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MBBS > 206 SSNS - Physiology > Flashcards

206 SSNS - Physiology Flashcards

1
Q

Functions of skin (7)

A 
Thermoregulation
Blood reservoir
Protection
Cutaneous sensations
Excretion
Absorption
Production of Vitamin D
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2
Q

What happens in the skin when there’s an increase in temperature?

A

Increase in temperature → sweat production
- Evaporation of sweat colls body

Increase heat loss - vasodilation

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3
Q

What happens in the skin when there’s a decrease in temperature?

A

Decrease in temperature → decrease sweat

Reduction in blood flow to dermal blood vessels - reduce heat loss

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4
Q

What happens to skin during shock?

A

Vasoconstriction of skin vessels occurs to divert blood to heart & brain; skin appears cold & pale

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5
Q

Keratin

Role in skin

A

Outermost layer of skin

Protects skin from abrasion, heat, chemicals
Tightly interlocked keratinocytes prevent entry of microbes

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6
Q

Oily sebum

Role in skin

A

Produced by sebaceous glands

Prevent drying of hair & skin
Contains bactericidal substances

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7
Q

Lipids

Role in skin

A

Prevent evaporation of water from skin surface & prevents dehydration
Also prevent entry of water into body during showers & swims

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8
Q

Acidic pH of sweat

Role in skin

A

Prevents growth of microbes

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9
Q

Melanin

Role in skin

A

Protects from damaging effects of UV rays

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10
Q

Epidermal and dermal macrophages

Role in skin

A

Phagocytose microbes that enter skin

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11
Q

What are the cutaneous sensations sensed by skin?

A 
Touch
Vibration
Pressure
Tickle
Itch
Pain
Temperature
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12
Q

What can be absorbed through skin?

A 
Fat soluble substances
Acetone
Carbon tetrachloride
Salts of heavy metal
Steroid
Transdermal patches
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13
Q

How does UV light aid the production of vitamin D?

A

Activates precursors - conversion of 7-dehydrocholesterol to vitamin D3

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14
Q

Fill in the blanks:

Rods with ______ receptive field has ______ acuity.

A

larger; low

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15
Q

Fill in the blanks:

Cones with ______ receptive field has ______ acuity.

A

smaller; high

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16
Q

What is the mechanism of phototransduction?

A
  1. Rhodopsin activated by light
  2. 11-cis retinal absorbs light → all-trans retinal
  3. All-trans retinal dissociates from opsin (retinal bleaching)
  4. Activated opsins activates G protein transducin
  5. Transducin activates cGMP phosphodiesterase, converts cGMP → GMP
  6. cGMP levels ↓, closing Na+ channels
  7. ↓ entry of Na+ → photoreceptor hyperpolarized
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17
Q

What supplies the inner layer of retina?

A

Central retinal artery

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18
Q

What supplies the outer layer of retina?

A

Choroid vessels

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19
Q

In retinal detachment, ______ detaches from ______?

A

Retina; pigment layer

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20
Q

Why is it possible for a detached retina to survive for few days?

A

Diffusion from choroid vessels & supply by central retinal artery still occurs

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21
Q

Vision cycle

regeneration of visual pigment in rods

A
  1. Light absorbed by rhodopsin
  2. Rhodopsin decompose → all-trans retinal (instant change from cis form) & scotopsin (retinal bleaching)
  3. Isomerase reconvert all-trans → 11-cis
  4. 11-cis retinal binds with scotopsin to reform rhodopsin
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22
Q

How does vitamin A play a role in the vision cycle?

A

Vit A is present in cytoplasm of rods & pigment of retina
Hence is always available to form new retinal when needed

If excess retinal in retina, converted back to vit A

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23
Q

During darkness, the photoreceptors are ______.

A

Depolarized

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24
Q

During light, the photoreceptors are ______.

A

Hyperpolarized

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25
Q

What aids light & dark adaptation?

A

Pupil
Pigment
Neurons

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26
Q

Exposure to bright light ______ sensitivity to light.

A

Reduces

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27
Q

Exposure to darkness ______ formation of pigment; ______ sensitivity to light

A

increases; increases

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28
Q

What are the 3 types of cones?

A

Red cone
Green cone
Blue cone

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29
Q

How do we perceive color?

A

Depends on how much of each cones are activated

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30
Q

Lack of green cones is ______

A

Deuteranopia

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31
Q

Lack of red cones is ______

A

Protanopia

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32
Q

Lack of blue cones is ______

A

Tritanopia

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33
Q

What causes nyctalopia?

A

Lack of vitamin A - night blindness

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34
Q

Connections between photoreceptors & bipolar cells

A

Photoreceptors > Horizontal cells
Horizontal cells > Bipolar cells
Bipolar cells > Amacrine cells
Amacrine cells > Ganglion cells

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35
Q

P cell function

A

Parvocellular
Has smaller receptive field
Provides fine details about image like color
Project to parvocellular LGN

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36
Q

M cell function

A

Magnocellular
Sensitive to rapid movement visual signals
Sensitive to low contrast black and white stimuli
Project to magnocellular LGN

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37
Q

Lateral inhibition

A

Capacity of an excited neuron to reduce the activity of its neighbors

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38
Q

Visual pathway

A

1° bipolar cells on retina
2° ganglion cells of retina
3° neurons in the 6 layers of LGN

II, III, V - receives inputs from temporal retina of same side
I, IV, VI - receive inputs from nasal retina of opposite eyes

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39
Q

Which cells receive from magnocellular cells & which receive from parvocellular cells?

