Special Senses Flashcards
1
Q
Cornea, pupil, aqueous humor, iris, lens, retina and optic nerve are all parts of?
A
The human eye
2
Q
_________is the transparent outer covering of the eye that refracts light?
A
The Cornea
3
Q
What Part of the eye has a similar composition to that of blood plasma and gives shape to the cornea as well as nourishment to the eye?
A
Aqueous humor
4
Q
The opening through which light passes into the eye is called?
A
Pupil
5
Q
The muscle that surrounds the pupil and determines the size of the pupil is?
A
The Iris
6
Q
What is the function of the eye’s lens?
A
The lens allows the eye to focus on either near or far objects.
Cilliary muscles surround the lens, relaxing to flatten it in order to image distant objects or Contracting to thicken the lens to image close-up objects
7
Q
Talk on the vitreous humor?
A
The vitreous humor is the clear watery gel that fills the eyeballs between the lens and the Retina.
8
Q
Talk about the Retina!
A
The Retina is the thin layer of cells on the interior back of the eye. The Retina has 2 cells (RODS & CONES) that get activated when struck by light and help to form images in light and dark conditions as well as monochrome and color vision.
9
Q
_____ cell is responsible for color vision
A
Cones
10
Q
_____ cell is responsible for for detection of light and darkness, as well as formation of images under dim conditions
A
Rods
11
Q
When you focus clearly on an object, light strikes a region known as?
A
The Fovea
12
Q
The fovea is a region packed with cones that allows for sharp vision. Rods outside the fovea are largely responsible for?
A
Peripheral vision
13
Q
Image focused by the lens on the Retina is ________ with respect to the object.
A
Inverted and Reversed
14
Q
Define Accommodation?
A
Accommodation is the ability of the eye to adjust and adapt to different conditions of vision.
It refers to the ability of the iris to contract the pupil to regulate the amount of light that enters the eye as well as the ability to focus near and far objects and optimize vision.
15
Q
What is the range of the pupils diameter?
A
1.5mm - 8mm
16
Q
The amount of light that enters the eye through the pupils is proportional to the area of the pupil or to the square of the diameter of the pupil!
Did you know this?
A
Yes or no?
17
Q
Emmetropia means?
A
Correct vision in which images are brought to focus on the Retina.
18
Q
List 5 eye defects
A
- Hyperopia or Hypermetropia
- Myopia
- Presbyopia
- Astigmatism
- Cataract
19
Q
Explain Presbyopia and it’s correction
A
Presbyopia refers to the natural irreversible diminishing of sight with age.
It is corrected with Biconvex lens
20
Q
Explain Astigmatism and it’s correction
A
Astigmatism is a refractive error of the eye, in which light rays that enter the eye are not properly brought to focus (they are scattered). Often due to irregular curvature of the cornea.
It is corrected using equal and opposite Cylindrical lens
21
Q
Explain Cataract and it’s correction
A
Cataract is a cloudy or opaque area in the lens due to denaturation of proteins in some of the lens fibres, mostly occurring in older people. The accumulation of this opaqueness impairs vision
It is corrected by Surgery
22
Q
Explain Myopia and it’s correction
A
Myopia (also called short sightedness) is characterised by the inability to see distant objects clearly. This is due to either long eyeball or too much refractive power in lens
It is corrected using concave lens
23
Q
Explain hyperopia
A
Hyperopia or hypermethropia (also called long sightedness) is characterised by inability to see near objects, light is brought to focus behind the Retina. This is due to short eyeball or too weak lens system.
It is corrected using convex lens
24
Q
Define intraocular fluid
A
Intraocular fluid functions to maintain sufficient pressure in eyeballs. This fluid is divided into 2;
Aqueous humor and Vitreous humor
25
Aqueous humor is formed or secreted by?
Cilliary processes
26
Explain Glaucoma?
Glaucoma is a disease of the eye in which the intraocular pressure of the eye becomes pathologically high. Rising acutely to 60-70mmhg. (Normal pressure ranges 25-30mmhg). Continued high intraocular pressure damages the optic nerve and causes loss of vision
27
The abnormally high intraocular pressure in glaucoma occurs as a result of?
Increased resistance to fluid outflow through trabecular spaces into the canal of schlemm at the iris and cornea junction.
28
The Retina has 9 layers, list them?
1. Pigmented layer
2. Layer of rods & cones
3. Outer nuclear layer
4. Outer plexiform layer
5. Inner nuclear layer
6. Inner plexiform layer
7. Ganglionic layer
8. Layer of optic nerve fibres
9. Inner limiting membrane
29
The light sensitive photo chemical in the Rods is called?
