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developmental concepts > lecture three: lifespan perspective of the sensory system > Flashcards

lecture three: lifespan perspective of the sensory system Flashcards

1
Q

sensory system overview

A

receptors —> sensory pathways —> central nervous system (CNS) —> motor system

  • receptors: receive stimulus
  • sensory pathways: nerve axons and afferent pathways; transmit signals
  • CNS: interpret or integrate sensory inputs
  • motor system: efferent pathways; produce response
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2
Q

what are the two types of receptors?

A

nerve cell and specialized-epithelial cell

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3
Q

receptor activation

A
  • stimulus specific
  • transform an external stimulus to an electrical signal
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4
Q

sensory pathways describe the _____ and ______ of the sensory stimulus

A

type, location

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5
Q

type of sensory stimulus

A

dependent on what type of receptor is activated

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6
Q

location of sensory stimulus

A

each receptor has a specific location on the sensory map in the brain

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7
Q

dorsal root ganglion (DRG)

A
  • collection of cell bodies of the afferent sensory fibers
  • associated with posterior or dorsal root of spinal nerve
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8
Q

what do the dorsal roots contain?

A
  • sensory fibers from the skin
  • subcutaneous and deep tissues
  • viscera
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9
Q

primary afferent fibers of the dorsal roots are either _____________ or ____________

A

myelinated, unmyelinated

  • cutaneous, joint, and visceral afferents are composed of myelinated
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10
Q

perception

A

the integration of sensory impressions into psychologically meaningful information

(involves peripheral sensory mechanisms and higher-level processing)

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11
Q

sensory maps

A

location of sensory receptors in the brain

(sensory homunculus: shows the somatic sensory projections from the body surface)

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12
Q

sensory integration

A

ability to use sensory information efficiently

(combining several sensory inputs to produce a desired movement; examples include drawing and writing)

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13
Q

what systems are involved in stable standing balance?

A
  • somatosensory system (proprioception)
  • vision
  • vestibular system
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14
Q

sensory pathways

A

transmits electrical signal to area of brain that corresponds with receptor location

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15
Q

somatosensory system receptors

A

receptors include
- mechanoreceptors (touch, pressure, vibration, proprioception)
- thermoreceptors (heat and cold)
- nociceptors (pain)

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16
Q

somatosensory system

A
  • provides sensory information about the body
    • cutaneous sensation of touch (exteroception)
    • proprioceptive sensation from ligaments, muscles, joints, and tendons
  • function
    • transmits information about senses of touch, pain, temperature, and body position from sensory receptors to CNS to regulate behavior
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17
Q

interoception

A

perception of sensation from inside the body

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18
Q

propioception

A

perception of one’s body in space

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19
Q

somatosensory system (prenatal)

A
  • order of sensory system development: touch —> vestibular —> smell —> hearing —> vision —> taste —> proprioception
  • proprioceptive receptors (muscle spindles and golgi tendon organs) are well developed by mid-fetal life
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20
Q

_____ is the first system to function in utero

A

touch (allows for communication and attachment)

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21
Q

prenatal timeline for somatosensory system

A

7 weeks: fetus responds to touch around mouth
12 weeks: muscle spindles formed
16 weeks: golgi tendon organs formed
17 weeks: cutaneous sensation spreads to entire body

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22
Q

somatosensory system (infancy and childhood part one)

A
  • all sensory systems are ready to function at birth (not matured)
    • peripheral nervous system is completely myelinated
  • complete structural maturation of sensory pathways occurs throughout childhood
    • increased nerve conduction velocity
    • redistribution of axon branching
    • increased synaptic efficiency
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23
Q

somatosensory system (infancy and childhood part two)

A
  • touch
    • used by infant to locate food (e.g. rooting reflex)
    • crucial role in parent-infant attachment, sociability, and cognitive development
  • further structural and functional changes occur as infant and child interact with the world
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24
Q

infancy and childhood timeline for somatosensory system

A

12-16 months: specific touch localization
5 years: identify objects by touch
7 years: two-point discrimination

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25
Q

somatosensory system (infancy and childhood part three)

