BCMB 415 - Foundations in Neurobiology (Part 2)

What is intra-neuronal communication?

Electrical signaling within a single neuron, including action potential generation and propagation.

What is inter-neuronal communication?

Chemical signaling between two cells at synapse via neurotransmitter release.

What is the typical resting membrane potential (Vm) of neurons?

About -50 mV to -80 mV.

Why is resting Vm negative?

Ion concentration differences and selective membrane permeability.

Which ion is highest inside the neuron?

K+

Which ions are highest outside the neuron?

Na+, Cl-, and Ca+

What determines ion movement across the membrane?

The electrochemical gradient (chemical + electrical forces)

Which ion is the membrane most permeable to at rest?

K+

Which ion has the lowest permeability?

Ca+

How do Na+, K+, and Ca+2 cross the membrane?

Via ion channels (passive) or pumps/transporters (active).

What maintains the resting membrane potential?

The Na+/K+ ATPase

Is the Na+/K+ ATPase active or passive?

Active transport

What ions does Na+/K+ ATPase move and in which direction

3 Na+ out, 2 K+ in

What did scientists observe in the giant squid axon after an action potential?

A rise in intracellular Ca+2 in the presynaptic terminal.

Why is Ca+2 entry important?

It triggers synaptic vesicle fusion and neurotransmitter release.

Intra-neuronal communication refers to:

A. Neurotransmitter release between two neurons

B. Electrical signaling within a single neuron

C. Communication between neurons via gap junctions

D. Chemical signaling between a neuron and a muscle cell

Electrical signaling within a single neuron

Inter-neuronal communication at chemical synapses occurs when:

A. An action potential propagates down the axon

B. Ion channels open within the dendrite

C. Neurotransmitters are released from the presynaptic neuron

D. K⁺ leaks out of the neuron at rest

Neurotransmitters are released from the presynaptic neuron

The typical resting membrane potential (Vm) of a neuron is:

A. +30 to +50 mV

B. 0 mV

C. −50 to −80 mV

D. −120 to −150 mV

-50 to -80 mV

The resting membrane potential of neurons is negative primarily because of:

A. Equal ion concentrations inside and outside the cell

B. Selective membrane permeability and ion concentration gradients

C. High permeability to Ca²⁺

D. Neurotransmitter release at synapses

Selective membrane permeability and ion concentration gradients

Which ion has a HIGH intracellular concentration in neurons?

A. Na⁺

B. Cl⁻

C. Ca²⁺

D. K⁺

K+

Which ion has the LOWEST intracellular concentration in neurons?

A. Na⁺

B. K⁺

C. Cl⁻

D. Ca²⁺

Ca+2

The electrochemical gradient of an ion is determined by:

A. Only its concentration gradient

B. Only its electrical charge

C. Chemical and electrical gradients combined

D. Membrane thickness

Chemical and electrical gradients combined

At rest, the plasma membrane of neurons is MOST permeable to which ion?

A. Na⁺

B. Cl⁻

C. Ca²⁺

D. K⁺

K+

Leakage of which ion plays the greatest role in establishing the resting membrane potential?

A. Na⁺

B. K⁺

C. Ca²⁺

D. Cl⁻

K+

Which transmembrane protein is responsible for maintaining the resting membrane potential?

A. Voltage-gated Na⁺ channel

B. Voltage-gated Ca²⁺ channel

C. Na⁺/K⁺ ATPase

D. K⁺ leak channel

Na+/K+. ATPase

The Na⁺/K⁺ ATPase is best described as:

A. Passive transport using ion gradients

B. Active transport requiring ATP hydrolysis

C. Facilitated diffusion

D. A voltage-gated ion channel

Active transport requiring ATP hydrolysis

For each cycle of the Na⁺/K⁺ ATPase, which ions are transported?

A. 2 Na⁺ out, 3 K⁺ in

B. 3 Na⁺ out, 2 K⁺ in

C. 3 Na⁺ in, 2 K⁺ out

D. 2 Na⁺ in, 3 K⁺ out

3 Na+ out, 2 K+ in

Which ion is LEAST permeable to the neuronal membrane at rest?

