Neural Control and Coordination MCQs

Consider the following statements regarding why neurons are classified as excitable cells:

Statement I: Neurons are excitable because their membranes exist in a polarized state.
Statement II: The neural membrane is selectively permeable to different types of ion channels.
Statement III: When a neuron is resting, the axonal membrane is completely permeable to sodium ions (Na⁺) and impermeable to potassium ions (K⁺).
Statement IV: The polarity of the neural membrane is maintained by concentration gradients of ions.

Evaluate these statements regarding the resting membrane potential of an axon:

Statement I: The resting potential is the electrical potential difference across the resting plasma membrane.
Statement II: At rest, the outer surface of the axonal membrane possesses a positive charge, while its inner surface is negatively charged.
Statement III: The resting membrane is highly permeable to the negatively charged proteins present in the axoplasm.
Statement IV: The sodium-potassium pump uses passive transport to move ions down their concentration gradient to maintain polarization.

Read these statements regarding the ionic concentration differences across a resting axonal membrane:

Statement I: The axoplasm inside the resting axon has a high concentration of K⁺ and negatively charged proteins.
Statement II: The axoplasm inside the resting axon has a high concentration of Na⁺ ions.
Statement III: The extracellular fluid outside the resting axon has a low concentration of K⁺ and a high concentration of Na⁺.
Statement IV: These concentration gradients are maintained by the active transport of ions.

Analyze the sequence of ion permeability changes when a stimulus is applied to a polarized membrane:

Statement I: A stimulus applied at a site causes the membrane to become freely permeable to Na⁺ at that site.
Statement II: This permeability change leads to a rapid influx of Na⁺ ions.
Statement III: The rapid influx of Na⁺ is followed by a reversal of polarity, rendering the inner surface negative and outer surface positive.
Statement IV: The action potential generated is equivalent to a nerve impulse.

Consider the mechanism of nerve impulse propagation from site A to site B along an axon:

Statement I: At site B (immediately ahead of site A), the outer membrane is positive and the inner membrane is negative.
Statement II: On the inner surface, current flows from site A to site B.
Statement III: On the outer surface, current flows from site A to site B to complete the circuit.
Statement IV: On the outer surface, current flows from site B to site A to complete the circuit.

Regarding the rapid recovery of a neuron after excitation:

Statement I: The rise in stimulus-induced permeability to Na⁺ is extremely short-lived.
Statement II: The increase in Na⁺ permeability is followed by a rise in permeability to K⁺.
Statement III: Within a fraction of a second, K⁺ diffuses inside the membrane to restore the resting potential.
Statement IV: Within a fraction of a second, K⁺ diffuses outside the membrane to restore the resting potential.

Evaluate the structural characteristics of synapses:

Statement I: A synapse is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron.
Statement II: The pre- and post-synaptic membranes must always be separated by a physical gap called the synaptic cleft.
Statement III: There are two types of synapses: electrical synapses and chemical synapses.
Statement IV: In electrical synapses, the membranes of pre- and post-synaptic neurons are in very close proximity.

Regarding the nature of electrical synapses in the human neural system:

Statement I: Electrical current can flow directly from one neuron into another across electrical synapses.
Statement II: Impulse transmission across an electrical synapse is always slower than across a chemical synapse.
Statement III: Impulse transmission across an electrical synapse is very similar to impulse conduction along a single axon.
Statement IV: Electrical synapses are very rare in the human neural system.

Read the statements below regarding chemical synapses:

Statement I: Pre- and post-synaptic membranes are separated by a fluid-filled space called the synaptic cleft.
Statement II: Chemicals called neurotransmitters are involved in impulse transmission at these synapses.
Statement III: Synaptic knobs at axon terminals contain vesicles filled with neurotransmitters.
Statement IV: Arrival of an action potential at the axon terminal stimulates the movement of synaptic vesicles towards the post-synaptic membrane.

Analyze the events that occur after neurotransmitters are released into the synaptic cleft:

Statement I: Neurotransmitters bind to specific receptors on the post-synaptic membrane.
Statement II: Binding of neurotransmitters opens ion channels, allowing the entry of ions.
Statement III: The entry of ions generates a new potential in the post-synaptic neuron.
Statement IV: The post-synaptic potential developed is strictly excitatory in nature.