Lecture 12- Sensory Systems: Anterolateral Pathways

Question 1

Low levels of _____
_____ are important during everyday tasks to tell us when a particular movement or prolonged posture is putting too much strain on our body

Answer 1

• nociceptive activity

Question 2

T/F: People born without the sensation of pain go through life in constant danger of destroying themselves because they do not realize the harm they are doing.

Answer 2

True

Question 3

What are the 2 main ascending sensory pathways?

Answer 3

• posterior column-medial lemniscus pathway

- anterolateral pathways

Question 4

what is the main function of the posterior column-medial lemniscus pathway

Answer 4

• conveys: fine, discriminative touch, proprioception, vibration sense

Question 5

What is the main function of the anetrolateral pathways?

Answer 5

• convey: pain, temperature sense, crude touch

Question 6

The sensory receptors for the anterolateral pathways are

____ ____ ___ with bare (free) nerve endings

Answer 6

• primary sensory neurons

Question 7

The sensory receptors for the anterolateral pathways recieve info about what? (3 things)

Answer 7

• pain (nociceptors)
• thermal sensation (thermal receptors)
• crude touch and pressure (tactile receptors)

Question 8

T/F: anterolateral pathways have large diameter axons that are unmylinated or thinly myelinated

Answer 8

• False: small diameter axons

Question 9

T/F: the anterolateral pathway neurons conduct AP’s more slowly than axons carrying information about fine touch, vibration and proprioception

Answer 9

• True

Question 10

where are nocieptors commonly found?

Answer 10

• in the superficial portions of the skin
• in the joint capsules
• within the periostea of bones
• around the walls of blood vessels

Question 11

describe chemoreceptors

Answer 11

• sensitive to concentration of irritant chemicals released by noxious thermal or mechanical stimuli

Question 12

describe type A fibers (A delta)

Answer 12

• carry sensations of fast pain, or prickling pain, such as that caused by an injection or a deep cut
• relayed to the primary sensory cortex and receive conscious attention
• sensations reach the CNS quickly and often trigger
  somatic reflexes

Question 13

describe type C fibers

Answer 13

• carry sensations of slow pain, or burning and aching pain

- You become aware of the pain but only have a general idea of the area affected

Question 14

thermoreceptors are free nerve endings located where

Answer 14

• the dermis
• skeletal muscles
• the liver
• the hypothalamus

Question 15

describe tactile receptors

Answer 15

• have relatively large receptive fields and provide poor localization
• give little information about the stimulus
• are primarily free nerve endings in the skin situated
  between epidermal cells

Question 16

Tactile receptors for crude ____ and ____

Answer 16

• touch

- pressure

Question 17

mechanoreceptors for fine, _____ touch are extremely sensitive and have a relatively ___ receptive field

Answer 17

• discriminative

- small

Question 18

afferent fibres that have encapsulated endings typically have ____ thresholds for action potential generation than ____ ____ endings

Answer 18

• lower

- free nerve

Question 19

True/False: afferent fibers that have encapsulated endings are more
sensitive to sensory stimulation than free nerve endings

Answer 19

• True

Question 20

the anterolateral pathways are most important for conveying ____ sensation as well as carries ____, ____ and ____ information

Answer 20

• pain

- thermal, touch and pressure

Question 21

what are the 3 anterolateral tracts

Answer 21

• spinothalamic tract
• spinoreticular tract
• spinomesencephalic tract

Question 22

spinothalamic tract controls…

Answer 22

• for pain, temperature sensation, crude touch, pressure

Question 23

spinoreticular tract controls…

Answer 23

• for emotional and arousal aspects of pain

Question 24

spinomesencephalic tract controls…

Answer 24

• for central modulation of pain

Question 25

- anterolateral pathway enters the spinal cord at the ____ root and projects on ____ ____ neurons

Answer 25

- dorsal | - second order

Question 26

True/False: axons from second order sensory neurons start ascending diagonally up and cross over completely to the opposite side of the spinal cord white matter by passing through anterior grey commissure

Answer 26

- true

Question 27

the axons that synapse with motor neurons mediate...

