12. CNS (Sensory) (2) Flashcards
1
Q
- A logarithmic scale —>
A
A sound of 10 decibels is NOT twice as loud as a sound of 5 decibels
2
Q
Decibel scale for common sounds: (2)
A
- It uses a non linear scale
- in humans, 0 decibels = threshold of hearing
3
Q
- A volume of _____ doesn’t mean the absence of sound but the sound level equal to that of the standard
A
0dB
3
Q
- A volume of _____ doesn’t mean the absence of sound but the sound level equal to that of the standard
A
0dB
4
Q
- The presence of one sound decreases the ability of an individual to hear other sounds —->
A
masking
5
Q
- The presence of one sound decreases the ability of an individual to hear other sounds —->
A
masking
6
Q
Sound localisation: (2)
A
- Pathways from both ears merge in the midbrain (inferior colliculus) auditory centres Compare signal + auditory cortex
- Sound localisation is markedly disrupted by lesions of the auditory cortex
7
Q
What are auditory pathways? (2)
A
- Each hemisphere receives info from both ears (bilateral projection) but mainly from the contralateral ear
- 1 degree auditory cortex has to no topic representation of cochlea Different frequencies at different areas of cortex
7
Q
What are auditory pathways? (2)
A
- Each hemisphere receives info from both ears (bilateral projection) but mainly from the contralateral ear
- 1 degree auditory cortex has to no topic representation of cochlea Different frequencies at different areas of cortex
8
Q
What is deafness? (4)
A
- Loss of hearing
- Can be complete or partial, temporary or permanent
- You can also have it as temporary complete or partial and permanent complete or partial
- Deafness is further classified according to its physiological cause either as conductive or sensorineural
8
Q
What is deafness? (4)
A
- Loss of hearing
- Can be complete or partial, temporary or permanent
- You can also have it as temporary complete or partial and permanent complete or partial
- Deafness is further classified according to its physiological cause either as conductive or sensorineural
9
Q
- Conduction deafness =
A
= decreased sound reaching cochlea
10
Q
Otitis media =
A
= inflammation of the middle ear, thickening the ear
drum
11
Q
otosclerosis =
A
= formation of spongy bone about the stapes
11
Q
otosclerosis =
A
= formation of spongy bone about the stapes
12
Q
Osteoporosis =
A
= decreased quantity of bone
12
Q
Osteoporosis =
A
= decreased quantity of bone
13
Q
Perforated eardrum =
A
= acuity 5dB (hearing can often be restored)
14
Q
- Nerve/sensorineural deafness =
A
= reduced hearing associated with damage to hair cells or neural pathways
15
Q
Audiometry and deafness = (2)
A
- Each ear must be tested separately for it’s capacity to hear a range of frequencies (tones/pitch) and loudness
- The loudness level for normal hearing of all frequencies should be within -10 to 20dB
15
Q
Audiometry and deafness = (2)
A
- Each ear must be tested separately for it’s capacity to hear a range of frequencies (tones/pitch) and loudness
- The loudness level for normal hearing of all frequencies should be within -10 to 20dB
16
Q
Hearing range classifications:
A
17
Q
Hearing range classifications:
A
18
Q
What is the vestibular apparatus?
A
- The vestibular apparatus has semicircular canals which are perpendicular to each other = 3 planes in space (horizontal, superior, posterior)
19
* The receptors respond maximally to _______ in one plane
* Ampulla = bulge in wall of s-c canal ----> Contains receptors
* The ____ and _____ are also important for proprioception
acceleration
utricle
saccule
20
Rotational acceleration: Semicircular canals
* hair cells are located in the crista ________
* They have a _____ on the apical surface which is displaced by fluid movement in the ducts
ampullaris
cupula
21
Rotational acceleration: Semicircular canals
* hair cells are located in the crista ________
* They have a _____ on the apical surface which is displaced by fluid movement in the ducts
ampullaris
cupula
22
Rotational acceleration: Semicircular canals
When happens when constant speed of rotation is reached?
* When constant speed of rotation is reached, the fluid spins at the same rate as the body and the cupula returns to the upright position Hair cells to resting position
22
Rotational acceleration: Semicircular canals
When happens when constant speed of rotation is reached?
* When constant speed of rotation is reached, the fluid spins at the same rate as the body and the cupula returns to the upright position Hair cells to resting position
23
Rotational acceleration: Semicircular canals
* Stop or deceleration ---->
* Movement in one direction ---->
* Stop or deceleration ----> Fluid moves in opposite direction
* Movement in one direction ---> Increased impulses in nerve, opposite inhibits
23
Rotational acceleration: Semicircular canals
* Stop or deceleration ---->
* Movement in one direction ---->
* Stop or deceleration ----> Fluid moves in opposite direction
* Movement in one direction ---> Increased impulses in nerve, opposite inhibits
24
Linear acceleration: Utricle and saccule
Utricle detects...
