Biology Chapter on Membrane Curvature

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Questions and Answers

What is the primary effect of hyperpolarization produced by inhibitory signals on excitatory synapses?

It enhances depolarization of excitatory synapses.

It creates a stronger action potential at the trigger zone.

It reduces the depolarization of excitatory synapses. (correct)

It prevents neurotransmitter release at the axonal terminal.

How does the summation of excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) influence action potential generation?

It determines the overall magnitude of depolarization reaching the trigger zone. (correct)

It singularly blocks the effects of excitatory synapses.

It eliminates the need for synaptic integration.

It always results in a higher frequency of action potentials.

What role does the amplitude of the depolarization play in action potential generation?

Lower amplitude leads to more neurotransmitter release.

Amplitude has no effect on neurotransmitter release.

Higher amplitude results in greater action potential frequency. (correct)

Higher amplitude inhibits action potential generation.

What is the main purpose of neural circuits in the nervous system?

To support specific functions through interconnected neurons. Signup and view all the answers

What initiates the depolarization of a neuron leading to an action potential?

Increased Na+ inflow Signup and view all the answers

Which phrase best describes the competitive effects of excitatory and inhibitory synapses?

They can cancel each other's effects to control signal transmission. Signup and view all the answers

What characterizes an action potential (AP) compared to excitatory postsynaptic potentials (EPSPs)?

AP has a consistent amplitude while EPSPs are graded Signup and view all the answers

How does the electrochemical strength of K+ change during the depolarization phase of an action potential?

It increases as membrane potential becomes less negative Signup and view all the answers

What is the role of excitatory postsynaptic potentials (EPSPs) in the generation of an action potential?

EPSPs must reach a threshold to trigger an action potential Signup and view all the answers

Which type of synapse is generally associated with inhibitory functions within the central nervous system?

Type II synapse Signup and view all the answers

What type of synapse is described as consisting of a presynaptic terminal and a postsynaptic dendritic spine?

Glutamatergic synapse Signup and view all the answers

Which proteins are found in the postsynaptic density of a glutamatergic synapse?

Glutamate receptors, protein kinases, and nitric oxide synthase Signup and view all the answers

What is the role of excitatory amino acid transporters (EAATs) in a glutamatergic synapse?

To clear glutamate from the synaptic cleft Signup and view all the answers

Which receptor types are found on the postsynaptic dendritic spine in a glutamatergic synapse?

Both ionotropic and metabotropic glutamate receptors Signup and view all the answers

What is the function of scaffolding proteins in the postsynaptic density?

To concentrate and stabilize effector proteins Signup and view all the answers

What role does clathrin play in vesicle formation?

It determines the curvature of the membrane. Signup and view all the answers

What facilitates the detachment of a neovesicle from the membrane?

Dynamine consuming GTP. Signup and view all the answers

Which neurotransmitter is classified as a classic neurotransmitter?

GABA Signup and view all the answers

During the docking process, how does α-synuclein change?

It folds into an α-helix structure. Signup and view all the answers

What occurs to the neurotransmitter after it is released?

It is taken up by glial cells or pre-synaptic terminals. Signup and view all the answers

What is responsible for synthesizing low molecular weight neurotransmitters?

Particular enzymes within synaptic terminals. Signup and view all the answers

What area are low molecular weight neurotransmitters synthesized and stored in?

Synaptic terminals. Signup and view all the answers

What method is used to transport neuropeptide precursors?

Transport along microtubules in vesicles. Signup and view all the answers

What is the role of NMDA receptors in synaptic transmission?

They act as coincidence detectors. Signup and view all the answers

Which components are involved in the presynaptic changes during LTP induction?

Glutamate and endocannabinoids. Signup and view all the answers

What effect does high-frequency stimulation (HFS) have on synaptic transmission?

It induces long-term potentiation (LTP). Signup and view all the answers

Under physiological conditions, what happens to synaptic transmission in the striatum following tetanic activation?

LTD occurs in synaptic transmission. Signup and view all the answers

What does intracellular Ca2+ primarily mediate in LTP?

Both early and late stages of LTP. Signup and view all the answers

Which statement about AMPA receptors is correct regarding LTP induction?

