DP Biology 6.5 Neurons & Synapses

The movement of which ion initiates an action potential?

• Calcium

• Magnesium

• Sodium

• Potassium

What is the role of active transport in the transmission of nerve impulses by neurones?

• Propagates an action potential by pumping sodium ions across the membrane out of the neurone.

• Propagates an action potential by pumping sodium ions across the membrane into the neurone.

• Initiates the action potential needed for the transmission of an impulse by pumping calcium ions out of the endoplasmic reticulum.

• Establishes the resting potential needed for the transmission of an impulse by pumping sodium and potassium ions across the membrane.

In a nerve impulse, what happens at the site following the highest point of the action potential?

• Voltage-gated sodium ion channels open and Na+ is pumped in.

• Voltage-gated sodium ion channels open and Na+ diffuses out.

• Voltage-gated potassium ion channels open and K+ is pumped out.

• Voltage-gated potassium ion channels open and K+ diffuses out.

......................... and ................... are parts of central nervous system.

Which structural feature enables saltatory conduction?

• Na+ channels under Schwann cells

• K+ channels under Schwann cells

• Nodes of Ranvier between Schwann cells

• Sodium–potassium pumps under Schwann cells

• A

• B

• C

• D

What happens when an action potential reaches motor end plates?

• Calcium ions are absorbed by the muscle fibres.

• Muscle relaxes.

• Neurotransmitter is released.

• Action potential is passed to the neuron.

• -80 mV

• -70 mV

• -55 mV

• 40 mV

What is the function of myelin sheath?

Neurotransmitters are released into the synaptic cleft from the presynaptic neuron and travel to a receptor on the postsynaptic neuron membrane. Which processes are required for this to happen?

• Release into synaptic cleft: exocytosis Travel to postsynaptic neuron membrane: diffusion

• Release into synaptic cleft: active transport Travel to postsynaptic neurone membrane: diffusion

• Release into synaptic cleft: exocytosis Travel to postsynaptic neuron membrane: active transport

• Release into synaptic cleft: active transport Travel to postsynaptic neuron membrane: active transport