Neural Control and Coordination MCQs

Regarding myelinated and unmyelinated axons, evaluate these statements:

Statement I: Myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon.
Statement II: Gaps between two adjacent myelin sheaths are called nodes of Ranvier.
Statement III: Unmyelinated nerve fibres completely lack any association with Schwann cells.
Statement IV: Unmyelinated nerve fibres are commonly found in the autonomous and somatic neural systems.

Consider the state of a resting, non-conducting axonal membrane:

Statement I: The resting axonal membrane is comparatively more permeable to potassium ions (K⁺) and nearly impermeable to sodium ions (Na⁺).
Statement II: The resting axonal membrane is completely permeable to negatively charged proteins present in the axoplasm.
Statement III: The axoplasm inside the resting axon contains a high concentration of K⁺ and negatively charged proteins, and a low concentration of Na⁺.
Statement IV: The extracellular fluid outside the resting axon contains a low concentration of K⁺ and a high concentration of Na⁺.

Regarding the active mechanism maintaining the polarized state of the resting neuron:

Statement I: The sodium-potassium pump actively transports 3 Na⁺ ions into the cell for every 2 K⁺ ions pumped outwards.
Statement II: The pump maintains the resting potential, leaving the outer surface of the axonal membrane positively charged and its inner surface negatively charged.
Statement III: The electrical potential difference across the resting plasma membrane is called the action potential.
Statement IV: The active transport of ions by this pump maintains the vital concentration gradients across the resting membrane.

Analyze what occurs at site A of a polarized axonal membrane when a stimulus is applied:

Statement I: The membrane at site A becomes freely permeable to sodium (Na⁺) ions.
Statement II: This permeability change causes a rapid efflux of Na⁺ out of the axoplasm into the extracellular fluid.
Statement III: Polarity at site A is reversed; the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged.
Statement IV: The electrical potential difference across the plasma membrane at site A is called the action potential, which is termed a nerve impulse.

Regarding the propagation of an action potential along an axon from site A to site B:

Statement I: At site B (immediately ahead), the outer membrane is positively charged and its inner surface is negatively charged.
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: This loop reverses the polarity at site B, generating a new action potential at site B.

Examine how a depolarized axonal membrane recovers its excitability:

Statement I: The stimulus-induced increase in permeability to Na⁺ is extremely short-lived.
Statement II: The increase in Na⁺ permeability is quickly 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: Once the resting potential is restored, the fibre becomes responsive to further stimulation.

Analyze the characteristics of electrical vs. chemical synapses:

Statement I: At electrical synapses, the membranes of pre- and post-synaptic neurons are separated by a wide, fluid-filled synaptic cleft.
Statement II: Electrical current can flow directly from one neuron into another across electrical synapses.
Statement III: Impulse transmission across an electrical synapse is always slower than across a chemical synapse.
Statement IV: Electrical synapses are rare in the human neural system.

Regarding synaptic transmission at a chemical synapse:

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 chemical synapses.
Statement III: The arrival of an action potential at the axon terminal stimulates the movement of synaptic vesicles towards the post-synaptic membrane.
Statement IV: Axon terminals contain vesicles filled with neurotransmitters.

Evaluate these statements regarding neurotransmitter binding on the post-synaptic membrane:

Statement I: Released neurotransmitters bind to specific receptors present on the post-synaptic membrane.
Statement II: This binding 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 always inhibitory.

Consider the functional capabilities of the human brain:

Statement I: The brain acts as the command and control system of our body.
Statement II: It controls voluntary movements, balance, and the functioning of vital involuntary organs.
Statement III: It controls thermoregulation, hunger, thirst, and circadian (24-hour) rhythms.
Statement IV: It is the processing site for vision, hearing, speech, memory, intelligence, emotions, and thoughts.