C2.2.
1 The Neuron Questions
1. An individual was presented with a stimulus resulting in the release of epinephrine. What
was the most likely nature of the stimulus?
A. Sunset and the onset of darkness
B. An image of a close friend
C. The intake of glucose
D. A coach shouting to begin physical activity
2. What is a feature of neurons?
A. Relay neurons transmit impulses from motor to sensory neurons
B. The cell body of a motor neuron is in the CNS
C. Sensory neurons carry impulses away from the CNS
D. Relay neurons form synapses with receptors
3. Between which structures do sensory neurons carry nerve impulses?
A. From effector to the central nervous system (CNS)
B. From effectors to receptors
C. From receptors to effectors
D. From receptors to the central nervous system (CNS)
4. Where do motor neurons conduct impulses from and to?
A. From effectors to the central nervous system
B. From receptors to the central nervous system
C. From neurons to other neurons
D. From the central nervous system to effectors
5. What is the role of nerves in human movement?
A. To cause muscles to stretch
B. To move joints
C. To transport pain signals that indicate muscle injuries
D. To stimulate muscle contraction
6. What role does the medulla of the brain have in controlling heart rate?
A. To secrete adrenaline to speed up the heart
B. To stimulate myogenic heart muscle contraction
C. To block pacemaker activity
D. To adjust heart rate to changing blood pressure
7. Which part of the brain has a role in the control of the heartbeat and how are messages
passed from this part of the brain to the heart?
Part of the brain Type of message
A Hypothalamus Hormone
B Hypothalamus Nerve
C Medulla Hormone
D Medulla Nerve
8. Neural pathways in living brains can now be mapped by tracking the movement of water
molecules inside axons. What keeps water molecules inside axons?
A. Plasma membrane
B. Hydrogen bonding
C. Pump proteins
D. Synapse
9. The image shows a diagram of a motor neuron
Which structure is correctly labelled in the diagram?
A. Cell body
B. Axon
C. Dendrite
D. Node of Ranvier
10. The diagram shows a motor neuron.
What are the biochemical nature and function of the myelin sheath?
A. The myelin sheath is mainly protein which allows growth of the axon.
B. The myelin sheath is mainly protein which acts as membrane carriers.
C. The myelin sheath is mainly lipid which allows saltatory conduction.
D. The myelin sheath is mainly lipid which provides an energy source.
11. The image shows a neuron.
What is the function of X?
A. Increases the speed of transmission along the axon
B. Increases the rate of exchange of sodium and potassium ions
C. Holds bundles of neurons together to form a nerve
D. Determines the direction of the action potential
12. The image shows a neuron. Which letter shows the myelin sheath?
A.
B.
C.
D. kkkcm
13. The electron micrograph shows a transverse section through a myelinated neuron
What process is facilitated by the presence of the structure labelled X?
A. Repolarization of the nerve cell membrane
B. Generation of an action potential
C. Saltatory conduction
D. Synaptic transmission
14. What is essential for conduction of nerve impulses to be saltatory?
A. Wrapping of myelin around the axon
B. Reaching the threshold potential in dendrites
C. Pumping potassium ions into the neuron
D. Releasing a neurotransmitter at the synapse
15. Which structural feature enables saltatory conduction?
A. Nodes of Ranvier between Schwann cells
B. Na+ channels under Schwann cells
C. K+ channels under Schwann cells
D. Sodium–potassium pumps under Schwann cells
16. Which statement applies to an axon at rest?
A. There is no electric potential difference between the external and internal surfaces of the
plasma membrane.
B. The external surface of the plasma membrane is positive relative to the internal surface.
C. The external surface of the plasma membrane is negative relative to the internal surface.
D. The internal surface of the plasma membrane has a much higher concentration of sodium
ions.
17. The diagram shows an action potential moving along a neuron. Which part of the diagram
represents depolarization?
A. Kmt,
B.
C.
D.
18. The diagram below shows part of the membrane of a neuron. What stage of the action
potential does it depict?