Rhodopsin
30
The light sensitive photo chemical in the Cones is called?
Photopsin
31
Both Rhodopsin and Photopsin are conjugated proteins, but they differ in ?
Spectral sensitivity
32
What role does melanin play in the Retina?
Melanin is found in the pigment layer of the Retina, it functions to prevent light reflection and the ability to distinguish normal contrast between dark and light spot for formation of precise images.
33
Young-Helmholz (Trichromatic theory) is the most generally accepted theory of colour vision.
Briefly explain what it assumes?
The Young-Helmholz (Trichromatic theory) assumes the existence of 3 separate colour detecting mechanisms. All colour sensations being resolved from all unequal stimulation of these 3, and white from universal stimulation.
The sensation of black is due to absence of stimulation.
34
The most commonly used test for detection of colour blindness is?
Ishihara charts
35
A situation where a person is severely deficient of vitamin A (retinol), leading to reduced amounts of retinal and rhodopsin. Causes?
Night blindness
36
The most commonly used test for visual acuity is?
Snellen chart
37
Talk about color blindness?
Color blindness is a sex linked trait. Females (x chromosome) are the carriers, but it is manifested in males.
38
When other sensory receptors are excited, the electrical response is depolarisation, but in photo receptors, the response is in the form of?
Hyper polarisation
39
Color blindness characterised by red cones lacking is called?
Protanopia
40
Color blindness characterised by green cones lacking is called?
Deuteranopia
41
Color blindness characterised by blue cones lacking is called?
Trianopia
42
Explain the visual pathway
The optic nerve carry visual impulses from the eye and runs backwards through the orbit and enters the cranium. The 2 optic nerves come together in the optic chiasma at the base of the brain, between the hypothalamus and pituitary gland.
43
Talk about the primary visual cortex.
The primary visual cortex is also known as Broadman's area 17. It is located in the occipital lobe of the cerebral hemisphere
44
The area seen to the nasal side is called?
Nasal field of vision
45
The area seen to the lateral side is called?
Temporal field of vision
46
47
What is Perimetry?
Perimetry is the process of testing to diagnose blindness in specific portions of the retina.
48
Visual field defects occur due to damage to the visual pathways or visual cortex. Lesion in the optic pathway may be detected using?
A perimeter, or crude testing can be done by using the confrontation method
49
A lesion at the optic chiasma which might be due to a pituitary tumor pressing on this part of the optic nerve and inept nerve pathways from the medial of the 2 retina is termed?
Heteronymous (Bi temporal) Hermanopia.
50
A lesion at the optic nerve will cause?
Blindness (Anopia) in only one eye
51
A lesion at the optic tract will cause loss of vision by both eye on the same side of the visual Field. This defect is termed?
Homonymous hemianopia
52
Explain how one can differentiate a lesion in the optic tract from a lesion in the visual cortex.
To differentiate, one must determine whether impulses can still be transmitted into the pretectal nuclei to initiate a pupillary light reflex.
53
What is visual acuity?
Visual acuity relates to the distinctness of objects and the ability to discriminate very fine details
54
There are 2 chemical senses, name them?
Sense of taste and Sense of smell.
55
Explain the Sense of taste (Gustation)
The sense of taste comes from the interaction of dissolved molecules within the taste buds. Taste occurs via taste receptors located on the tongue, palate, and epiglottis.
The surface of the tongue is lined by stratified squamous epithelium containing bumps called papillae. Taste buds are found in the papillae and
Taste buds are responsible for transduction of taste sensation.
56
Currently, There are 5 primary sensations recognised, they are;
1. Sweet
2. Salty
3. Bitter
4. Sour
5. Umami
57
Mention the nerves involved in nervous transmission of taste signals to the CNS
The lingual nerve which later joins the facial nerve, supplies the anterior ⅔of the tongue, whereas the glossopharyngeal nerve supplies the posterior ⅓.
Also taste signals from the pharynx pass by way of the vagus nerve.
58
Explain the mechanism of transmission of taste signals to the CNS
All the nerves pass signals to the tractus solitaries located in the medulla. Then signals are transmitted to the thalamus, and from there to the primary taste cortex of the **opercular insular region**at the foot of the post central gyrus in the parietal lobe where it curls deep into the sylvian fissure. The signals also pass into surrounding taste association areas and into the common integrative region which integrates all sensations.
