3.6.2.1 Nerve impulses

Front

What is the primary function of myelin in a motor neurone?

Back

To increase the speed of nerve impulse transmission

Answer explanation

The primary function of myelin in a motor neurone is to increase the speed of nerve impulse transmission. Myelin acts as an insulating layer, allowing impulses to jump between nodes, which enhances conduction velocity.

Front

Which ions are primarily involved in establishing the resting potential of a neurone?

Back

Sodium and potassium ions

Answer explanation

The resting potential of a neurone is primarily established by the movement of sodium (Na+) and potassium (K+) ions across the cell membrane, with potassium ions playing a key role in maintaining the negative charge inside the cell.

Front

Term for rapid change in membrane potential during an action potential.

Back

Depolarisation

Answer explanation

The rapid change in membrane potential during an action potential is called depolarisation. This phase involves the influx of sodium ions, causing the membrane potential to become more positive.

Front

What principle states that an action potential either occurs fully or not at all?

Back

All-or-nothing principle

Answer explanation

The all-or-nothing principle states that an action potential will either fully occur or not at all, meaning it does not vary in strength. This distinguishes it from graded responses, which can vary in magnitude.

Front

How does the refractory period affect nerve impulse transmission?

Back

It produces discrete impulses

Answer explanation

The refractory period prevents the immediate reactivation of a neuron after an impulse, ensuring that impulses are discrete rather than continuous. This allows for clear signaling and prevents overlapping signals.

Front

Which factor does NOT affect the speed of conductance in a neurone? Options: Myelination, Axon diameter, Temperature, Neurone length

Back

Neurone length

Answer explanation

Neurone length does not significantly affect the speed of conductance. In contrast, myelination, axon diameter, and temperature all enhance the speed of nerve impulse transmission.

Front

What is saltatory conduction?

Back

The jumping of action potentials from one node of Ranvier to the next

Answer explanation

Saltatory conduction refers to the process where action potentials jump from one node of Ranvier to the next along a myelinated axon, allowing for faster signal transmission compared to continuous conduction.

Front

What happens to the membrane potential during depolarisation?

Back

It becomes more positive

Answer explanation

During depolarisation, the membrane potential becomes more positive as sodium ions enter the cell, reducing the negative charge inside relative to the outside. This shift is crucial for initiating action potentials.

Front

Characteristic of non-myelinated axons?

Back

Slower impulse transmission

Answer explanation

Non-myelinated axons transmit impulses more slowly than myelinated ones because they lack the insulating myelin sheath, which facilitates faster conduction through saltatory propagation.

Front

Role of potassium ions during the repolarisation phase of an action potential?

Back

They leave the cell

Answer explanation

During the repolarisation phase of an action potential, potassium ions (K+) leave the cell. This efflux of K+ helps restore the negative membrane potential after depolarisation, making 'They leave the cell' the correct answer.