A

Magnocellular - I & II

Parvocellular - others

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40
Q

Visual cortex area #

A

17

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41
Q

Which fibre cross and which remain uncross in the visual pathway?

A

Nasal fibres cross, temporal fibres remain uncrossed

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42
Q

Mechanism of light reflex

A
  1. Light fall on retina carried to midbrain via optic nerve
  2. Reaches pretectal nucleus
  3. Impulses pass to Edinger-Westphal nucleus
  4. Preganglionic neurons reach ciliary ganglion
  5. Postganglionic neuron reach pupil
  6. Circular muscles contract
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43
Q

Mechanism of accomodation reflex

A

Contraction of ciliary muscle - increased refractive power - close object

Relaxation of ciliary muscle - decreased power - distant object

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44
Q

Refractive index

A

Speed of light in air / Speed of light in medium

45
Q

Convex lens

A

Converges parallel light rays to a point

46
Q

Focal length

A

Distance between focal point from centre of lens

47
Q

Increase curvature of lens; ______ refractive power; ______ focal length

A

increase; decrease

48
Q

Decrease curvature of lens; ______ refractive power; ______ focal length

A

decrease; increase

49
Q

Power of lens

A

1 / focal length

50
Q

Convex lens has ______ power

A

positive

51
Q

Concave lens has ______ power

A

negative

52
Q

Which surfaces of eye does refraction occurs?

A

Anterior & posterior surface of cornea

Anterior & posterior surface of lens

53
Q

Reduced eye

A

Combining all refractive surfaces to form a single lens

59 diopters

54
Q

Accommodation for near objects

A

Contraction of ciliary muscle
Relaxation of suspensory ligaments
Increase curvature & power of lens

55
Q

3 things in accommodation reflex

A

Lens curvature increase
Eyeballs converge
Pupil becomes smaller

56
Q

Hyperopia (hypermetropia)

A

Farsightedness 遠視
Image is focused behind retina when ciliary muscle is relaxed

Corrected with convex lens

57
Q

Myopia

A

Near-sighted 近視
Distant object is focused in front of retina when ciliary muscle is relaxed

Corrected with concave lens

58
Q

Astigmatism

A

散光
Image in one plane is focused at distance diff from plan right angles to it

Corrected using cylindrical lens

59
Q

Where is vitreous humor found?

A

Found between lens & retina

No free flow

60
Q

Where is aqueous humor found?

A

Found between lens & cornea
Free flowing
Formed from ciliary processes of ciliary body behind iris

61
Q

Flow of aqueous humor

A

Posterior chamber → (through pupil) anterior chamber → trabeculae → canal of Schlemm → aqueous veins

62
Q

Cause of Glaucoma

A

Blocking of drainage of aqueous humor

63
Q

Treatment of glaucoma

A

Treated w drugs that reduce formation of aqueous humor

or drugs that increase drainage/absorption

64
Q

How does external ear conduct sound to middle ear?

A

By causing vibrations of tympanic membrane

Handle of malleus attached to tympanic membrane → malleus connected to incus → incus connected to stapes → foot plate of stapes pushes on oval window

65
Q

Which muscle keeps tympanic membrane tensed?

A

Tensor tympani

66
Q

Stapedial reflex

A

Activated by loud sounds - stapes pulled out of oval window: protects cochlea

67
Q

2 ways of sound conduction

A

Air conduction

Bone conduction

68
Q

3 coiled tubes & 2 membranes in the cochlea

A

3 coiled tubes:

  1. Upper scala vestibuli
  2. Middle scala media
  3. Lower scala tympani

2 membranes:

  1. Reissner’s membrane (vestibular membrane)
  2. Basilar membrane
69
Q

Where is organ of Corti located?

A

In the basilar membrane of cochlea

70
Q

What happens when hair cells of organ of Corti vibrate?

A

Transduce sound vibration into electrical activity

71
Q

How is sound waves transmitted in the cochlea?

A
  1. Vibration of tympanic membrane moves foot plate of stapes inward & outward
  2. Causing movement of fluid in scala vestibuli & media
  3. Causing vibration of basilar membrane
  4. Pushing of fluid at oval window causes bulging of membrane in round window
72
Q

What regions of basilar membrane vibrate maximally at diff frequencies?

A

High - base of chochlea
Medium - middle
Low - tip

73
Q

Movement of hair cells towards larger hair causing ______ of channel - ______

A

opening; depolarization

74
Q

Movement of hair cells towards smaller hair causing ______ of channel - ______

A

closing; hyperpolarization

75
Q

Stereocilia

A

Mechanosensing organelles of hair cells; increase in size away from modiolus

76
Q

Endolymph

A

Fluid in scala media

Rich in K+

77
Q

What is direction of sound determined by?

