BMS11004 WEEK 10 - THURSDAY

Question 1

name 2 major input components in somatic sensory system

Answer 1

mechanical stimuli (light touch, vibration, pressure, cutaneous tension)
painful stimuli and temperature

Question 2

what does the somatic sensory system allow us to do

Answer 2

identify shape, object textures
monitor internal/external forces
detect harmful situation
sense of self within environment and planning actions

Question 3

name 3 sensory receptors with encapsulated nerve endings

Answer 3

Meissner (tactile) corpuscles
Pacinian (lamellated) corpuscles
Ruffini corpuscles

Question 4

what are Meissner (tactile) corpuscles - encapsulated nerve endings of SNS
including location, modality, Hz, adaptations

Answer 4

in dermal papillae of skin, light touch modality (texture, movement), sensitive to 30-50H, rapidly adapting

Question 5

what are Pacinian (lamellated) corpuscles - encapsulated nerve endings of SNS
including location, modality, Hz, adaptations

Answer 5

in dermis, joint capsules, viscera
deep pressure modality (stretch, tickle, vibration)
sensitive to 250-350Hz
rapidly adapting

Question 6

what are Ruffini corpuscles - encapsulated nerve endings in SNS
including location, modality, Hz, adaptations

Answer 6

dermis, joint capsules, subcutaneous tissue
heavy touch, pressure, skin stretch, joint movements (proprioceptor
slowly adapting

Question 7

name 2 unencapsulated nerve endings in SNS

Answer 7

Merkel (tactile) discs
Free-nerve endings

Question 8

what are merkel (tactile) discs in unencapsulated nerve endings of SNS
including location, modality, Hz, adaptations

Answer 8

superficial skin (epidermis)
light touch, texture, edges, shapes
slowly adapting

Question 9

what are free-nerve endings - uncapsulated nerve endings of SNS
including location, modality, Hz, adaptations

Answer 9

widespread in epithelia, connective tissue
heat and cold

Question 10

what are cellular receptors made up of, with example

Answer 10

made up of multiple cells (merkel’s disc, free nerve endings, meissners corpuscle)

Question 11

what are molecular receptors made up of with an example

Answer 11

made up of multiple components (stretch receptors)

Question 12

name 2 types of mechanoreceptors (based on response)

Answer 12

rapidly adapting/phasic receptors
slowly adapting/tonic receptors

Question 13

describe rapidly adapting (phasic) mechanoreceptors

Answer 13

when stimulated, neuron fires rapidly over time then stop= transient response, giving into about change to stimulus

Question 14

give an example of a rapidly adapting (phasic) mechanoreceptor

Answer 14

pacinian corpuscle

Question 15

describe slowly adapting (tonic) mechanoreceptors

Answer 15

continue to respond as long as stimuli present
giving into on persistence of stimulus

Question 16

give example of slowly adapting (tonic) mechanoreceptor

Answer 16

ruffini corpuscle

Question 17

how are primary afferent axons classified

Answer 17

by conduction velocity, reflecting diameter of axon
faster = wider diameter

Question 18

primary afferent axon subtypes - what are axons coming from skin classified as

Answer 18

designated by letters (A, B, C) from fastest to smallest
A group further broken down to alpha, beta

Question 19

primary afferent axon subtypes - what are axons coming from muscles classified as

Answer 19

designated by Roman numeral (I, II, III from largest - smallest)
I group broken into Ia…

Question 20

why are pain fibres slower than proprioceptors

Answer 20

need info from proprioceptors (regarding balance) quicker so we dont collapse but pain can be slower

Question 21

name 2 main routes (tracts) that somatosensory projection get to brain via

Answer 21

medial lemniscal tracts
spinothalamic tracts

Question 22

what does medial lemniscal tract carry to brain (somatosensory projection)

Answer 22

carry mechanoreceptive and proprioceptive signals to thalamus

Question 23

what does spinothalamic tract carry to brain (somatosensory projection)

Answer 23

carry pain and temperature signals to thalamus

Question 24

what 3 type of neurons does somatosensory projections (medial leminiscal and spinothalamic tracts) travel by

Answer 24

first/second/third order neurons

Question 25

what does first-order neurons in medial leminscal and spinothalamic tracts do

Answer 25

detect stimulus, transmits to spinal cord

Question 26

what does second-order neurons in medial leminscal and spinothalamic tracts do

Answer 26

relay signal to thalamus "gateway" to cortex

Question 27

what does third-order neurons in medial leminscal and spinothalamic tracts do

Answer 27

carry signal from thalamus, to cortex

Question 28

explain topological arrangement of axons (regarding 1st order) for upper body

Answer 28

1st order axon from upper body follows lateral pathway, synapses onto 2nd order in cuneate nucleus

Question 29

explain topological arrangement of axons (regarding 1st order) for lower body

Answer 29

1st order axons from lower body follow medial pathway, synapses onto gracile nucleus neurons

Question 30

together, what is topological organisation of 1st order axons from upper/lower body known as

Answer 30

dorsal column nuclei

Question 31

describe topological arrangement of 2nd order axons in medial-leminiscal system

Answer 31

crosses midline and ascend in medial lemniscus reverses topology so lower body axons are more lateral on reaching thalamus

Question 32

describe topological arrangement of 3rd order axons in medial lemniscus system

Answer 32

reverse topology - lower body axon synapses onto medial cortical neurons, but upper body axons map to lateral cortex

Question 33

what does topological mean

Answer 33

mapping body and physiological distributions in cortex

Question 34

what are dermatomes

Answer 34

specific patch of skin innervated by sensory ganglion, with dermis from specific somite in embryo

Question 35

what does somatosensory homonculus mean?

Answer 35

map along the cerebral cortex of where each part of the body is processed, representations not proportional

Question 36

what does receptive fields mean, and how is it measured

Answer 36

size depends on where it is located, measured by assessing ability to discriminate 2 sharp points set apart at different distances

Question 37

when measuring receptive field, what does it mean when subject can feel 2 pin point

Answer 37

distance between points is larger than receptive field

Question 38

what does large receptive field mean (in terms of discrimination)

Answer 38

low discrimination= arms and legs

Question 39

what does small receptive field mean, in terms of discrimination

Answer 39

high discrimination cortex more dedicated to regions for smaller receptive field

Question 40

whereabouts in brain is somatotopic map preserved

Answer 40

coronal plane, postcentral gyrus with different sensory modalities being localised along our sagittal axis

Question 41

what does loss of stimulation of specific body area lead to in the cortex

Answer 41

disappearance of area devoted to area and increase in neighbouring patch