Nervous System

The posterior (or dorsal) grey horn contains interneurons that receive stimuli from sensory axons (whose cell bodies reside in the dorsal root ganglion).

Apart from the two “cere” (cerebrum and cerebellum), diencephalon and brainstem must be included.

A convex lens causes light rays to converge. This additional convergence, provided by corrective lenses, allows light that enters the eye to be focussed on the retina rather than behind it.

The optic tracts leaving the optic chiasma synapse with neurons in the lateral geniculate body (of the thalamus). Many axons then continue as the optic radiation of fibres into primary visual cortex.

The axon. Prior to ravelling along the axon, the potential is referred to as a “graded potential”.

These substances would alter the function of, or damage, the brain. Glucose, oxygen, carbon dioxide, ethyl alcohol and nicotine can cross the BBB easily.

The air in the external ear canal resonates (at about 3000 Hz), the ossicles are a lever system that amplifies the movement of the tympanic membrane; the oval window, being about one twentieth the size of the tympanic membrane, also amplifies the pressure applied to the cochlear fluid compared to that applied to the tympanic membrane.

A special sense is one that is localised into a specific organ such as the ear. Sight is also a special sense being localised in the eye. The sense of touch is not localised as the entire skin is sensitive to touch.

Presbyopia refers the progressive loss of the ability to focus on nearby objects (e.g. books) after about age 45–50. It is due to the lens becoming stiffer so being less able to ooze into the highly convex shape required to bring light from nearby objects to focus on the retina.

They are found in the spinal cord (in the ventral grey horns). Choice B is also correct, but choice D is more specific. The dorsal root ganglia contain cell bodies of sensory neurons.