BISC 220 Neurology Exam Questions
With 100% Verified Answers!!
How do we convert resting membrane potential to action potential?
• Membrane at resting potential contains manyopen K+ channels but few open Na+ channels
• Neurons contain gated ion channels that openor close in response to stimuli (changes
inmembrane potential)
• Action potential depends on the spatial andtemporal differences in gating propertiesbetween
K+ and Na+ channels
4 states of Voltage-Gated Sodium Channel Cycle
- Closed (Resting State)
- Open (Activated)
- Inactivated (Ball-and-chain plug)
- Closed (Reset)
Closed (Resting State) (Voltage-Gated Sodium Channel Cycle)
- Membrane is more negative (around -70 mV).
- Channel is closed, but ready to open.
Open (Activated) (Voltage-Gated Sodium Channel Cycle)
- Membrane depolarizes (becomes less negative, ~-55 mV or higher).
- Gate opens fast → Na⁺ rushes into the cell, making the inside more positive.
Inactivated (Ball-and-chain plug) (Voltage-Gated Sodium Channel Cycle)
- After 1-2 ms, a separate part of the protein blocks the channel.
- Na⁺ can't enter anymore. This ensures one-way signal flow.
Closed (Reset) (Voltage-Gated Sodium Channel Cycle)
- During repolarization (membrane becomes more negative again),
- Inactivation gate opens, but main gate closes → back to starting (resting) state.
- Takes 2-5 ms.
,Measuring Resting Membrane Potential
- Recording electrode is placed inside the axon, and a reference electrode is placed in
the extracellular fluid.
- The voltage difference between them shows the resting membrane potential (usually around -
70 mV).
- The volt meter or voltage amplifier records and displays this electrical difference.
Measuring Action Potentials
- A stimulating electrode (connected to a pulse generator) injects a brief electrical pulse into
the axon at point A.
- This initiates an action potential.
- A recording electrode at point B detects the action potential after it has traveled down the axon.
- A voltmeter shows the characteristic spike of the action potential.
Synapses can be broadly classified into two types:
electrical and chemical.
What is a electrical synapse and how does it function?
There is a direct connection between cells, This connection is via GAP JUNCTION
CHANNELS--these are relatively non-selective pores that allow ionic current flow between the
two cells.
What is a chemical synapse and how does it function?
A chemical synapse is a junction between two neurons where they do not touch directly but are
separated by a synaptic cleft. Neurotransmitters are stored in synaptic vesicles in
the presynaptic neuron. When an action potential reaches the terminal, vesicles fuse with
the membrane and release neurotransmitters into the cleft. These neurotransmitters bind
to receptors on the postsynaptic membrane, altering its ion permeability and triggering a
response. Unlike electrical synapses, chemical synapses rely on vesicles and neurotransmitter
release, not direct current flow.
What are the 3 key features of chemical synapses?
, 1. Signal amplification: A single synaptic vesicle releases thousands of neurotransmitter
molecules that can open or close thousands of ion channels in the postsynaptic neuron,
potentially triggering an action potential.
2. Rapid, transient signaling: Neurotransmitter receptors have low affinity, requiring high
concentration for activation. This allows fast binding/unbinding, enabling brief,
repeatable signaling.
3. Versatility: The neurotransmitter's effect depends on the receptor, not the transmitter itself.
• Example: Acetylcholine (ACh) slows heart rate (hyperpolarization) but triggers
muscle contraction at neuromuscular junctions (depolarization).
What are the 6 steps of neurotransmission at a chemical synapse?
1. Action potential arrives and opens voltage-gated Ca²⁺ channels in the presynaptic terminal.
2. Calcium enters the presynaptic terminal.
3. Calcium activates synaptic vesicle proteins that help vesicles move.
4. Synaptic vesicles fuse with the presynaptic membrane and release neurotransmitter into
the synaptic cleft.
5. Neurotransmitter binds to ligand-gated ion channels on the postsynaptic membrane, causing
EPSP or IPSP.
6. Neurotransmitter unbinds, closing the ion channel and stopping the signal.
What is an EPSP?
An Excitatory Postsynaptic Potential is a depolarization that makes the postsynaptic neuron
more likely to fire an action potential. It results from cation (Na⁺, Ca²⁺) channels opening.
What neurotransmitters commonly cause EPSPs?
Glutamate (in the CNS) and acetylcholine (in the PNS).
What happens to membrane potential during an EPSP?
It becomes less negative (depolarizes), moving closer to threshold for firing an action potential.