A
  • proprioception
    • used very early after birth
      • execution of purposeful movements such as imitation, reaching, and locomotion
      • ability to achieve and maintain upright postures
      • muscle spindles mature as early as 3 years old
    • proprioceptive acuity for movements improves between age 5-12
      • allows for beginning mastery of skills such as hopping, dancing, and gymnastics
    • integration of sensation and movement occurs during childhood and continues to develop through adolescence
26
Q

somatosensory system (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
27
Q

somatosensory system (adulthood)

A
  • sensory function begins to decline in adulthood
    • sensory receptor functions decline in middle age
    • peripheral and central changes are small and gradual (do not always correlate with decline in function)
    • skin becomes dry and less elastic —> compromised precision of cutaneous receptors
28
Q

reaction time peaks in ________, then slows by ______ during middle adulthood

A

mid-20’s, 20%

29
Q

somatosensory system (aging part one)

A
  • gradual decline in sensory functioning
    • decrease in number of sensory neurons
    • decline in functioning of remaining sensory neurons
    • structural and physiological changes within CNS
  • impact on tactile system
    • skin receptors decrease in number and undergo structural changes
    • decrease in number of receptors —> decline in fine touch, pressure, and vibration sense
  • impact on proprioceptive system
    • atrophy of muscle spindles, joint receptors, and GTO’s —> decreasing feedback that CNS normally receives during movement
30
Q

loss of up to ______ of sensory fibers innervating peripheral receptors leads to _________ ___________

A

30%, peripheral neuropathy

31
Q

_________ changes affect the ability of joint receptors to detect _______ _______

A

arthritic, joint motion

32
Q

somatosensory system (aging part two)

A
  • redundancy of sensory information is decreased by age-related changes —> older adults are forced to compensate more
  • functional consequences
    • postural instability
    • exaggerated body sway
    • balance problems
    • gait disturbances
    • diminished fine motor coordination
    • tendency to drop things held in hands
    • difficulty recognizing body or limb positions in space
33
Q

what is the dominant sensory modality in humans?

A
  • visual system
    • vision provides individuals information about
      • the external world
      • identification of external objects and determination of their movement
      • where the body is in space, relationship of one’s body parts, and motion of one’s body
34
Q

vision is vital in control of ________, _________, _______, and ______ ________

A

posture, locomotion, balance, hand function

35
Q

visual system anatomy overview

A
  • peripheral anatomy
    • structures and receptors in the eyeball
    • 6 extraocular muscles
  • central anatomy
    • optic nerve
      -carries nerve impulses
    • optic chiasm
    • optic tract
    • optic radiations
    • occipital cortex
      • visual cortex
36
Q

visual system eye movements

A
  • head position and head control are important elements leading to visual function
  • 4 types of eye movements are controlled by 6 extraocular muscles
37
Q

saccades

A

quick, simultaneous movement of both eyes in the same direction

38
Q

slow pursuit or tracking

A
  • slow, smooth eye movements
  • allow the eyes to closely follow moving object
39
Q

vestibulo-ocular reflex (VOR)

A
  • reflex eye movement that stabilizes images on retina
  • produces eye movement in opposite direction to head movement
40
Q

vergence

A
  • simultaneous movement of both eyes in opposite direction
  • convergence: eyes rotate towards each other
  • divergence: eyes rotate away from each other
41
Q

visual system (prenatal)

A
  • derived from thalamus in diencephalon
    • most peripheral structure develops into the eyeball
    • 4th week: eye forms
    • 13th week: myelinated begins
  • once formed, visual system extends to occipital poles and forms horizontal axis of brain
    • neurons in the occipital cortex are organized into their adult layers during 2nd half of gestation and ready to receive input by birth
    • 6 months of gestation: reflexive eye blinking
42
Q

visual system (newborns)

A
  • central visual pathways develop postnatally
  • complete maturation of sensory pathways occur after birth
  • visual development
    • visual acuity is 20/800
    • initially see in black and white
    • sustained ocular fixation on an object observed at birth
    • pattern preference, especially for a human face
43
Q

for newborns, the best distance for fixation is _______ inches away from eyes

A

7 to 9

44
Q

visual system (infancy and childhood part one)

