You're viewing 3 free preview questions for Biology SL — subscribe to unlock 87 more, plus the Full Question Bank, Mock Papers & Worksheets.Upgrade

Neural Signaling · Paper 2 — Free Biology SL Practice Questions

1MasterySAQ-SStructure of neurons8 marksPaper 2~12 min

A patient with multiple sclerosis (MS) has damage to the myelin sheaths of their neurons, slowing signal transmission. A researcher measures the speed of an action potential along a myelinated neuron from a healthy individual and finds it travels at

120\,\text{m s}^{-1}

. The distance between two adjacent Nodes of Ranvier is

1.2\,\text{mm}

(a)

State two roles of the myelin sheath in a motor neuron. [2 marks]

(b)

Describe how the Nodes of Ranvier facilitate rapid signal transmission along a myelinated axon. [2 marks]

(c)

Calculate the time, in milliseconds, for an action potential to travel between two adjacent Nodes of Ranvier in the healthy neuron. [1 mark]

(d)

A patient with MS has myelin sheath damage that reduces conduction speed to

6\,\text{m s}^{-1}

. Explain, with reference to ion movement, why demyelination causes this reduction in conduction speed. [3 marks]

Solutions

2MasterySAQ-SStructure of neurons5 marksPaper 2~8 min

A biologist stains two neurons from a rat: a sensory neuron from the skin and a motor neuron from the spinal cord. The sensory neuron has a long dendrite and a short axon; the motor neuron has a short dendrite and a long axon.

(a)

State one structural difference between a sensory neuron and a motor neuron. [1 mark]

(b)

Explain how the structure of the sensory neuron is adapted for its function in detecting stimuli and transmitting signals to the central nervous system (CNS). [2 marks]

(c)

The sensory neuron has

12

dendrites each

0.5\,\text{mm}

long and an axon

2.0\,\text{mm}

long. The motor neuron has

4

dendrites each

0.3\,\text{mm}

long and an axon

18.0\,\text{mm}

long. Calculate the total length of all neuronal processes for each neuron, then deduce which neuron is better structurally adapted for receiving multiple simultaneous inputs. [2 marks]

Solutions

3ChallengeSAQ-LStructure of neurons7 marksPaper 2~11 min

A researcher investigates how neuron structure affects the speed of nerve impulse conduction in the sciatic nerve of the frog Rana temporaria. She records the diameter and myelination status of three neuron types. Neuron — Myelination — Axon diameter A — Unmyelinated —

2.5\,\mu\text{m}

B — Myelinated —

2.5\,\mu\text{m}

C — Myelinated —

10\,\mu\text{m}

For unmyelinated neurons, conduction speed

v \propto \sqrt{d}

, where

d

is axon diameter. For myelinated neurons,

v \propto d

(a)

State what is meant by saltatory conduction. [1 mark]

(b)

Calculate the ratio of conduction speed of Neuron C to Neuron B. [2 marks]

(c)

Explain how myelination increases the speed of impulse conduction, comparing Neuron B with Neuron A. [2 marks]

(d)

Evaluate the hypothesis that a larger axon diameter is always advantageous for neural signalling, using data from all three neurons in your answer. [2 marks]

Solutions

Questions 4-90

Unlock these questions with Premium

That's every free question here — 3 of 90.

+87 more questions, plus Mock Papers & Worksheets, are waiting in Premium.

Upgrade