Neuroanatomy|Neurons Flashcards
What are dipoles?
Charge distributions at the synapses that create measurable electrical potentials
What is volume conduction?
How electrical currents get from the brain to the scalp. Body tissues have capacity for conduction or spread of electricity.
What part of the neuron receives messages from other neurons?
Dendrites
What part of the neuron is covered with myelin?
Axon
What term refers to the cell body of a neuron?
Soma
What type of cells provide maintenance and support for neurons?
Glial cells
What types of neurons carry sensory information from the periphery to the central nervous system?
Afferent (Sensory) neurons [Afferent Arrives]
What types of neurons carry motor signals from the CNS to the peripheral nervous system?
Efferent (Motor) neurons [Efferent Exits]
What do descending nerves do?
Transmit motor impulses from the brain to the peripheral nervous system
What do ascending nerves do?
Transmit sensory impulses to the brain
Nerve cells produce signals that are called what?
Action Potentials
What are LTP and LTD?
Long-Term Potentiation and Long-Term Depression
LTP and LTD are terms that refer to what?
Neuroplasticity
What do brainwaves measure?
EPSPs and IPSPs- not a direct measure of action potentials. These are graded potentials that occur at and near the synapses.
What is the max rate a neuron can produce action potentials?
About 1000 per second
What 2 terms define the process of making brain waves?
Excitatory post-synaptic potential (EPSP) and Inhibitory post-synaptic potential (IPSP)
What does an excitatory neurotransmitter do?
Increases depolarization and the likelihood of an action potential
What does an inhibitory neurotransmitter do?
Increases polarization and decreases the likelihood of an action potential.
What are sensory-evoked potentials (EPs)?
Electric responses generated by the CNS when sensory receptors in the brain are stimulated by auditory, visual, or somatosensory activity. For example, flashes of light generate visual evoked potentials and matching brain wave frequencies.
What are event-related potentials (ERPs)?
Similar to EPs but more generally reflect responses to mental, motor, or psychophysiological tasks. For example, some ERPs are triggered by novel or unexpected stimulation.
What are slow cortical potentials (SCPs)?
Shifts in the DC or standing polarity of the cerebral cortex. Negative shifts occur when the brain is preparing to do a cognitive task. Positive shifts occur and can be recorded when the brain is executing a cognitive task. They are considered slow because they may continue for several seconds in a frequency range usually less than 2 hz.
A negative slow cortical potential has what effect on cortical excitability?
It increases excitability
What focal site measures the max amplitude of SCPs?
Cz
What effect would the self-regulation of SCPs at Cz likely have?
Improved cognitive performance
What determines whether a neuron is considered part of the central or peripheral nervous system?
Location of its soma (cell body)
In what order does neural information travel through parts of a neuron?
Neural information flows from dendrites to the cell body, to the axon hillock, down the axon, and ends at the synaptic terminal. Synaptic terminals can send information to either the dendrites of postsynaptic cells or cell bodies, but cannot transmit information directly to axons.
What is myelin?
Fatty substance that wraps around some axons and helps determine the speed at which action potentials travel along axons. Myelin wraps around the axon create areas where the signal can jump over instead of passing through the axon, which accelerates transmission.
What effect do demyelinating diseases have on the body?
Demyelinating diseases can slow or entirely disrupt the transmission of information.
What are three examples of demyelinating diseases?
Multiple sclerosis, Charcot-Marie-Tooth, Guillain-Barre
What causes multiple sclerosis?
Failure of oligodendrocytes in the CNS to produce myelin.
What causes Charcot-Marie-Tooth (a chronic, hereditary condition) and Guillain-Barre (an acute condition)?
Failure of Schwann cells in the PNS to produce myelin.
What are the three types of glial cells?
- Oligodendrocytes (CNS) and Schwann Cells (PNS)
- Astrocytes
- Microglia
What are oligodendrocytes?
Glial cells in the CNS that produce myelin.
What are Schwann cells?
Glial cells in the PNS that produce myelin.
What cells are considered the “sanitation workers of the brain”?
Astrocytes, a type of glial cell
What are astrocytes?
Glial cells that keep synaptic environments clean and help neurons develop and go where they need to go.
What are microglia?
Glial cells that serve as medics. They are immune cells that come from the blood and repair problems, but that can cause problems if overactive.
Oligodendrocytes/Schwann cells comprise what percentage of all glial cells?
75%
Astrocytes comprise what percentage of all glial cells?