59
Explain the correlation of salivation to gustation (sense of taste)
Impulses are transmitted from the tractus solitaries into nearby nuclei that control the secretion of the parotid, sub maxillary and sublingual glands.
60
Talk on taste blindness.
To demonstrate taste blindness, a frequently used substance is **Phenylthiocarbamine (PTC), for which 15 - 30%of people are taste blind
61
What is Ageusia?
Ageusia refers to loss of taste sensation.
In the anterior ⅔, It is caused by lesion to the facial nerve, chorda tympani or mandibular division of trigeminal nerve
In the posterior ⅓, it is caused by lesion in gloss I pharyngeal nerve.
62
Temporal loss of taste sensation can occur due to drugs e.g?
1. Captopril
2. Penicillamine, which contains sulfhydryl group of substances.
63
What is hypogeusia?
Hypogeusia is the decreased sensation of taste, although taste sensation is not completely lost
64
What is dysgeusia?
Dysgeusia is the disturbance in the taste sensation, it is found in the temporal lobe syndrome, particularly when the anterior region of the temporal lobe is affected.
In this condition, the paroxysmal hallucination of taste and smell occurs, which are usually unpleasant
65
Explain olfaction.
Olfaction (the sense of smell) is vested in 2 small areas called the olfactory epithelium. The olfactory epithelium contains numerous nerve receptors called olfactory cells, any 100 million cells in the olfactory epithelium.
Olfactory cells have rod-like projecting called olfactory hair from the nasal epithelium into the overlying mucus. It is the olfactory hair that detect different odours
66
How many odors can humans distinguish
2000-4000
67
Explain olfactory transduction
Olfactory transduction is the process by which olfactory receptors convert chemical energy into action potentials in olfactory nerve fibre. Odor only stimulates the olfactory receptors if it dissolves in mucus, covering the olfactory mucus membrane. Molecules of the dissolved substance binds with receptor proteins (G protein) in the cilia and form substance receptor complex, which then activates adenylcyclase that causes the formation of CAMP. And generation of receptor potential which is then transmitted to the CNS
68
Olfactory area in the brain include?
The median olfactory area(lies laterally on the under surface that can be used, and
Lateral olfactory area: is associated with higher functions of the nervous system
69
Briefly explain transmission of smell impulse to the CNS.
Impulses collected by the olfactory cells are transported to the brain via the olfactory nerve in the olfactory tract
70
Explain Anosmia?
Anosmia refers to total loss of sensation of smell. It is the inability to recognize or detect any odour. It at be temporary or permanent.
Temporary anosmia is due to obstruction of noise, which occurs during common cold, nasal sinus or allergic conditions.
Permanent anoraks occurs due to lesson in olfactory tract, meningitis and degenerative conditions such as Parkinson's disease & Alzheimer's.
71
What is Hyposmia
Hyposmia is the reduced ability to recognize and detect any odour. Odour can only be detected at very high concentration. It may be temporary or permanent, having the same causes as anosmia.
72
What is Hyperosmia?
Also known as Olfactory Hyperesthesia.
Hyperosmia is the increased or exaggerated olfactory sensation. It occurs in brain injury, epilepsy & neurotic conditions.
73
Give an overview about the Ear!
The ear is the body organ responsible for hearing, and equilibrium (balance). The ear has 3 distinguishable parts; the outer, middle, and inner ear.
The different parts of the ear, collect, amplify and then transduce sound into impulses, which are then to the brain for interpretation
74
Talk about the middle ear?
The middle ear is a narrow air filled cavity in the temporal bone. It is spanned by a chain of 3 tiny bones; malleus, Incus, stapes. Collectively called auditory ossicles. These ossicular chain conducts sound from the tympanic membrane to the inner ear.
74
Talk about the outer ear
The outer ear consists the visible portion called the auricle or pinna (which projects from the side of the head) and the sorry auditory canal which ends at the tympanic membrane.
The function is to collect sound waves and guide them to the tympanic membrane.
75
Talk about the inner ear
The inner ear known as the labyrinth is a complicated system of fluid filled cavities located within the petrous portion of he temporal bone.
The inner ear consists of 2 functional units;
1. Vestibular apparatus
2. The Cochlear
76
What is the vestibular apparatus?
The vestibular apparatus consist of the vestibule and semi circular canals. The vestibule contains the utricle & saccule
77
What is the Eustaschian tube?
Is a tube connecting the tympanum to the nasopharynx. It is 1.2 -1.5 inches long
78
What is the role of tensor tympani in hearing?