A. Na⁺

B. K⁺

C. Cl⁻

D. Ca²⁺

Ca+2

In studies of the giant squid axon, stimulation with a positive electrical current resulted in:

A. Hyperpolarization of the membrane

B. Neurotransmitter binding to postsynaptic receptors

C. Generation of an action potential

D. Inhibition of Ca+2 entry

Generation of an action potential

After an action potential was generated in the giant squid axon, scientists observed:

A. A decrease in intracellular Ca+2

B. An increase in intracellular Ca+2 in the presynaptic terminal

C. Immediate neurotransmitter binding to DNA

D. Complete loss of membrane potential

An increase in intracellular Ca+2 in the presynaptic terminal

Why is the rise in intracellular Ca+2 in the presynaptic terminal important?

A. It restores the resting membrane potential

B. It opens K+ leak channels

C. It triggers synaptic vesicle fusion and neurotransmitter release

D. It inhibits action potential propagation

It triggers synaptic vesicle fusion and neurotransmitter release

Calcium imaging using furs-2 allows researchers to:

A. Measure neurotransmitters concentrations

B. Visualize changes in membrane voltage

C. Detect changes in intracellular Ca+2 levels

D. Observe Na+/K+ ATPase activity

Detect changes in intracellular Ca+2 levels

Which statement best distinguishes intra-neural from inter-neuronal communication?

A. Both involve neurotransmitter release

B. Intra-neuronal communication is chemical; inter-neuronal is electrical

C. Intra-neuronal communication involves action potentials within one neuron

D. Inter-neuronal communication occurs only in the axon

Intra-neuronal communication involves action potentials within one neuron

How does the Na+/K+ ATPase maintain ionic concentration in the ICM and ECM?

A. It pumps Na+ and K+ ions across the plasma membrane with their electrochemical gradients

B. It pumps only Na+ ion across the plasma membrane down it electrochemical gradient

C. It pumps Na+ and K+ ions across the plasma membrane against their electrochemical gradients

D. It pumps only K+ ions across the plasma membrane against electrochemical gradient

It pumps Na+ and K+ ions across the plasma membrane against their electrochemical gradients

Calcium binding to synaptotagmin results in all the following:

A. Synaptic vesicle fusion with the plasma membrane

B. Synaptotagmin mediating the activation of the SNARE complex

C. Neurotransmitter release into the synaptic cleft

D. Increased synaptic vesicle pooling at the plasma membrane

Synaptic vesicle fusion with the plasma membrane; synaptotagmin mediating the activation of the SNARE complex; neurotransmitter release into the synaptic cleft

What triggers neurotransmitter release?

Ca+2 influx into the presynaptic terminal

Where does neurotransmitter release occur?

The active zone of the presynaptic terminal

What opens the voltage-gated Ca+2 channels?

Presynaptic membrane depolarization

What protein sense Ca+2 in synaptic vesicle?

Synaptotagmin

What is the y-SNARE?

Synaptobrevin

What are the t-SNAREs?

Syntaxin and SNAP-25

How to SNAREs cause fusion?

Zipper-like binding generates force that pulls membranes together

What does Rab3 do?

Helps recruit vesicles to the active zone

What does RIM do?

Anchors vesicles near Ca+2 channels

Function of neurexins and cadherins?

Align presynaptic and postsynaptic membranes

What creates the proton gradient in vesicles?

Vesicular ATPase (V-ATPase)

How do vesicular transporters work?

Antiport H⁺ out while transporting NT in

How are neurotransmitters cleared from the synaptic cleft?

Plasma membrane transporters (PMTs)

What type of transporter are PMTs?

Na⁺-dependent symporters

What is kiss-and-run in regards to vesicle recycling?

Transient fusion without full collapse

What protein mediates classic endocytosis?

Clathrin

Why is vesicle recycling important?

Maintains a readily releasable pool for continuous signaling