20%
Microglia comprise what percentage of all glial cells?
5%
What causes neurons to fire?
Changes in the electrical charge (ions) of cells.
Ions are molecules where the number of protons and electrons are unequal. It is the influx and efflux of positively- and negatively-charged ions that changes the electrical state or neurons and activates action potentials via the processes of depolarization and repolarization.
Positively-charged ions contain more ______ than ______.
Protons; electrons.
Negatively-charged ions contain more ______ than ______.
Electrons; protons.
Cell membranes are comprised primary of ______ that is surrounded by a thin layer of ______ on the inside and outside of the cell membrane.
Fat; water.
Because ions cannot pass directly across cell membranes, they require the use of _______ that work like cat/dog doors.
Ion channels
What are the two different types of ion channels?
Ligand-gated and voltage-gated
What activates ligand-gated ion channels?
Neurotransmitters
What activates voltage-gated ion channels?
Changes in electrical charge.
What is the resting membrane potential of cells in millivolts?
Around -65 mV
The flow of what three ions in and out of the cell is primarily responsible for changing the polarity or charge of the cell?
Potassium (K+)
Sodium (Na+)
Chloride (Cl-)
In a word, what causes a neuron to trigger an action potential?
Depolarization
What causes depolarization?
The membrane voltage increases its positive charge and crosses a Threshold of Excitation of -55 mv.
This can occur from channels letting in more positive ions (e.g., Na+) or letting out more negative ions (e.g., Cl-). Once this threshold is reached, voltage-gated Na+ channels open and allow a flood of positively-charged Sodium ions into the cell, triggering an Action Potential.
[Sodium rushes in; chloride rushes out]
What is repolarization?
Return of the cell body to its resting membrane potential
When does repolarization occur?
When the cell voltage reaches a peak positive charge of +30-40 mV
What happens during repolarization?
After the cell voltage reaches a peak positive charge of +30-40 mV, the sodium-channels inactivate/close. At this point, potassium (K+)-gated channels open, allowing potassium to rush out of the cell. This brings the charge of the cell back towards the resting membrane potential of -55 mV.
What is hyperpolarization?
As cells repolarize (i.e., regain negative charge), potassium-gated channels remain open a little longer than necessary for the cell to reach its resting membrane potential. The voltage of the cell therefore briefly dips negatively lower than resting potential before coming back to rest. During this brief period of time the cell is considered hyperpolarized. This is considered the undershoot period.
What are refractory periods?
After an action potential occurs, the cell cannot immediately fire again due to the recent inactivation of the sodium-gated channels. These inactivated sodium channels cannot open, even if the membrane potential goes above threshold. The slow closure of the voltage-gated potassium channels, which results in undershoot, also contributes to the refractory period by making it harder to depolarize the membrane (even once the voltage-gated sodium channels have returned to their active state). The refractory period ensures that action potentials will only travel forward down the axon, not backwards through the portion of the axon that just underwent an action potential.
Communication between ______ and ______ neurons is the true driver of neuronal activity.
pre-synaptic; post-synaptic.
What are Excitatory Post-Synaptic Potentials (EPSPs)?
Graded potentials that bring the membrane of the postsynaptic neuron closer to generating an action potential (i.e., depolarization). EPSPs bring the membrane potential of the postsynaptic membrane closer to threshold (-55 mV; the point at which the neuron can generate an action potential). EPSPs result from both IONOTROPIC (i.e., fast) and METABOTROPIC (i.e., slow; G-protein linked receptors) channels.
What does EPSP stand for?
Excitatory Post-Synaptic Potential
What does IPSP stand for?
Inhibitory Post-Synaptic Potentials
What are Inhibitory Post-Synaptic Potentials (IPSPs)?
Graded potentials that repolarize/hyperpolarize or stabilize the membrane of the postsynaptic neuron at rest (i.e., decreases chance of action potential). IPSPs bring the membrane potential further away from threshold (make neuron more negative) and/or stabilize the membrane at its resting potential. This decreases the chances of generating an action potential. IPSPs result only from IONOTROPIC (i.e., fast) channels. IPSPs act either by opening fast potassium (K+) channels (efflux) or fast, negatively-charged chloride channels (influx).
What word describes fast-acting ion channels?
Ionotropic
What word describes slow-acting, G-protein linked ion channels?
Metabotropic
IPSPs result only from what type of channels?
Ionotropic
What neurotransmitter is related to mood, sleep, depression, and addictions?
