Topic 8 - principles of sensory systems

Question 1

What is sensory transduction?

Answer 1

when energy from the environment gets transduced into electrochemical signals in sensory receptors.

Question 2

What are sensory receptors?

Answer 2

Sensory receptors are are cells not just proteins.

Sensory receptor proteins can have ion channels and g-protein coupled receptors

Question 3

What is the difference between graded receptor potentials and action potentials?

Answer 3

GRADED = increase in size when increase in stimulus amplitude.

ACTION potential = always the same size, but have threshold for activation

Question 4

What type of receptor potentials do all sensory receptor cells respond with?

Answer 4

• ALL sensory receptors respond with…..graded receptor potentials.

Question 5

What are the 4 types of information that sensory receptors can convey?

Give their definitions

Answer 5

1. Modality
2. Location
3. Intensity
4. Timing

modality is determined by stimulus energy and anatomy of the sensory organ/receptors.

Location is determined by the activation of spatially distributed sensory neurons

Intensity (of sensation) is determined by stimulus apmplitude and neuronal firing.

timing is sensation duration determined by adaptation rates of receptors.

Question 6

What is the labelled line code?

Answer 6

• Receptor is selective for one type of stimulus
• The axons of the receptor/afferent neuron act as modality line of communication.
• Axons from these neurons make connections with specific areas in the cns.

The labelled line code is faulty in synaesthesia: when someone sense a type of modality, but perceived as a different modality.

Question 7

What are slow adapting receptors?

Answer 7

Tonic receptors – respond to prolonged stimulation

Question 8

What are rapidly adapting receptors?

Answer 8

Phasic receptors – respond at beginning and end of a stimulus.

Question 9

What is the definition of an adaptation?

Answer 9

in response to a continuous stimuli the firing rate of action potential decreases.

Question 10

what is the definition of divergence?

Answer 10

allows primary afferent neurons to signal more than one neuron.

Question 11

what is the defintition of convergence?

Answer 11

ensures relay neurons have a larger receptive field than that of primary afferent neurons.

Question 12

what are inhibitory neurons?

Answer 12

ensure signal in the most active neuron is propagated.

Question 13

In the somatic system, what is the receptive field?

Answer 13

A receptive field is the region of skin innervated by the terminals of the receptor neuron.

Question 14

In the visual system, what is the receptive field of a photoreceptor?

Answer 14

It is the region of the visual field projected onto that receptor.

Question 15

What is the definition of intensity?

Answer 15

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

• The lowest stimulus strength that can be detected is known as the sensory threshold
• Intensity is determined by the response amplitude of the receptor and thus the firing frequency of the afferent neurons

Question 16

What is the defition of onset timing?

Answer 16

is determined by when the stimulus energy is received by the receptor and causes it to fire.

Question 17

What is the definition of stimulus duration?

Answer 17

stimulus duration = is determined by adaptation rates of receptors