Aufgabe 3 - Teilaufgabe 2: Nervenzelle: Membranpo… · Abitur NRW Biologie GK · Haupttermin · bilingual Englisch 2023

Material A: Overwintering of Burgundy Snails

The Burgundy snail¹ ( Helix pomatia) overwinters from October until the beginning of May. During this period, it lives withdrawn into its shell, which is tightly sealed by a calcareous lid², and is buried under leaves in the soil. When temperatures fall below 8° Celsius, their metabolism switches to a cold-induced torpor. The snails do not feed during the cold-induced torpor. Their metabolic rate, their oxygen consumption, their heart rate and the activity of their nervous systems are reduced. During this time, the Burgundy snail lives on nutrients it stored while feeding. Starting in May, Burgundy snails actively start looking for food if enough moisture is present. They feed on soft, wilting plant parts and algae.

¹ Weinbergschnecke

² Kalkdeckel

Material B: Signal Conduction in the Burgundy Snail

The formation and conduction of action potentials in the Burgundy snail are made possible by voltage-gated ion channels. Based on their characteristics, different types of voltage-gated sodium ion channels, $\text{Na}_\text{v}$ for short, can be distinguished. These $\text{Na}_\text{v}$-channels show various degrees of conductivity during various stages of the action potential (Figure 1). The higher the conductivity, the more sodium ions can flow through the $\text{Na}_\text{v}$-channel.

Material C: Neurophysiological Investigations

In order to investigate the activity of neurons in the Burgundy snails' brains in more depth, a number of experiments were conducted on active and on hibernating Burgundy snails. The active snails were kept at room temperature. The hibernating snails, which were in a cold-induced torpor, were collected in autumn and kept at 3° Celsius.

The relative density of specific $\text{Na}_\text{v}$-channels in the brain was investigated in active and in hibernating Burgundy snails (Figure 2).

Neurophysiological measurements were conducted on neurons in the brain of Burgundy snails. The maximum flow of sodium ions through $\text{Na}_\text{v}1.9$-channels after stimulation was measured in the neurons of active Burgundy snails as well as in hibernating individuals (Figure 3).

2.

Summarise what Figure 1 shows and illustrate how important the respective sodium ion channels are for the progression of an action potential (Material B). Summarise the findings presented in Figures 2 and 3 and illustrate what effects they have on signal conduction in the Burgundy snail during cold-induced torpor (Materials A to C).

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