Serotonin
Is serotonin an excitatory or inhibitory neurotransmitter?
Inhibitory
What neurotransmitter is related to the reward system, pleasure centers, and attentional networks?
Dopamine
Is dopamine an excitatory or inhibitory neurotransmitter?
It can be either.
What neurotransmitter is related to fight-or-flight responses to fear and stress?
Epinephrine
Is epinephrine an excitatory or inhibitory neurotransmitter?
Excitatory
What neurotransmitter increases heart rate and blood pressure, and is used to stimulate attention and alleviate depression?
Norepinephrine (precursor of epinephrine)
Is norepinephrine an excitatory or inhibitory neurotransmitter?
Excitatory
What neurotransmitter is the main neurotransmitter involved in muscle contraction and the autonomic nervous system?
Acetylcholine
Is acetylcholine an excitatory or inhibitory neurotransmitter?
Excitatory
Is acetylcholine an amino acid or monoamine neurotransmitter?
Monoamine
Is norepinephrine an amino acid or monoamine neurotransmitter?
Monoamine
Is epinephrine an amino acid or monoamine neurotransmitter?
Monoamine
Is dopamine an amino acid or monoamine neurotransmitter?
Monoamine
Is serotonin an amino acid or monoamine neurotransmitter?
Monoamine
Is glutamate an amino acid or monoamine neurotransmitter?
Amino acid neurotransmitter
Is GABA an amino acid or monoamine neurotransmitter?
Amino acid neurotransmitter
Is glycine an amino acid or monoamine neurotransmitter?
Amino acid neurotransmitter
Is glutamate an excitatory or inhibitory neurotransmitter?
Excitatory
Is GABA an excitatory or inhibitory neurotransmitter?
Inhibitory
Is glycine an excitatory or inhibitory neurotransmitter?
Inhibitory
What amino acid neurotransmitter plays a key role in thinking, learning, and memory?
Glutamate
What amino acid neurotransmitter regulates brain activity to prevent problems with arousal disorders (anxiety, irritability, concentration, sleep, seizures, and depression).
GABA
What does GABA stand for?
Gamma Aminobutryic Acid
What amino acid neurotransmitter, found in the spinal cord, is involved in hearing processing, pain transmission, and metabolism?
Glycine
What three ways are neurotransmitter removed from the synaptic cleft?
- Diffused away from synapse and degraded.
- Degraded by enzymes in the synapse.
- Reuptake
What are the Nodes of Ranvier?
Spaces between myelin sheath along the axon
The spaces between myelin sheath along the axon are called what?
Nodes of Ranvier
What is saltatory conduction?
Jumping of electrical current across myelin sheath
What term describes the jumping of electrical current across myelin sheath?
Saltatory conduction
What is Local Field Potential (LFP)?
The synchronized excitation of neurons generated by the sum of postsynaptic potentials from a localized region. Greater firing synchrony produces larger field potentials on the scalp surface which in turn create electrical dipoles that are detected as EEG waves. (SYNCHRONOUS FIRING = SPIKES OF HIGHER VOLTAGE). Higher amplitude indicates larger field of synchronous firing. The EEG shows changes in local field potential (greater/lesser synchrony).
What are Slow Cortical Potentials?
Slow, event-related direct-current shifts of the EEG, near to 0 Hz
What neurotransmitter is released by sympathetic neurons to create flight-or-flight response?
Norepinephrine
What neurotransmitter is released by parasympathetic neurons to regulate rest and digest functions?
Acetylcholine
What is the main hormone secreted by the adrenal medulla?
Epinephrine
What type of receptors transmit acetylcholine?
Cholinergic receptors/fibers
What type of receptors transmit norepinphrine?
Adrenergic receptors/fibers
What inhibitory neurotransmitter influences attentional networks and pleasure centers and is associated with schizophrenia, ADHD, and addictions?
Dopamine
What inhibitory neurotransmitter influences mood centers and is associated with sleep cycles, depression, and addictions?
Serotonin
What excitatory neurotransmitter is related to general arousal levels and attentional networks?
Norepinephrine
What neurotransmitter is associated with memory networks and memory problems?
Acetylcholine
What inhibitory neurotransmitter is associated with anxiety disorders?
GABA
Research indicates that an increase in serotonin has what effect on EEG?
Hypercoupling and slowing down
Research indicates that increases in acetylcholine, norepinephrine, and dopamine have what effect on EEG?
Hypocoupling and increased activity
