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MBBCh 2- PHSL2004A > 12. CNS (Sensory) (2) > Flashcards

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

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2
Q

Decibel scale for common sounds: (2)

A
  • It uses a non linear scale
  • in humans, 0 decibels = threshold of hearing
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3
Q
  • A volume of _____ doesn’t mean the absence of sound but the sound level equal to that of the standard
A

0dB

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3
Q
  • A volume of _____ doesn’t mean the absence of sound but the sound level equal to that of the standard
A

0dB

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4
Q
  • The presence of one sound decreases the ability of an individual to hear other sounds —->
A

masking

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5
Q
  • The presence of one sound decreases the ability of an individual to hear other sounds —->
A

masking

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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
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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
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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
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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
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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
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9
Q
  • Conduction deafness =
A

= decreased sound reaching cochlea

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10
Q

Otitis media =

A

= inflammation of the middle ear, thickening the ear
drum

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11
Q

otosclerosis =

A

= formation of spongy bone about the stapes

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11
Q

otosclerosis =

A

= formation of spongy bone about the stapes

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12
Q

Osteoporosis =

A

= decreased quantity of bone

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12
Q

Osteoporosis =

A

= decreased quantity of bone

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13
Q

Perforated eardrum =

A

= acuity 5dB (hearing can often be restored)

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14
Q
  • Nerve/sensorineural deafness =
A

= reduced hearing associated with damage to hair cells or neural pathways

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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
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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
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16
Q

Hearing range classifications:

A
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17
Q

Hearing range classifications:

A
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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)
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19
Q
  • 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
A

acceleration
utricle
saccule

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20
Q

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

A

ampullaris
cupula

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21
Q

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

A

ampullaris
cupula

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22
Q

Rotational acceleration: Semicircular canals

When happens when constant speed of rotation is reached?

A
  • 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
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22
Q

Rotational acceleration: Semicircular canals

When happens when constant speed of rotation is reached?

A
  • 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
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23
Q

Rotational acceleration: Semicircular canals

  • Stop or deceleration —->
  • Movement in one direction —->
A
  • Stop or deceleration —-> Fluid moves in opposite direction
  • Movement in one direction —> Increased impulses in nerve, opposite inhibits
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23
Q

Rotational acceleration: Semicircular canals

  • Stop or deceleration —->
  • Movement in one direction —->
A
  • Stop or deceleration —-> Fluid moves in opposite direction
  • Movement in one direction —> Increased impulses in nerve, opposite inhibits
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24
Q

Linear acceleration: Utricle and saccule

Utricle detects…
Saccule detects…

A
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24
Q

Linear acceleration: Utricle and saccule

Utricle detects…
Saccule detects…

A
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25
Q

Head upright:
Head tilted:

A
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26
Q

Spatial orientation and balance:

A
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27
Q

Vestibulo-ocular reflex:
Vertigo:
Nystagmus:

A
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27
Q

Vestibulo-ocular reflex:
Vertigo:
Nystagmus:

A
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28
Q

Caloric stimulation:

A
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29
Q

The lacrimal glands
- tears contain: (4)

A

Hypotonic fluid
Mucus
Antibodies
Lysozyme

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30
Q

The lacrimal glands
What is the function?

A
  • Their function is to cleanse, protect, moisten, and lubricate the eye
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31
Q

Extrinsic muscles of the eye:

A
  • Important for the movements of the eyeballs
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32
Q

Innervation of the extra-ocular muscles of the eyes:
* Extra-ocular muscles are innervated by

A

3 cranial nerves —-> Abducens VI, Trochlear IV, and mostly occulomotor III

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33
Q

Innervation of the extra-ocular muscles of the eyes:
* The eyelids are closed by:

A

VII

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33
Q

Innervation of the extra-ocular muscles of the eyes:
* The eyelids are closed by:

A

VII

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34
Q

Innervation of the extra-ocular muscles of the eyes:
* Upper eyelids are raised by:

A

Occulomotor III and some smooth muscles

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35
Q

Innervation of the extra-ocular muscles of the eyes:
* Upper eyelids are raised by:

A

Occulomotor III and some smooth muscles

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36
Q

Innervation of the extra-ocular muscles of the eyes:
* Touch sensation is provided by:

A

trigeminal (Vth) cranial nerve

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37
Q

Summation of innervation of the extraocular muscles of the eyes:

A
38
Q

Normal vision:
* When light from a distant source (>6m) reaches…
* Without any adjustments on the eye, it is able to focus the ….