A

2 months
- see 2 colors (red and yellow)
- track vertically, horizontally, and in circular path
3 months
- preference for a colored object
- perception of form
4 months
- full color vision
- binocular vision matures between 3-5 months; adult-like binocular vision occurs by 2 years old
12 months
- adult levels of visual acuity achieved (20/20)

45
Q

visual system (infancy and childhood part two)

A
  • postural control promotes visual interest
    • head control facilities visual fixation on objects
    • postural adjustments allow child to maintain a position in space to visually explore environment
    • greatest requirement for visual feedback during first 3 months after child begins sitting and standing
  • visual perception becomes increasingly more accurate during preschool years
46
Q

children between ______ years old are highly dependent on visual feedback for upright postural control and balance

A

4 to 6

47
Q

visual system (adolescence)

A
  • visual system matures and becomes sophisticated
  • eye-hand coordination and perception-action coupling
    • smooth tracking of small objects in activities such as baseball, pinball, and computer games
    • age 11: perceptual judgements regarding size of objects
    • age 12: adult levels of depth perception achieved
48
Q

visual system (adulthood)

A
  • changes in visual acuity
    • increases in 20s and 30s and remains stable during 40s and 50s
    • most rapid decline occurs between 60-80 years old
  • age related changes
    • cataracts begin to form in individuals over 30
    • after age 40, decline in ability to quickly adapt from light to dark environments
49
Q

at what age does presbyopia develop?

A

age 45

50
Q

visual system (older adults)

A
  • decrease in visual acuity
    • increased visual threshold with older age —> more light required to see; decreased ability to adapt from dark to light environments
  • field of vision diminishes —> loss of depth perception
    • contrast sensitivity decreases between 65 to 75
  • slowed peripheral and central processing impairs postural control, balance, safety, and independence
51
Q

cataract formation in _____ of adults over 65

A

60%

52
Q

macular degeneration in ____ of adults over 75

A

28%

53
Q

vestibular system

A

function
- provides information regarding position of head in space
- detects sudden changes in direction of movement of head
- linear (otolith organs) and rotational (semicircular canals) accelerations
- vestibular inputs integrate visual and proprioceptive information to coordinate motor responses
- assists with eye stabilization and static and dynamic postural stability during standing and walking

54
Q

vestibular system (prenatal)

A
  • vestibular structures begin as a thickening of the ectoderm within primitive ear in the 4th week of gestation
    • 10 weeks: semicircular canals, utricle, and saccule completely formed
  • as fetus moves in utero, vestibular apparatus provides information about that movement
    • fetus show a generalized body response to changes in body position, including ability to right the head
55
Q

vestibular system (infancy and childhood)

A
  • vestibular system completely myelinated at birth
    • movement behavior developed by movement experience and acquiring postural control against gravity
      • leads to development of trunk righting and equilibrium reactions
    • rocking and spinning contribute to maturation of vestibular system
  • develop ability to relate eye movements to head movements
    • increase vestibular sensitivity from birth to a peak between 6 and 12 months of age; gradually decline from 2.5 years to puberty
56
Q

normal vestibular ocular reflex present by ____ months of age

A

2 months

57
Q

vestibular system (adolescence)

A
  • full maturity of vestibular system achieved between 10 and 14 yrs of age
    • contributes to healthy body scheme and gravitational security
    • vestibular, visual, and somatosensory systems coordinate to control balance
      • 9 to 12 yrs: gains in static balance
      • 12 yrs: gains in dynamic balance
  • sports and dancing contribute to further maturation and refinement
58
Q

vestibular system (adulthood)

A
  • age relegated changes: begin at 40s
    • decreased number of sensory cells and nerve fibers in the peripheral nervous system
    • neural changes possible in the vestibular nerve
59
Q

vestibular system (older adults)

A
  • vestibular system shows a decline in function with aging
    • common issues for over 50: dizziness and vertigo
    • 40% reduction in hair cells and 36% reduction in peripheral nerve fibers in adults over 70
    • deterioration in central vestibular integrative functions —> impaired balance
      • increased thresholds of excitation of vestibular nuclei
      • vestibular system becomes unreliable when visual and proprioceptive input conflicts
60
Q

somatosensory, visual, and vestibular systems develop concurrently to allow growth in ________, ________, and _______

A

balance, motor coordination, upright postural control

developmental concepts (5 decks)

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