lecture 13- sensory I

Question 1

somatic senses

Answer 1

touch, temperature, pain and itch

Question 2

special senses

Answer 2

sight, smell, taste, hearing

Question 3

somatic senses information goes to the

Answer 3

primary sensory cortex

Question 4

stimulus is determined by a —-

Answer 4

sensory receptor

Question 5

sensory receptor detects stimulus and sends signal via

Answer 5

neurons to/within the CNS

Question 6

after sensory signal reaches the CNS, 2 things can happen:

Answer 6

1. the signal reaches cerebral cortex and enters our consciousness
2. signal does not reach the cerebral cortex
   - stimulus is processed and a response is elicited without our conscious awareness

Question 7

give examples of a signal that does not reach the cerebral cortex (or our conscious awareness)

Answer 7

rate of gastric motility in small intestine

heart rate minute to minute

blood pressure…

Question 8

at each synapse, sensory info is modulated and shaped by —- pathways

Answer 8

3 pathways

-pathways contain a primary, secondary and tertiary neuron

Question 9

convergence and divergence would be an example of

Answer 9

modulation at each synapse

Question 10

stimuli: subconscious processing example

Answer 10

muscle length, tension
proprioception
blood pressure
blood glucose
internal body temp
pH of cerebrospinal fluid
lung inflation

Question 11

perceived stimuli examples

Answer 11

special senses= vision, hearing, taste, smell, equilibrium

somatic senses= touch, temp, pain, itch, proprioception

Question 12

incoming sensory afferent info goes to the

Answer 12

primary sensory cortex in the parietal lobe!!!
that is where it is perceived :)

Question 13

sensory receptors are —-

Answer 13

transducers

Question 14

sensory receptors convert

Answer 14

a stimulus into an intracellular response

they may or may not be neurons

Question 15

4 main types of sensory receptors

Answer 15

chemoreceptors
-pH, Na+, oxygen, glucose

mechanoreceptors
-pressure, vibration, gravity, acceleration, sound waves

thermoreceptors
-hot/cold

photoreceptors
- light

Question 16

receptor potential

Answer 16

a stimulus changes the membrane potential of the receptor cell
(a graded potential occuring in a sensory cell)

• can be depolarization OR hyperpolarization

Question 16

adequate stimulus

Answer 16

favourite stimuli!!!

the form of energy that the sensory receptor is most responsive to
–> the receptor may respond less strongly to other types of stimuli

Question 17

when light photons fall on to the retina in the eye, rods and cones…

Answer 17

hyperpolarize

Question 18

when skin is touched, touch receptors…

Answer 18

depolarize

Question 19

Threshold stimulus
(and what are the 2 possible responses)

Answer 19

the minimum stimulus needed to generate enough of a receptor potential to produce an intracellular response

–> AP firing (if the receptor is a neuron)
OR
–> NT release (non-neuron receptors)

Question 20

where does transduction occur? (in sensory receptors that are neurons)

Answer 20

transduction occurs at the receptor end of primary sensory neurons

Question 21

sensory receptors that are not neurons

Answer 21

receptor cell is separate from the primary sensory neuron

Question 22

most special senses receptors are cells that …

Answer 22

release NT onto sensory neurons, initiating an AP

Question 23

what is the exception for special senses cells that release NT onto sensory neurons and initiate an AP

Answer 23

olfaction

Question 24

2 groups of threshold stimulus

Answer 24

1. sensory neurons - fire APs, transmitted to CNS 2. specialized sensory receptors (not a neuron) - generate graded potentials that lead to NT release - NT released onto partner neuron

Question 25

example of a slow sensory receptor

Answer 25

pain and temp receptors (unmyelinated) synapses in the gray matter of the spinal cord in the dorsal (afferent) region

Question 26

example of a fast sensory receptor

Answer 26

touch receptor myelinated neuron, not specialized - stimulus (pressure) leads to AP in sensory neuron - AP travels up spinal cord, primary neuron --> secondary neuron

Question 27

how are stimulus properties distinguished? 4 things

Answer 27

1. Modality: what kind is it? -labeled line coding 2. Location: where is it? - receptive fields, input convergence, lateral inhibition, anatomical map 3. Intensity: how strong is it? -population and frequency coding 4. Duration: how long does it last

Question 28

each stimulus moduality has its own unique...

Answer 28

pathway (sight, hearing)

Question 28

cerebral cortex: where is more cortical tissue found?

Answer 28

cortical tissue is found in more sensitive areas

Question 28

Synesthesia

Answer 28

"crossed wires" - ex. hearing colours

Question 28

Thalamus=

Answer 28

the central hub through which sensory info has to pass

Question 28

perception threshold

Answer 28

the minimum stimulus needed to activate secondary and tertiary neurons in the pathways (not just the primary neuron)

Question 28

small receptive fields are found in more ---- areas

Answer 28

sensitive --> two stimuli activate separate pathways to the brain --> the two points are perceived as distinct stimuli and there is two point discrimination

Question 29

Convergence creates --- receptive fields

Answer 29

larger --> two stimuli in the same receptive field means no two-point discrimination. it is perceived as a single point.

Question 29

lateral inhibition

Answer 29

inhibits a neuron laterally (on either side) one pathways is maximally activated while the other is "turned down"

Question 29

cerebral cortex receptive field properties:

Answer 29

specific areas in the cerebral cortex correspond to specific receptive fields ex. somatosensory cortex has ascending tracts from a body part that has a specific corresponding region of the cerebral cortex (labeled line coding)

Question 30

larger areas on the humunculus are more likely to have

Answer 30

two point discrimination

Question 31

stimulus intensity is coded by 2 things:

Answer 31

1. number of receptors activated (population coding) 2. frequency of action potentials (frequency coding)

Question 32

coding for stimulus duration

Answer 32

stimulus duration is coded by duration of action potential trains --> some receptors can adapt or cease to respond

Question 33

Tonic receptors vs phasic receptors

Answer 33

tonic receptors adapt slowly (fire for the duration of stimulus) phasic receptors adapt quicky (fire only when a stimulus changes)

Question 34

sensory neurons use AP ---- to code stimulus ----

Answer 34

frequency to code stimulus intensity

Question 34

cutaneous receptors (3)

Answer 34

1. touch (mechanoreceptors) - pressure, vibration, stretch, flutter... 2. pain and itch (nociceptors) 3. temperate (thermoreceptors)

Question 34

sensory neurons use ---- to code stimulus ---

Answer 34

burst duration to code stimulus duration

Question 34

pacinian corpuscles (a cutaneous receptor)

Answer 34

stimulus= vibration location= deep layers of skin stucture= encapsulated in connective tissue rapid adaptation