Sensory Receptors And Tracts

Question 1

What are somatosensory pathways?

Answer 1

Ascending pathways that carry information like touch, pain, temperature, vibration, and proprioception from the body to the brain.

Question 2

Name the two major somatosensory pathways

Answer 2

Dorsal column pathway and anterolateral (spinothalamic) pathway

Question 3

What are the three types of neurons in sensory pathways?

Answer 3

First-order, second-order, and third-order neurons

Question 4

Where are the cell bodies of first-order neurons located?

Answer 4

Dorsal root ganglia

Question 5

Where do second-order neurons project?

Answer 5

From spinal cord or medulla to thalamus

Question 6

Where do third-order neurons project?

Answer 6

From thalamus to the primary somatosensory cortex.

Question 7

What determines the speed of a sensory signal?

Answer 7

Axon diameter and myelination.

Question 8

Which axons conduct faster: larger or smaller diameter?

Answer 8

Larger diameter.

Question 9

Do myelinated fibers conduct faster or slower than unmyelinated?

Answer 9

Faster.

Question 10

What do mechanoreceptors detect?

Answer 10

Touch, pressure, stretch, and vibration

Question 11

What do nociceptors detect?

Answer 11

Pain from damaging stimuli.

Question 12

What do thermoreceptors detect?

Answer 12

Temperature changes.

Question 13

What are exteroceptors?

Answer 13

Receptors detecting stimuli from outside the body.

Question 14

What are proprioceptors?

Answer 14

Receptors sensing position/movement of the body.

Question 15

What are unencapsulated receptors?

Answer 15

Free nerve endings, Merkel discs, and hair follicle receptors.

Question 16

What do Pacinian corpuscles sense?

Answer 16

Vibration and pressure.

Question 17

What do Meissner corpuscles detect?

Answer 17

Fine touch.

Question 18

What do Ruffini corpuscles detect?

Answer 18

Stretch and deep pressure.

Question 19

What do muscle spindles detect?

Answer 19

Muscle stretch and length

Question 20

What do Golgi tendon organs detect?

Answer 20

Tension in tendons.

Question 21

What type of sensations does the dorsal column pathway carry?

Answer 21

Fine touch, pressure, vibration, and proprioception.

Question 22

Where does the dorsal column pathway ascend initially?

Answer 22

Ipsilaterally in the spinal cord.

Question 23

Where does decussation (crossing over) occur in this pathway? (Dorsal column)

Answer 23

In the medulla.

Question 24

Which tracts carry signals from upper and lower limbs?

Answer 24

Fasciculus cuneatus (upper limbs), Fasciculus gracilis (lower limbs).

Question 25

Where does the third-order neuron carry information? (Dorsal column)

Answer 25

To the primary somatosensory cortex (postcentral gyrus)

Question 26

What does the anterolateral pathway transmit?

Answer 26

Pain, temperature, itch, tickle, and crude touch.

Question 27

Which fibers carry fast and slow pain?(antrolateral)

Answer 27

Aδ fibers (fast), C fibers (slow, burning pain).

Question 28

Where do these fibers synapse in the spinal cord? (Anterolateral)

Answer 28

Aδ: Lamina I & V; C fibers: Lamina II (substantia gelatinosa).

Question 29

Where does decussation occur in this pathway? (Anterolateral)

Answer 29

At the anterior white commissure in the spinal cord.

Question 30

Where does the third-order neuron project? (Anterolateral)

Answer 30

To the somatosensory cortex, cingulate cortex, and insular cortex.

Question 31

What is the cortical homunculus?

Answer 31

A map of the body on the somatosensory cortex based on sensory input.

Question 32

Which areas have the largest representation? (Cortical Homunculus)

Answer 32

Face and hands.

Question 33

What is a positive Romberg sign?

Answer 33

Swaying or falling with eyes closed due to loss of proprioception.

Question 34

What does damage to the dorsal column pathway cause?

Answer 34

Ipsilateral loss of vibration and proprioception below the lesion

Question 35

What does damage to the anterolateral pathway cause?

Answer 35

Contralateral loss of pain and temperature.

Question 36

What is tabes dorsalis?

Answer 36

Degeneration of dorsal columns due to late-stage syphilis.

Question 37

What is syringomyelia?

Answer 37

A spinal cord cyst that compresses the anterior white commissure, causing “cape-like” loss of pain and temperature

Question 38

In the dorsal column pathway, which neuron decussates and at what level of the central nervous system? A. The first order neuron decussates at the dorsal root ganglion B. The second order neuron decussates at the anterior white commissure C. The second order neuron decussates at the medulla D. The third order neuron decussates at the medulla E. The third order neuron decussates at the thalamus

Answer 38

C. The second-order neuron decussates at the medulla

Question 39

Which of the following correctly describes the receptor and the type of sensory information it detects? A. Free nerve endings detect vibration B. Meissner corpuscles detect pain C. Merkel discs detect slippage of objects along skin surface D. Pacinian corpuscles detect temperature E. Ruffini corpuscles detect stretch and deep and sustained pressure

Answer 39

E. Ruffini corpuscles detect stretch and deep and sustained pressure.

Question 40

What is pain according to the International Association for the Study of Pain?