The top end of the handle of the malleus is attached to the center of the tympanic membrane. This point of attachment is constantly pulled by the Tensor tympani muscle, which keeps the tympanic membrane tensed to allow sound vibrations on any portion of the tympanic membrane to be transmitted to the ossicles.
79
What is the function of the tensor tympani & stapedius muscle in attenuation reflex?
To protect the cochlea from damaging vibrations caused by excessively loud sound.
Another function is to decrease a person's hearing sensitivity to his or her own speech
80
Briefly explain the functional anatomy of the cochlea
The cochlea is a system of coiled tubes. The 3 coiled tubes are;
1. Scala vestibuli
2. Scala media
3. Scala tympani.
The Scala vestibuli and Scala media are separated from each other by **Reissner membrane (vestibular membrane)**
The Scala tympani & Scala media are separated by the **basilar membrane.**
On the surface of the basilar membrane lies the Organ of Corti.
81
Talk about the organ of Corti
The organ of Corti contains a series of electromechanically sensitive cells, The Hair Cells. They are the receptive end organs that generate nerve impulses in response to sound vibrations.
There are 2 specialized types of nerve cells; the internal hair cells (about 3500 in number).
The external(outer) hair cells (numbering 12,000 in number)
82
Can you explain the neural mechanism for detecting sound directive
Neural analysis for detection of sound process begins in the superior Olivary nuclei in the Brainstem.
82
Can you explain how a person can determine the direction from which sound comes?
This happens by 2 principal means:
1. The time lag between sound into one ear and its entry into the opposite ear
2. The difference between the intensities of the sound in the two ears.
If a person is looking straight towards the source of the sound, the sound reached the both ears at the exact same instant, whereas if the right ear is closer to the sound than the left ear is, the sound signals from the right ear enter the brain ahead of those from the left ear.
83
The superior olivary nuclei is divided into 2 sections:
Medial superior Olivary nucleus
Lateral superior olivary nucleus
What is the function of the lateral superior olivary nucleus
The lateral nucleus is concerned with detecting the direction from which a sound is coming by comparing the difference in intensities of sound reaching the 2 ears
84
Explain the function of the cerebral cortex in hearing
There are 2 subdivisions;
The primary auditory cortex is directly excited by projections from the medial geniculate body
2. The auditory association areas are excited secondarily by impulses from the primary auditory cortex as well as by some projections from the thalamic association areas adjacent to the medial geniculate body
85
At least 6 tonotopic maps have been found in the primary auditory cortex and auditory association areas.
Why does the auditory cortex have so many different tonotopic maps?
These different tonotopic maps exist to cater to different aspects of sound, some maps discriminate; the pitch, distance, quality, frequency, etc
86
Mention 6 important areas for language
1. Broca's area
2. Motor cortex
3. Angular gyrus
4. Primary auditory cortex
5. Wernicke's area
6. Motor control of mouth & lips
87
Briefly talk on auditory defects?
An auditory defect or hearing impairment refers to the inability of an individual to hear sounds adequately. This may be due to improper development, damage or disease to any part of the hearing mechanism.
88
Extensively explain types of hearing impairment?
There are 3 types of hearing loss
1. Conductive hearing loss (CHL): results from anything that decreases the transmission of sound from the outside works to the cochlea. That is, defects in the middle or outer ear such as abnormal formation of auricle or helix, impaction of cerumen(ear wax) in the ear canal, effusion in the middle ear or dysfunction of the ossicular chain. E.g in Otosclerosis.
2. Sensorineural hearing loss (SNHL): Is caused due to damage or disease of the auditory nerve (CN VIII: vestibucoclear nerve). It could also result as an after effect of infectious disease e.g, measles, mumps, meningitis and tuberculosis. Or congenital SNHL causes e.g; Rh incompatibility, acoustic neuroma, exposure to xray, birth asphyxia, etc
3. Mixed hearing loss: has components of both Conductive hearing loss and Sensorineural hearing loss. One of the main causes of this long standing ear infection known as Chronic suppurative otitis media.
4. Central Hearing loss: is due to a damage, malformation or infection of neural pathways, and the hearing centers in the brain
89
The gradual loss of hearing ability with age is called?
Presbycusis
90
Mention several Test for Auditory defects you know?
1. Pure-tone testing
2. Bone conduction testing
3. Speech testing
4. Tympanometry
5. Auditory Brainstem response (ABR)
6. Otoacoustic Emission test
91
Mention available treatments for auditory defects
1. Hearing aid
2. Cochlear implants
3. Sign language