Saccule detects...
24
Linear acceleration: Utricle and saccule
Utricle detects...
Saccule detects...
25
Head upright:
Head tilted:
26
Spatial orientation and balance:
27
Vestibulo-ocular reflex:
Vertigo:
Nystagmus:
27
Vestibulo-ocular reflex:
Vertigo:
Nystagmus:
28
Caloric stimulation:
29
The lacrimal glands
- tears contain: (4)
Hypotonic fluid
Mucus
Antibodies
Lysozyme
30
The lacrimal glands
What is the function?
* Their function is to cleanse, protect, moisten, and lubricate the eye
31
Extrinsic muscles of the eye:
* Important for the movements of the eyeballs
32
Innervation of the extra-ocular muscles of the eyes:
* Extra-ocular muscles are innervated by
3 cranial nerves ----> Abducens VI, Trochlear IV, and mostly occulomotor III
33
Innervation of the extra-ocular muscles of the eyes:
* The eyelids are closed by:
VII
33
Innervation of the extra-ocular muscles of the eyes:
* The eyelids are closed by:
VII
34
Innervation of the extra-ocular muscles of the eyes:
* Upper eyelids are raised by:
Occulomotor III and some smooth muscles
35
Innervation of the extra-ocular muscles of the eyes:
* Upper eyelids are raised by:
Occulomotor III and some smooth muscles
36
Innervation of the extra-ocular muscles of the eyes:
* Touch sensation is provided by:
trigeminal (Vth) cranial nerve
37
Summation of innervation of the extraocular muscles of the eyes:
38
Normal vision:
* When light from a distant source (>6m) reaches...
* Without any adjustments on the eye, it is able to focus the ....
* When light from a distant source (>6m) reaches the cornea, the rays are parallel
* Without any adjustments on the eye, it is able to focus the image onto the retina
38
Normal vision:
* When light from a distant source (>6m) reaches...
* Without any adjustments on the eye, it is able to focus the ....
* When light from a distant source (>6m) reaches the cornea, the rays are parallel
* Without any adjustments on the eye, it is able to focus the image onto the retina
39
* Emmetropia =
* Emmetropia = normal eye ----> Distant object focused when ciliary muscles are completely relaxed
40
When does accommodation happen? (2)
* When the image is brought closer, it falls behind the retina (the focal distance is increased)
* The eye then needs to adjust its refractive capacity Accommodation so that the focal distance is reduced back to normal
41
Visual accommodation:
What happens for the unaccommodated eye (far vision)? (3)
* For the unaccommodated eye (far vision), the most refraction of light occurs at the cornea (air-solid surface)
* When the object of visual interest is brought closer, there is need for the lens to adjust and increase its refractive capacity
* The shape of the lens at rest is flat due to tension by the zonular fibres
41
Visual accommodation:
What happens for the unaccommodated eye (far vision)? (3)
* For the unaccommodated eye (far vision), the most refraction of light occurs at the cornea (air-solid surface)
* When the object of visual interest is brought closer, there is need for the lens to adjust and increase its refractive capacity
* The shape of the lens at rest is flat due to tension by the zonular fibres
42
* To view near objects ---->
Ciliary muscles contraction, the zonular fibres slacken and the lens becomes more convex (round)
43
* To view near objects ---->
Ciliary muscles contraction, the zonular fibres slacken and the lens becomes more convex (round)
44
What is Visual acuity? (2)
* Visual acuity is the ability to resolve fine detail
* Each retina ---> 6 million cones & 120 million rods, 1.2 million nerve fibres in optic nerve
45
What is the blindspot test? (2)
* Blindspot test: close the left eye and look at the cross with the right eye
* Move the head closer to the screen slowly ---> Circle will eventually disappear from the visual field of the eye indicating that the image is focused on the blind spot
46
What is Presbyopia?
Progressive denaturalise of lens proteins, lens hardens with age (inelastic)
46
What is Presbyopia?