Answer 40

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

Question 41

What are the components of pain perception?

Answer 41

Affective (emotions), Behavioral (expression), Cognitive (beliefs), and physiological response.

Question 42

What are the four main types of pain based on source?

Answer 42

Cutaneous – sharp, brightDeep somatic – from muscles, joints, vesselsVisceral – diffused pain from internal organsPsychogenic – emotional origin

Question 43

What is nociceptive pain?

Answer 43

Pain from tissue injury, heat, or pressure

Question 44

What is breakthrough pain?

Answer 44

Acute flare-up of chronic nociceptive pain (e.g., in cancer).

Question 45

What is inflammatory pain?

Answer 45

Pain caused by inflammatory molecules (e.g., IL-1, TNF-α).

Question 46

What is neuropathic pain?

Answer 46

Pain from damage to the somatosensory nervous system

Question 47

What is functional pain?

Answer 47

Pain without clear physical cause (e.g., Irritable Bowel Syndrome , fibromyalgia).

Question 48

What is fast pain?

Answer 48

Sharp pain that occurs rapidly (0.1s), e.g., needle prick

Question 49

What is slow pain?

Answer 49

Chronic, dull, aching pain that increases over time.

Question 50

What is referred pain?

Answer 50

Pain perceived at a site different from its origin.

Question 51

Why does referred pain occur?

Answer 51

Due to convergence of nerve fibers at the same spinal level.

Question 52

Example: Where is cardiac pain referred?

Answer 52

Retrosternal area, left shoulder, inner arm (T2–T5 segments).

Question 53

What types of stimuli excite nociceptors?

Answer 53

Mechanical, thermal, and chemical stimuli.

Question 54

What kinds of pain do mechanical and thermal stimuli produce?

Answer 54

Fast pain

Question 55

What kind of pain can all three stimuli produce?

Answer 55

Slow pain.

Question 56

What is peripheral neuropathic pain?

Answer 56

Pain due to damage to peripheral nerves.

Question 57

What is central neuropathic pain?

Answer 57

Pain due to damage in the CNS (stroke, trauma).

Question 58

What is paresthesia?

Answer 58

Pins-and-needles sensation.

Question 59

What is anesthesia dolorosa?

Answer 59

Pain after trigeminal nerve lesion.

Question 60

What is dysesthesia?

Answer 60

Burning/acid-like pain, often with abnormal sensations.

Question 61

What are the four phases of pain perception?

Answer 61

Transduction Transmission Central processing Modulation

Question 62

What are nociceptors?

Answer 62

Free nerve endings that detect noxious stimuli (painful stimuli).

Question 63

Are nociceptors found in the CNS?

Answer 63

no

Question 64

What are unimodal nociceptors?

Answer 64

Respond to one type of stimulus (mechanical, thermal, or chemical).

Question 65

What are polymodal nociceptors?

Answer 65

Respond to mechanical, thermal, and chemical stimuli.

Question 66

Which fibers innervate polymodal nociceptors?

Answer 66

Unmyelinated C fibers.

Question 67

What are silent nociceptors?

Answer 67

Normally inactive but become responsive after tissue injury/inflammation.

Question 68

What are the two ascending (afferent) pain pathways?

Answer 68

Neospinothalamic and Paleospinothalamic tracts

Question 69

What fibers transmit fast pain?

Answer 69

Aδ fibers via the neospinothalamic tract (NTT).

Question 70

What neurotransmitter is used in NTT?

Answer 70

Glutamate.

Question 71

What fibers transmit slow pain?

Answer 71

C fibers via the paleospinothalamic tract (PTT)

Question 72

What neurotransmitter is used in PTT?

Answer 72

Substance P.

Question 73

Which parts of the brain process dull, long-lasting pain?

Answer 73

Thalamus, brainstem, and reticular formation.

Question 74

Which systems manage emotional responses to pain?

Answer 74

Reticular formation and limbic system

Question 75

What are the 3 major components of the analgesia system?

Answer 75

Periaqueductal gray (PAG)Raphe magnus nucleus (RMN)Dorsal horn of spinal cord

Question 76

What neurotransmitters are involved in the analgesia system?

Answer 76

Enkephalin and serotonin.

Question 77

What does the gate control theory of pain propose?

Answer 77

A-beta fibers can inhibit C-fiber pain transmission via spinal interneurons.

Question 78

What are examples of therapies using this principle? (Gate control hypothesis)

Answer 78

Rubbing the skin, TENS, acupuncture.

Question 79

What are examples of natural opiate-like substances in the body?

Answer 79

β-endorphinMet-enkephalinLeu-enkephalinDynorphin

Question 80

What is allodynia?

Answer 80

Pain from a normally non-painful stimulus (e.g., light touch).

Question 81

What is hyperalgesia?

Answer 81

Excessive pain response to a mild painful stimulus