3.6.3: Nervous Coordination Flashcards
1
Q
Explain how a resting potential is maintained
across the axon membrane in a neurone.
A
- Higher concentration of potassium ions inside and higher
concentration of sodium ions outside (the neurone) OR
potassium ions diffuse out - (Membrane) more permeable to potassium ions (leaving than
sodium ions entering) OR
(Membrane) less permeable to sodium ions (entering than potassium
ions leaving);
Accept for ‘less permeable to sodium ions’ is ‘impermeable to sodium
ions’ or ‘sodium
gates/channels are closed’ (alternative explanation). - Sodium ions (actively) transported out and potassium ions in;
reference to ions or Na+ and K+ is required. If mentioned once allow for
all mark points.
If an answer provides two or three of these mark points without any
reference to ions – award one maximum mark.
Accept 3 Na+ out and 2 K+ in but reject if numbers used are incorrect.
2
Q
Explain why the speed of transmission of
impulses is faster along a myelinated axon than
along a non-myelinated axon.
A
- Myelination provides (electrical) insulation;
Reject thermal insulation.
Accept description of (electrical) insulation. - (In myelinated) saltatory (conduction) OR
(In myelinated) depolarisation at nodes (of Ranvier); - In non-myelinated depolarisation occurs along whole/length (of axon);