Lecture 13

Question 1

All senses require 3 common steps but what are they?

Answer 1

They require a physical stimulus
They all must transform the stimulus into nerve inpulses
- this occurs in the PNS
They all evoke a response to the signal in the form of perception or conscious experience of sensation
- this occurs in the CNS

Question 2

Where does sensation begin?

Answer 2

With sensory receptors in the periphery

Question 3

What do sensory receptors enable?

Answer 3

Sensory transduction, the conversion of energy from the environment into electrochemical signals
- sound/touch/light to electrical signals

Question 4

What do many sensory receptors contain?

Answer 4

Ion channels and G-protein coupled receptors that are common to many bodily functions

Question 5

How is specifity of sensory modalities achieved by?

Answer 5

The structure and position of the sensory receptor

Question 6

What are sensory modalities?

Answer 6

Vision, smell, taste, touch, hearing, thermal senses, pain, balance, proprioception

Question 7

How are receptors classified?

Answer 7

Modality: Chemo, thermo, mechano etc
Origin:
- exteroceptors: vision, hearing, touch, cutaneous pain
- interoceptors: internal organs, visceral pain, nausea, stretch
- proprioceptors: muscles, tendons, joints - position and movement
- nociceptors: high threshold mechano and thermoreceptors
Distribution:
- General senses (somesthetic): touch, pressure, stretch hot, cold, blood pressure/composition
- Special senses: Head, innervated by cranial nerves

Question 8

What is the stimulus in taste receptors?

Answer 8

Chemical; e.g. Na in salt

Question 9

How do membranes depolarize in taste receptors?

Answer 9

Graded response

Question 10

What is the stimulus in olfactory receptors?

Answer 10

Chemical; an odorant

Question 11

How are graded receptor potential within a receptor cilium caused?

Answer 11

Local changes in membrane permeability

Question 12

What happens when large enough receptor potentials are generated?

Answer 12

Cause depolarization in the cell soma, triggering action potentials that travel along the olfactory nerve

Question 13

Sensory receptors conveys four types of information:

Answer 13

Modality (quality)
Location
Intensity
Timing

Question 14

How is modality determined?

Answer 14

By the type of energy transmitted by the stimulus and the receptor \s that are specialized to detect that energy

Question 15

What is the labelled line code?

Answer 15

The receptor is selective for one type of stimulus energy
The axons of the receptor/associated afferent neuron acts as a modality specific line of communication
Axons from these neurons make connections with specific areas in the CNS

Question 16

How is the labelled line code like a transducer?

Answer 16

e.g. initial receptor and where it’s located that sets the system

Question 17

What does stimulating afferent neurons electrical lead to?

Answer 17

A perception of the associated sensation

Question 18

What happens when the labelled line code is faulty?

Answer 18

Synesthesia

Question 19

What happens in synesthesia?

Answer 19

“Rare variants in axonogenesis genes connect three families with sound-color synesthesia”
- New research in PNAS only 9 days ago has found genes that are likely to be responsible
“The name Catherine tastes like Chocolate cake.”

Question 20

What does spatial arrangement of activated receptors provide?

Answer 20

Information about the stimulus

Question 21

What is the receptive field in the somatic system?

Answer 21

The region of skin innervated by the terminals of the receptor neurons

Question 22

What is the receptive field of a photoreceptor?

Answer 22

The region of the visual field projected onto that receptor

Question 23

What does the spatial arrangement of receptors allow in the auditory system?

Answer 23

Frequency discrimination

• large stimuli will activate more neurons
  e. g. a large object in the hand will activate receptive fields in many areas of the hand, whereas a small object will only activate a few receptive fields

Question 24

What is stimulus intensity?

Answer 24

Intensity is the total amount of stimulus energy delivered to the receptor

Question 25

What is the sensory threshold?

Answer 25

The lowest stimulus strength that can be detected

Question 26

How is intensity determined?

Answer 26

The response amplitude of the receptor and thus the firing frequency of the afferent neurons

Question 27

What does an increased neural response lead to?

Answer 27

Perception of a larger stimulus

Question 28

How is onset timing is determined by?

Answer 28

When the stimulus energy is received by the receptor and causes it to fire

Question 29

How is stimulus duration determined by?

Answer 29

Adaptation rates of receptors

Question 30

What is adaptation?

Answer 30

In response to continuous stimuli; the firing rate of action potentials decrease

Question 31

What do slowly adapting receptors (tonic receptors) respond to?

Answer 31

Respond to prolonged stimulation

Can tell duration of stimuli

Question 32

What do Rapidly adapting receptors (phasic receptors) respond to?

Answer 32

The beginning and end of a stimulus

Question 33

What is divergence?

Answer 33

Allows primary afferent neurons to signal to more than one relay neuron

Question 34

What is convergence?

Answer 34

Ensures that relay neurons have larger receptive fields than primary afferent neurons

Question 35

What are inhibitory neurons?

Answer 35

Ensures the signal in the most active neuron is propagated e.g. this enables contrast enhancement in the eye