Lecture 11 - Sensory Systems: Posterior Column- Medial Lemniscus Pathways

Question 1

What are the 4 modalities ?

Answer 1

Touch, proprioception, pain, temperature

Hint: Double TT, Double PP

Question 2

Is pain a chemical or mechanical irritation?

Answer 2

chemical

Question 3

what are the 4 types of somatosensory receptors?

Answer 3

Mechanorecptors, chemoreceptors, thermoreceptors, nociceptors

Question 4

True or false.. free nerve endings have a fast rate of conduction?

Answer 4

false

Question 5

Mechanoreceptors for proprioception in and around joints detect which functions?

Answer 5

Detect limb position, joint movement and pressure

Question 6

Golgi tendon organs are located where ?

Answer 6

muscle tendon junction

Question 7

What is the connective tissue surrounding the entire peripheral nerve?

Answer 7

Epineurium

Question 8

What is the delicate connective tissue surrounding each individual nerve fibre (axon)?

Answer 8

Endoneurium

Question 9

T/F: The dorsal pathway conveys crude touch?

Answer 9

False.

Question 10

Higher order neurons relay somatosensory information to other higher centres to modulate ______ and _____.

Answer 10

level of arousal and alertness

Question 11

Sensory receptors are located at the _____ (distal or proximal) ends of peripheral nerves.

Answer 11

Distal

Question 12

Define receptive field

Answer 12

The area of skin supplied by a single afferent

neuron is the receptive field for that neuron.

Question 13

receptive fields are smaller ____ and ____ proximally

Answer 13

distally; larger

Question 14

what are the advantages of a parallel system?

Answer 14

• adds to perceptual experience

- offers a measure of insurance

Question 15

List the 4 types of information all sensory systems conveyed when stimulated.

Answer 15

modality, location, intensity, duration

Hint: MILD

Question 16

What is the term for precision of stimulus location?

Answer 16

acuity

Question 17

What is Lateral Inhibition.

Answer 17

a strong stimulus applied to the receptive field of one neuron causes that neuron to inhibit transmission of signals by neurons with neighboring receptive fields.

Question 18

Duration is a relationship between _____ and ______.

Answer 18

stimulus intensity and perceived intensity

Question 19

Rapidly adapting receptors burst when stimuli initiated only and responds best to _______ (changing or unchanging) stimuli

Answer 19

changing

Question 20

List the Four major mechanoreceptors in the skin

Answer 20

Meissner’s corpuscles, Merkel’s disc receptors, Pacinian corpuscles, Ruffini endings

Question 21

Define a dermatome

Answer 21

a peripheral region innervated by sensory fibers from a single nerve root

Question 22

Where are sensory neuron cell bodies are located?

Answer 22

dorsal root ganglion

Question 23

What is the 1st relay of sensory information to sites higher in the nervous system?

Answer 23

dorsal horn

Question 24

What are the two main pathways of the sensory system?

Answer 24

posterior column-medial lemniscus pathway

anterolateral pathways

Question 25

mechanoreceptors have ____ (large or small)diameter, ______ (myelinated or unmyelinated) axons that conduct AP’s rapidly

Answer 25

large; myelinated

Question 26

What stimulates mechanoreceptors?

Answer 26

indentation of skin or motion across its surface

Question 27

what are the 2 sub modalities for Mechanoreceptors for proprioception?

Answer 27

• joint position sense/proprioception

- speed and direction of limb movement (kinesthesia)

Question 28

Mechanoreceptors for proprioception in and around joints include what 3 types of mechanoreceptors ?

Answer 28

Ruffini endings, pacinian corpuscles, free nerve endings

Question 29

Primary sensory endings: group 1a afferents are stimulated at onset of _____.

Answer 29

stretch

Question 30

Secondary sensory ending: group II afferents, respond to _______

Answer 30

tonic (sustained) stretch

Question 31

T/F: Golgi tendon organs are innervated by 1a sensory axons ?

Answer 31

false

Question 32

which mechanoreceptors for proprioception function via autogenic inhibitor ?

Answer 32

Golgi tendon organs

Question 33

T/F: The Medial Lemniscus Pathway: majority of axons pass directly to the posterior or ventral column

Answer 33

false: dorsal

Question 34

The gracile fasciculus conveys information from ____.

Answer 34

legs and lower trunk

Question 35

The cuneate fasciculus conveys information from ____.

Answer 35

upper trunk (above T6) arms and neck

Question 36

T/F: For the Posterior Column- Medial Lemniscus Pathway at the medulla, primary sensory neurons synapse on second order sensory neurons

Answer 36

true

Question 37

T/F: At medulla the PCML axons of the first order neurons cross over to other side as internal arcuate fibres

Answer 37

false: second

Question 38

True or False: medial lemniscus axons synapse on third order neurons in thalamus

Answer 38

true

Question 39

The posterior limb of internal capsule is called ___ ____ _____.

Answer 39

thalamic somatosensory radiations

Question 40

what does the analogous pathway (the trigeminal lemniscus) convey?

Answer 40

touch sensation for the face

Question 41

From the internal capsule, ascending sensory fibres project to primary somatosensory cortex on the _____ _____.

Answer 41

postcentral gyrus

Question 42

Do unilateral lesions from the level of the nuclei Gracilis and Cuneatus down through the cord produce unilateral or bilateral deficits ?

Answer 42

unilateral