6- Nervous Coordination =)

Question 1

Explain why different channel proteins are required for the diffusion of different ions through the
membrane. (2)

Answer 1

• each protein has specific tertiary struc
• ions have diff sizes

Question 2

Protein C requires ATP to function. Describe the role of protein C in maintaining membrane potential. (2)

Answer 2

• transports Na+ & K+
• a.t.
• restores ion balance after action potential

Question 3

Explain how a resting potential is maintained across the axon membrane in a neurone. (3)

Answer 3

• ↑ K+ conc inside , ↑ Na+ conc outside (K+ diffuse out, Na+ diffuse in)
• mem ↑ permeable to K+ (so ↑ K+ leave than Na+ enter)
• Na+ a.t. out, K+ in

Question 4

Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon. (3)

Answer 4

• myelination = electrical insulation
• myelinated: saltatory conduction (depolarisation at nodes of Ranvier)
• non-m: depolarisation along whole length of axon

Question 5

A scientist investigated the effect of inhibitors on neurones. She added a respiratory inhibitor to a neurone. The resting potential of the neurone changed from –70 mV to 0 mV.
Explain why. (3)

Answer 5

• ↓ ATP
• ↓ a.t. (thru Na+/ K+ pump)
• electrochemical gradient x maintained (x net movement of iona)

Question 6

GABA is a neurotransmitter released in some inhibitory synapses in the brain. GABA causes negatively charged chloride ions to enter postsynaptic neurones.
Explain how this inhibits postsynaptic neurones. (3)

Answer 6

• inside of postsynaptic neurone ↑ -ve (hyperpolarisation)
• ↑ Na+ required to reach threshold
• for depolarisation ( /a.p.)

Question 7

Some of the symptoms of AD that are associated with
communication between nerve cells are reduced by taking the drug donepezil.
Donepezil inhibits the enzyme acetylcholinesterase.
Explain how donepezil could improve communication between nerve cells. (3)

Answer 7

• ↓ acetylcholine broken down
• attaches to receptors
• ↑ Na+ enter –> reach threshold –> depolarisation

Question 8

During an action potential, inside of the axon mem becomes more positive than outside.
Describe how the change occurs when an action potential is produced. (2)

Answer 8

• Na+ channels open –> axon mem ↑ permeable to Na+
• Na+ enter axon

Question 9

After exercise, some ATP is used to re-establish the resting potential in axons.
Explain how the resting potential is re-established. (2)

Answer 9

• active transport
• Na+ out, K+ in to axon

Question 10

Describe how the resting potential is established in an axon by the movement of ions across the membrane. (2)

Answer 10

• a.t. of Na+ out of axon
• K+ diffuse out

Question 11

Sodium and potassium ions can only cross the axon membrane through proteins.
Explain why. (2)

Answer 11

• x pass thru phospholipid bilayer
• ∵ water soluble (x lipid soluble)

Question 12

The KDR plus allele codes for the sodium ion channels found in neurones.
When DDT binds to a sodium channel, the channel remains open all the time.
Use this infromation to suggest how DDT kills insects. (2)

Answer 12

• neurones remain depolarised
• x a.p.

Question 13

The KDR plus allele codes for the sodium ion channels found in neurones.
When DDT binds to a sodium channel, the channel remains open all the time.
Suggest how the KDR minus allele gives resistance to DDT. (2)

Answer 13

• mutation Δ shape of Na+ channel
• x longer complementary to DDT