Synapses

The electron micrograph shows the junction between two neurones.

State the name given to the region labelled B.

Identify whether structure A or structure C is the first neurone in the pathway.

Use one piece of evidence visible in the electron micrograph to explain your choice.

Complete the sentences about the action potential.

The action potential involves rapid opening of voltage-gated sodium ion channels.

This is an example of........ feedback. During the action potential,

the inside of the neurone becomes more positive than the outside. This is known as

Mutations in genes coding for proteins in the cytoskeleton have been associated with several diseases of the nervous system, including neurodegenerative disorders.

Give three functions of the cytoskeleton.

Suggest how a mutation in cytoskeleton genes could cause a disease of the nervous system.

Questions 14 and 15 refer to the diagram below of a synapse.

Which of the following statements, A to D, describes events occurring at a synapse?

A Acetylcholine is broken down by enzymes so that it can bind to structure K.

B An action potential causes structure J to close.

C Structure J is a voltage gated Ca²⁺ channel.

D Structure L is released by exocytosis.

Your answer

Questions 14 and 15 refer to the diagram below of a synapse.

GABA is a neurotransmitter.

GABA reduces the number of action potentials in the postsynaptic neurone by opening chloride ion channels in the post-synaptic membrane.

Which of the following statements, A to D, describes the action of GABA?

A GABA binds to structure K in competition with acetylcholine.

B GABA causes hyperpolarisation of the post-synaptic membrane.

C GABA causes depolarisation of the post-synaptic membrane.

D GABA inhibits release of neurotransmitter from structure L.

Your answer

FURA-2 is a fluorescent dye that can be used to measure the concentration of Ca²⁺ ions inside 18 cells.

The structure of FURA-2 is shown below.

Use the information in the figure to explain why FURA-2 is unable to cross cell membranes.

Scientists have used FURA-2 to study the role of Ca²⁺ ions in the synapses of living nerve (b) tissue.

FURA-2 was injected into a single sensory neurone that was connected by a synapse to a relay neurone.

FURA-2 fluorescence inside the neurone was observed using a confocal microscope.

Explain one advantage of using a confocal microscope in this study.

The sensory neurone was stimulated electrically and the FURA-2 fluorescence in the synaptic bulb was measured. At the same time, an electrode recorded the membrane potential in a postsynaptic neurone.

The results of this study are shown in the table.

The intensity of FURA-2 fluorescence is proportional to the concentration of Ca²⁺ ions.

The scientists concluded that changes in the concentration of Ca²⁺ ions in the presynaptic neurone caused an action potential in the postsynaptic neurone.

Evaluate and explain the scientists’ conclusion.

The image below shows a synaptic bulb.

Which of the following rows, A to D, correctly names the parts labelled H to J in the image?

Your answer

The table below shows the membrane potentials of different neurones at a cholinergic synapse. The data were recorded on five separate occasions, as shown in the five rows.

Which of the following, A to D, explains these data?

A divergence

B hyperpolarisation

C spatial summation

D temporal summation

Your answer