Sensory Receptors 1

Question 1

What is a transducer

Answer 1

Something that converts various forms of energy to into Action Potentials. With energy stength represented by AP frequency

Question 2

Define sensory modality:

Answer 2

The type of stimulus activating a specific receptor

Question 3

Define adequate stimulus:

Answer 3

The type of energy a receptor normally responds to. can also respons to extremes of other energies (i.e. the eye normally repsons to light but youll see stars if someone pokes you in the eye)

Question 4

What do mechanoreceptors detect?

Answer 4

Pressure, touch, hearing, balance, blood pressure

Question 5

What do proprioceptors detect?

Answer 5

Postion of limbs or body parts from the joints and muscles

Question 6

What receptors detect painful stimuli?

Answer 6

Nociceptors.

Question 7

What type of graded membrane potential change is produced by an adequate potential?

Answer 7

A generator potential or receptor potential

Question 8

What is the adequate stimulus in cutaneous mechanoreceptors and how does it trigger a generator potential?

Answer 8

Membrane deformation from pressure and activates stretch-sensitive ion channels in the membrane.

Question 9

What effect does increasing the stimulus intensity have on APs?

Answer 9

It increases the number (or frequency) of APs.

lager stimulus = larger receptor (generator) potential = higher frequency of APs

Question 10

What does the number of receptors activated refelct?

Answer 10

Stimulus intensity.

Question 11

What do merkel receptors detect?

Answer 11

Steady pressure & texture

Question 12

What receptors detects flutter or stroking movements?

Answer 12

Meissners corpuscles

Question 13

What part of a nociceptor detects noxious stimuli?

Answer 13

Free nerve endings

Question 14

What do ruffini corpuscles respond to?

Answer 14

SKin stretch

Question 15

How is vibration detected in the skin?

Answer 15

By pacinian corpuscles

Question 16

How is har movement detected?

Answer 16

By free nerve endings in the root.

Question 17

What does adaptation mean in reference to mechanoreceptors?

Answer 17

Some mechanoreceptors only respond to changes in stimuli, i.e. they adapt to a maintained stimulus. i.e. the feel of putting clothes on stops until we take them off again (changes in the stimuli)

Question 18

What is the diffence between rapidly and slowly adapting receptors?

Answer 18

rapidly adapting stop sendin APs very quickly then send them again briefly when the stimulus drops off again.
Slowly adapting send many fewer APs but dont stop completely and dont increase aain when the stimulus ends.

Question 19

Name two types of rapidly adapting receptors?

Answer 19

Pacinian corpuscles and meissners corpuscles.

Question 20

Name two types of slowly adapting corpuscles:

Answer 20

Merkels discs and ruffini endings.

Question 21

Why dont Nociceptors adapt?

Answer 21

Because its important not to ignore painful stimuli

Question 22

Explain the structure of a pacinian corpuscle:

Answer 22

Onion like. A conncetive tissue capsule made from layers of membrane lamellae seperated by fluid.
Contains a naked nerve ending attaching to a myelinated nerve.

Question 23

How does a pacinian corpuscle detect vibration?

Answer 23

Stimulus deforms the capsule and nerve ending
Stretchin nerve ending opens stretch-sensitive ion channels
Allows influx of Na+ which causes local depolarisation. (generator potential)
APs fire at myelinated nerve

Question 24

How do pacinian corpuscles adapt?

Answer 24

Fluid redistribution quickly removes the mechanical stretch on the nerve ending, essentially dissipating the stimulus.
When the stimulus withdraws the capsule springs back and APs fire again.

Question 25

What happens if the connective tissue capsule is removed from a pacinian corpuscle?

Answer 25

Then it loses the ability to adapt and continues to produces generator potentials.

Question 26

What non-neural accessory structure is cirtical to a pacinian corpuscle?

Answer 26

The connective tissue capsule (membrane lamellae seperated by fluid)

Question 27

What is a receptive field?

Answer 27

A receptive field is the area of receptors in which a stimuli will acitvate a specific somatic sensory neuron.

Question 28

What determines our ability to tell between feelingon two points of our skin?

Answer 28

Receptive field size for each neuron and neuronal convergance.

Question 29

Why is converance of senseory neurons useful?

Answer 29

Allows simultaneous sub-threshhold stimuli from multiple nearby sensory neurons to sum at the secondary sensory neuron and trigger an AP. (i.e. forms a large secondary receptive field.)

Question 30

A relatively insensitive area (e.g. back) has what qualities?

Answer 30

Convergance of sensory neurons and a large secondary receptive field.

Question 31

Define acuity:

Answer 31

The ability to locate a stimulus on the skin and differentiate from another close by

Question 32

What is lateral inhibition?

Answer 32

Sensory receptors at the edge of stimuli are heavily inhibited compared with those at the centre.

Question 33

Why is lateral inhibition useful?

Answer 33

It enhances the contrast between relavent and irrelevant info. making the stimulus more obvious.

Question 34

How does lateral inhibition occur?

Answer 34

The secondary neuron of the pathway closest to the stimulus inhibits its neighbours.

Question 35

Where does sensory information go?

Answer 35

To the brain to be relayed through the thalamus to the somatosensory cortex

Question 36

Why is our cortical body map distorted?

Answer 36

The most sensitive areas occupy the bigest cortical space