This set of Biology Question Papers for NEET Exam focuses on “Neuron-2”.
1. At resting membrane potential, the axonal membrane is impermeable to which ions?
a) Calcium ions
b) Sodium ions
c) Potassium ions
d) Chlorine ions
Explanation: The axonal membrane of the neuron or nerve cell is semi-permeable in nature. At resting membrane potential, the membrane is permeable to potassium ions but nearly impermeable to sodium ions.
2. Which of the following is not true regarding resting potential?
a) There is a potential difference across the plasma membrane
b) The potential difference is maintained by the Na-K pump
c) The outer surface of the membrane is negatively charged
d) The axonal membrane is polarized
Explanation: The axonal membrane is positively charged on the outer surface and negatively charged on the inner surface. This makes the membrane polarized. The potential difference is maintained by the Na-K pump.
3. Which of these does not take place when a stimulus is applied to a polarized axonal membrane?
a) It becomes permeable to sodium ions
b) The membrane is depolarized
c) There is a slow influx of sodium ions
d) Outer surface of the membrane becomes negatively charged
Explanation: When a stimulus is applied to a polarized axonal membrane, the polarity of the membrane is reversed. It becomes permeable to sodium ions and leads to its rapid influx. Outer surface of the membrane becomes negatively charged.
4. What is a nerve impulse also known as?
a) Action potential
b) Graded potential
c) Resting potential
d) Membrane potential
Explanation: A nerve impulse is also known as an action potential. It changes the resting membrane potential as it reverses the polarity of the axonal membrane. It becomes permeable to sodium ions and leads to its rapid influx.
5. How is the resting potential restored after a nerve impulse?
a) Potassium ions diffuse inside the membrane
b) Potassium ions diffuse outside the membrane
c) The membrane becomes impermeable to potassium ions
d) There is no movement of potassium ions
Explanation: After a nerve impulse, the permeability of the membrane to sodium ions reduces and increases for potassium ions. Potassium ions diffuse outside the membrane and hence restore the resting potential.
6. Nerve impulses are transmitted from one neuron to another via which of these?
a) Schwan cells
b) Nissl’s granules
d) Myelin sheath
Explanation: Synapses are the gaps or junctions between two adjacent neurons via which nerve impulses are transmitted. This occurs by the release of chemical compounds known as neurotransmitters.
7. Which of these is not a component of the synapse?
a) Synaptic vesicles
b) Pre-synaptic membrane
c) Post-synaptic membrane
d) Synaptic cleft
Explanation: A synapse is present between two adjacent neurons. The pre-synaptic membrane of one neuron, the post-synaptic membrane of the next neuron and the synaptic cleft make up the synapse.
8. Which of the following statements is false regarding electrical synapses?
a) Membranes of pre and post-synaptic neurons are in very close proximity
b) Transmission is always faster than that across a chemical synapse
c) It is similar to impulse conduction along a single axon
d) Electrical synapses are common in our system
Explanation: In electrical synapses, the membranes of pre and post-synaptic neurons are in close proximity. It is similar to impulse conduction along a single axon and is always faster than transmission across a chemical synapse. It is rare in our system.
9. Which of these is false regarding synaptic clefts?
a) It lies between the membranes of pre and post-synaptic neurons
b) It is a fluid filled space
c) Electrical synapses have large synaptic clefts
d) It is a portion of the synapse
Explanation: Synaptic clefts are fluid filled spaces that lie between the membranes of pre and post-synaptic neurons. These together make up the synapse. Electrical synapses have very small synaptic clefts.
10. The outer surface of the axon has a positive charge at resting membrane potential. True or false?
Explanation: At resting membrane potential, the concentration of sodium ions is high outside the axonal membrane. Due to the sodium-potassium pump, the outer surface of the axon has a positive charge.
11. Which of these are involved in the transmission of nerve impulses?
a) Synaptic knob
b) Schwan cells
c) Nissl’s granules
Explanation: Neurotransmitters are chemical compounds that help in the transmission of nerve impulses or action potentials. Nissl’s granules, Schwan cells and synaptic knobs do not participate in this process.
12. What happens to synaptic vesicles during an action potential?
a) They degrade their contents
b) They open up inside the synaptic knob
c) They move towards and fuse with the plasma membrane
d) They are released into the synapse
Explanation: During an action potential, the synaptic vesicles move towards the membrane of the neuron and fuse with the plasma membrane. This results in the release of neurotransmitters in the synaptic cleft.
13. Which of these structures are present on the post-synaptic membrane?
a) Synaptic knobs
b) Synaptic vesicles
d) Schwan cells
Explanation: The post-synaptic membrane contains receptors. These are receptors for the neurotransmitters which are released from the pre-synaptic membrane at the terminal end of the adjacent neuron.
14. What happens when a neurotransmitter binds to a receptor on the post-synaptic membrane?
a) Opening of ion channels
b) Conformational changes in the neuron
c) Graded potential is transmitted across the neuron
d) It becomes impermeable to all ions
Explanation: When a neurotransmitter binds to a receptor on the post-synaptic membrane, it leads to the opening of ion channels. This allows the entry of ions which results in the generation of a new action potential.
15. Action potentials can be inhibitory. True or false?
Explanation: Action potentials or nerve impulses can be excitatory as well as inhibitory. They are conducted from neuron to neuron with the help of chemical compounds known as neurotransmitters.
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