Exam #6: Introduction to Sensory

Question 1

Define proprioceptor.

Answer 1

Receptors that provide a sense of self i.e. information about joint angles, muscle length, and muscle tension

Question 2

Define adequate stimulus.

Answer 2

Under normal circumstances, a receptor is only affected by a certain threshold of a specific stimulus

Question 3

Define nociceptor.

Answer 3

Pain receptor

Question 4

Define sensory modality.

Answer 4

Different types of sensory stimuli e.g. vision, hearing, taste, smell, touch, pain, temperature, itch

Question 5

Define receptive field.

Answer 5

Region of tissue within which a stimulus can evoke a change in the firing rate of a neuron

Question 6

Define graphesthesia & agraphesthesia.

Answer 6

Sense through which figure or numbers drawn on skin are recognized

Question 7

Define sterognosis & asterognosis.

Answer 7

Ability to recognize objects through touch alone

Question 8

What is the difference between a receptor potential & an action potential?

Answer 8

Receptor potential= graded potentials produced by signal transduction of a sensory stimulus

Action potential= depolarization once threshold has been reached

**Receptor potentials of a sufficient strength will trigger action potentials

Question 9

How does the nervous system can code for the “what” of a sensory stimulus?

Answer 9

Labeled line principle= chain of connected neurons from sensory receptor to brain area that perceives the stimulus

Question 10

How does the nervous system can code for the “where” of a sensory stimulus?

Answer 10

Receptive field

Question 11

How does the nervous system can code for the intensity of a sensory stimulus?

Answer 11

1) Increase frequency of nerve firing

2) Increase number of nerves firing

Question 12

How does the nervous system can code for the duration of a sensory stimulus?

Answer 12

On/off signaling with continuous firing during stimulation

Question 13

What is adaptation of a receptor?

Answer 13

When maintained/ constant stimulus leads to a decrease in firing in the associated sensory nerve over time

Question 14

What is the difference between phasic, tonic, rapidly adapting, & slowly adapting? Give an example of somatosensory receptors of each type of adaptation.

Answer 14

Tonic= slowly adapting & signal intensity/ duration of stimulus
- E.g. merkel’s disk (detects steady pressure)

Phasic= rapidly adapting, signals onset & offset
- Pacinian corpuscle (detects rapid changes in stimulus)

Question 15

How are nerve fibers classified?

Answer 15

Roman numeral (sensory only) & letter schemes (motor & sensory): I-IV & A-C

• I-III/ A & B are myelinated
• IV/C are NOT myleinated

Question 16

State which type of nerve fibers is fastest & slowest.

Answer 16

Fastest= I/ A-alpha
Slowest= IV/ C

Question 17

Which type of nerve fiber conducts action potentials at 100 m/s, 50 m/s, 20 m/s, 1 m/s?

Answer 17

100= I/Aa
50= II/ Ab
20= III/Ad
1= IV/ C

Question 18

How could you measure spatial resolution in the somatosensory system?

Answer 18

Two-point discrimination test

Question 19

What is “two-point discrimination”? Which areas of the body show the best discrimination? The worst?

Answer 19

Two-point discrimination is a test of tactile acuity

• Good discrimination at lips and finger tips
• Poor on back & calf

Question 20

List the receptors involved in proprioception. What is the difference between these receptors?

Answer 20

• Joint receptors
• Muscle spindles & golgi tendon organs
• Skin tactile receptors

Question 21

What kinds of information are carried by the dorsal column and anterior column systems?

Answer 21

DC/ML=

1) Proprioception
2) Two-point discrimination
3) Vibration

Anterolateral i.e. Spinothalamic=

1) Pain
2) Temperature

Question 22

Where does information in the dorsal column & anterior column cross the midline?

Answer 22

DC/ML= midline in the brainstem–decussation of the medial lemniscus

Anterolateral i.e. Spinothalamic= spinal cord

Question 23

What kinds of deficits are associated with damage to each system, dorsal column and anterior column?

Answer 23

DC/ML= deficits in:

1) Proprioception
2) Two-point discrimination
3) Vibration

Anterolateral i.e. Spinothalamic= deficits in:

1) Pain
2) Temperature

Question 24

What is the location of the somatosensory cortex? How is the somatosensory cortex organized?

Answer 24

• Parietal lobe (post-central gyrus)
• Broadmann 3,1,2

Medial= foot, leg, & genitals 
Lateral= face, trunk, arms

Question 25

What type of information is carried by A-alpha nerve fibers?

Answer 25

Alpha-motoneurons

Question 26

What type of information is carried by A-beta nerve fibers?

Answer 26

Touch & pressure

Question 27

What type of information is carried by A-gamma nerve fibers?

Answer 27

gamma motoneurons to muscle spindles

Question 28

What type of information is carried by A-delta nerve fibers?

Answer 28

Touch, pressure, temperature, & fast pain

Question 29

What type of information is carried by B nerve fibers?

Answer 29

Preganglionic ANS

Question 30

What type of information is carried by C nerve fibers?

Answer 30

Slow pain
Postganglionic ANS
Olfaction

Question 31

What type of information is carried by Ia nerve fibers?

Answer 31

Muscle spindle afferents

Question 32

What type of information is carried by Ib nerve fibers?

Answer 32

Golgi tendon organ afferents

Question 33

What type of information is carried by II nerve fibers?

Answer 33

Secondary afferents of muscle spindles
Touch
Pressure

Question 34

What type of information is carried by III nerve fibers?

Answer 34

Touch
Pressure
Fast pain
Temperature

Question 35

What type of information is carried by IV nerve fibers?

Answer 35

Pain
Temperature
Olfaction