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Developmental Concepts > Sensory System Overview > Flashcards

Sensory System Overview Flashcards

1
Q

Two types of receptors

A
  • nerve cell
  • specialized epithelial cells

Activation of receptors:
- stimulus-specific
- transform an external stimulus to an electrical signal

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2
Q

Sensory Pathways

A

describe type and location of the sensory stimulus

type; dependent on what type of receptor is activated

location; each receptor has a specific location on the sensory map in the brain (ex; midbrain, pons)

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3
Q

Dorsal Root Ganglion

A
  • collection of cell bodies of the afferent sensory fibers
  • associated with dorsal root of the spinal nerve
  • dorsal roots contain sensory fibers from the skin, subcutaneous and deep tissues and viscera
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4
Q

What primary afferent fibers are myelinated? (Dorsal root ganglion)

A
  • cutaneous, joint and visceral afferents are composed of myelinated (some are not, these are)
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5
Q

CNS Perception

A

the integration of sensory impressions into psychological *meaningful info

  • involves peripheral sensory mechanisms and higher-level processing
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6
Q

CNS Sensory map

A
  • location of sensory receptors in the brain
  • sensory homunculus shows the somatic sensory projections from the body surface
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7
Q

CNS Sensory Integration

A

the ability to use sensory information efficiently

combining several sensory inputs to produce a desired movement (drawing, writing)

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8
Q

What systems are involved in stable standing balance?

A

Somatosensory (proprioception, muscle length and where we are in space)
Vision
Vestibular

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9
Q

Somatosensory System Receptors

A
  1. Mechanoreceptors (touch, pressure, vibrator proprioception)
  2. Thermoreceptors (heat and cold)
  3. Nociceptors (pain) unmylenated
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10
Q

Sensory info from the body - exteroception, proprioception and interception

A
  • cutaneous sensation of touch (exteroception)
  • proprioceptive sensation from ligaments, muscles, joints, and tendons

interception - perception of sensation from inside the body

proprioception - perception of ones body in space

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11
Q

Function of somatosensory system

A

transmits information about the senses of touch, pain, temperature, and body position from sensory receptors to the CNS to regulate behavior

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12
Q

Somatosensory Prenatal order of system development

A

Order of system development: touch - vestibular - smell - hearing - vision - taste - proprioception

*Touch is the first system to function in utero, allows for communication and attachment

Proprioceptive receptors (muscle spindles and golgi tendon organs) are well-developed by mid-fetal life

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13
Q

7 weeks fetus

A

fetus responds to touch around mouth

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14
Q

12 weeks somatosensory fetus

A

muscle spindles formed

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15
Q

16 weeks after birth somatosnesory

A

golgi tendon organs formed

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16
Q

17 weeks somatsensory fetus

A

cutaneous sensation spreads to entire body

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17
Q

Somatosensory Infancy and Childhood

A
  • all sensory systems are ready to fxn at birth (not matured)
  • PNS completely myelinated

complete structural maturation of sensory pathways occurs throughout childhood;
- increased nerve conduction velocity,
- redistribution of axon branching,
- increased synaptic efficiency

(getting rid of old neurons, pruning, making more efficient)

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18
Q

What is touch sensation used for in infancy?

A

used by infant to locate food

rooting relex* (turning towards touch on side of the mouth)?

crucial role in parent-infant attachment, sociability and cognitive development

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19
Q

12-16 months

A

specific touch localization

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20
Q

5 years

A

identify objects by touch

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21
Q

7 years

A

two-point discrimmination

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22
Q

Proprioception in infancy and childhood

A
  • used very early after birth
  • allows them to execute purposeful movements like imitation, reaching and locomotion, achieve and maintain upright posture
  • integration of sensation and movement occurs during childhood and continues to develop through adolescence
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23
Q

When do muscle spindles mature?

A

As early as three weeks

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24
Q

When does proprioceptive acuity for movements improve? What does this allow for?

A

5-12 years

allows for beginning mastery of skills such as hopping, dancing, and gymnastics

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25
Q

Somatosensory Adolescence

A
  • tactile and proprioceptive senses are further refined
  • maturation and integration of somatosensory system processing guide motor abilities and skill refinement
  • **sensory system is keenest during late adolescence into early adulthood
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26
Q

When is sensory system is keenest?

A

late adolescence into early adulthood

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27
Q

Somatosensory Adulthood

A
  • sensory system begins to decline
  • sensory receptor fxn decline in middle age (do not always correlate with decline in fxn)
  • skin becomes dry and less elastic (comprised precision of cutaneous receptors)
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28
Q

When does reaction time peak?

A

mid 20s, then slows by 20% during middle adulthood

29
Q

Somatosensory Aging

A
  • gradual decline in sensory fxning (decrease in number and fxn of sensory neurons, structural and psyio changes within CNS)
  • impact on tactile system (decrease in number and fxn of skin receptors, loss of up to 30% of sensory fibers intervating PNS leads to peripheral neuropathy**)
  • impact on proprioceptive (atrophy of muscle spindles, joint receptors, GTO’s - decreasing feedback to CNS)

*Arthritic changes affect the ability of joint receptors to detect joint motion

30
Q

What are the fxnal consequences of the redundancy of sensory info being decreased in old age

A
  • postural instability
  • exaggerated body sway
  • balance problems
  • gait disturbances
  • diminished fine motor coordination
  • the tendency to drop things held in hands
  • difficulty recognizing body or limb positions in space
31
Q

What is the dominant sensory modality in humans?

