1
Q
can we study electrical activity of a single neuron?
A
No
instead the brain waves reflect the synchronized electrical activity of millions of neurons occurring simultaneously
2
Q
what can cause abnormal neural activity?
A
Reduced inhibition
Increased excitation
Ion imbalances/abnormalities in ion channels
3
Q
what is the primary excitatory neurotransmitter?
A
Glutamate
released by excitatory neurons
4
Q
what is the primary inhibitory neurotransmitter?
A
GABA
Released by inhibitory neuron activity
5
Q
what controls the balance in neural activity?
A
Glutamate – excite
GABA — inhibit
Efficiency of ion channels
Intact electrical impulses
6
Q
what are brain waves?
A
Synchronized electrical pulses from masses of neurons communicating with each others
7
Q
what are the important factors we focus on in brain waves?
A
Amplitude ( 0-200 microvolts )
Frequency ( 1-50 hertz )
Degree of activity
8
Q
which factor we focus on the most?
A
Frequency –> number of waves per second
We use it to describe brain waves as it is more consistent than amplitude
its reliable
9
Q
what does the amplitude mean?
A
it reflects the number of neurons synchronized given a moment ( Firing )
10
Q
what does amplitude depend on?
A
mental activity
more activity recruits more neurons- increasing amplitude
that why it varies a lot and its not consistent – because its influenced by mental state
11
Q
what does degree of activity depend on?
A
recording site and mental states of consciousness/wakefulness/sleepiness/performing tasks
12
Q
what is the crest of a wave?
A
the peak of a wave
13
Q
what is the distance between two waves in a grapH?
A
Frequency
14
Q
what is the through on the graph?
A
lowest point of a wave
15
Q
what are the waves of the brain?
A
Alpha
Beta
Gamma
Theta
Delta
16
Q
what is the fastest type of waves?
A
GAMMA
17
Q
what is the wave with the highest frequency?
A
Gamma
More than 30 Hz ( 30-90 can be below 30 )
its above the frequency of average neuronal firing and its generation is mystery
18
Q
what does gamma wave represent ?
A
Simultaneous processes from different brain areas
19
Q
what is gamma wave associated with in the brain activity?
A
Formation of novel ideas, various types of learning , etc
Modulates perception and consciousness
20
Q
what does greater presence of gamma waves mean?
A
Expanded consciousness
21
Q
what is the frequency of Beta waves?
A
more than 13-30 ( 12 and above ) — less than 20 microvolts
High and irregular frequency
22
Q
what does the Beta wave represent ?
A
Fast and alert activity
Dominates during day time activities
Cognitive tasks ( Problem solving, decision making etc )
23
Q
Where is Beta wave recorded?
A
Parietal and frontal regions during specific activation
Cuz pre frontal
24
Q
what are the subdivisions of Beta wave?
A
Beta 1
Beta 2
Beta 3–> Highly frequency processing – > Tremendous amount of energy
25
what is the frequency of alpha waves?
> 8-13 Hz ( 8 to 12 Hz ) -- more than 30-50 microvolts
26
when is alpha waves seen?
Awake but still relaxed -- EYES CLOSED
Quiet flowing of the thoughts
27
where does alpha waves originate from?
Most intensely ----> Occipital region
But also seen in -- Parietal and frontal of scalp
28
when does the alpha waves disappear?
Deep sleep
29
what is the origin of alpha waves?
Connection between cerebral cortex and thalamus
Result from spontaneous feedback oscillation in the DIFFUSE thalamocortical system possibly including the RAS in the brain stem
Stimulation in the nonspecific layers of reticular nuclei that surround the thalamus sets up ELECTRICAL WAVES in the thalamocortical system at frequency of alpha waves ( the RAS involvement )
30
where DOESNT the alpha waves come from?
Any place in the cerebral cortex that doesnt have connections with the thalamus
31
what happens if you transect the fiber tracts from the thalamus?
Elimination of alpha waves
because we said its from THALAMOCORTICAL SYSTEM
32
Which brain waves are usually detected by EEG?
usually from CORICAL POST SYNAPTIC potentials primarily from SUPERIFICAL LAYERS OF CORTEX
Pyramidal cells are multipolar and vertically oriented, allowing their synchronous activity to summate and produce DETECTABLE SIGNALS AT THE SCALP
However alpha waves originate from DEEPER THALAMOCORTICAL CIRCUITS rather than the cortex alone ;--> so if you cut thalamocortical fibers will eliminate Alpha waves and will not be seen in EEG
33
what is the frequency of THETA waves?
4-8 Hz ( around 30 microvolts )
34
when does theta waves appear?
Light sleep and extreme relaxation
Hypotherapy and deep meditation
35
what do Theta waves represent ?
Dreams ( previous experience )
Senses are withdrawn from external environment
36
which regions do the theta waves come from?
Parietal and temporal regions in children
37
what is the frequency of delta waves?
0.5 - 4 hz ( around 100-200 microvolts )
Slow waves -- VERY LOW FREQUENCY ( lowest )
38
when does delta waves come?
