Nervous System

When the ciliary muscle contracts, it forms a smaller diameter circle around the lens causing the fibres that connect it to the lens to slacken, which allows the elastic lens to recoil (ooze) into a rounder shape. This has a shorter focal length.

The reticular formation is located in the brainstem, and so all sensory information from receptors for pressure touch, pain and limb position pass through here. Vision and sound stimulate the reticular formation. Choices A and B refer to the limbic system. Our circadian rhythm involves the pineal gland.

The cerebrum is the cortex (the outer part) of the brain made up of folds called gyri and sulci.

Grey matter refers to cell bodies of neurons, while white matter is aggregations of myelinated axons. The spinothalamic “tract” is a bundle of nerves (axons) carrying information to the brain.

The temporal lobe contains the auditory cortex. It interprets sound from the hearing mechanism in the adjacent ears.

The tensor tympani pulls the malleus and stiffens the ear drum, while the stapedius pulls the stapes to reduce its movement against the oval window. In this way, the damage that loud sounds may do to the hearing mechanism is reduced.

The “notch” in someone’s measured audiogram at about 4000 Hz is characteristic of all noise-induced hearing loss.

The fovea centralis is at the centre of the macula lutea. The optic disc is insensitive to light.

When a neuron is stimulated by a sensory stimulus, a graded potential is produced.

The epidural space is on the outside of the spinal cord hence does not contain CSF. It is into this space that the analgesia for a spinal block is injected.