread to the rest of the cortex, creating a generalized seizure

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25
What what two ion channels are responsible for inhibitory or excitatory activity
1. Voltage gated channels 2. Ligand gated channels
26
GABA binding Cl- causes ___
Hyperpolarization
27
Glutamate binding AMPA and NMDA causes
Depolarization
28
What is the resting state of Na+ channels
Channel is closed
29
What is the active state of Na+ channels
Channel is briefly open
30
What is the inactive state of Na+ channels
Channel is closed again and not sensitive to membrane depolarization
31
Describe a normal action potential
1. Na+ channels open causing depolarization 2. Ca2+ open if present 3. Potassium channels open causing them to repolarize
32
What is epilepsy channelopathies
Mutations to these channels results in enhanced excitatbility or loss of inhibition
33
___depolarization is a characteristic of a seizure
Paroxysmal
34
What is a paroxysmal depolarization shift
Sudden, large (50-200mV), long (50-200msec) depolarization Triggers a train of action potentials
35
What is the depolarization phase of the PDS
Ca2+ and glutamate channel activation Initial depolarization mediated by AMPA receptors, sustained by NMDA
36
What receptors cause the initial depolarization during the PDS
AMPA
37
What receptors cause the sustained depolarization in PDS
NMDA
38
What is the hyperpolarization phase during the PDS
Termination of the PDS the cell hyperpolarizes because Cl- and K+ flux via GAVA receptors, causing a prolonged period of hyerpolarization
39
When do PDSs remain localized
In a healthy nervous system where there are less than 1000 neurons involved
40
What happens when there are more than 1000 neurons involved in PDSs
Activity spreads across the cortex, recurrent axons of affected cells activity inhibitory interneurons, increased inhibition dampens spread of seizure to neighboring cells
41
___inhibition contains seizure focus by limiting PDSs
Surround
42
When surround inhibition breaks down the ___spreads
Seizure
43
Seizure spread can occur in what 2 scenarios
1. Neurons die- loss of inhibitory neurons may occur because of head injury, clot or scarring tumor 2. Channelopathies- disorders in ion channels, causing increase Na+ and Ca2+ and decrease K+
44
What ions increase when a a seizure occurs due to channelopathies
Na+ and Ca2+
45
What ions decrease when a seizure occurs due to channelopathies
K+
46
what is indicated by #1
Paroxysmal depolarization shift
47
A positive voltage change will cause a ___deflection in the EEG
Downward
48
A negative voltage change will cause an ___deflection in the EEG
Upward
49
When are EEG’s useful
1. Identifying and classifying epilepsies 2. Localizing lesions in the cortex 3. Sleep studies 4. Legal determination of brain death
50
What do the alpha waves show in an awake EEG
Regular, high amplitude, sweeping pattern
51
What do beta waves show in an awake EEG
Irregular and have lower amplitude
52
Are alpha or beta waves activated when eyes are closed
Alpha
53
Are alpha or beta waves activated when eyes are open
Beta
54
What waves are indicated by 1-3
1. Alpha 2. Beta 3. Alpha
55
What do delta waves characterize in a sleeping EEG
Characterize slow wave sleep
56
What does paradoxical sleep (aka REM) look like during sleeping EEG
Characterized by low amplitude, irregular EEG
57
What waves are indicated by 1-2
1. Delta 2. REM
58
___are bursts of activity from the thalamus to the cortex
Sleep spindles
59
___ are extensive activities in the primary sensory cortices
K complexes
60
Identify the waves 1-7
1. Awake- beta waves 2. Drowsy, relaxed- alpha waves 3. Stage 1 sleep- theta waves 4. Sleep spindle 5. K complex 6. Stage 3/4 sleep- delta activity 7. REM sleep
61
Is the following EEG representative of a partial or generalized seizure
Partial seizure
62
Is the following EEG indicative of a partial or generalized seizure
Generalized seizure
63
How do flashing lights induce seizures
Photosensitive epilepsy brain responds to excessively to certain visual stimuli, triggering seizures. Flashes of light at 20Hz are most likely to induce seizures

Physiology III (34 decks)

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