Psychobiology part 2 unit 7 Flashcards
What is a neuron, and why is it important?
Neurons are the basic functional units of the nervous system.
They form a vast network for processing and transmitting information, connecting up to 50,000 other neurons each.
Name the key parts of a neuron and their functions.
Dendrites: Receive signals through synaptic receptors.
Cell body: Integrates incoming signals.
Axon: Transmits signals to other neurons, muscles, or organs.
Presynaptic terminal: Releases neurotransmitters to communicate with the next cell.
What does the neuron’s cell membrane do?
The cell membrane acts as a barrier, controlling the movement of ions like Na⁺ and K⁺, which is crucial for generating nerve impulses.
What is the resting potential of a neuron?
The resting potential is the difference in charge across the membrane at rest (~-70 mV).
Maintained by:
Sodium-potassium pumps (3 Na⁺ out, 2 K⁺ in).
Negatively charged proteins (A⁻) inside the cell.
What causes an action potential?
The threshold of excitation is reached (around -55 mV).
Depolarization: Na⁺ rushes in, making the inside positive.
Repolarization: K⁺ exits, restoring negativity.
Hyperpolarization: The cell briefly becomes more negative than at rest.
What is saltatory conduction, and why is it efficient?
In myelinated axons, action potentials jump between nodes of Ranvier.
It speeds up conduction and conserves energy by limiting ion exchange to the nodes.
What is the resting potential, and how is it maintained?
Resting potential is the charge difference across the membrane at rest (~ -70 mV).
Maintained by:
Sodium-potassium pumps (3 Na⁺ out, 2 K⁺ in).
Negatively charged proteins (A⁻) inside the cell.
What triggers an action potential in a neuron?
When the membrane reaches the threshold of excitation (~-55 mV), Na⁺ channels open.
Na⁺ rushes in, causing depolarization and making the inside positive.
Describe the key phases of an action potential.
Depolarization: Na⁺ enters, making the inside positive.
Repolarization: K⁺ exits, restoring the negative charge.
Hyperpolarization: The membrane temporarily becomes more negative than the resting potential.
How does the action potential travel along the axon?
Continuous conduction: In unmyelinated axons, the impulse moves as a wave.
Saltatory conduction: In myelinated axons, it jumps between nodes of Ranvier, making it faster.
What are the two types of refractory periods in a neuron?
Absolute refractory period: No action potential can occur.
Relative refractory period: A stronger stimulus can trigger an action potential.
What is the role of voltage-gated ion channels in neural impulses?
Na⁺ channels: Open during depolarization to allow sodium ions to enter.
K⁺ channels: Open during repolarization to allow potassium ions to exit.
Both are critical for generating and propagating the action potential.
What are nodes of Ranvier, and what is their role in neural impulses?
Nodes of Ranvier are gaps in the myelin sheath along myelinated axons.
They allow the action potential to be regenerated by exposing the axon membrane to the extracellular fluid.
This enables saltatory conduction, where the action potential jumps between nodes, making signal transmission faster and more efficient.
What is the All-or-None Law in neural impulses?
The All-or-None Law states that a neuron either fires a full action potential or does not fire at all.
Once the threshold of excitation (~-55 mV) is reached, the action potential is generated with the same strength and speed regardless of the stimulus size.
A stronger stimulus does not produce a stronger action potential, but it may increase the frequency of firing.
What role does K⁺ play in repolarisation?
K⁺ channels open, and potassium ions leave the cell, taking positive charges with them.
This movement makes the inside of the neuron more negative, restoring the resting potential.
