Overview Of The Sensory System: From Receptors To Perception

Front 1

What are exteroreceptors?

Back 1

Resond to stimuli from the outside environment (cutaneous sense, vision, olfaction, hearing)

Front 2

What are interoreceptors?

What are some types? (4)

Back 2

Respond to stimuli inside body

1. Proprioceptor = respond to movement and body position
2. Visceroreceptor = stretch of internal organ or muscular contraction
3. Chemoreceptor = changes n chemical environment
4. Baroreceptor = changes in pressure

Front 3

What is sensation?

Back 3

Conscious or unconscious awareness of external or internal stimuli

Front 4

What is perception?

Back 4

Conscious awareness and interpretation of a sensation

Allows us to create a perceptual representation of our environment

Front 5

What is modality?

Back 5

Specific type of sensation

Front 6

What is transduction?

Back 6

Conversion of one form of energy to another

Front 7

What is conduction?

Back 7

Propagation of a signal to a distant site in the nervous system --> APs

Front 8

Type A-alpha (I) fibers
a. Morphology
b. Sensory modalities
c. Conduction

Back 8

a. Large, myelinated
b. muscle spindles, motor axons
c. fast (50 m/s)

Front 9

Type A-beta (II)
a. Morphology
b. Sensory modalities
c. Conduction

Back 9

a. Large, myelinated
b. Vibration, pressure, touch, stretch
c. Fast (50m/s)

Front 10

Type A delta (III)
a. Morphology
b. Sensory modalities
c. Conduction

Back 10

a. Small myelinated
b. Touch, cold, pain
c. Moderate (20m/s)

Front 11

Type C (IV)
a. Morphology
b. Sensory modalities
c. Conduction

Back 11

a. Small unmyelinated
b. cold, warm, thermal pain
c. Slow (2m/s)

Front 12

Type B
a. Morphology
b. Sensory modalities
c. Conduction

Back 12

a. Small, myelinated
b. Autonomics
c. Medium (10 m/s)

Front 13

What are deep tendon reflexes?

Back 13

Comprised of large fibers that carry muscle stretch information

Front 14

What is the result of a process that affects large, myelinated sensory fibers?

Back 14

Absence of deep tendon reflexes

Front 15

What happens in tabes dorsalis (damange to large, myelinated fibers)?

Back 15

Balance problems due to loss of joint position sense

Pain sensitivity increase

Front 16

What is the implication of the fact that large fibers have a lower activation threshold for clinical treatment?

Back 16

Can stimulate large fibers with low, non-painful electrical currents applied to the skin or nerve and suppress painful stimuli

Front 17

Where do sensory bodies of sensory neurons lie?

Back 17

Outside of the spinal cord in the DRG

Front 18

What is the pathway of large fiber sensation (vibration, proprioception, stretch)?

Back 18

Enters spinal cord via medial part of dorsal root --> ascend in ipsilateral dorsal column --> nucleus gracilis/fasciculis) ipsilaterally

Front 19

What is the pathway for small fiber sensation (pain and temp)?

Back 19

Enter lateral division of dorsal root --> ascend dorsal horn --> synapse on secondary neuron in cord and cross to contralateral side --> up anterolateral tract

Front 20

Hair receptors
a. Innervation
b. adaption speed
c. Arrangement
d. Consist of what?

Back 20

a. A-beta and A-delta
b. fast adapting (respond quickly, recover quickly)
c. Arranged parallel to shaft
d. Neurites (nerve terminals) sandwiched between two buns of Schwann cell cytoplasm

Front 21

Pacinian corpuscles
a. Fibers
b. adaption speed
c. Sensitive to...?
d. Consist of...?

Back 21

a. A-beta
b. fast adapting
c. Minimal skin distortion, vibration (up to 500 Hz)
d. Laminated corpuscles with central naked axon (can have more than one)

Front 22

WHat are some places to find Pacinian corpuscles (8)?

Back 22

Dermis
Subcutaneous tissue
Ligaments
Joint capsules
Pleura
Peritoneum
Nipples
External genitalia

Front 23

How does one test Pacinian corpuscle integrity in the skin?

Back 23

Vibratory testing

Front 24

Meissner's corpuscles
a. Fibers
b. adaptation
c. Sensitive to...?
d. consist of...?

Back 24

a. A-beta
b. fast-adapting
c. Low frequency oscillation up to 40 Hz (flutter)
d. laminated corpuscle supplied by several nerve fibers that intertwine through the lamellae

Front 25

Where are Meissner's corpuscles located?

Back 25

Superficially in dermal papillae of fingers, palmar surface of hands, plantar surface of feet

Front 26

What is the difference between flutter and vibration?

