lecture 24 - somatic sensation

Question 1

What are the two types of senses?

Answer 1

Somatic and special

Question 2

What are somatic senses?

Answer 2

Senses detected by generalised receptors found throughout the body

Question 3

What are special senses?

Answer 3

Senses detected by a special/specific organ or structure

Question 4

What are the 4 key types of somatic sense receptors?

Answer 4

Mechanoreceptors, nociceptors, thermoreceptors, chemoreceptors

Question 5

What do mechanoreceptors sense?

Answer 5

Touch, pressure, vibration, proprioception

Question 6

What do nociceptors sense?

Answer 6

Noxious stimuli (pain)

Question 7

What do thermoreceptors sense?

Answer 7

Change in temperature

Question 8

What do chemoreceptors sense?

Answer 8

Chemicals

Question 9

What senses are considered ‘special senses’?

Answer 9

Vision, hearing, balance, taste, smell

Question 10

What is signal transduction in terms of somatic sensation?

Answer 10

When sensory receptors are activated, leading to the opening of ion channels and a change in membrane potential causing a receptor potential which will cause an action potential if the threshold is reached.

Question 11

How are mechanoreceptors stimulated?

Answer 11

By physical forces that distort their plasma membrane, causing mechanically gated ion channels to open.

Question 12

What are the 3 main types of mechanoreceptors?

Answer 12

Proprioreceptors, baroreceptors, tactile receptors

Question 13

What is an example of a proprioreceptor?

Answer 13

Muscle spindles

Question 14

What do baroreceptors detect?

Answer 14

Pressure - e.g. blood pressure

Question 15

What do tactile receptors sense?

Answer 15

Touch, pressure and vibration

Question 16

In free nerve endings, what type of stimulus is detected by those with myelinated axons?

Answer 16

Temperature

Question 17

In free nerve endings, what type of stimulus is detected by those with unmyelinated or thinly myelinated axons?

Answer 17

Pain/noxious stimuli

Question 18

What are tonic receptors?

Answer 18

Receptors that are continually active (firing APs), with the frequency of APs changing to reflect the intensity of the stimulus.

Question 19

Are tonic receptors slow or fast adapting?

Answer 19

Slow adapting

Question 20

What are phasic receptors?

Answer 20

Receptors that are normally ‘silent’/inactive, but will respond briefly with APs to changes/stimulus.

Question 21

What are the 4 types of information encoded in sensory stimuli?

Answer 21

Modality, Intensity, Location & Duration - (MILD acronym)

Question 22

What is modality in terms of information coding?

Answer 22

The type of receptor activated, and therefore the type of sensation.

Question 23

What is intensity in terms of information coding?

Answer 23

The stimulus strength, encoded by the frequency of action potential firing and the number of axons activated.

Question 24

What is duration in terms of information coding?

Answer 24

The time period over which stimulus exists, encoded by the time period over which action potentials are fired in the afferent neuron.

Question 25

What is location, in terms of information coding?

Answer 25

The place in the body where receptors are activated, which is then mapped in the brain (somatosensory cortex)

Question 26

When sensory stimulus intensity is weak, what will occur?

Answer 26

Threshold will not be reach, so there will be no response in the afferent neuron.

Question 27

What are muscle spindles?

Answer 27

Stretch receptors that signal the length and and changes in length of muscles in response to stretch stimulus. They lie parallel to the main muscle and stretch as muscles lengthens and shorten as they contract