Quiz 1: EEG, Action Potential, Neurons, Brain Anatomy Flashcards
Purpose of dendrites
Receives information/signals from other neurons
Purpose of cell body (a.k.a. soma)
Process and integrates received information/signal from dendrites
Purpose of axon
Joins to the cell body at junction called axon hillock. Carries signals across long distances from one part of the neuron to another. Covered in Myelin sheath that allows more rapid transmission by jumping along nodes of Ranvier between Schwann cells
Purpose of axon terminal
Transmits signal to next cell in the chain
What is the synapse?
Gap between the axon of one neuron and the dendrite of the next. Presynaptic is the axon neuron and postsynaptic is the dendrite neuron.
When action potential arrives from presynaptic neuron, it causes neurotransmitters to be released in the synaptic cleft . These bind to ionic channels of the postsynaptic neuron and opens the channel.
Describe the membrane potential at rest
Abundant sodium (+) outside cell, abundant potassium (-) inside cell, electrochemical equilibrium, -70mV
Describe graded potential
Neuron was not stimulated enough to reach threshold of membrane potential. Resulting change can be positive or negative. Neuron uses sodium-potassium pump to restore back to resting state
Describe depolarization
When the stimulus is high and passes the threshold of -55mV, the axon hillock is triggered.
Sodium channel opens > membrane potential becomes more positive > goes to overshoot/action potential > sodium channel closes
Describe repolarization
Action potential was achieved and sodium channel closes > potassium channel opens > membrane potential becomes more negative > because potassium channel is slower to close it hits hyperpolarization (pass resting state) > potassium channel closes
How does membrane potential go back to resting state when it is at hyperpolarization?
Sodium-Potassium channel continues to pump until membrane potential reaches resting.
What is absolute refractory period?
During repolarization when the sodium channel closes, the neuron cannot fire no matter how strong the stimulus. This prevents action potentials from happening too quickly of signals to travel backwards down the axon
What is the relative refractory period?
During hyperpolarization, the sodium channel could open but it takes a larger stimulus to reach the threshold.
Does action potential amplitude change for a neuron?
No, even with a larger stimulus. The frequency can change based on the intensity, for example the rate is faster for intense pain versus a breeze
Ions move through channels through passive diffusion. What type of ion channels are there?
Voltage-gated : based on membrane potential
Ligand : bounded by type of molecule
Mechanical : external forces or movement
Inhibitory vs Excitatory Synapses
Inhibitory temporarily decreases the membrane potential of the postsynaptic cell. Excitatory temporarily increases
What is synaptic plasticity? What are the different types?
Neurons change the strength of the connections between themselves.
LTP (long term potentiation): If neuron A is consistently involved in causing neuron B to fire, the strength of the connection between the increases
LTD (long term depression): decrease strength due to uncorrelated firing
STDP (spike timing dependent plasticity): presynaptic spike occurs slightly before the post-synaptic, the strength increases. If it occurs slightly after, the strength decreases
STD (short term depression): successive spike causes lesser change in potential until equilibrium
STF (short term facilitation): successive spike has a larger effect than predecessor until saturation point
What is central nervous system (CNS)?
Consist of brain(clusters of neurons- nuclei, separated into two cerebral hemispheres, distributed and localized) and spinal cord (pathway to convey signals from brain to muscles).
What is the brain stem?
Consist of medulla, pons and midbrain. It conveys all information from brain to rest of the body.
Medulla and pons: basic regulatory functions like sleep and breathing
Midbrain: Eye movement, reflexes, pain perception
What is the brain’s cerebellum?
Highly structures network of neurons located at the base of the brain for movement coordination
What is the brain’s thalamus?
“relay station” that conveys info from sensory organs to neocortex (consist of billions of neurons)
What is the brain’s basal ganglia?
motor control and action selection
What is the brain’s amygdala?
Regulation of emotions
What is the brain’s hippocampus?
memory and learning
What is EEG?
Electroencephalography
- neuron firing within brain
- thousands of neuron firing patterns
What is EMG?
Electromyography
- skeletal muscle nerve signals
- easily evoked
What is an invasive BCI?
Electrocorticography (ECOG)
- electrodes under the skull
EMG vs EEG, why EEG?
EMG is figuring out how to move one area to control another whereas EEG is natural
What are the different stages to reach action potential?
Rest > gradient potential (failed initiation) > threshold (achieved initiation) > depolarization > action potential / overshoot> repolarization> hyperpolarization > rest
What is the peripheral nervous system (PNS)?
Somatic: skeletal muscles and sensory organs
Autonomic: pumping of heart, breathing
What are the frontal lobes?
movement, expressive language, planning, judgement, decisions, attention
What are the parietal lobes?
sensory processing, navigation, control, size judgment, interpretation (math and language)
What are the temporal lobes?
memory, perception, emotions, remembering verbal info, speech recognition
What are the occipital lobes?
color and visuals
ventral stream: “what” of vision
dorsal stream: “where/how”
What is the homunculus?
motor or sensory distribution along cerebral cortex
What is the 10-20 system?
Layout to place electrodes. These are the intervals to place between the Naison and Inion
Naison 10%, 20%, 20%, 20%, 20%, 10% Inion
How to record EEG?
Use differential amplifier to amplify small voltage ( 2 electrode readings -> 1 channel)
What is EEG Bipolar Montage vs Common Average Reference Montage?
Bipolar: subtract ECG from raw data (5 electrodes -> 4 channels)
Common: compare voltage of electrode of average across electrodes
What are biopotential electroides?
Electrodes serve as transducer to change an ionic current into an electronic current. Body current is carried by ions and electrode it is carried by electrons
What is the electrode-electrolyte interface?
Current crosses from left to right. Electrode consists of compatible metallic atoms. Electrolyte is aqueous. Current passes from electrode to electrolyte.
Electrons move in opposite direction of current in electrode. Cations move in same direction as current. Anions move in opposite direction of current in electrolyte.
Cation discharged into electrolyte. Anion oxidized and electrons freed to electrode.
Potential difference between electrode and electrolyte (voltage)
How does circuits model biopotential electrodes?
DC-bias > Voltage divider (Current Divider > Resistor)
