Section 5 - Sensory receptors and somatic sensation

Question 1

Define sensation

Answer 1

Ability to feel something physically, especially by touching

Question 2

Define perception

Answer 2

Conscious interpretation of those stimuli

Question 3

Each of the principal types of sensation that we can experience (touch, pain, sight, sound) are called ______

Answer 3

Modality of sensation

Question 4

T or F: nerve fibers transmit only impulses

Answer 4

True

Question 5

Type of sensation felt when a nerve fiber is stimulated is determined by : _____

Answer 5

the termination point in the CNS, unique neurons in the CNS are capable of decoding specific modalities

Question 6

Name the 3 types of sensory information

Answer 6

Mechanoreceptive sensation
Nociceptive sensation
Thermoreceptive sensation

Question 7

Name the 2 branches from the mechanoreceptive sensation

Answer 7

1. Tactile sensation (skin)

2. Proprioceptive sensation

Question 8

Give examples of tactile sensation

Answer 8

Touch
Pressure
Vibration
Tickle and itch

Question 9

Give examples of proprioceptive sensation

Answer 9

Muscle stretch sense

Joint position sense

Question 10

T or F: thermoreceptive sensation detects pain

Answer 10

False, detects heat and cold

Nociceptive sensation detect pain

Question 11

Name the 3 somatosensory receptors based on the type of sensation they detect

Answer 11

1. Mechanoreceptors detect tissue deformation
2. Thermoreceptors detect change in temperature
3. Nociceptors detect pain

Question 12

What are the two types of mechanoreceptors?

Answer 12

Skin tactile receptors

Muscle receptors

Question 13

Name the 4 mechanisms of stimulation of the receptor

Answer 13

1. Mechanical deformation
2. Application of chemicals
3. Change in temperature
4. Tissue damage

Question 14

Increasing the intensity of the stimulus will lead to a greater receptor potential and, eventually, to a greater AP _____

Answer 14

Frequency

*** same amplitude, more APs

Question 15

When talking about adaptation of receptors, speed of adaptation varies with type of receptors, name them

Answer 15

Rapidly adapting receptors

Slowly adapting receptors

Question 16

T or F: rapidly adapting receptors are best at detecting rapidly changing signals, while slowly adapting receptors are capable or detecting a long, continuous signal

Answer 16

True

Question 17

Name the 6 receptors

Answer 17

1. Free nerve endings
2. Hair-end organ
3. Pacinian corpuscle
4. Meissner’s corpuscle
5. Merkel’s discs
6. Ruffini’s end-organ

Question 18

T or F: Area of each receptor field varies directly with the density of receptors in the region

Answer 18

False, inversely (more density = small receptor field and vice-versa)

Question 19

To get the best sensory discrimination (accuracy of sensation), is it better to have small or large receptive fields?

Answer 19

Small

Question 20

Define the two-point discrimination

Answer 20

Method used to measure tactile acuity in rehab

Question 21

Which provides more acuity?
When many primary sensory neurons converge onto a single secondary neuron OR when fewer neurons converge, secondary receptive fields are smaller so they are perceived as distinct stimuli

Answer 21

2nd part

Question 22

Which tactile receptors are located in the epidermis vs dermis?

Answer 22

• Epidermis: Meissner corpuscule, Merkel discs and free nerve endings
• Dermis: Pacinian corpuscules and Ruffini organ

Question 23

Name the 6 TACTILE receptors

Answer 23

1. Free nerve endings
2. Meissner’s corpuscules
3. Merkel’s discs
4. Hair end organ
5. Ruffini’s end organ
6. Pacinian corpuscules

Question 24

Free nerve endings are found where and detecte what kind of touch?

Answer 24

• They are found everywhere on the skin

- Detect crude touch and pressure sensations

Question 25

Meissner's corpuscules are found where and detecte what kind of touch?

Answer 25

- They are located in the superficial layer of the skin (non-hairy part) - Detect fine touch

Question 26

Merkel's discs are found where and detecte what kind of touch?

Answer 26

- They are located in the epidermis | - Detect touch and light pressure

Question 27

Hair end - organ are found where and detecte what kind of touch?

