Sensory Receptors 1

Question 1

what are 5 general classes of sensory receptors?

Answer 1

1. mechanoreceptors
2. thermal receptors
3. pain receptors
4. chemoreceptors
5. photoreceptors

Question 2

what are cutaneous sensory receptors?

Answer 2

+ located at ends of sensory nerve dendrites

+ function to transduce sensory info signals the brain can read

+ have specialised structures to detect sensory info from surroundings

Question 3

what sensation is linked to Aδ fibres?

Answer 3

sharp pricking pain

Question 4

what sensation is linked to C fibres?

Answer 4

hot cold burning ache

Question 5

what are features of free nerve endings?

Answer 5

+ slow adapting

+ high activation

Question 6

what are the different types of receptors?

Answer 6

\+ pacini's corpuscles
\+ meissner's corpuscles
\+ merkel disks
\+ ruffini corpuscles
\+ skin hair cell receptors

Question 7

what are features of pacini’s corpuscles?

Answer 7

\+ largest mechanoreceptor
\+ 2mm long
\+ onion-like encapsulation of nerve endings
\+ found in deep layers of dermis
\+ detects high frequency vibration (40-500Hz)
\+ Aβ  fibres
\+ glabrous and hairy skin types
\+ low activation threshold

Question 8

what are features of meissner’s corpuscles?

Answer 8

+ encapsulated nerves but smaller than pacini’s
+ stacks of discs interspersed with nerve branch endings
found between dermal papillae
+ detects touch, flutter and low frequency vibration (2-40Hz)
+ Aβ fibres
+ glabrous skin types
+ low activation threshold

Question 9

what are features of merkel disks?

Answer 9

+ non-encapsulated nerve endings
+ detect static touch and light pressure
+ Aβ fibres
+ all skin types
+ consists of specialised epithelial cell and nerve fibre
+ slowly adapting
+ found just under skin surface: good discrimination
+ multiple branches found in ‘Iggo Dome”
+ work with meissner’s corpuscles to help determine texture

Question 10

what are features of ruffini corpuscles?

Answer 10

+ responds to skin stretch
+ located in deeper layers of skin, tendons and ligaments
+ encapsulated nerve endings
+ in all skin types esp. fingers, hands and soles
+ nerve endings weave between collagen fibres which activate nerve when pulled longitudinally

Question 11

what are features of skin hair cell receptors?

Answer 11

+ each type has a mechanosensitive receptor wrapped around its follicle
+ detect muscular movements of hair (erector muscle) and external displacements of hair

Question 12

how is the brain informed about stimuli?

Answer 12

+ when a sensory nerve ending or receptor is stimulated enough it causes APs to travel to CNS

+ APs from pain receptors in the leg are indistinguishable in character from stretch related impulses from the arm

Question 13

how does the CNS distinguish APs via leg pain receptors, from stretch related arm impulses?

Answer 13

+ each sensory nerve is recognised by CNS as particular modality
+ CNS reads final destination of nerve fibre
+ modal info delivered to CNS is topographical fashion

Question 14

how does phantom limb sensation arise?

Answer 14

when sensory neurons from absent limbs are spontaneously, and can be mimicked by electrical stimulation

Question 15

how does CNS determine signal strength?

Answer 15

+ APs have fixed potential and amplitude
+ intensity of signal determined by frequency of impulse
+ the higher the frequency the more intense the signal

Question 16

what is generator potential (GP)?

Answer 16

+ a graded depolarisation of sensory neuron
+ proportional to strength of stimulus
+ GP initiates impulses in sensory nerves

Question 17

what is the link between GP and signal strength?

Answer 17

the bigger the GP (depolarisation), the faster the frequency of sensory nerve impulses (so bigger signal intensity/strength)

Question 18

what effect does distance from site of origin have on GPs?

Answer 18

amplitude decreases

Question 19

what effect does distance from site of origin have on APs?

Answer 19

no effect as they are self propagating

Question 20

what happens when there is a receptor cell that synapses onto a sensory neuron?

Answer 20

+ the sensory cells produce a receptor potenial when stimulated instead of GP

+ this causes receptor cells to release NTs into synapse and normal neurotransmission takes place

Question 21

how are GPs and post-synaptic potentials (PSPs) the same?

Answer 21

+ both trigger action potentials

+ local in nature

Question 22

how are GPs different to PSPs?

Answer 22

+ GPs can last as long as the receptor is stimulated (provided no adaption)

+ amplitude is determined directly by intensity of sensory stimulus (not NT concentration)