Lecture 13 - Sensory Systems: Touch, Taste, and Smell

Question 1

Sensation

Answer 1

Detection of a stimulus

Question 2

Perception

Answer 2

Processes of awareness and assigning meaning to it

Question 3

What do sensory (afferent) pathways do?

Answer 3

They transduce information about stimuli and transmit them to the CNS

Question 4

What is perception associated with?

Answer 4

Cortical activity

Question 5

How is stimulus intensity encoded?

Answer 5

This is encoded by the rate (frequency) of action potentials (AP)

Question 6

What do larger graded potentials generate?

Answer 6

They generate more action potentials in the same amount of time

Question 7

What does the absolute refractory period set?

Answer 7

It sets the maximum firing rate (APs/s)

Question 8

Phasic and rapidly adapting (RA) afferents

Answer 8

Can precisely encode stimulus onset (and sometimes offset)

Question 9

Tonic and slowly adapting (SA) afferents

Answer 9

Can encode stimulus duration

Question 10

Receptor field

Answer 10

The location where appropriate stimuli can generate neuronal responses - can infer location of stimulus

Question 11

What do afferents do?

Answer 11

They make targeted synapses inside the CNS so receptive fields are “inherited” by interneurons at later processing stages

Question 12

Sensory acuity proportion to receptive field and receptor density

Answer 12

Sensory acuity is inversely proportional to receptive field size and directly proportional to receptor density

Question 13

What do receptor cells do and name 2 types

Answer 13

Transduce stimuli using receptor proteins, which create graded potentials

Receptor cells can be:
1. Neurons
2. Special epithelial cells that make synapses on afferent neurons

Question 14

Divisions of somatosensation

Answer 14

1. Nociceptors (pain)
2. Thermoreceptors (temperature)
3. Mechanoreceptors

Question 15

Touch and proprioception sensing mechanism

Answer 15

Both rely on mechanoreceptors, which express mechanically-gated ion channels

Question 16

True or False: Mechanoreceptor cells can detect multiple different types of stimuli

Answer 16

True - they are sensitive to different types of stimuli because of their location and cell structure

Question 17

Name 5 types of stimuli mechanoreceptor cells can detect

Answer 17

1. Sustained pressure
2. Coarse pressure
3. Fine texture
4. Vibrations (ex. during gripping an object)
5. Skin stretch (ex. during movement)

Question 18

True or False: Sensory neurons involved in thermosensation and thermal nociception cannot respond to different stimulus

Answer 18

False - sensory neurons involved in thermosensation and thermal nociception respond to different stimulus ranges because they express different receptor proteins

Question 19

Where is the distinction of pain/temperature and tactile sensation maintained?

Answer 19

Afferent fibres

Question 20

Transduction

Answer 20

Conversion of a stimulus to a change in membrane potential

Question 21

How are distinctions in afferent fibres maintained?

Answer 21

Through spinal processing and ascending pathways

Question 22

True or False: Nociceptive pathways can be modulated?

Answer 22

True - tactile sensation and descending inhibition can both modulate the activity of nociceptive pathways
ie. somatosensory pathways can interact

Question 23

Name 2 chemosensory exteroreceptive sense and which perceptions do they produce?

Answer 23

1. Olfaction - smell
2. Gustation - taste

The integration of these 2 senses is called flavour!

Question 24

Olfaction

Answer 24

Detects odorants via olfactory sensory neurons located in the nasal epithelium

Question 25

Transduction mechanism and encoding principle of olfaction

Answer 25

Mech: olfactory receptor proteins are examples of metabotropic receptors which indirectly cause graded potentials by activating an enzyme that converts ATP to cAMP, causing Na+ channels to open –> AP occurs

Olfactory info enters the cerebrum directly, without passing through the brainstem or thalamus

Question 26

Transduction mechanism and encoding principle of gustation

Answer 26

Mech: the 5 basic qualities of taste (sour, sweet, bitter, umami, and salty) is transduced by taste receptor cells located in taste buds. Each of these taste qualities is transduced with distinct mechanisms and primary afferent neurons

Taste info enters the CNS at the hindbrain and is relayed to the cerebrum via the thalamus