This set of Class 11 Biology Chapter 21 Multiple Choice Questions & Answers (MCQs) focuses on “Neuron-1”.
1. Which of these structures is not a part of a neuron?
a) Cell body
b) Axon
c) Dendrite
d) Glomerulus
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Explanation: The neuron is the structural and functional unit of the nervous system. The neuron or the nerve cell has three main parts-the cell body, the axon and the dendrites. Glomerulus is a part of nephron.
2. Where are Nissl’s granules present?
a) Axon
b) Dendrites
c) Cell body
d) Dendrons
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Explanation: Nissl’s granules are present in the cell body of the neuron or nerve cell. The cell body contains the cytoplasm, in which the various cell organelles are present. Nissl’s granules are also present along with them.
3. Which of these is not characteristic of dendrites?
a) They contain Nissl’s granules
b) They branch repeatedly
c) They project out from the axon
d) They transmit impulses
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Explanation: Dendrites are a part of the nerve cell or the neuron. They are short fibers that project out from the cell body, but not the axon. They branch repeatedly and help in the transmission of impulses.
4. What are the terminal branched ends of axons known as?
a) Synaptic knobs
b) Synaptic vesicles
c) Dendrons
d) Dendrites
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Explanation: An axon is a part of the nerve cell or the neuron. Each axon is a long fiber that projects from the cell body. The terminal end of the axon branches out and each end terminates with a synaptic knob.
5. Where are neurotransmitters present inside the neuron?
a) Synaptic knob
b) Synaptic vesicles
c) Nissl’s granules
d) Schwan cells
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Explanation: Neurotransmitters are the chemicals which help in the transmission of impulses from neuron to neuron and from to neuron the target tissue or cell. They are stored in the synaptic vesicles.
6. Which of these statements is not true regarding axons?
a) They carry impulses away from the cell body
b) They transmit impulses to synapses
c) They are short fibers
d) Their terminal ends are branched
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Explanation: Axons are long fibers while dendrites are short fibers. Axons carry or transmit nerve impulses away from the cell body towards synapses. Their terminal ends are branched and end with synaptic knobs.
7. How many types are neurons classified into?
a) 3
b) 4
c) 1
d) 2
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Explanation: Neurons or nerve cells are classified into three types based on the number of axon and dendrites. The three types of neurons are namely, multipolar neurons, unipolar neurons and bipolar neurons.
8. Where are bipolar neurons found?
a) Autonomic ganglia
b) Embryo
c) Cerebral cortex
d) Retina of eye
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Explanation: Bipolar neurons are found in the retina of the eye. They possess one axon and one dendrite. The cerebral cortex and autonomic ganglia have multipolar neurons. Unipolar neurons are found in embryo.
9. Which of these structures is present in both non-myelinated and myelinated neurons?
a) Myelin forming Schwan cells
b) Myelin sheath
c) Nissl’s granules
d) Nodes of Ranvier
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Explanation: Non-myelinated neurons lack myelinated axons. Hence, myelin forming Schwan cells, which surround and form myelin, are absent. Nodes of Ranvier are also absent as they are the points between two adjacent myelin sheaths.
10. Unipolar neurons lack dendrites. True or false?
a) True
b) False
View Answer
Explanation: There are three types of neurons or nerve cells. These types are multipolar neurons, unipolar neurons and bipolar neurons. Unipolar neurons lack dendrites. They have a cell body with only one axon.
11. Identify the structure shown in the diagram.
a) Synaptic knob
b) Node of Ranvier
c) Nissl’s granule
d) Schwan cell
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Explanation: The given diagram is that of a neuron or nerve cell. The indicated structure is identified to be a Schwan cell. Schwan cells form the myelin sheath which envelops the axon and helps in the transmission of impulses.
12. Identify the structure shown in the diagram.
a) Synaptic knob
b) Node of Ranvier
c) Nissl’s granule
d) Schwan cell
View Answer
Explanation: The given diagram shows a nerve cell or neuron. The indicated region lies between two adjacent myelin sheaths. Hence, it is identified to be a Node of Ranvier. It is the gap between two myelin sheaths.
13. At resting membrane potential, the axonal membrane is permeable to which ions?
a) Calcium ions
b) Sodium ions
c) Potassium ions
d) Chlorine ions
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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.
14. At resting membrane potential, which ion concentration is high outside the axonal membrane?
a) Sodium ions
b) Calcium ions
c) Potassium ions
d) Chlorine ions
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Explanation: At resting membrane potential, the membrane is permeable to potassium ions but nearly impermeable to sodium ions. Hence, the concentration of sodium ions is higher outside the membrane.
15. How many sodium ions are transported for every 2 potassium ions by the Na-K pump?
a) 2
b) 3
c) 1
d) 0
View Answer
Explanation: At resting membrane potential, to maintain the ionic gradient, 3 sodium ions are transported out of the axonal membrane for every 2 potassium ions moving into the cell, by the Na-K pump.
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