Sensory system

Question 1

what info is encoded by stimulus

Answer 1

modality - chemical, photic, noxious, thermal, mechanical

spatial info - location of touch/temperature in body, location of sound or light from external environment

quality - colour, pitch, sharpness of pain

Question 2

what is stimulus detected by

Answer 2

receptor (5 classes)
- either a separate specialised cell or a nerve ending

Question 3

labelled line concept

Answer 3

each sensory pathway only transmits 1 modality of sensation to a specific location
receptor does not dictate what the brain understands, rather the pathway that the sensory neuron is part of

Question 4

encoding intensity of stimulus

Answer 4

more intense, stronger receptor potentials, increase action potential firing rate

Question 5

rapidity of stimulus

Answer 5

depends on myelination of first order neuron
c, Aδ, Aβ, Aα

Question 6

adaptation of receptors

Answer 6

rapid: respond well to dynamic stimuli, respond poorly to steady stimuli
slow: opposite

Question 7

receptor fields and central convergence

Answer 7

receptor fields - smaller ones have more acuity
central convergence - small part of spinal cord surveys large area, due to a large receptive field

Question 8

density of peripheral receptors and lateral inhibition

Answer 8

increase density, increase acuity
stronger signal switches off smaller signals on the side, allows for more acuity

Question 9

skin receptors (detecting touch)

Answer 9

mechanoreceptors in skin, all Aβ
Lamellar corpuscle: deep, RA - pressure, vibrations
bulbous corpuscle: deep, SA - stretch receptors
tactile corpuscle: shallow, RA - changing light touch
tactile disks: shallow, SA - steady light touch

also free nerve endings for hot cold pain, Aδ or C fibres

Question 10

receptors measuring position

Answer 10

golgi tendon organs - mesure tension at tendon, SA, Aα/β

muscle spindles - measuring length and tension of muscles, RA/SA, Aα/β
joint capsule receptors - info on joint angles

Question 11

receptors measuring temp

Answer 11

TRP channels - temp sensitive excitatory channels
TRPM8 - cold receptors
TRPV1/3 - warm receptors

Question 12

2 distinct afferent pathways

Answer 12

dorsal column-medial lemniscal pathway: fast fibres, more spatial organisation
anterolateral pathway: slow fibres, less spatial organisation

Question 13

nociceptors

Answer 13

generally have higher thresholds
mechanical - stretch gated excitatory channels (pain from skeletal muscle/viscera)
temperature - TRPV1/3, TRPM8 channels
chemical - molecules released by cell injury, toxins
polymodal - multiple receptors