Lecture 14 Sensory Physiology

Question 1

Sensory receptors

Answer 1

• specialized cells that detect a specific type of stimulus

- sensory receptors are transducers that convert stimuli into changes in membrane potential

Question 2

Transducer

Answer 2

a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa.

Question 3

Structural types of sensory receptors

Answer 3

free nerve endings
modified nerve ending
separate sensory receptor cells

Question 4

Sensitivity of sensory receptors

Answer 4

each sensory receptor has an adequate stimulus that it responds best to

Question 5

Functional classes of sensory receptors

Answer 5

responsive to particular sensory modalities

chemoreceptors, mechanoreceptors, photoreceptors, thermoreceptors, nociceptors

Question 6

Chemoreceptors

Answer 6

specific chemicals (taste, olfaction), pH, O2

Question 7

Mechanoreceptors

Answer 7

touch, pressure, stretch, vibration, sound, acceleration

Question 8

photoreceptors

Answer 8

light

Question 9

nociceptors

Answer 9

pain
noxious stimuli (chemical, mechanical, thermal)
*noxious is harmful, poisonous or unpleasant

Question 10

Sensory transduction

Answer 10

sensory receptors produce graded receptor potentials in response to sensory stimuli
sensory neurons convert receptor potentials into streams of action potentials.

Stimulus -> sensory receptor(receptor potential) -> sensory neuron(action potentials) -> CNS

Question 11

receptive field

Answer 11

area supplied by one sensory neuron

Question 12

two point discrimination test

Answer 12

smaller receptive fields result in more sensitive discrimination

Question 13

Afferent Division of PNS

Answer 13

Conveys APs from sensory neurons to the CNS

somatic sensory, visceral sensory, special senses

Question 14

Somatic Sensory

Answer 14

touch, temperature, pain, proprioception (general sesnes)

Question 15

Visceral Sensory

Answer 15

Mechanical and chemical stimuli from internal organs

Question 16

special senses

Answer 16

vision, hearing, equilibrium, olfaction, taste

Question 17

Sensory pathways in the CNS

Answer 17

ascending tracts in the spinal cord (somatic senses)
1st order neurons, second order neurons, third order neurons.
Cranial nerve sensory pathways

Question 18

First order sensory neurons

Answer 18

from receptors to spinal cord or brainstem

Question 19

second order neurons

Answer 19

from spinal cord or brainstem to thalamus

Question 20

third order neurons

Answer 20

from thalamus to cerebral cortex

Question 21

Sensory areas of the cerebral cortex

Answer 21

somatosensory cortex - parietal lobe
visual cortex - occipital lobe
auditory cortex - temporal lobe

Question 22

CNS integration of sensory information

Properties of stimuli

Answer 22

modality, location, intensity, duration

Question 23

Modality of stimulus indicated by

Answer 23

specificity of receptors and sensory neurons activated

specific neural pathways in the CNS -> specific areas in the brain (“labeled line coding”)

Question 24

Location of stimulus

Answer 24

specific neural pathways connect receptive fields to specific locations in the cortex
sound localization uses differences in timing form R and L ears
lateral inhibition- increases contrast between adjacent receptive fields

Question 25

Intensity of stimulus encoded by

Answer 25

number of receptors activated

frequency of action potentials in sensory neurons

Question 26

Duration of stimulus

Answer 26

coded by duration of APs

Question 27

Receptor Adaptation

Answer 27

decreases in response to a persistent stimulus over time

Tonic receptors and Phasic receptors

Question 28

Tonic Receptors

Answer 28

non-adapting or slowly adapting
fairly constant response to sustained stimulus
e.g. muscle spindle stretch receptors

Question 29

Phasic receptors

Answer 29

rapidly adapting
respond to initial change in stimulus, then decrease response
e.g. olfactory receptors