Deep sleep when its dominant
39
what is the role of delta waves?
restore/heal/resetting internal parameters
No active dreams and completely unconscious
Physical healing
Plays a role in tissue repair and regeneration
40
from where does delta waves come from?
SUPERIFICIAL CORTICAL LAYERS
independent from lower structures in brain
41
what happens to delta waves if you transect the thalamus fibers?
Nothing
They come from superficial cortical layers
alpha waves they are affected cuz they come from deeper thalamocortical circuits
42
describe the infra-low waves?
Basic cortical activity
Not much known about
Few studies investigated the nature of these waves
Not easily to detect or measure accuractly
less than 0.5 frequency
Slow cortical potentials
Involve basic regulatory and networking function
43
what is EEG?
recording system which reflects the activity of the brain ( BRAIN WAVES )
Recording electrodes attached to specific points on the scalp and connected to EEG machine
Detect monit, filter, amplify waves
DETECT POSTYNAPTIC POTENTIALS FROM SUPERFICIAL CORTEX -- WITH 90% ORIGINATING FROM PYRAMIDAL CELLS
44
what does EEG represent?
voltage that are recorded from electrodes connected to different points in the scalp -- More connects = more coverage
45
where are the electrodes typically placed ?
PAIRED ( Two )
are placed in 19 or more positions
F, frontal, P= Parietal, O = Occipital , C= central , T = temporal
46
why do variation in recordings happen?
because each pair of electrodes samples the neuronal activity in a different regions of the cortex
+
Neuronal structures and Electrophysiology of cortex is complex
47
describe the neuronal structure of the cortex?
Different layers ( 6 layers ) of the cortex
Several millions vertical columns of neuronal cells
Each column having diameter of 30 to 50 micrometers and 1000+ neurons
Bidirectional processing of the neuronal activity facilitated mainly by PYRAMIDAL CELLS
Also there are horizontal communication within each layer
48
what is the most dominant type of cells in neurons of cortex?
Pyramidal cells -- 70-90%
49
what are the characteristics of pyramidal cells?
Apical dendrite
Basal dendritic tree
50
describe the arrangement of pyramidal cells?
Arranged in identical anatomical order
Longitudinal orientation
51
what plexus is found in the pyramidal cells?
Complex and rich in plexus of :
Corticocortical connections ( ipsi and contralateral
Subcortical connections
52
what is the main contributor from pyramidal cells to EEG?
Postsynaptic potentials ( PSPs ) of pyramidal cells
Post synaptic potentials mean graded potential
53
what are the other electrophysiological characteristics of pyramidal cells?
Multi-synaptic connections between pyramidal cells
Variation in the synaptic connections among different layers of the cortex
Mainly produce Excitatory Post synaptic potentials but there are some inhibitory post synaptic potentials as well
54
describe the multipolar structure of pyramidal cells?
Pyramidal cells have long dendrites and axons with many synaptic inputs
These inputs can happen at different levels ( APICAL dendrites, soma, basal dendrites )
55
what happens when one part of the pyramidal cell depolarizes becomes positive inside?
The outside of that region becomes NEGATIVE
Cuz the positive came from outside to inside making outside less positive ( negative)
56
how does electrode record this difference?
Intracellular electrode 1 --> shows depolarization ( more positive )
Extra-cellular electrode 2 --> Shows hyperpolarization ( More negative )
57
what is the difference between distal and proximal recordings?
if you place an electrode further away ( like electrode 3 )
you will see the opposite effects :
EXTRA of the cell --> Positive (depolarization )
Intra --> Negative --> Hyperpolarization
this is due to the current flowing there
58
what is source and sink?
Sink --> Where current enters the cells ( Inward current, usually Na + Influx during excitation )
Source --> Where current exist the cell ( outward current, balancing the sink )
creating a dipole
Sink = inward current --> outside becomes negative ( cuz positive is going in ) = hyperpolarization
Source = outward current --> inside becomes positive ( because + is going out ) = depolarization
59
what is a dipole ?
formed when theres a source at one end and a sink at the another
60
describe the dipoles in pyramidal cells?
Pyramidal cells can have MULTIPLE dipoles at different dendritic levels because of multiple synaptic inputs
this is what the surface electrode picks up not a single cell firing but SUMMATION OF MULTIPLE DIPOLES
61
Why do we use pair of electrodes?
Due to the dipole model -- Different charges ( positive and negative ) separated by distance
Because voltage is always measured by difference between two points + Difference produced by different dipoles across the cortex
62
why does the brain have different charges?
Dipoles created by sink and source
63
What are the types of PSPs?
Excitatory Postsynaptic potentials (EPSP ) - Na
Inhibitory postsynaptic potentials - Cl
64
what does the EPSP cause ?
like inward current ( Sink ) :
Inside is more positive ( current going in )
Outside is more negative ( current going in )
Its like sink cuz Na influx in and its positive ( brining positive inside )
65
what does IPSP cause?
like outward current ( SOURCE ):
Inside is more negative (cuz current going out )
Outside is more positive ( cuz current going out )
Its like source cuz its Cl influx ( chloride is negative so we are bringing negative in )
66
what is the distanced of neuron of for EPSP?
opposite
Inside is negative
Outside is Positive
Opposite to its previous sink current
67
what is distanced end neuron for IPSP?
