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AP2 Test Prep Module 3 Nervous System Part 3
Vision and the Eye
- What are the five special senses? vision, smell, taste, hearing, equilibrium
- What are the two parts of the outer layer of the eye? the sclera and the cornea
- What is included in the middle layer of the eye? The choroid, ciliary muscle and the iris.
- The pupil is a hole in the iris.
- The inner sensory layer is the retina.
- What are the two types of photoreceptors and their functions? The more numerous cells are rods which are stimulated in dim light. Rods are more sensitive to light but do not generate sharp or color images. The cones operate in bright light helping to generate sharp color images.
- The interior of the eye (posterior to the lens) is filled with vitreous fluid .(helps to hold retina firmly to the choroid)
- True or False: The vision pathway begins as the optic tracts, crosses at the optic chiasm and then moves through the optic nerve. False - it starts at the optic nerve, goes through the optic chasm and then the optic tract to the LGN of the thalamus and eventually to the occipital lobe)
- Where is the LGN located? the thalamus (lateral geniculate nucleus)
- True or False: The nasal visual field is the visual field on the lateral sides of each eye. False - it is on the medial side.
Vision and the Eye
- The medial rectus turns the eye medially. The medial rectus is controlled by CN III, oculomotor
- Review all the extrinsic eye muscle locations.
- What is a cataract? It is a condition caused when the lens of the eye becomes hardened and cloudy over time. Vision becomes blurry as light is
unable to freely enter the lens to be refracted onto the retina.
- What does diplopia mean? double vision
The Auditory and the Vestibular Systems
- What is the purpose of the auricle?The auricle (Figure 1) is shaped to funnel sound waves into the external acoustic canal so that sounds can be detected.
- What is the purpose of cerumen? Earwax which serves to trap foreign materials.
- The inner end of the external acoustic meatus terminates at the tympanic membrane.
- What bone touches the inner ear to transmit vibrations? stapes
- The semicircular canals contribute in this way to the body's vestibular (balance and equilibrium) sense.
- The organ of Corti i s the sense organ for the auditory system.
- The movement of the stereocilia stimulates the neurons to send impulses through the cochlear nerve to the temporal lobe of the brain.
- What is unique about the way the auditory pathway travels to the brain? The auditory pathway is a unique sensory pathway because the ascending pathways cross in addition to sending signals to the same side of the brain. The result is that sounds from each ear are equally interpreted on the left and right sides of the brain.Pathways cross to opposite sides of the brain but also send signals to the same side of the brain.
- What is the difference between nerve deafness vs. conduction deafness? Conduction deafness occurs from damage to the outer or middle ear structures. Nerve deafness occurs from damage to the nerve pathway.
The process of hearing happens in a series of events. First, sound waves are funneled into the external auditory canal causing the eardrum to vibrate. The vibrations transmit
to the ossicles, which push against fluid inside the cochlear duct. The movement of the fluid causes movement of the stereocilia in the organ of Corti. The movement of the stereocilia then stimulates the neurons to send impulses through the cochlear nerve to the primary auditory cortex of the temporal lobe. The auditory pathway is a unique sensory pathway because the ascending pathways cross in addition to sending signals to the same side of the brain. The result is that sounds from each ear are equally interpreted on the left and right sides of the brain.
Olfactory and Gustatory Systems
- Olfactory nerves contain what type of receptor cells? They contain bipolar receptor cells that are activated by airborne chemical substances dissolved in fluid from mucous membranes,
- The olfactory nerves travel through what bone? the ethmoid bone (cribriform plate)
- What is the order of the olfactory nerve pathway? olfactory nerves in the nasal cavity travel through the ethmoid bone to the olfactory bulb in the frontal lobe where they synapse with other neurons along the olfactory tract. The nerve impulses are then carried to the temporal lobe for interpretation. Olfactory nerves → olfactory bulbs → olfactory tracts→ temporal lobes
- What is smell? Smell is a combination of a limited number of primary odors detectable by the brain. These include: floral, ethereal, camphorates, musky, peppermint, pungent and putrid odors.
- Label all olfactory landmarks.
- What is anosmia? It is the loss of the sense of smell
- Review all figures of the gustatory system.