A

Difference in arrival of sound in both ears

Intensity of sound reaching both ears

78
Q

Conductive deafness

A

Problems in tympanic membrane or ossicles
Air conduction affected

Rinne’s test: BC > AC
Weber test: sound lateralized to affected ear

79
Q

Sensory neural deafness

A

Problem in cochlea, nerve, auditory pathway
Both air & bone conduction affected

Rinne’s test: both AC & BC affected, AC still > BC
Weber test: sound lateralized to normal ear

80
Q

Weber test

A

Vibration tuning fork placed on top of head or forehead

Normal: vibrations perceived equally on both ears
Conductive deafness: sound lateralized to affected ear
Sensory neural deafness: sound lateralized to normal ear

81
Q

Rinne’s test

A

Vibration tuning fork placed on mastoid
Once person stops perceiving vibrations, place in front of ear

Normal: hear sound - positive Rinne; AC > BC
Conductive deafness: BC > AC
Sensory neural deafness: both AC & BC affected, AC still > BC

82
Q

Vestibular apparatus

A

For detecting sensations of equilibrium

Composed of membranous labyrinth

83
Q

Membranous labyrinth

A

Membranous tubes & chambers

84
Q

What’s the sense organ in utricle and saccule?

A

Macula

85
Q

Utricle macula

A

Lies horizontally
Determine orientation when it’s upright
Stimulated by movement of head forwards & backwards

86
Q

Saccule macula

A

Lies vertically
Determine orientation when lie down
Stimulated by vertical acceleration & deceleration

87
Q

Statoconia

A

Calcium carbonate crystals in gelatinous layer

88
Q

Kinocilium

A

Long hair cell in one side

89
Q

Stereocilium

A

Other hair cells

90
Q

3 semicircular ducts in inner ear

A

Anterior
Posterior
Lateral

91
Q

Ampulla

A

Enlargement at one end of semicircular ducts

92
Q

What does the duct & ampulla of the ear contain?

A

Endolymph (rich in K+)

93
Q

What happens in the semicircular ducts when head rotates?

A

The fluid within remains stationary due to inertia → when movement stop fluid continues to move → bend hair in opposite direction

94
Q

Medial longitudinal fasciculus

A

Links the 3 main nerves which control eye movements, i.e. the oculomotor, trochlear and the abducent nerves, & vestibulocochlear nerve.
Function to integrate movement of the eyes and head movements.

95
Q

What are the 5 primary tastes?

A 
Sour
Salty
Sweet
Umami
Bitter
96
Q

3 types of papillae on tongue

A
  1. Circumvallate papilla - V shaped - posterior tongue
  2. Fungiform papillae - mushroom like - anterior surface of tongue
  3. Filiform papillae - thread like - lateral side of tongue
97
Q

Mechanism of taste transduction

A
  1. Taste chemical bind to protein receptors
  2. Open ion channels → depolarization

Salt - Na+
Sour - H+
Sweet, bitter, umami - G-protein coupled receptor → activate second messenger

98
Q

Taste pathway

A

1°
• Anterior 2/3 of tongue - supplied by lingual nerve → through chorda tympani into facial nerve → tractus solitarius (brainstem)
• Posterior 1/3 of tongue - glossopharyngeal nerve → tractus solitarius
• Base of tongue & pharynx - vagus nerve → tractus solitarius

2°
Synapse at nuclei of tractus solitarius → ventro posterior medial nucleus (thalamus)

3°
Thalamus → gustatory cortex (Brodmann area 43) = anterior insula + frontal operculum

99
Q

Where is olfactory epithelium located?

A

Superior part of nostrils

100
Q

Smell transduction

A
  1. Odorant molecule bind to receptor in olfactory cilia
  2. Activates G protein complex
  3. α subunit separates from β & γ subunits
  4. Activates adenyl cyclase
  5. Which converts ATP → cAMP
  6. cAMP activates/opens gated sodium channel → depolarization
  7. Action potential generated
101
Q

Physical factors that affect degree of stimulation in smell

A

Volatile substance
Water soluble
Slightly lipid soluble

102
Q

Olfactory pathway

A

1°
• Olfactory cells enter olfactory bulb (lie over cribriform plate) → glomerulus

2°
• Synapse with mitral or tufted cells in olfactory glomerulus

3°
• Medial pathway → hypothalamus - feeding & salvation
• Lateral olfactory pathway → limbic system (hippocampus) - olfactory memory
• New pathway → orbitofrontal cortex (by passing through dorsomedial nucleus of thalamus) - conscious analysis of odors

103
Q

Ageusia

A

Lack of taste

  • frontal lobe tumours, head injury
  • can be due to injury to CN VII & IX
104
Q

Hypogeusia

A

Reduced sensation of taste

- chewing tobacco

105
Q

Dysgeusia

A

Abnormal taste sensation

106
Q

Anosmia

A

Lack of smell

  • COVID
  • can be due to fracture of cribriform plate
107
Q

Hyposmia

A

Reduced sensation of smell

- can be due to cold

108
Q

Parosmia

A

Abnormal sensation of smell

109
Q

What secretes endolymph?

A

Stria vascularis

MBBS (28 decks)

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