Answer 27

- sensorimotor reflex behaviours, such as withdrawing hand from hot object

Question 28

the axons that synapse with ____ neurons in to bring about responses to pain

Answer 28

- autonomic

Question 29

Describe spinothalamic tract

Answer 29

- Second order neurons reach medulla and travel in groove between olives and inferior cerebellar peduncles - ascend through brainstem and synapse in VPL nucleus of thalamus (third order neurons) - proections to other thalamic nuclei

Question 30

the thalmus relays to what 3 areas?

Answer 30

- primary somatosensory cortex - frontal lobes and limbuc system - hypothalamus

Question 31

Spinoreticular tract terminates on the ____ _____ in the medulla and pons

Answer 31

- reticular formation

Question 32

Spinoreticular tract project to the _____ _____ nuclei

Answer 32

- intralaminar thalamic

Question 33

Spinomesencephalic tract projects to midbrain _____ _____ _____ participates in central modulation of pain

Answer 33

- periaqueductal gray area

Question 34

describe the Trigeminothalamic tract (what it does, where it terminates, where does it project to?)

Answer 34

- carries information about pain, temperature, crude touch from the face - terminates at ventral posterior medial nucleus (VPM) of the thalamus - then projects to the different brain areas that mediate perception of and responses to pain

Question 35

sensory information from the primary somatosensory cortex is conveyed to the ____ ____ area and the ____ ____ cortex

Answer 35

- secondary somatosensory | - parietal association

Question 36

the secondary somatosensory area also has extensive connections with ____ ____ for sensorimotor integration

Answer 36

- motor cortex

Question 37

True/False: Unilateral lesion of spinothalamic tract anywhere in brainstem: produces loss of pain and temperature and sense of touch from same side of the body

Answer 37

- fasle: opposite side of body

Question 38

True/False: Unilateral lesion of spinothalamic tract in spinal cord produces loss of pain and temperature on opposite side beginning one level above the level of the lesion

Answer 38

- False: one level below the level of the lesion

Question 39

describe the symptoms of a lesion of the somatosensory cortex

Answer 39

- produce contralateral deficits - discriminitive touch and joint position sense most severely affected, but all sensations may be affected - accompanied by cortical sensory loss extinction, decreased stereognosis, graphesthesia

Question 40

Most common pattern of diabetic neuropathy is...

Answer 40

- distal symmetrical polyneuropathy

Question 41

diabetic neuropathy produces...

Answer 41

- decreased sensation: impaired vibration is often first sign - paresthesia: nonpainful abnormal sensations (prickling, tingling) - dysesthesia: painful abnormal sensations, including burning and aching - loss of pain sensation

Question 42

Describe PCML

Answer 42

- A person who has had the posterior column-medial lemniscal (PCML) pathway affected will be able to sense pain and temperature and will have a crude sense of touch retained. - A person who has the PCML pathway intact but not the spinothalamic pathway will have a better sense of touch, but not pain or temperature. - If there is substantial, but not total, damage to both pathways, there will likely be some crude ability to sense touch retained

Question 43

True/False: sensory testing should occur before manual muscle testing, coordination assessment, gait analysis, or functional assessment

Answer 43

- True

Question 44

Typical order of testing

Answer 44

1. Superficial sensations pain, temperature, light touch, pressure 2. Deep sensations kinesthesia, proprioception, vibration 3. Combined cortical testing stereognosis, graphesthesia, two-point discrimination, tactile extinction

Question 45

Sensory testing should be performed ____ to ___ direction and once deficit noted testing becomes more _____

Answer 45

- distal - proximal - focused

Question 46

intact primary sensation with deficits in cortical sensation (such as agraphesthesia, astereognosis) suggest a lesion in ____ ____ ____

Answer 46

- contralateral sensory cortex

Question 47

extinction with intact primary sensation is a form of ____ that is most commonly associated with lesions of ____ ____ lobe

Answer 47

- hemineglect | - right parietal