Nervous System and Neurons

This is the correct option. The pons take part in regulating respiration. The cerebellum helps in maintaining posture and balance of the body. The medulla controls various involuntary actions like heart beat, breathing, blood pressure and peristaltic movements of the alimentary canal.

This is the correct option. The spinal cord begins in continuation with medulla and extends downwards.

This is the correct option. Phonoreceptors are present in the inner ear to determine sound.

This is the correct option. 

Sodium remains outside the cell fluid and helps in nerve signal transmission.

The Hering-Breuer inflation reflex, named for Josef Breuer and Ewald Hering, is a reflex triggered to prevent over-inflation of the lung. Pulmonary stretch receptors, present in the smooth muscle of the airways, respond to excessive stretching of the lung during large inspirations.

Schwann cells wrap nerve cell axons in the peripheral nervous system with layers of myelin (a type of plasma membrane that provides electrical insulation).

Abducens is a purely motor nerve which  orginates form the ventral side of the medulla and supplies to the posterior rectus muscles of the eye ball. 

A reflex arc is a neural pathway that controls a reflex action. The key characteristic is that the impulse travels from sensory neuron to motor neuron via interneuron in the spinal cord, without necessarily going to the brain. This allows for rapid involuntary responses. Option B is false because reflex arcs can bypass the brain entirely.

A nerve impulse (action potential) travels along the neuron and leaves through the axon, which is the long fiber-like extension that conducts electrical signals away from the cell body. The axon terminal is where neurotransmitters are released to pass the signal to the next neuron. Dendrites receive signals, and the cyton contains the nucleus.

The neuron (nerve cell) is the fundamental structural and functional unit of the nervous system. Neurons are specialized cells that transmit electrical and chemical signals throughout the body. Nephrons are kidney units, sarcomeres are muscle units, and while the brain is an organ composed of neurons, it's not the basic unit itself.

Cranial nerves are 12 pairs of nerves that emerge directly from the brain (including the brainstem), unlike spinal nerves which originate from the spinal cord. They connect the brain to various parts of the head, neck, and trunk. This is a fundamental anatomical distinction between cranial and spinal nerves.

At the axon terminal, an incoming electrical impulse (action potential) triggers the release of chemical neurotransmitters into the synaptic cleft. This conversion from electrical to chemical signal is crucial for passing information between neurons. The electrical impulse travels down the axon and causes vesicles to release neurotransmitters.

When neurotransmitters bind to receptors at the dendritic tip, they trigger a chemical reaction that generates an electrical impulse (action potential). This conversion from chemical to electrical signal is fundamental to neuronal signaling. Physical, mechanical, and chemical impulses do not accurately describe the electrical nature of nerve transmission.

A synapse is the tiny junctional gap between two neurons where neurotransmitters are released to transmit signals. Veins, arteries, and capillaries are all blood vessels, not neural structures. The synaptic gap is essential for neuronal communication and signal transmission.