Answer 27

- In contact with the root of the skin hair | - Detects hair movement

Question 28

Ruffini's end organ are found where and detecte what kind of touch?

Answer 28

- They are located in the deeper layer of the skin | - Detects heavy and prolonged touch and pressure signals

Question 29

Pacinian corpuscules are found where and detecte what kind of touch?

Answer 29

- They are located in the deeper layer of the skin | - Detects tissue vibration or other rapid changes in the mechanical state of the tissue

Question 30

Which receptors are rapidly adapting?

Answer 30

- Meissner's corpuscules, Hair end organ and Pacinian corpuscules

Question 31

True or false: Ruffini's end organs are fast adapting receptors

Answer 31

FALSE

Question 32

When does a pain sensation occur?

Answer 32

When the tissue is being damaged

Question 33

Why is pain a protective mechanism?

Answer 33

Because it brings awareness of tissue damage and can prevent further damages to the body

Question 34

What is the difference between fast and slow pain?

Answer 34

- Fast pain is a pricking sensation, sharp in character that is felt 0.1 sec after the stimulus - Slow pain is an aching sensation that begins after a second or more

Question 35

What kind of receptors are pain receptors?

Answer 35

Specialized free nerve endings

Question 36

Where are the nociceptors located?

Answer 36

- Superficial layers of the skin - Internal tissues - Arterial walls - Bones, joints and muscle surface

Question 37

True or false: Nociceptors are stimulated by thermal, mechanical and chemical stimulus

Answer 37

True

Question 38

Nociceptors are slow adapting receptors, true or false?

Answer 38

True

Question 39

What are thermoreceptors

Answer 39

Free nerve endings that code changes in temperature

Question 40

Thermoreceptors change within what range

Answer 40

the innocuous range

Question 41

Temperatures that are likely to damage an organism are sensed by what receptors

Answer 41

nociceptors

Question 42

True or False: nociceptors respond only to noxious heat

Answer 42

false they also respond to noxious cold

Question 43

how do we determine sense of temperature

Answer 43

by comparison of the signals from each of the two types of thermoreceptors

Question 44

Thermoreceptors respond to a temperature change with 2 phases (components), name them

Answer 44

with a phasic component followed by a tonic component

Question 45

What is the difference between a phasic and tonic component

Answer 45

phasic is rapidly adapting and tonic is a slowly adapting component

Question 46

Give a real-life example of the phasic and tonic components

Answer 46

when you get in a hot bath and it feels hot until your body adapts and then it's only warm

Question 47

Meissner's corpuscles, merkel's dics, hair receptors, Pacinian corpuscles and Ruffini's end organs transmits their signals through what type of nerve fibers

Answer 47

type A-beta myelinated nerve fibers at 30-70 m/sec

Question 48

Free nerve endings transmit their signals through what type of fibers

Answer 48

type A-delta nerve fibers at 6-30 m/sec (fast pain, cold sensation) or through type C unmyelinated fibers at 0.5-2 m/sec (slow pain, cold, warmth, crude touch & pressure sensations)

Question 49

What is faster between high and low discrimation

Answer 49

high discrimination

Question 50

where does the sensory information enter the spinal cord

Answer 50

through the dorsal roots of the spinal nerves

Question 51

what are the 2 pathways for sensory information

Answer 51

the dorsal column (medial lemniscal system) and the antero-lateral system

Question 52

what does decussate mean

Answer 52

crossing over on the other side

Question 53

True or False sensory fibers only decussate on one pathway

Answer 53

false they decussate on both pathways

Question 54

where is the sensory information from one side of the body transmitted

Answer 54

to the brain hemisphere on the opposite side of the body

Question 55

what makes the relay to transmit sensory information from the receptor to the final point of the cerebral cortex

Answer 55

three order neurons

Question 56

where is the dorsal column located

Answer 56

on the back of the spinal cord

Question 57

which types of sensations does the dorsal column transmit

Answer 57

the tactile sensations (touch, vibration and fine pressure) and the proprioceptive sensations (i.e. limb position)

