07 Special Senses Lab Ctemp Version PDF

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Lab – Special Senses Exercise 23, p 349 Objective: This lab is closely linked to the lecture content. It is usuallt taught before the lecture, so background information will be provided. Most of the lab will address the basic features of the eye and ear, although we do have microscope slides of gustatory/ taste receptors. Both the text and lab manual have excellent images. The only issue is an image or two of the eye wherein the optic nerve is drawn directly in the center of the eye, in a line intersecting the center of the cornea and lens. While it is possible to orient the eyball in this way, this is the anatomical location of the macular/foveal region, which makes these images confusing.

I Somatosensory Receptors

(largely covered in integument) Lab Manual: Take a look at page 353, Figure 23.2. (This is lecture content) Note two things about crossing over and the thalamus: Pathways – two places to cross over: Pain receptors (nociceptors) typically enter the spinal cord, synapse with their interneurons, go up or down the length of 2-3 vertebrae (even though the right side shows that), and then cross over in the spinal cord in the anterolateral region Most other receptors (including most mechanoreceptors) typically enter the spinal cord, synapse with their interneurons, and the latter’s axons move up the dorsal tracts, crossing over in the medulla The Thalamus: ALL of the above interneurons MUST stop and synapse in the thalamus. Thalamic neurons then send signals to the primary somatosensory cortex on p361 (end lecture content)

II Vision A. Eye Models: Learn all this now – you will need it for lecture. Text: p517-520 Lab manual Exercise 24, pp363-372 The retinas on these models are quite confusing – one looks like a beehive, another is shown as clear and all one sees are the blood vessels of the choroid. Locate the following structures: cornea

ciliary body

sclera

retina (as close as possible)

iris

vitreous body

choroid

lacrimal glands

pupil

conjunctiva

rectus muscles (medial, lateral, superior, inferior) punctae

oblique muscles (superior, inferior) trochlear ligament of the superior oblique

optic nerve

lacrimal ducts/canals

Be able to identify where the conjunctiva, retina, canals of Schlemm, and macula/fovea would be on the models. B. Cow Eye: [these are preserved in the CTEMP labs, since we can’t dissect] Lab manual p 368 1. Look for the following external features: the cornea, sclera, stumps of rectus and oblique muscles, the stump of the optic nerve. The cornea would also be surrounded by the conjunctiva 2. Look for the following internal features: The retina (possibly missing). In the cow eye dissection, it usually turns into a glob, attached only to the optic nerve – Why is that? The black surface is the layer

between the retina and choroid. In humans, as in cows, this layer contains melanin to prevent light scattering. In cows, cats and deer, this layer reflecxts back at you at night, and is referred to as the tapetum lucidum. Structures on the inner, anterior side of the globe. The lens, often adhering to the vitreous body, may have a margin of black dots. These are the stumps of the suspensory ligaments. These fragile structures were attached to the ciliary body muscles. The ciliary body is clearly visible (see excellent textbook illustration of the lens and ciliary body – looks a bit like a trampoline...). Note the dark, smooth walls of the iris muscles that surround a horizontal pupil (the hole), and the cornea beneath. Normally, the cornea and lens would be transparent, but this tissue has been preserved with protein-crosslinking formaldehyde solution. The lens, normally soft and elastic, becomes as stiff as a hockey puck! C. Find your blind spot (p372) and check for astigmatism (p374)

III Hearing and Equillibrium B. Hearing and Balance Models: Learn all this now – you will need it for lecture. There are two types of ear models – models of the vestibulocochlear system and cross sections of the cochlea. The outer and middle ears, and the cochlea of the inner ear contribute to auditory perception. The semicircular canals and maculae comprise the systems providing dynamic and static balance, respectively (see the text). There are three sets of structures in this model, covering the senses of hearing/ auditory perception, static balance, and dynamic balance. Also be able to point out the locations of features that are not clearly marked or visible. These are the: maculae, ampullae, hair cells (3 locations), endolymph, and perilymph. Watch that word macula – it is used in both eye and ear for very different structures! Auditory canal (external acoustic meatus) needs to be clearly distinguished from auditory tube – hence I strongly prefer the use eustacean tube on test responses. pinna/ auricle auditory canal/ext acoustic meatus tympanum

external ear middle ear

inner ear

ossicles

cochlea

eustacean/ auditory tube

round window

oval window

organ of Corti

tectorial membrane basilar membrane locations of endolymph vs perilymph

cochlear hair cells

ampullae

vestibulochochlear nerve

location of maculae

semicircular canals

Look for the following features on the vestibulocochlear models: petrous process of the temporal bone, carotid artery and canal, styloid process, and internal acoustic meatus. Be prepared to add some function onto these structures, since we should know all of that by the final lab practical! C. Taste Bud Microscope Slides and Olfactory Structures Taste: Locate the papillae, taste buds, gustatory receptors on the microscope slides. Olfaction: Just recall the locales of the olfactory bulbs and olfactory punctae of the cribiform plate....