Back 26

Flutter = feeling of repetitive movement

Vibration = diffuse and penetrating, like humming

Front 27

What special sensory function are Meissner's corpuscles important for?

Back 27

two-point discrimination

Front 28

Merkel's Disc
a. Fibers
b. Adaptation
c. sensitive to...?
d. mode of signaling

Back 28

a. A-beta
b. slow-adapting
c. Light static pressure for discrimination of shapes, edges, and textures
d. Rapid initial burst, followed by a sustained rate of discharge proportional to the degree of skin indentation (steady state)

Front 29

Where are Merkel cells found? (4)

Back 29

Hairless skin such as fingertips, lips, external genitalia, hair follicles

Front 30

What is the role of proprioceptors?

Where are they found?

Back 30

Provide information about static limb position, sense of movement

Located in muscle, tendons, joint capsules, and ligaments

Front 31

What do large diameter type Ia sensory fibers innervate?

What are the role of the structures that these innervate?

Back 31

Coil around and innervate muscle spindles

Muscle spindles provide information about muscle stretch

Front 32

What do type 1b fibers innervate?

What is the role of the organs they innervate?

Back 32

Golgi tendon organ receptors

Golgi tendon organs inform the CNS of the degree of muscle tension

Front 33

What do afferents from muscle spindles connect with? (2)

Back 33

1. Excitatory monosynaptic connections with alpha motor neurons innervating the respective muscle --> deep tendon reflex

2. Inhibitory polysynaptic contact with motor neurons innervating muscle antagonists

Front 34

What do afferents from the Golgi tendon organ synapse with? (2)

Back 34

1. Interneurons in spinal cord --> inhibit motor neurons innervating muscle of origin

2. Excitatory connections with motor neurons of antagonistic muscles

Front 35

How do thermoreceptors sense temperature?

Back 35

Warming of the skin --> activate warm fibers, silence cold fibers

Cooling of the skin --> activate cool fibers, silence warm fibers

Front 36

What type of adaptation speed do warm and cold fibers have?

Back 36

Slow adapting = sustained discharge related to skin temperature

Front 37

What are cold fibers?

Warm fibers?

Back 37

Cold = A-delta, C

Warm = C

Front 38

What is fast pain?

Back 38

Short latency, short duration, well-localized pain conducted through A delta fibers

Front 39

What is slow pain?

Back 39

More diffuse, longer-duration, burning sensation conducted by slower C fibers

Front 40

What is the structure of all pain receptors?

Back 40

Free nerve endings with terminal specializations

Front 41

What are mechanical nociceptors?

Back 41

Respond to pinch or pressure

NOT to light touch or temp

Front 42

What are polymodal nociceptors?

Type of fibers?

Back 42

Respond to chemicals, high intensity mechanical and thermal stimulation

C fibers

Front 43

What senses visceral pain?

Back 43

Nocireceptors sensitive to stretch or distension of visceral organs

Front 44

How do pain fibers show traits of slow and fast adaptation?

Back 44

Recover slowly after a stimulus

BUT do not discharge continuously

Front 45

What is sensitization?

Back 45

Repeated stimulations are increasingly effective in generating a response in some pain fibers eg. polymodal nociceptors

Front 46

What do chemoreceptors detect?

What is the pathway?

Back 46

Detect chemical stimulus

GPCR --> adenylate cyclase --> cAMP --> increase channel conductance --> depolarize receptor membrane

Front 47

What do mechanoreceptors sense?

What is the pathway?

Back 47

Stretch or tension

Stimulus pulls carbohydrate chains anchored in EC space/membrane cytoskeleton --> stress on conformation of channel proteins --> increased conductance

Front 48

What are 4 examples of mechanoreceptors?

Back 48

Pacinian corpuscles
Meissner's corpuscles
Free nerve endings
Proprioceptors

Front 49

What happens with increased intensity of stimulus?

With increased duration of stimulus?

Back 49

Increased intensity --> greater number and frequency of APs

Longer stimulus duration --> longer the train of APs generated

Front 50

What is sensory adaptation?

Back 50

Decline in generator potential with time

Slow and fast

Front 51

What are 2 examples of slow adaptation?

Back 51

Merkel's cells
thermal receptors

Front 52

What are 3 examples of fast adaptation?

Back 52

hair receptors
Pacinian corpuscles
Meissner's corpuscles

Front 53

What is a receptive field?

Back 53

Region of skin within which a tactile stimulus evokes a sensory response

Front 54

What are 2 features of sensation over the fingers?

Back 54

1. Finer two-point discrimination
2. Smaller receptive fields