Question 58

where do the dorsal column signals originate from

Answer 58

they originate from tactile receptors or proprioceptive receptors

Question 59

What type nerve fibers are used in the dorsal column, for what reason and with what type of degree

Answer 59

large myelinated nerve fibers for fast signal transmission with a high degree of spatial fidelity

Question 60

Describe the 3 different order neurons for the dorsal column

Answer 60

the 1st order neurons synapse with the 2nd at the dorsal column nucleus the 2nd order neurons decussate at the level of the medulla (brain stem) The 2nd order neurons synapse with th 3rd in the thalamus The 3rd order neurons transmit info to the primary somasensory cortex

Question 61

what does the antero-lateral pathway transmit

Answer 61

a broad spectrum of modalities such as pain, thermal sensations, crude touch and pressure, tickle and itch, sexual sensations

Question 62

where do the signals from the antero-lateral pathways originate

Answer 62

they originate from free nerve endings receptors (pain and thermal receptors)

Question 63

what type of nerve fibers are used in the antero-lateral pathway for what use and with what type of degree

Answer 63

smaller myelinated and unmyelinated fibers for slow transmission and with a low degree of spatial orientation

Question 64

Describe the 3 different order neurons for the antero-lateral pathway

Answer 64

The 1st order neurons synapse with the 2nd in the substantia gelatinosa The 2nd order neurons decussate at the level of the spinal cord The 2nd order neurons synapse with the 3rd in the thalamus The 3rd order neurons transmit info to the primary somatosensory cortex

Question 65

Where are fast pain fibers transmitted into

Answer 65

the neospinothalamic tract

Question 66

Where are slow pain fibers transmitted into

Answer 66

the paleospinothalamic tract

Question 67

what do neo and paleo mean

Answer 67

neo = new paleo = old

Question 68

where do the fast pain fibers terminate

Answer 68

at the somatosensory cortex

Question 69

where do the slow pain fibers terminate

Answer 69

at the thalamus level or below (even in the brain stem)

Question 70

T or F slow pain fibers can be highly localized if it is simultaneously activated with tactile sensations

Answer 70

False the fast-sharp pain can

Question 71

slow pain is ____ localized

Answer 71

poorly

Question 72

Where is the primary somatosensory cortex located

Answer 72

in the post-central gyrus (in the parietal lobe)

Question 73

How would you describe the primary somatosensory cortex

Answer 73

highly organized with distinct spatial orientation and each side of the cortex receives info from the opposite side of the body

Question 74

T or F the somatosensory area II is much more extensive than the somatosensory area I

Answer 74

False

Question 75

What is the name of the famous montrealer neurosurgeon who did the mapping of the somatosensory cortex

Answer 75

Dr Wilder Penfield

Question 76

Penfield's Homunculus gives an ____ representation of the body. Explain

Answer 76

unequal because the more a region of the body has receptors, the better it's area of representation in the somatosensory cortex is

Question 77

Classify these body regions in order of the ones with more receptors to the ones with the less receptors

Answer 77

lips

Question 78

the somatosensory cortex is composed of how many cellular layers

Answer 78

6

Question 79

within the cellular layers, the neurons are arranged in what direction

Answer 79

vertical columns

Question 80

T or F the columns in the somatosensory cortex each have a specific modality and they interact between each other

Answer 80

True, the interaction allows the beginning of the analysis of the meaning of the sensory signals

Question 81

T or F the degree of pain is the same for everyone

Answer 81

False it varies tremendously from person to person

Question 82

How does the brain suppress inputs of pain signals

Answer 82

through the activation of the analgesia system

Question 83

What are the three parts of the analgesia system

Answer 83

the periaqueductal gray of the mesencephalon and upper pons the raphe magnus nucleus located in the lower pons the pain inhibitory complex located in the dorsal horns of the spinal cord

Question 84

what is the main neurotransmitter involved in the analgesia system

Answer 84

enkephalin (released at the 3 levels)

Question 85

How do we call a pain in the internal organs that is often sensed on the surface of the body

Answer 85

reffered pain

Question 86

How would you describe CIPA (congenital insensitivity to pain with anhidrosis)

Answer 86

inability to feel pain and temperature, inability to sweat