Regarding the conduction of a nerve impulse from site A to site B along an axon, analyze the following statements:
I. At site B (immediately ahead of site A), the outer membrane surface is positively charged and the inner membrane surface is negatively charged. II. Current flows on the inner surface of the axon from site A to site B. III. Current flows on the outer surface from site A to site B to complete the circuit. IV. The current flow on the outer surface completes the circuit and reverses the polarity of site B, generating an action potential at site B.
Statements I, II and IV are correct. Statement III is incorrect because current on the outer surface flows from site B back to site A, thereby completing the electrical circuit.
Question 12 of 100
📘 CLASS XI
Analyze the following statements regarding the recovery of a depolarized axonal membrane:
I. The rise in stimulus-induced permeability to Na+ is extremely long-lived. II. The increase in Na+ permeability is quickly followed by a rise in permeability to K+. III. Within a fraction of a second, K+ diffuses outside the membrane to restore the resting potential at the site of excitation. IV. Once the resting potential is restored, the fibre becomes responsive to further stimulation again.
Statements II, III and IV are correct. Statement I is incorrect because the increase in Na+ permeability during depolarization is extremely short-lived.
Question 13 of 100
📘 CLASS XI
Consider the following statements regarding the types of synapses in the human neural system:
I. At electrical synapses, the membranes of pre- and post-synaptic neurons are separated by a wide, fluid-filled synaptic cleft. II. Electrical current can flow directly from one neuron into another across electrical synapses. III. Impulse transmission across an electrical synapse is always faster than across a chemical synapse. IV. Electrical synapses are very common in the human neural system.
Statements II and III are correct. Statement I is incorrect because membranes are in very close proximity at electrical synapses. Statement IV is incorrect because electrical synapses are rare in the human nervous system.
Question 14 of 100
📘 CLASS XI
Evaluate the statements below regarding synaptic transmission:
Statement I: At chemical synapses, the membranes of the pre- and post-synaptic neurons are separated by a fluid-filled space called synaptic cleft. Statement II: Axon terminals contain synaptic vesicles filled with chemicals called neurotransmitters. Statement III: When an action potential arrives at the axon terminal, it stimulates the movement of synaptic vesicles towards the post-synaptic membrane receptors. Statement IV: The synaptic vesicles fuse with the pre-synaptic plasma membrane and release their neurotransmitters into the synaptic cleft.
Statements I, II and IV are correct. Statement III is incorrect because the arrival of an action potential stimulates the movement of synaptic vesicles towards the pre-synaptic plasma membrane, where they fuse and release neurotransmitters into the synaptic cleft.
Question 15 of 100
📘 CLASS XI
Analyze the following statements regarding the events occurring after neurotransmitter release:
Statement I: Released neurotransmitters bind to specific receptors present on the post-synaptic membrane. Statement II: Receptor binding opens ion channels, allowing the entry of ions into the post-synaptic neuron. Statement III: The new potential generated in the post-synaptic neuron is always excitatory, never inhibitory. Statement IV: The ions entering the post-synaptic membrane generate a new potential.
Statements I, II and IV are correct. Statement III is incorrect because the new potential generated on the post-synaptic membrane may be either excitatory or inhibitory.
Question 16 of 100
📘 CLASS XI
Consider the following statements regarding the protective coverings of the human brain:
Statement I: Inside the skull, the brain is covered by cranial meninges consisting of three distinct layers. Statement II: The outermost layer is a very thin layer called arachnoid. Statement III: Dura mater is the outer layer, whereas pia mater is the inner layer in contact with the brain tissue. Statement IV: Arachnoid is the middle layer of the cranial meninges.
Statements I, III and IV are correct. Statement II is incorrect because dura mater is the outermost layer, whereas the arachnoid mater forms the thin middle layer.
Question 17 of 100
📘 CLASS XI
Read the statements below regarding the major division of the human brain:
Statement I: Cerebrum forms the major part of the human brain. Statement II: A deep cleft divides the cerebrum longitudinally into left and right cerebral hemispheres. Statement III: The cerebral hemispheres are connected by a tract of nerve fibres called corpus callosum. Statement IV: The corpus callosum is an outer covering of grey cells.
Statements I, II and III are correct. Statement IV is incorrect because the corpus callosum is a thick band of myelinated nerve fibres (white matter) connecting the two cerebral hemispheres.
Question 18 of 100
📘 CLASS XI
Regarding the cerebral cortex, analyze these statements:
Statement I: The layer of cells covering the cerebral hemisphere is called the cerebral cortex and is thrown into prominent folds. Statement II: The cerebral cortex is referred to as grey matter because neuron cell bodies are concentrated here, giving it a greyish appearance. Statement III: The cerebral cortex is entirely sensory and motor in function, containing no other regions. Statement IV: Association areas in the cerebral cortex are responsible for complex functions like memory, communication, and intersensory associations.
Statements I, II and IV are correct. Statement III is incorrect because the cerebral cortex also contains association areas responsible for memory, communication, intelligence and integration.
Question 19 of 100
📘 CLASS XI
Examine the following statements regarding the inner parts of the cerebral hemispheres:
Statement I: Fibres of the nerve tracts in the inner part of cerebral hemispheres are covered with myelin sheath. Statement II: These myelinated fibres give an opaque white appearance to the layer, hence called the white matter. Statement III: Motor, sensory, and association areas are concentrated in this white matter region. Statement IV: The white matter forms the outer covering of the cerebrum.
Statements I and II are correct. Statement III is incorrect because motor, sensory and association areas are located in the grey matter (cerebral cortex). Statement IV is incorrect because white matter forms the inner part of the cerebrum.
Question 20 of 100
📘 CLASS XI
Regarding the core structures wrapped by the cerebrum, analyze these statements:
Statement I: The cerebrum wraps around the thalamus, which is a major coordinating centre for sensory and motor signaling. Statement II: The hypothalamus lies at the base of the thalamus. Statement III: Hypothalamus contains centres controlling body temperature, urge for eating, and urge for drinking. Statement IV: Hypothalamus contains groups of neurosecretory cells which secrete hypothalamic hormones.
All four statements are correct. The thalamus functions as a major coordinating centre for sensory and motor signalling. The hypothalamus lies below the thalamus and regulates body temperature, hunger, thirst and contains neurosecretory cells that produce hypothalamic hormones.