A

visual system

32
Q

What info does the visual system provide

A
  • external world
  • identification of external objects and determination of their movements
  • *where the body is in space, the relationship of ones body parts and the motion of ones body
  • vital in control of posture, locomotion, balance, hand fxn (hand eye coordination)
33
Q

Peripheral anatomy of visual system

A
  • structures and receptors in the eyeball
  • 6 extraocular muscles
34
Q

Saccades

A
  • quick simultaneous movement of both eyes in the same direction (looking one point to another)
35
Q

Slow Pursuit or Tracking

A
  • slow, smooth eye movements
  • allow the eyes to closely follow moving object
36
Q

Vestibulo-ocular reflex (VOR)

A
  • reflex eye movement that stabilizes images on retina
  • produce eye movement in opposite direction of head movement
37
Q

Vergence

A

simultaneous movement of both eyes in the opposite direction

convergence - eyes rotate towards each other

divergence - eyes rotate away from each other

38
Q

Prenatal visual system development

A
  • derived from thalamus in the diencephalon
  • 4th week - eye forms
  • 13th week myelination begins
  • once formed, extends to occipital poles and forms the horizontal axis of brain
39
Q

When are neurons in occipital cortex ready to receive (visual) input in their adult layers?

A

in adult layers during 2nd half of gestation

ready to receive input at birth

40
Q

When does reflexive eye blinking occur

A

6 months of gestation

41
Q

When does the central visual pathway develop and mature?

A

Develops postnatally

Complete maturation of sensory pathways occur after birth

42
Q

Visual development in newborns

A
  • acuity is 20/800
  • inability to see in black and white
  • pattern preference (human face)
  • best distance fixation is 7-9 inches away from eyes
  • sustained ocular fixation of an object observed at birth
43
Q

Visual system 2 months

A

see 2 colors (red and yellow)

track vertically, horizontally and in circular path

44
Q

3 months visual

A

prefernce for a colored object
perception of form

45
Q

4 months visual

A

full color vision

Binocular vision matures 3-5 months, adult like binocular vision by 2 years

46
Q

12 months visual

A

adult like levels of visual acuity achieved (20/20)

47
Q

Binocular vision

A

Binocular vision matures 3-5 months, adult like binocular vision by 2 years

48
Q

Visual system in Infancy and Childhood

A
  • postural control promotes visual interest (can explore environment)
  • visual perception becomes increasingly more accurate during preschool years
49
Q

What is the greatest requirement for visual feedback during first 3 months?

A

postural control (to see)

50
Q

What age are children dependent on visual feedback for upright postural control?

A

4-6

51
Q

Visual System Adolescence

A
  • visual system matures and becomes sophisticated
  • eye hand coordination and perception-action coupling (smooth tracking of small objects like baseball)
52
Q

Visual developments age 11 and age 12

A

11 - perceptual judgments regarding size of objects

12 - adult levels of depth perception

53
Q

Visual system Adulthood

A
  • increases in 20a and 30s, remains stable during 40s-60s
  • rapid decline between 60-80
  • cataracts, light to dark decline, presbyopia
54
Q

When do cataracts begin to form?

A

over 30 years

55
Q

when does a decline in ability to adapt from light to dark environments occur

A

after 40

56
Q

When does presbyopia occur

A

45

(far sightedness)

57
Q

Visual System older adults

A
  • decrease in visual acuity (increased visual threshold, more light required to see)
  • loss of depth perception (think using stairs), contrast sensitivity decreases between 6-75
  • slowed peripheral and central processing impairs postural control, balance and saftey and independence
58
Q

Fxn of Vestibular System

A

provides info regarding the position of the head in space

detects sudden changes in the direction fo movement of the head

integrate visual and proprioceptive info ot coordinate movements

assits with eye stabilization and postural stability during standing and walking

59
Q

Otolith organs and Semicircular canals

A
  • otolith = linear
  • semicircular = rotational
60
Q

Vestibular prenatal

A
  • structures come from the thickening of ectoderm within ear at 4th week of gestation
  • as a fetus moves in utero, vestibular apparatus provides info about the movement (important for mom to move a lot to stimulate it)
61
Q

When are the semicircular canals, saccule completely formed?

A

10th week (gestation)

62
Q

Vestibular infancy and childhood

A

vestibular system completely mylenated at birth

movemnt behavior developed by movment experience, devleopment of trunk righting and equilibrium reactions

(rocking and spinnig contribute to the maturation of the vestibular system)

  • relate eye movements to head movements (VOR present at 2 motnhs)
63
Q

When is the vestibular system sensitive and when does it decline

A

increase snesitivity from birth to peak between 6-12 motnhs

gradually decline from 2.5 years to puberty

64
Q

When is full maturity of vestibular system

A

10-14 years of age

65
Q

When is balance gained?

A

9-12 years; static balance
12 years; dynamic balance

sports and dancing contribute to further maturation and refinement

66
Q

What systems contributes to balance control

A

vestibular, visual, somatosensory

67
Q

Vestibular adulthood

A
  • age related changes begin at 40s
  • decreased number of sensory cells and nerve fibers in the peripheral nervous system
  • neural changes possible in the vestibular nerve
68
Q

What are common issues for over 50?

A
  • dizziness and vertigo
69
Q

Vestibular older adults

A
  • 40% reduction in hair cells and 36% redcution in peripheral nerve fibers in adults over 70
  • deterioration in central vestibular integrative functions - impaired balance
  • increased thresholds of excitation of vestibular nuclei (so decreased responsiveness bc cant meet threshold)
  • vestibular system becomes unreliable when visual and proprioceptive input conflicts

Developmental Concepts (4 decks)

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