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Human Systems > Senses and perception > Flashcards

Senses and perception Flashcards

1
Q

How do we convert a stimulus into an electrical signal (action potential)

A

Modality-specific sensory receptors

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2
Q

Sensory nerve cell structure

A

Receptor ending
Axon
Central terminal
Cell body

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3
Q

What are sensory mechanisms

A

Types of receptors
Transduction of stimulus
Coding of stimulus properties

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4
Q

What receptor and sensation does a mechanical stimulus use

A

Mechanoreceptor
touch sensation

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5
Q

What stimulus and receptor produces a pain sensation

A

Noxios stimulus
Nociceptor

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6
Q

What stimulus and sensation are used with thermoreceptor

A

Thermal stimulus
Temperature sensation

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7
Q

What are ‘special senses’

A

Chemical - Chemoreceptor - smell
Light - Photoreceptor - sight

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8
Q

Free nerve endings are characteristic of what receptor

A

Nociceptors (pain)

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9
Q

What types of mechanoreceptor endings are there

A

Meissner’s corpuscle
Merkel disk
Hair follicle receptor
Pacinian corpuscle
Ruffini ending

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10
Q

What is a neuron’s receptive feild

A

The distribution of the sensory neuron’s peripheral nerve branches receptor endings

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11
Q

How do receptive fields ensure complete coverage of the body

A

Receptive fields will overlap

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12
Q

Where are larger receptive fields found

A

On the trunk (middle of body)

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13
Q

Where are the smallest receptor fields found

A

Lips
Thumb
Fingers
Toes

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14
Q

What is two point discrimination

A

Ability to discern two separate mechanical stimuli from each other

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15
Q

Why is two point discrimination needed

A

To measure spatial resolution
Offers an indication of receptive field size

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16
Q

When are two stimuli only perceived as one

A

When both stimuli fall within one receptor field and only activate one sensory neuron

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17
Q

What is the temporal sequence of stimulus transduction

A

Stimulus
Change in receptor membrane permeability (provided the right receptor is activated)
Influx of cations
Depolarisation: Receptor potential
Action potential

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18
Q

What are the receptor subtypes

A

Ionotropic
G-protein coupled

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19
Q

What receptors possess fast kinetics

A

Ionotropic

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20
Q

Which receptors are used for slow kinetics

A

G-protein coupled

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21
Q

What modalities do ionotropic receptors fall under

A

Mechanoreceptors
Chemoreceptors

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22
Q

What modality is G-protein coupled receptors

A

Chemoreceptors

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23
Q

How do ionotropic mechanoreceptors open

A

Ion chanel pore initially closed preventing movement of Na+ in and K+ out
When mechanical stimulus is applied to the cell membrane it causes a deformation of cell membrane which pulls of the underlying fibrils and as a consequence the pore will then open allowing movement of ions allowing depolarisation to occur

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24
Q

How do Ionotropic chemoreceptors act in stimulus transduction to cause an action potential

A

Ligand binding receptor sites present on extra cellular membrane which is activated by the specific ligands binding causing change to the structure and allowing pore to open and ions to flow through

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25
Q

Why do G-protein coupled receptors take longer to open channels

A

Specific ligand binds to site stimulating complex chain of events to cause opening of ion channel (events take much more time)

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26
Q

What does the quality of the stimuus depend on

A

Type of receptor

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27
Q

What determines the magnitude and intensity of a stimulus

A

Action potential frequency and the number of neurons activated

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28
Q

What is the duration of a stimulus determined by

A

Duration of the action potential firing

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29
Q

What codes for stimulus intensity

A

Number of neurons activated

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30
Q

How can action potential frequency be increased

A

By increasing the stimulus intensity

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31
Q

What is a slowly adapting response

A

High frequency at onset of stimulus but frequency decreases towards the end of the stimulus

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32
Q

What action potential firing pattern does a rapidly adapting response have

A

Very high frequency at onset and then goes silent very quickly for remainder of stimulation

33
Q

Which receptor fields have greater cortical representation

A

Smaller fields on that of the facial areas, fingers and toes etc

34
Q

What is a sensory hormunculus

A

Body map on the brain illustrating the primary somatosensory cortex

35
Q

How do receptor endings lead to cortical representation

A

Receptor endings
Peripheral nerves
Ascending sensory pathways
Cortical representation

36
Q

What cells give rise to an axon within the peripheral nerve

A

Sensory neurons (afferents)
Motor neurons (efferents)

37
Q

What are large bundles of axons

A

Fascicle (fasciculi)

38
Q

What are fasciculi surrounded by

A

Epineurium - structural integrity and mechanical protection

39
Q

what does the Perineurium surround

A

individual fasicles

40
Q

What is the purpose of the vascular element of the peripheral nerves

A

Supply oxygen and glucose
Remove metabollic by products

41
Q

What are the different types of axons in a Peripheral nerve

A

Myelinated
-A alpha
-A beta
-A delta

Unmyelinated
-C fibres

42
Q

How quickly can A alpha axons conduct action potentials

A

80-120 m/sec

43
Q

What are A apha axons involved in

A

Relay info from spinal chord out to required muscle groups, as they are derived from motor neurons
Proprioception - send sensory info from muscle spindles