A. Depolarization
B. Repolarization
C. Resting potential
D. Hyperpolarization
19. The diagram shows a potassium channel in an axon membrane. The three dots represent
potassium ions.
What is the function of the potassium channel?
A. Facilitated diffusion of potassium ions into the axon
B. Passage of potassium ions by active transport out of the axon
C. Facilitated diffusion of potassium ions out of the axon
D. Passage of potassium ions by active transport into the axon
20. What initiates an action potential along a neuron?
A. Potassium and sodium ions diffuse out of a neuron
B. Potassium and sodium ions diffuse into a neuron
C. Neurotransmitters cause depolarization of membrane
D. Acetylcholinesterase breaks down acetylcholine
21. What occurs during the establishment of a resting membrane potential of a neuron?
A. Both sodium and potassium ions are pumped outside the neuron.
B. Sodium ions are pumped out while potassium ions are pumped into the neuron.
C. Both sodium and potassium ions are at rest inside the membrane of the neuron.
D. Sodium ions leave by diffusion and potassium ions enter the neuron by active transport
22. Which element or ion is required for transmission of a nerve impulse?
A. Phosphorous
B. Sodium
C. Sulfur
D. Iron
23. Which term describes the phase of rapid entry of sodium ions (Na +) into an axon during an
action potential?
A. Active transport
B. Depolarization
C. Ion pumping
D. Repolarization
24. Neurons transmit electrical impulses. Which statement describes part of this process?
A. K+ ions are pumped out of the cell to depolarize the membrane.
B. Ion channels let K+ diffuse into the cell to depolarize the membrane.
C. Na+ ions are pumped into the cell to repolarize the membrane.
D. Ion channels let Na+ diffuse into the cell to depolarize the membrane.
25. What is a characteristic of axons in motor neurons?
A. When there is a resting potential, the outside of the axon is negative relative to the inside
B. During an action potential, Na+ ions diffuse out of the axon
C. K+ ions diffusing out of the axon repolarizes it
D. Impulses in the axon travel towards the cell body
26. How does potassium move across the membrane of a neuron during repolarization?
A. Simple diffusion
B. Facilitated diffusion
C. Endocytosis
D. Active transport
27. Immediately after an action potential, which event causes the neuron membrane to
repolarize?
A. Voltage-gated sodium channels open.
B. Voltage-gated potassium channels open.
C. Voltage-gated calcium channels close.
D. Voltage-gated potassium channels close.
28. What happens when an action potential reaches motor end plates?
A. Calcium ions are absorbed by the muscle fibres
B. The sarcomeres relax
C. Neutransmitter is released
D. Action potential is passed to the neuron
29. What is a function of neurotransmitters?
A. To stimulate the axon of a neuron
B. To destroy hormones in a post-synaptic membrane
C. To diffuse across the synapse and affect the permeability of a neuron
D. To block calcium uptake in a pre-synaptic neuron
30. What happens during synaptic transmission?
A. K+ enters the postsynaptic membrane
B. A neurotransmitter is absorbed through the pre-synaptic membrane
C. Na+ is released from the presynaptic membrane
D. A neurotransmitter binds to a postsynaptic membrane receptor
31. What causes the formation of a nerve impulse on the post-synaptic membrane?
A. Ca+ binding with a receptor site
B. K+ leaking into the post-synaptic membrane
C. Neurotransmitter binding with receptor sites
D. Neurotransmitter being removed from the synapse
32. What happens first when a neurotransmitter binds to a postsynaptic neuron?
A. Ions diffuse
B. Electrophoresis begins
C. Ca2+ channels open
D. Repolarization
33. If schizophrenia is caused by an overabundance of the neurotransmitters dopamine and
serotonin in the synapses of some areas of the brain, which drug action could work in
treating the symptoms?