Opposite to its normal source type
Inside is positive
Outside is negative
68
what is epilepsy?
Brain disorder characterized by PERIODIC AND UNPREDECTIBLE SEIZURES
Abnormal electrical changes in the cortical circuit that are critical for pathogenesis of this disorder
69
what are the several etiologies of epilepsy?
Idiopathic
Head injuries
Brain tumors
Infections
Strong genetic predisposition
70
describe the pathophysiology of epilepsy?
1- Uncontrolled excessive neural activity ( Part of or all the CNS )
2-Seizure threshold is low ( so any minor thing would lead to it )
3- Neuronal hyperexcitiability -
71
what happens in neuronal hyperexcitability ?
1- Increased excitatory system ( Glutamatergic pathways/glutamate receptors e.g AMPA and NMDA )
2- Inhibition of inhibitory system ( GABAergic pathways/GABA receptors A/B )
3- Abnormalities in ion channels -- Na/K/Ca
72
how does Seizure starts?
Extreme neuronal overactivity
Massive stimultaneous activation of many reverberating neuronal pathways throughout the brain
73
How does Seizure end?
Due to neuronal fatigue
which is association with depletion of synaptic vesicles, neurotransmitters , desensitization of receptors
in addition to activation of inhibitory pathways
74
what are the types of epileptic seizures ?
Generalized seizures ( BOTH CEREBRAL HEMISPHERES )
Partial Seziures ( SPECIFIC AREA OF ONE HEMISPHERE )
75
what are the types of generalized seizures?
Tonic-clonic - Grand mal
Absence - Petit Mal
Myoclonic - Motor cortex
Atonic - Loss of muscle tone
Status epilepticus - Emergency conditions
76
what are the types of partial seizures?
Simple -- No loss of consciousness JACKSONIAN/FOCAL
Complex -- Counsciousness is impaired psychomotor
77
describe grand mal epilepsy? TONIC CLONIC?
Extreme neuronal discharge in all areas of the brain - Cerebral cortex, Cerebrum and brain stem
Grand = all areas
78
what does Petit Mal Epilepsy involve? (ABSENCE )
Thalamocortical regions of the brain ( so abnormal activity between thalamus and cortex )
Appear during childhood and disappear by the AGE OF 30
CAN INIATE GRAN MAL
Absence epilepsy or absence syndrome
3 to 3- seconds of unconsciousness
78
what are the characteristics of Grand Mal Epilepsy?
High voltage and frequency - VERY!!
Generalized tonic seizures of the entire body ( Alternating tonic and spasmodic muscle contractions --> TONIC CLONIC
Contraction of the respiratory muscles ( ABNORMAL SOUNDS)
Control over visceral functions is lost (URINATION AND DEFECATION LOST)
Few seconds up to 4 minutes
79
How does petit mal epilepsy happen?
we said its in thalamus and cortex by oscillation between :
Inhibitory thalamic reticular neurons ( GABAergic --> suppress activity )
Excitatory thalamocortical and corticothalamic neurons ( Glutamatergic --> they activate the activity )
Back and forth between inhibition and excitation produces SPIKE AND DOME PATTERN ON EEG- -> very special about absence seizure
80
what does focal epilepsy involve?
involve any one part of the brain
( partial seizure, limited to one area in one hemisphere )
81
what causaes focal epilepsy?
localized lesion of functional abnormality by :
Scar tissue
Tumor
Destroyed area of the brain
Congenitally deranged local circuitry
82
how does focal epilepsy happen?
These lesions promotes rapid discharge in local regions
Localized reverberating circuits that gradually recruit adjacent areas of the cortex into epileptic discharge zone
Discharge more than 100/sec synchronous waves spread to adjacent areas
83
Describe the jacksonian seizure/march of focal epilepsy?
Cause progressive march of muscle contraction throughout the body --> most imp in the mouth region and marching progressively downward to the legs
84
from where does Psychomotor epilespy originate ( COMPLEX PARTIAL SEIZURE )?
Limbic lobe --> Hippocampus, amygdala, septum
and or
Temporal cortex
85
what does psychomotor epilepsy result in?
illusions and semipurposeful motor activity :
Causes :
Short period of amnesia
Sudden anxiety, discomfort and fear
Incoherent speech
Sometimes the person cant remember any activities during seizure
RECTANGULAR WAVE WITH FREQUENCY OF 2-4 secs
Physiology Year 3 SEM1
flashcards
Decks in class (15)
# Cards
-
ORAGNIZATION of nerves53
-
conduction system45
-
CSF physiology94
-
physiology of RASS84
-
brain waves86
-
basal gangli86
-
memory100
-
PHOTORECEPTORS88
-
cerebral blood flow75
-
neuro of retina109
-
Central processing of vision115
-
Vesti and equil part 199
-
Vesti and equil part 247
-
physiology of hearing108
-
processing of hearing125