44
Q

What is the purpose of A beta axons

A

Not as quick as A beta
Involved in touch sensations, linked to mechanoreceptors

45
Q

What sensory receptors link to A delta axons

A

Pain and temperature receptors

46
Q

Were you to fall and graze your knee, which axon would the information travel along to indicate pain

A

A delta axon

47
Q

When are C fibres used

A

Temp, pain, itch

48
Q

What speed do action potentials travel across C fibres

A

0.5-2 m/sec

49
Q

What 3 principle regions of grey matter are there

A

Dorsal horn
Intermediate horn
Ventral horn

50
Q

How does a pin prick cause a pain response

A

Pin prick stimulus
Activate free nerve endings A delta and C fibres
Transduction of the noxious stimulus to cause generation of electrical signal which is conducted as an action potential through the peripheral nerve and into the spinal chord
Dorsal roots lead straight into the brain from spinal chord

51
Q

What do the medial dorsal root projection of the dorsal root ganglia contain

A

Nothing but the centrally projecting axons of the sensory neurons

52
Q

How many pairs of dorsal root gangliaare there

A

31

53
Q

Where do cell bodies of motor neurons originate from in the spinal chord

A

Ventral horn of grey matter

54
Q

How do motor efferents exit the spinal chord

A

Via ventral roots

55
Q

What is a myotome map

A

Main levels of spinal chord associated with each movement of the body

56
Q

What is a dermatome

A

Sensory distribution of specific areas of skin supplied by individual spinal nerves across the body

57
Q

What 3 interconnected neurons make up sensory pathways

A

Primary
Secondary
Tertiary

58
Q

What are each neurons in the sensory pathway found

A

Primary - periphery
Secondary - spinal chord/brainstem
Tertiary - Thalamus

59
Q

Which neuron crosses the midline boundary

A

Seconday neuron

60
Q

Why is the body imagine on a sensory homunculus distorted

A

Every sensory neuron and its receptive field is represented in the cortex and body regions with a high sensory innervation (more receptor endings) have greater cortical representation

61
Q

What pathway relays somatic mechanosensation

A

Dorsal Column-Medial Lemniscal Pathway

62
Q

What pathway do the 3 interconnected neurons take in the Dorsal Column-Medial Lemniscal Pathway (somatic mechanosensation)

A

Receptor - brainstem (medulla)
Medulla - thalamus
Thalamus - somatosensory cortex

63
Q

What is the pathway for somatic mechanosensation of the FACE

A

Posterior (dorsal) trigeminothalamic pathway

64
Q

What is the perception of pain pathway called

A

Spinothalamic pathway

65
Q

What is unique about the spinothalamic pathway

A

Sensory neuron only projects into dorsal horn of spinal chord

66
Q

What pathway does the secondary neuron in the spinothalamic pathway do

A

Second order sensory neuron meets the primary neuron in the dorsal horn and crosses to the opposite side of the same segmental level as the primary afferent fibre entered and then travels the whole length of the spinalchord to the thalamus

67
Q

Where do the neurons of the spinothalamic pathway start and terminate

A

Pain/temp receptor - dorsal horn
Dorsal horn (across body) - Thalamus
Thalamus - sensory atopic (somatosensory) region of cortex

68
Q

What is the somatic nociception pathway called

A

Anterior (Ventral) Trigeminothalamic Pathway

69
Q

Where do the central terminals in the Anterior (Ventral) Trigeminothalamic Pathway end

A

Spinal nucleus

70
Q

Where do the neurons meet in the anterior trigeminothalamic pathway

A

Trigeminal ganglion - spinal nucleus
Spinal nucleus - thalamus
thalamus - somatosensory cortex

71
Q

Who discovered the cortical regions

A

Wilder G Penfield

72
Q

What is sensation

A

The process of sensing our environment
(touch, taste, sight, smell) by activation of
sensory receptors and associated
sensory pathways

73
Q

What is perception

A

The interpretation of sensory input
(interpretation of sensation)

74
Q

What is stereognosis

A

The mental perception of objects
referenced by touch

75
Q

How does stereognosis work

A

Involves high degree of cortical processing:
* Generate a 3-D ‘mental image’
* Ability to retrieve previous experiences
* Integration of information on several
aspects of touch e.g. texture, weight, size

76
Q

What parts of the brains does stereognosis use

A

Sensory cortex (bilateral); hippocampus;
basal ganglia; motor cortex

77
Q

What is proprioception (kinesthesia)

A

The sense of self-movement and
body position

78
Q

What mechanosensory inputs are used in proprioception

A
  • Balance organs in the inner ear
    Utricle, saccule; semi-circular canals
  • Muscle receptors/Joint receptors
    Muscle length, tension; Joint position
  • Mechanoreceptors
    Skin stretching; tension from clothes
  • Peridontal receptors

Human Systems (34 decks)

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