Progressive denaturalise of lens proteins, lens hardens with age (inelastic)
47
* Accommodation with ____
* Age 40-45 ----> Reading close work becomes difficult (glasses with conveying lenses are prescribed)
* Advanced _______ complain that their arms have become “too short” to hold reading material at a comfortable distance
age
presbyopes
48
What is the retina? (2)
* Light sensitive lining of the back of the eye
* contains photoreceptors (rods&cones), bipolar, ganglion, horizontal and amacrine cells
49
The retina:
Where are the photoreceptors located? (3)
* Photoreceptors are nearest to the pigment and choroid
* Light goes through the other layers first before reaching the photoreceptors
* The retina also contains some photoreceptors that have melanopsin
50
The retina:
Where are the photoreceptors located? (3)
* Photoreceptors are nearest to the pigment and choroid
* Light goes through the other layers first before reaching the photoreceptors
* The retina also contains some photoreceptors that have melanopsin
51
What is Melanopsin? (3)
* Melanopsin containing photoreceptors have axons which project to the suprachiasmatic nuclei and the lateral geniculate body
* Loss of the gene for melanopsin results in the loss of circadian entrainment which is important for light-dark changes
* Horizontal cells are involved in lateral inhibition which helps to sharpen the visual images (improve contrast)
52
* Visual spectrum =
wavelengths 380 to 740 nm.
53
Vision:
* All colours we see fall somewhere in the _______
* Outside limits e.g UV, infrared We can’t see
* We can produce all colours by mixing 3 ____ colours
spectrum
primary
54
What is phototransduction?
* Phototransduction is the conversion of electromagnetic light energy into electrical signals
55
Phototransduction in rods:
What happens in the dark?
* In the dark, electrical current is generated in the discs of the rods ----> Due to Na ion entering the cells and depolarising them
56
* Rods contain the photo pigment _______.
rhodopsin
57
What happens when light shines on these pigments? (2)
* When light shines on these pigments, they change conformation from cis to trans isomers
* This then triggers a series of events which result in the current being reduced and the cells hyperpolarising
58
* All receptor potentials of the various cells in the retina are _______ potentials except for ganglion cells which are the only cells that support/generate action potentials.
GRADED
59
* Potentials in rods, and horizontal cells are _________
* Bipolar cell potentials are _________ and hyperpolarising
* Amacrine cells are depolarising with spikes
hyperpolarising
depolarising
60
* There are two types of ganglion cells ---->
Large (mangno or M cells) and small (parvo or P cells)
61
Trichromat theory of colour vision:
What is the 3 cone system?
* 3 cone system (different pigments) with different absorption maxima = sensitive to different wavelengths
62
* The colour we see is determined by the ______ frequency of impulses from each cone system
relative
63
Rods vs Cones (10)
64
Visual adaptation:
* Dark adaptation (becoming accustomed to the dark) =
= adaptation to low illumination, decline in visual threshold, max 25min
65
* Retinene and _____ recombine to form photopigment and additional pigment generated via A route
opsin
66
Monocular and binocular vision:
67
Adaptations to changes in illumination
* when bright light is shone in one eye and the pupil constricts =
* when the opposite pupil constricts =
* when bright light is shone in one eye and the pupil constricts = direct pupillary reflex
* when the opposite pupil constricts = consensual pupillary reflex
68
What are ocular reflexes?
69
What are the eye movements? (5)
70
Lesions affecting the eyes:
What are the Visual pathways? (2)
* The key pathways are from the ganglion axons to the optic nerve (some decussate in the optic chiasm) then the optic tract and the lateral geniculate body (in the thalamus)
* These project Rutherford to the geniculocalcarine tract (optic radiation) and the the occipital lobe which is the primary visual cortex
71
* Fibres from temporal field Nasal hemiretina ----> Desccusate in optic ______
* Fibres from nasal field ----> _______
chiasm
Ipsilateral
72
* The LGN (thalamus) ---->
Primary processing centre for visual information
73
* Two major pathways:
Magnocellular pathway & parvocellular pathway
74
What is the Magnocellular pathway?
* Magnocellular pathway carries signals for detection of movement and depth (abnormalities in dyslexia)
75
What is the parvocellular pathway?
* The parvocellular pathway carries signals for colour vision, texture, shape, fine detail
76
What is colour blindness?
