Chapter 9 - General Principles of Sensory Systems in Biology

sensory systems divided into

special & somatosenses

special senses

vision, olfactory, taste (chemoreceptors) , hearing, sense of balance (equil)

4 types of somatosensory system

touch, proprioception, temp , pain (nociception)

general principles of sensory systems

1. differential sensitivity of sensory receptors

2. transduction

3. stereotypic code of stimulus intensity

- freq code

- population code

4. labeled line code of sensory quality

- stimulus quality = sensory modality

5. adaption

differential sensitivity of sensory receptors

sensory receptors = specialized structures that detect stimuli ; only some neurons but all relay info to neurons (ex: cochlear hair cells)

adequate stimuli = specificity of stimulus quality that sensory receptor responds to

which of following is adequate stimulus for sense of proprioception

a. noxious stimulus

b. mechanical deformation

c. thermal energy

d. odors

b. mechanical deformation

which sensory receptors are located deep in dermal layer & detect pressure

a. merkels disks

b. hair follicle receptor

c. free nerve endings

d. pacinian corpuscle

d. pacinian corpuscle (ruffinis endings is a smilar type of mechanorecptor )

2 types of thermorecptors

cold & warm & each have adequate stimulus

cold - 15-37 C

hot (warm) - 30 -50 C

increasing skin temp from 30-40 degrees C will cause a decrease in rate of AP firing in which thermoreceptor sub-type

cold thermoreceptor

transduction

process of changing physical energy into electrical signals in sensory receptor

receptor (or generator) pot - adequate stimulus causes change in memb pot

EX: depolarization (mechanoreceptor ) or hyperpolarization (photoreceptor)

sensory transduction is process of conversion of _________ energy to _________

a. physical, receptor pot

b. thermal, neurotransmitter release

c. physical, AP

d. receptive field, receptor pot

a. physical, receptor pot

the axons of Pacinian corpuscle sensory neurons synapse onto second order neurons which have their cell bodies located in DRG

true or false

False

are 1st order neurons

in response to sensory stimulus, receptor pot of Pacinian corpuscle is depolarizing due to

a. efflux of Na+ ions

b. efflux of K+ ions

c. influx of Na+ ions

d. influx of K+ ions

c. influx of Na+ ions

adequate stimulus will always lead to AP

true or false

false

stereotypic encoding of stimulus intensity

* intensity of stimulus in encoded by freq of APs ( # of a.p.s per time)

2 TYPES:

- freq code (temoral summation) = increase in a.p freq of an individual sensory receptor

- population code (spatial summation) = additional sensory receptors are activated & fire a.ps.

either mech will increase freq of A.P transmitted in sensory pathway

labeled line code of sensory modality - quality of stimulus is encoded by pathway of transmission

- stimulus modality (sensory modality) is type of physical energy that can be sensed (vision, touch, smell, etc)

- signals about diff sensory modalities travel in diff sensory pathways

- modality = quality = sensory communication channel

what statement below is FALSE about general principle termed "the labelled line code of sensory modality"?

a. example of labelled line code is that sensory modality processed by nose is specifically smell sensation

b. labelled line code refers to multiple senses (modalities or labels) being transmitted in one pathway (sensory communication channel)

c. origin & destination of signals transmitting one sensory modality (sensory communication channel) is diff from those representing another sensory modality

d. quality of pain travels in diff sensory pathway from quality of touch

b. labelled line code refers to multiple senses (modalities or labels) being transmitted in one pathway (sensory communication channel)

adaptation - sensory neurons adjust to prolonged or repetitive stimuli

dynamic receptors > mixed > static

prolonged mechanical deformation causes

depolarizing receptor pot followed by adaptation

removing capsule reduces

adapation due to reconfiguration of capsule

which is correct about pacinian corpuscle

a. adaption measured in pacinian corpuscle is not dependent on onion-like design of corpuscle encapsulating peripheral nerve endings

b. slowly adapting receptor showing dynamic response when stimulus duration is prolonged

c. fire AP in response to tactile vibration pressures of 300 or more Hz

d. responds only to ON stimulus

c. fire AP in response to tactile vibration pressures of 300 or more Hz