A. Release of cholinesterase into the synaptic cleft
B. Increased re-uptake of dopamine and serotonin in the presynaptic neuron
C. Increased permeability of the presynaptic neuron to sodium
D. Blockage of dopamine and serotonin on presynaptic neurons
34. Atropine drops are used by opticians to dilate the pupil, so that a thorough examination of
the retina can be performed. Atropine binds to acetylcholine receptors in synapses.
What is the effect of atropine binding in synapses?
A. Inhibits the binding of acetylcholine at the presynaptic membrane
B. Inhibits the release of acetylcholine from the presynaptic neuron
C. Prevents binding of acetylcholine at the postsynaptic membrane
D. Prevents transport of acetylcholine through the postsynaptic membrane
35. Neurotransmitters are released into the synaptic cleft from the presynaptic neuron and
travel to a receptor on the postsynaptic neuron membrane. Which processes are required
for this to happen?
Release into synaptic cleft Travel to postsynaptic neuron membrane
A Exocytosis Diffusion
B Active transport Diffusion
C Exocytosis Active transport
D Active transport Active transport
36. Draw a labeled diagram to show the structure of a motor neuron. [4 marks]
37. Explain the propagation of electrical impulses along a neuron including the role of myelin. [7
marks]
1. Resting Potential:
o A neuron at rest has a negative internal charge of about -70 mV due to the
sodium-potassium pump (Na+/K+ pump).
o This pump actively transports 3 Na⁺ ions out and 2 K⁺ ions in, maintaining the
resting potential.
2. Depolarization:
o When a neuron is stimulated, voltage-gated sodium (Na⁺) channels open, allowing
Na⁺ ions to rush into the neuron.
o This causes the inside of the neuron to become positively charged (about +30
mV).
o This change in charge is called an action potential.
3. Propagation of Action Potential:
o The depolarization of one section of the axon triggers adjacent voltage-gated Na⁺
channels to open, allowing the impulse to move along the axon like a wave.
o This ensures that the nerve signal is transmitted in one direction.
4. Repolarization:
o After depolarization, voltage-gated potassium (K⁺) channels open, allowing K⁺ to
exit the neuron.
o This restores the negative internal charge, returning the neuron to resting
potential.
5. Saltatory Conduction and the Role of Myelin:
o In myelinated neurons, the myelin sheath acts as an insulator, preventing ion
leakage.
o The action potential can only occur at the Nodes of Ranvier, where the axon
membrane is exposed.
o This causes the impulse to "jump" from node to node, a process called saltatory
conduction, which significantly increases the speed of transmission.
o This allows faster responses and more efficient nerve sign ,aling.
38. Explain the principles of synaptic transmission [8 marks]
Arrival of Action Potential at the Synapse:
When an action potential reaches the axon terminal of the presynaptic neuron, it depolarizes
the membrane.
Calcium Ion Influx:
Depolarization causes voltage-gated Ca²⁺ channels to open, allowing calcium ions (Ca²⁺) to enter
the presynaptic neuron.
Neurotransmitter Release:
The influx of Ca²⁺ triggers vesicles containing neurotransmitters (e.g., acetylcholine) to fuse with
the presynaptic membrane.
Neurotransmitters are released into the synaptic cleft by exocytosis.
Binding to Receptors on Postsynaptic Neuron:
Neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the
postsynaptic membrane.
Generation of a New Action Potential:
Binding of neurotransmitters opens ligand-gated Na⁺ channels, causing Na⁺ to enter the
postsynaptic neuron.
If the depolarization reaches the threshold potential, a new action potential is generated.
Neurotransmitter Degradation or Reuptake:
To stop the signal, neurotransmitters are broken down by enzymes (e.g., acetylcholine is broken
down by acetylcholinesterase) or reabsorbed by the presynaptic neuron for reuse.
Unidirectional Transmission:
Synaptic transmission occurs in one direction because neurotransmitters are only released from
the presynaptic neuron and receptors are only on the postsynaptic neuron.
Role of Excitatory and Inhibitory Synapses:
Some neurotransmitters (., glutamate) excite the postsynaptic neuron, while others (e.g., GABA)
inhibit it, regulating ne