A
  • 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
Q

Normal vision:
* When light from a distant source (>6m) reaches…
* Without any adjustments on the eye, it is able to focus the ….

A
  • 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
Q
  • Emmetropia =
A
  • Emmetropia = normal eye —-> Distant object focused when ciliary muscles are completely relaxed
40
Q

When does accommodation happen? (2)

A
  • 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
Q

Visual accommodation:
What happens for the unaccommodated eye (far vision)? (3)

A
  • 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
Q

Visual accommodation:
What happens for the unaccommodated eye (far vision)? (3)

A
  • 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
Q
  • To view near objects —->
A

Ciliary muscles contraction, the zonular fibres slacken and the lens becomes more convex (round)

43
Q
  • To view near objects —->
A

Ciliary muscles contraction, the zonular fibres slacken and the lens becomes more convex (round)

44
Q

What is Visual acuity? (2)

A
  • 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
Q

What is the blindspot test? (2)

A
  • 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
Q

What is Presbyopia?

A

Progressive denaturalise of lens proteins, lens hardens with age (inelastic)

46
Q

What is Presbyopia?

A

Progressive denaturalise of lens proteins, lens hardens with age (inelastic)

47
Q
  • 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
A

age
presbyopes

48
Q

What is the retina? (2)

A
  • Light sensitive lining of the back of the eye
  • contains photoreceptors (rods&cones), bipolar, ganglion, horizontal and amacrine cells
49
Q

The retina:
Where are the photoreceptors located? (3)

A
  • 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
Q

The retina:
Where are the photoreceptors located? (3)

A
  • 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
Q

What is Melanopsin? (3)

A
  • 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
Q
  • Visual spectrum =
A

wavelengths 380 to 740 nm.

53
Q

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
A

spectrum
primary

54
Q

What is phototransduction?

A
  • Phototransduction is the conversion of electromagnetic light energy into electrical signals
55
Q

Phototransduction in rods:
What happens in the dark?

A
  • In the dark, electrical current is generated in the discs of the rods —-> Due to Na ion entering the cells and depolarising them
56
Q
  • Rods contain the photo pigment _______.
A

rhodopsin

57
Q

What happens when light shines on these pigments? (2)

A
  • 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
Q
  • 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.
A

GRADED

59
Q
  • Potentials in rods, and horizontal cells are _________
  • Bipolar cell potentials are _________ and hyperpolarising
  • Amacrine cells are depolarising with spikes
A

hyperpolarising
depolarising

60
Q
  • There are two types of ganglion cells —->
A

Large (mangno or M cells) and small (parvo or P cells)

61
Q

Trichromat theory of colour vision:
What is the 3 cone system?

A
  • 3 cone system (different pigments) with different absorption maxima = sensitive to different wavelengths
62
Q
  • The colour we see is determined by the ______ frequency of impulses from each cone system
A

relative

63
Q

Rods vs Cones (10)

A
64
Q

Visual adaptation:
* Dark adaptation (becoming accustomed to the dark) =

A

= adaptation to low illumination, decline in visual threshold, max 25min

65
Q
  • Retinene and _____ recombine to form photopigment and additional pigment generated via A route
A

opsin

66
Q

Monocular and binocular vision:

A
67
Q

Adaptations to changes in illumination
* when bright light is shone in one eye and the pupil constricts =
* when the opposite pupil constricts =

A
  • when bright light is shone in one eye and the pupil constricts = direct pupillary reflex
  • when the opposite pupil constricts = consensual pupillary reflex
68
Q

What are ocular reflexes?