AMPA receptor activity is essential for LTP induction. Signup and view all the answers

What role does the presence of Mg2+ play in NMDA receptor activation?

It prevents NMDA receptor activation. Signup and view all the answers

Which brain structures are involved in memory formation?

Hippocampus, cortex, and amygdala. Signup and view all the answers

Study Notes

Clathrin and Vesicle Formation

Clathrin shapes membrane curvature for coated vesicle formation.
Dynamin is responsible for vesicle detachment, utilizing GTP.
Neovesicles transport neurotransmitters to reserve pools via transporters.

α-Synuclein Function

Initially unstructured; undergoes conformational changes upon vesicle binding.
Transforms into α-helical structures, facilitating SNARE complex assembly during docking and priming.

Neurotransmitter Release and Reuptake

After release, neurotransmitters may:
- Be reabsorbed by pre-synaptic terminals through transporters like H+-ATPase and H+-NT exchanger.
- Be metabolized or diffuse into extra-synaptic zones.
- Be taken up by glial cells for metabolization.

Categories of Neurotransmitters

Classic neurotransmitters include:
- Low molecular weight: Acetylcholine, monoamines (dopamine, noradrenaline, histamine, serotonin), and amino acids (GABA, glycine, glutamate).
Neuropeptides encompass over 50 types, such as opioids, substance P, hormones, and insulin.

Low Molecular Weight Neurotransmitter Synthesis

Synthesized at synaptic terminals and stored in small vesicles (40-60 nm).
Slow axonal transport of substances occurs at a rate of 0.5 – 5 mm/day.

Neuropeptide Synthesis

Precursors are modified by specific enzymes while transported in vesicles along microtubules.

Action Potential (AP) Dynamics

During depolarization, Na+ influx surpasses K+ efflux, shifting the membrane potential to less negative values.
AP is a rapid polarity inversion characterized by voltage-gated Na+ and K+ channel activation.
Threshold for AP determined by synaptic excitatory post-synaptic potentials (EPSPs).

Synaptic Integration

Neurons integrate multiple excitatory and inhibitory signals to determine responses.
Morphological synapse types include:
- Type I: Typically excitatory.
- Type II: Typically inhibitory.

Inhibition and Competitive Effects

Localized inhibitory synapses on the cell body decrease excitatory synapse effects through Cl- channel activation.
Simultaneous excitatory and inhibitory signals result in EPSP and inhibitory post-synaptic potential (IPSP) summation.

Frequency of Action Potentials

Amplitude of synaptic current summation dictates the frequency of APs, influencing neurotransmitter release at axonal terminals.
Increased depolarization correlates with increased AP frequency and information transmission.

Neural Circuits and Brain Networks

Neural circuits consist of interconnected neurons achieving specific functions.
Glutamatergic synapses involve presynaptic terminals rich in glutamate transporters and mitochondria.

Postsynaptic Density and Receptors

Dendritic spines concentrate effector proteins like glutamate receptors and signaling enzymes in lipid rafts and scaffolding proteins.
Changes in presynaptic glutamate release are modulated by retrograde messengers.

Memory Formation Structures

Key brain regions for memory include hippocampus, cortex, basal ganglia, cerebellum, and amygdala.
Long-Term Potentiation (LTP) and Long-Term Depression (LTD) arise from repeated neuronal stimulation.

Role of Receptors in LTP

AMPA and NMDA receptors are critical in LTP formation, with NMDA receptors acting as coincidence detectors.
Intracellular Ca2+ is involved in both early and later LTP stages.

Electrophysiology in Brain Slices

High-frequency stimulation induces changes in synaptic transmission in the striatum.
NMDAR antagonists prevent LTP and reveal LTD under specific conditions.
AMPAR antagonists do not inhibit LTP induction, illustrating the distinct roles of receptor types in synaptic plasticity.

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Description

Explore the role of clathrin in membrane curvature and the formation of coated vesicles. This quiz delves into the mechanisms of vesicle detachment involving dynamin and GTP consumption, as well as the transport processes of newly formed vesicles. Test your understanding of these critical cellular processes.