Unit 2 Flashcards
(22 cards)
What is a dendritic spine? Describe its structure and function.
A dendritic spine is a small membranous protrusion from a neuron’s dendrite that typically receives input from a single axon at the synapse
Describe the different types of postsynaptic potentials. How might similar or different types of postsynaptic potentials interact to influence the likelihood of reaching the threshold of excitation?
EPSPs and IPSPs. EPSPs allow in cations which increase the likelihood of pushing the cell past threshold. IPSPs allow in cloride (inhibitory) which decreases the likelihood of pushing a cell past threshold.
Compare electrical conduction with chemical transmission in a neuron.
1) Electrical conduction: Current is carried along the axon by electrically charged ions and passes down axon as a propagating wave of depolarization.
2) Chemical transmission: Changes in electrical properties of the neurons following the electrical conduction induce neurotransmitter activity. A signal between neurons - chemical transmission - is transmitted at the synapse via neurotransmitters
Match the four types of ion channels that we have discussed so far to their proper descriptions Ligand-gated ion channels, voltage-gated ion channels, mechanically-gated ion channels, leaky/always open ion channels
[ Receptor on channel acts more like an open pore/Receptor on channel binds neurotransmitter/ Voltage change causes a change in ion channel protein structure/Mechanical deformation of the cell membrane causes a change in ion channel protein structure
Ligant gated = B
Voltage gated = C
mechanically =D
leaky = A
Describe the events that take place during an action potential. Begin at the point where summation of EPSPs at the axon hillock exceeds the threshold for initiating an action potential and continue to the synaptic terminal. Include all ion channels, ion movements and potential changes that take place during the various phases of the action potential.
voltage gated ion channels open allowing in sodium, this continues to move across the axon opening new channels, while closing previous ones. Once towards the synaptic terminal, calcium enters in through the pre-syanpic receptors allowing for the vesicles to merge with the synapse in a process known as exocytosis, neurotransmitter is then released
Describe a concentration gradient and an electrical gradient. How do they contribute to the electrochemical force?
Concentration gradient – the process of particles, which are sometimes called solutes, moving through a solution or gas from an area with a higher number of particles to an area with a lower number of particles.
Electrical gradient – In biological solutions, the term electrical gradient refers to the electrical potential that acts on an ion to drive the movement of the ion in one or another direction.
The forces involved in the concentration and electrical gradients combine to form the electrochemical force, the overall driving force across the cell membrane.
At what structure of the neuron is the action potential initiated
Axon hillock
Explain what the resting membrane potential is, and describe the forces involved in maintaining it.
The resting membrane potential is the electrical difference between the outside and inside of the neuronal membrane, usually set to around -70mV.
What happens if the myelin sheath is disrupted in the adult brain
A loss of myelin in the adult brain will slow down neural signals, typically resulting in behavioral deficits. For example, diseases such as Multiple Sclerosis, myelin is degraded and eventually absent in affected neurons
Fill in the correct number of each ion moved by the sodium-potassium pump across the cell membrane. ___ sodium (Na) ions are pumped out of the cell for every ___ potassium (K) ions that go in
3 sodium for 2 potassium
Compare the absolute refractory period of the action potential with the relative refractory period.
Refractory period – a period immediately following an action potential during which further stimulation has no effect.
The absolute refractory period coincides with nearly the entire duration of the action potential
The relative refractory period immediately follows the absolute one. As voltage-gated potassium channels open to terminate the action potential by repolarizing the membrane, the potassium conductance of the membrane increases dramatically.
Compare and contrast retrograde and anterograde axonal transport. Include specific protein names.
Similarities: Both transport systems occur in the axon and allow for proteins and membrane components to travel bidirectionally
Anterograde axonal transport: Transport along the axoplasm from the cell body/soma to the axon terminal/synapse; the motor protein in anterograde transport is Kinesin, which travels from the minus end (soma) to the plus end (synapse)
Retrograde axonal transport: Transport along the axoplasm from the axon terminal/synapse to the cell body/soma; the motor protein in retrograde transport is Dynein, which travels from the plus end (synapse) to the minus end (soma)
What are three ways neurotransmitters are removed from the synaptic cleft?