What is an IPSP?
With 100% Verified Answers!!
How do we convert resting membrane potential to action potential?
• Membrane at resting potential contains manyopen K+ channels but few open Na+ channels
• Neurons contain gated ion channels that openor close in response to stimuli (changes
inmembrane potential)
• Action potential depends on the spatial andtemporal differences in gating propertiesbetween
K+ and Na+ channels
4 states of Voltage-Gated Sodium Channel Cycle
- Closed (Resting State)
- Open (Activated)
- Inactivated (Ball-and-chain plug)
- Closed (Reset)
Closed (Resting State) (Voltage-Gated Sodium Channel Cycle)
- Membrane is more negative (around -70 mV).
- Channel is closed, but ready to open.
Open (Activated) (Voltage-Gated Sodium Channel Cycle)
- Membrane depolarizes (becomes less negative, ~-55 mV or higher).
- Gate opens fast → Na⁺ rushes into the cell, making the inside more positive.
Inactivated (Ball-and-chain plug) (Voltage-Gated Sodium Channel Cycle)
- After 1-2 ms, a separate part of the protein blocks the channel.
- Na⁺ can't enter anymore. This ensures one-way signal flow.
Closed (Reset) (Voltage-Gated Sodium Channel Cycle)
- During repolarization (membrane becomes more negative again),
- Inactivation gate opens, but main gate closes → back to starting (resting) state.
- Takes 2-5 ms.
,Measuring Resting Membrane Potential
- Recording electrode is placed inside the axon, and a reference electrode is placed in
the extracellular fluid.
- The voltage difference between them shows the resting membrane potential (usually around -
70 mV).
- The volt meter or voltage amplifier records and displays this electrical difference.
Measuring Action Potentials
- A stimulating electrode (connected to a pulse generator) injects a brief electrical pulse into
the axon at point A.
- This initiates an action potential.
- A recording electrode at point B detects the action potential after it has traveled down the axon.
- A voltmeter shows the characteristic spike of the action potential.
Synapses can be broadly classified into two types:
electrical and chemical.
What is a electrical synapse and how does it function?
There is a direct connection between cells, This connection is via GAP JUNCTION
CHANNELS--these are relatively non-selective pores that allow ionic current flow between the
two cells.
What is a chemical synapse and how does it function?
A chemical synapse is a junction between two neurons where they do not touch directly but are
separated by a synaptic cleft. Neurotransmitters are stored in synaptic vesicles in
the presynaptic neuron. When an action potential reaches the terminal, vesicles fuse with
the membrane and release neurotransmitters into the cleft. These neurotransmitters bind
to receptors on the postsynaptic membrane, altering its ion permeability and triggering a
response. Unlike electrical synapses, chemical synapses rely on vesicles and neurotransmitter
release, not direct current flow.
What are the 3 key features of chemical synapses?
, 1. Signal amplification: A single synaptic vesicle releases thousands of neurotransmitter
molecules that can open or close thousands of ion channels in the postsynaptic neuron,
potentially triggering an action potential.
2. Rapid, transient signaling: Neurotransmitter receptors have low affinity, requiring high
concentration for activation. This allows fast binding/unbinding, enabling brief,
repeatable signaling.
3. Versatility: The neurotransmitter's effect depends on the receptor, not the transmitter itself.
• Example: Acetylcholine (ACh) slows heart rate (hyperpolarization) but triggers
muscle contraction at neuromuscular junctions (depolarization).
What are the 6 steps of neurotransmission at a chemical synapse?
1. Action potential arrives and opens voltage-gated Ca²⁺ channels in the presynaptic terminal.
2. Calcium enters the presynaptic terminal.
3. Calcium activates synaptic vesicle proteins that help vesicles move.
4. Synaptic vesicles fuse with the presynaptic membrane and release neurotransmitter into
the synaptic cleft.
5. Neurotransmitter binds to ligand-gated ion channels on the postsynaptic membrane, causing
EPSP or IPSP.
6. Neurotransmitter unbinds, closing the ion channel and stopping the signal.
What is an EPSP?
An Excitatory Postsynaptic Potential is a depolarization that makes the postsynaptic neuron
more likely to fire an action potential. It results from cation (Na⁺, Ca²⁺) channels opening.
What neurotransmitters commonly cause EPSPs?
Glutamate (in the CNS) and acetylcholine (in the PNS).
What happens to membrane potential during an EPSP?
It becomes less negative (depolarizes), moving closer to threshold for firing an action potential.
What is an IPSP?