A
69
Q

What are the eye movements? (5)

A
70
Q

Lesions affecting the eyes:
What are the Visual pathways? (2)

A
  • 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
Q
  • Fibres from temporal field Nasal hemiretina —-> Desccusate in optic ______
  • Fibres from nasal field —-> _______
A

chiasm
Ipsilateral

72
Q
  • The LGN (thalamus) —->
A

Primary processing centre for visual information

73
Q
  • Two major pathways:
A

Magnocellular pathway & parvocellular pathway

74
Q

What is the Magnocellular pathway?

A
  • Magnocellular pathway carries signals for detection of movement and depth (abnormalities in dyslexia)
75
Q

What is the parvocellular pathway?

A
  • The parvocellular pathway carries signals for colour vision, texture, shape, fine detail
76
Q

What is colour blindness?

A
  • Living with colour blindness —-> Learning difficulties, eat unripe bananas, green vegetables look awful, traffic lights
77
Q

What is Error of refraction - myopia? (3)

A
  • 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
Q

What is Error of refraction - myopia? (3)

A
  • 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
Q

What are the causes of myopia? (5)

A
80
Q

Error of refraction - Hyperopia

What is hyperopia? (5)

A
  • 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
Q

What is Astigmatism? (3)

A
  • 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
Q

What is Astigmatism? (3)

A
  • 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
Q

What are Cataracts? (3)

A
  • 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
Q

What is Gustation? (2)

A
  • Sensation of taste
  • There are taste receptors further down the GIT including the intestine
84
Q
  • 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
A

Modalities
Humans
30

85
Q
  • The threshold for taste of different substances varies with compound:
    HCl =
    NaCl =
    Strychnine =
    Glucose =
    Sucrose =
    Saccharin =
A
86
Q
  • The threshold for taste of different substances varies with compound:
    HCl =
    NaCl =
    Strychnine =
    Glucose =
    Sucrose =
    Saccharin =
A
87
Q

Pathways to the CNS:

A
  • increasing the temperature of food increase its tastiness
88
Q

Disorders to taste:
* Ageusia
* Hypogeusia
* dysgeusia

A

Inability to taste
Decreased sense of taste
Distortion of sense of taste

89
Q

What is Olfaction?

A
  • 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
Q
  • 30% change is required before the change is ______
  • Dogs have a ______ concentration of olfactory receptors in the nose than humans
A

discerned
higher

91
Q
  • The sense of smell is more acute in women especially at _______
  • The nasal cavity is poorly ventilated —–>
A

ovulation
—-> Sniffing increases ventilation of receptors

92
Q
  • Olfactory receptors are _______ adapting
  • Several hundred odours are distinguishable and this occurs through direct stimulation of the receptors and also via _______ _________ systems
A

rapidly
second messenger

93
Q

What are odourant-binding proteins? (3)

A
  • 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
Q

What are odourant-binding proteins? (3)

A
  • 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
Q

How do olfactory neurones project?

A
  • 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
Q

What are the olfaction pathways? (3)

A
  • 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
Q

What are the olfaction pathways? (3)

A
  • 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
Q
  • Some smells depend on activation of ______ receptors and pain receptors e.g peppermint, ammonia, chlorine
A

olfactory

96
Q
  • Some smells depend on activation of ______ receptors and pain receptors e.g peppermint, ammonia, chlorine
A

olfactory

97
Q

What are pheromones?

A
98
Q

What are the disorders of smell? (3)

A
99
Q

What is Hyposmia? (2)

A
  • 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
Q
  • Alzheimer’s Loss of nerve cells = _________
  • Partial _______ are very common; affected people lack receptors molecules
A

= early diagnosis tool
anosmias

101
Q

What is dysosmia?

A

Lack of some neurones/receptors, altered sensory integration, same causes as hyposmia.

MBBCh 2- PHSL2004A (19 decks)

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