* Living with colour blindness ----> Learning difficulties, eat unripe bananas, green vegetables look awful, traffic lights
77
What is Error of refraction - myopia? (3)
* Myopia Eyeball too long ( most common) or too much refractive power (or a combination of both)
* For distant object, the image is focused in front of the retina Cannot decrease curvature & cannot focus on distant objects only near objects
* Corrected with a biconcave/ diverging lens
78
What is Error of refraction - myopia? (3)
* Myopia Eyeball too long ( most common) or too much refractive power (or a combination of both)
* For distant object, the image is focused in front of the retina Cannot decrease curvature & cannot focus on distant objects only near objects
* Corrected with a biconcave/ diverging lens
79
What are the causes of myopia? (5)
80
Error of refraction - Hyperopia
What is hyperopia? (5)
* Eyeball is too short or the lens system is too weak
* When viewing a near object, the image is focused behind the retina Must accommodate for close objects Tiring, headaches
* Patients cant focus on near objects because there is little accommodative power left
* If the patient is presbyopic, they can’t accommodate for distant objects
* Therefore a converging lens is required
81
What is Astigmatism? (3)
* Most common defect of refraction
* It can occur from birth, with refractive errors, after injury or surgery
* it is corrected using contact lenses, cylindrical lenses or refractive surgery
81
What is Astigmatism? (3)
* Most common defect of refraction
* It can occur from birth, with refractive errors, after injury or surgery
* it is corrected using contact lenses, cylindrical lenses or refractive surgery
82
What are Cataracts? (3)
* Common in elderly
* They can also be caused by diseases e.g diabetes mellitus and hypertension, trauma, exposure to radiation and UV light
* They are the leading cause of blindness
83
What is Gustation? (2)
* Sensation of taste
* There are taste receptors further down the GIT including the intestine
84
* The tongue is able to distinguish several _______
* All parts of the tongue are responsive to all modalities
* Ability to discriminate differences in intensity of tastes is poor in ______
* A ____% change in concentration is required before the intensity difference can be discerned
Modalities
Humans
30
85
* The threshold for taste of different substances varies with compound:
HCl =
NaCl =
Strychnine =
Glucose =
Sucrose =
Saccharin =
86
* The threshold for taste of different substances varies with compound:
HCl =
NaCl =
Strychnine =
Glucose =
Sucrose =
Saccharin =
87
Pathways to the CNS:
* increasing the temperature of food increase its tastiness
88
Disorders to taste:
* Ageusia
* Hypogeusia
* dysgeusia
Inability to taste
Decreased sense of taste
Distortion of sense of taste
89
What is Olfaction?
* Olfaction has a high sensitivity ---> One molecule is enough to activate a receptor
* The ability to discriminate changes in intensity of odour in humans is poor
90
* 30% change is required before the change is ______
* Dogs have a ______ concentration of olfactory receptors in the nose than humans
discerned
higher
91
* The sense of smell is more acute in women especially at _______
* The nasal cavity is poorly ventilated ----->
ovulation
----> Sniffing increases ventilation of receptors
92
* Olfactory receptors are _______ adapting
* Several hundred odours are distinguishable and this occurs through direct stimulation of the receptors and also via _______ _________ systems
rapidly
second messenger
93
What are odourant-binding proteins? (3)
* Special proteins called odourant binding proteins are produces and bind inhaled chemicals, concentrating them and then transferring them to the olfactory receptors where they can be detected
* The olfactory receptor cells are dilated endings of neurones
* 10-50 million receptor cells, life span 4-8 weeks Theses neurones are replaced unlike most other neurones
93
What are odourant-binding proteins? (3)
* Special proteins called odourant binding proteins are produces and bind inhaled chemicals, concentrating them and then transferring them to the olfactory receptors where they can be detected
* The olfactory receptor cells are dilated endings of neurones
* 10-50 million receptor cells, life span 4-8 weeks Theses neurones are replaced unlike most other neurones
94
How do olfactory neurones project?
* Olfactory neurones (cranial nerve I) project to the piriform cortex (area between frontal and temporal cortex = olfactory cortex), olfactory tubercle, entorhinal cortex and amygdala
95
What are the olfaction pathways? (3)
* Pathways to the frontal cortex or via thalamus to the orbitofrontal cortex are important for conscious discrimination of odours
* The pathway to the amygdala is involved with olfactory memories
* There are also naked nerve endings of trigeminal nerve in olfactory membrane for detection of other physical modalitie
95
What are the olfaction pathways? (3)
* Pathways to the frontal cortex or via thalamus to the orbitofrontal cortex are important for conscious discrimination of odours
* The pathway to the amygdala is involved with olfactory memories
* There are also naked nerve endings of trigeminal nerve in olfactory membrane for detection of other physical modalitie
96
* Some smells depend on activation of ______ receptors and pain receptors e.g peppermint, ammonia, chlorine
olfactory
96
* Some smells depend on activation of ______ receptors and pain receptors e.g peppermint, ammonia, chlorine
olfactory
97
What are pheromones?
98
What are the disorders of smell? (3)
99
What is Hyposmia? (2)
* Hyposmia Reduced olfaction with age (over 80 years, reduced glomeruli and olfactory epithelium scarred with age, central changes too)
* Common with upper respiratory tract infections and head trauma, frequent use of vasoconstricting nasal sprays
100
* Alzheimer’s Loss of nerve cells = _________
* Partial _______ are very common; affected people lack receptors molecules
= early diagnosis tool
anosmias
101
What is dysosmia?
Lack of some neurones/receptors, altered sensory integration, same causes as hyposmia.
