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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
Why do G-protein coupled receptors take longer to open channels
Specific ligand binds to site stimulating complex chain of events to cause opening of ion channel (events take much more time)
26
What does the quality of the stimuus depend on
Type of receptor
27
What determines the magnitude and intensity of a stimulus
Action potential frequency and the number of neurons activated
28
What is the duration of a stimulus determined by
Duration of the action potential firing
29
What codes for stimulus intensity
Number of neurons activated
30
How can action potential frequency be increased
By increasing the stimulus intensity
31
What is a slowly adapting response
High frequency at onset of stimulus but frequency decreases towards the end of the stimulus
32
What action potential firing pattern does a rapidly adapting response have
Very high frequency at onset and then goes silent very quickly for remainder of stimulation
33
Which receptor fields have greater cortical representation
Smaller fields on that of the facial areas, fingers and toes etc
34
What is a sensory hormunculus
Body map on the brain illustrating the primary somatosensory cortex
35
How do receptor endings lead to cortical representation
Receptor endings Peripheral nerves Ascending sensory pathways Cortical representation
36
What cells give rise to an axon within the peripheral nerve
Sensory neurons (afferents) Motor neurons (efferents)
37
What are large bundles of axons
Fascicle (fasciculi)
38
What are fasciculi surrounded by
Epineurium - structural integrity and mechanical protection
39
what does the Perineurium surround
individual fasicles
40
What is the purpose of the vascular element of the peripheral nerves
Supply oxygen and glucose Remove metabollic by products
41
What are the different types of axons in a Peripheral nerve
Myelinated -A alpha -A beta -A delta Unmyelinated -C fibres
42
How quickly can A alpha axons conduct action potentials
80-120 m/sec
43
What are A apha axons involved in
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
What is the purpose of A beta axons
Not as quick as A beta Involved in touch sensations, linked to mechanoreceptors
45
What sensory receptors link to A delta axons
Pain and temperature receptors
46
Were you to fall and graze your knee, which axon would the information travel along to indicate pain
A delta axon
47
When are C fibres used
Temp, pain, itch
48
What speed do action potentials travel across C fibres
0.5-2 m/sec
49
What 3 principle regions of grey matter are there
Dorsal horn Intermediate horn Ventral horn
50
How does a pin prick cause a pain response
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
What do the medial dorsal root projection of the dorsal root ganglia contain
Nothing but the centrally projecting axons of the sensory neurons
52
How many pairs of dorsal root gangliaare there
31
53
Where do cell bodies of motor neurons originate from in the spinal chord
Ventral horn of grey matter
54
How do motor efferents exit the spinal chord
Via ventral roots
55
What is a myotome map
Main levels of spinal chord associated with each movement of the body
56
What is a dermatome
Sensory distribution of specific areas of skin supplied by individual spinal nerves across the body
57
What 3 interconnected neurons make up sensory pathways
Primary Secondary Tertiary
58
What are each neurons in the sensory pathway found
Primary - periphery Secondary - spinal chord/brainstem Tertiary - Thalamus
59
Which neuron crosses the midline boundary
Seconday neuron
60
Why is the body imagine on a sensory homunculus distorted
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
What pathway relays somatic mechanosensation
Dorsal Column-Medial Lemniscal Pathway
62
What pathway do the 3 interconnected neurons take in the Dorsal Column-Medial Lemniscal Pathway (somatic mechanosensation)
Receptor - brainstem (medulla) Medulla - thalamus Thalamus - somatosensory cortex
63
What is the pathway for somatic mechanosensation of the FACE
Posterior (dorsal) trigeminothalamic pathway
64
What is the perception of pain pathway called
Spinothalamic pathway
65
What is unique about the spinothalamic pathway
Sensory neuron only projects into dorsal horn of spinal chord
66
What pathway does the secondary neuron in the spinothalamic pathway do
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
Where do the neurons of the spinothalamic pathway start and terminate
Pain/temp receptor - dorsal horn Dorsal horn (across body) - Thalamus Thalamus - sensory atopic (somatosensory) region of cortex
68
What is the somatic nociception pathway called
Anterior (Ventral) Trigeminothalamic Pathway
69
Where do the central terminals in the Anterior (Ventral) Trigeminothalamic Pathway end
Spinal nucleus
70
Where do the neurons meet in the anterior trigeminothalamic pathway
Trigeminal ganglion - spinal nucleus Spinal nucleus - thalamus thalamus - somatosensory cortex
71
Who discovered the cortical regions
Wilder G Penfield
72
What is sensation
The process of sensing our environment (touch, taste, sight, smell) by activation of sensory receptors and associated sensory pathways
73
What is perception
The interpretation of sensory input (interpretation of sensation)
74
What is stereognosis
The mental perception of objects referenced by touch
75
How does stereognosis work
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
What parts of the brains does stereognosis use
Sensory cortex (bilateral); hippocampus; basal ganglia; motor cortex
77
What is proprioception (kinesthesia)
The sense of self-movement and body position
78
What mechanosensory inputs are used in proprioception
* 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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