Degradation via enzymes (e.g. AChE): can be reuptaken in pieces via pre-synaptic neuron.
Diffusion: NTs will want to go down their concentration gradient and simply leave the synaptic cleft because there is a lower concentration of NTs outside.
Reuptake: Pre-synaptic neuron will reuptake entire NTs whole (e.g. 5HT) for direct recycling/reuse in chemical synaptic transmission.
Outline the basic structures and functions of ionotropic and metabotropic receptors. Specifically list the similarities and differences between these two types of receptors.
Ionotropic receptors (ligand-gated ion channels): receptors that result in an ion gate opening after a neurotransmitter (NT) binds with the receptor, allowing ions to flow in immediately; very rapid, short-lived; excellent for sending a message along a pathway.
Metabotropic receptors: receptors that gradually lead to ion gates opening via the use of a 2nd messenger; when NT binds to receptor, G protein is released and 2nd messenger binds with G protein to form a complex that opens an ion channel from the inside of the cell; slow-acting signaling; used for condition-setting, such as mood or attention
Similarities: both receptors lead to the opening of ion channels that results in a change in the post-synaptic membrane potential, which can then result in an action potential occurring or not.
Match each neurotransmitter or neuromodulator with the correct definition
Glutamate, GABA, Acetylcholine, 5-HT, Dopamine, Epinephrine, Norepinephrine, Substance P, Endorphins
[signals pain/ role in arousal and attention/ counters the pain signal/ role in mood and sleep/ role in reward, atten, and motor control/ primary excitatory nt/ primary inhibitory nt/ role in neuromuscular junction and arousal or consciousness]
Glutamate - Primary EXCITATORY neurotransmitter
GABA - Primary INHIBITORY neurotransmitter
Acetylcholine - Role in neuromuscular junction and arousal/consciousness
Serotonin - Role in mood and sleep
Dopamine - Role in reward, attention, and motor control
Epinephrine (adrenalin) - Role in arousal and attention
Norepinephrine (noradrenalin) - Role in arousal and attention
Substance P - Signals pain (e.g., damage, itch, extreme temperatures)
Endorphins - Counters the pain signal
Describe how an electrical synapse differs from a chemical synapse.
An electrical synapse involves direct, passive ion (current) flow from one axon terminal to the next dendrite via intercellular (gap junction) channels, which then leads to changes in the post-synaptic potential.
A chemical synapse involves no intercellular channels for direct ion flow; rather, neurotransmitters are released by one axon terminal into the synapse, and those neurotransmitters bind to protein chemical receptors on the receiving dendrite, which can then activate/open ion channels.
Discuss three factors that can modify neurotransmitter availability.
early childhood experience, diet, drugs -> changes in gene transcription, epigenetics
What is an autoreceptor?
An autoreceptor is a type of receptor located in the membranes of presynaptic nerve cells. It serves as part of a negative feedback loop in signal transduction that limits the amount of neurotransmitter that is released.
Match each type of synapse to its general role
Axo-dendritic, Axo-somatic, Axo-axonic, Dendro-dendritic
[More involved in the regulation and modulation of action potentials/Drives the initiation of action potentials for communication]
Axo-dendritic -Drives the initiation of action potentials for communication
Axo-somatic - Drives the initiation of action potentials for communication
Axo-axonic - More involved in the regulation and modulation of action potentials
Dendro-dendritic - More involved in the regulation and modulation of action potentials
Concentration gradient
the process of particles, which are sometimes called
solutes, moving through a solution or gas from an area with a higher number of
particles to an area with a lower number of particles
Electrical gradient
– In biological solutions, the term electrical gradient refers
to the electrical potential that acts on an ion to drive the movement of the ion in
one or another direction.
Electrochemical force
the combined force of the chemical force of the
concentration gradient and the electrical force of the electrical gradient
