2.04 Sensation Flashcards
Exteroceptive sensation is from?
Surface of body
cutaneous sense
Low threshold mechanoreceptors mediate which senses?
touch
vibration
pressure
Low threshold thermoreceptors mediate which senses?
cold cool indifferent warm hot
high threshold units respond to which senses?
noxious stimuli
high threshold mechanoreceptors respond to
high intensity mechanical stimuli
thermal nociceptors respond to
extrems of heat > 45 degrees or
cold
chemical nociceptors respond to
substances eg. in inflammation prostaglandins bradykinin serotonin histamine K+ H+ ATP others
polymodal nociceptors respond to
2 or more of noxious stimuli
Which sensory receptors are slowly adapting
stretch receptors
they are needed to provide continuous information about position, degree of stretch, or force
Which sensory receptors are rapidly adapting
some muscle spindle afferents, hair follicle afferents
detect changes in stimulus strength; non-threatening
which sensory receptors are very rapidly adapting?
pacinian corpuscle
rapid vibration is picked up and then quickly adapted to.
What is adaptation?
feature of primary sensory neurones that determines if they change firing rate in response to stimulus of changing intensity, or stay the same.
which sensory receptor is the fastest, and most myelinated?
Group I axons - a-alpha
proprioceptors of skeletal muscle
which sensory receptor is the slowest, least myelinated?
Group IV - c
temperature
pain
itch
Which is faster, mechanoreceptors or pain/temperature receptors?
mechanoreceptors are more myelinated, thus faster. Thy are group II/a-beta axons from skin
Where is two point discriminated greatest on the body?
Fingers
Where is two point discrimination lowest on the body?
Calf
What is the distribution of free nerve endings?
What do they sense?
ubiquitous
pain, heat, cold
Where is the highest distribution of meissner’s corpuscles?
What do they sense?
where two point discrimination highest (hands, face) but not in hairy skin.
Touch
What is the distribution of merkel’s discs. What do they do?
Distributed as for meissner’s, in areas of high 2pt discrimination. but also present in hairy skin. Grouped in Iggo domes.
Senses touch.
What do krause end bulbs sense?
Where are they located?
They sense touch.
Located between dry skin and mucous membrane - at the border
What are ruffini endings? Where are they located?
Pressure sensory organs.
Located in dermis and joint capsules.
What are pacinian corpuscles? Where are they located?
Pressure sensory organs
Dermis and fascia
What channel gives the Iggo dome, and multiple merkel cells the ability to sense mechanical touch?
The mechanosensitive cation channel Piezo2.
Which receptor types are conducted by A-beta fibres?
Every receptor except hair-down, and C mechanoreceptors
Which receptor types are conducted by a-delta fibres?
hair(D)-down.
It is triggered by light stroking
Which receptor types are conducted by c-fibres?
C-mechanoreceptor
It is triggered by stroking, social and erotic touch.
Which receptive field is bigger-
pacinian corpuscles
meissners corpuscles?
Pacinian corpuscles- that sense pressure have larger receptive fields that are less specific compared to meissner’s corpuscles that sense touch.
How many laminae of Rexed are there? What types of fibres synapse where?
10 laminae
Laminae 1-2: nociceptors a-delta and C
Laminae 3-6: LTMs)touch) a-beta
Laminae 7-9: proprioceptors a-alpha
