Anatomy - Lab 7

Question 1

Name the main types of sensory receptors.

Answer 1

Meissners corpuscles

Pacinian corpuscles

Question 2

Where are meissners corpuscles found and what do they sense?

Answer 2

Sense of touch

Present on only non-hairy skin, particularly dense on fingertips

Question 3

What do Pacinian corpuscles sense and where are they found?

Answer 3

Sense pressure, but are more sensitive to vibration
Deep subcutaneous skin all over the body
Looks like an onion

Question 4

What do free nerve endings sense?

Answer 4

Pain and temperature: crude and non-discriminative touch

Question 5

Name the structures that are proprioceptive and position sense receptors.

Answer 5

Muscle spindles, golgi tendon organs and joint receptors

Question 6

What is the golgi tendon made up of?

Answer 6

Collagen fibres innervated by proprioceptive sensory neurons

Question 7

Which tract is more medial? Gracile or cuneate?

Answer 7

Gracile

Question 8

What does the dorsal column pathway carry?

Answer 8

Carries discriminative sensation - discriminative touch, vibration, proprioception

Question 9

Where will the axons forming the gracile and cuneate tracts terminate?

Answer 9

Gracile and cuneate nuclei of the closed medulla

Question 10

How is information added onto the spinal cord?

Answer 10

Added laterally
Information from most superior part of the body will be more lateral
Information form inferior part of body will be medial

Question 11

What are the internal arcuate fibres and where are they found?

Answer 11

Found in closed medulla

This is where cell bodies of gracile and cuneate nuclei cross and ascend

Question 12

What is the layout of HAL in the rostral/open medulla?

Answer 12

HAL vertically (up to bottom)

Question 13

What would a dorsal loss of the medial lemniscus in the open medulla cause compared to a ventral loss?

Answer 13

Dorsal loss = loss of fine touch in fingers

Ventral loss = loss of fine touch in toes

Question 14

How does information from the dorsal column pathway vary between the thalamus and primary somatosensory cortex?

Answer 14

Information in thalamus: leg info in lateral region, head in medial region
Cortex: opposite - legs medial, head lateral

Question 15

What does the anterior vs lateral spinothalamic tract carry?

Answer 15

Lateral = pain and temperature
Anterior = light touch

Question 16

What is the dorsolateral fasciculus?

Answer 16

Laterally placed small diameter axons entering the spinal cord from the dorsal root ganglion, carrying info for pain, light touch and temperature

Question 17

Where do the 2nd neurons cross in the spinothalamic tract?

Answer 17

Ventral white commissure

Question 18

Where do the spinothalamic fibres sit in the rostral (open) medulla?

Answer 18

Just dorsal to the inferior olivary nucleus

Question 19

What does the cuneocerebellar pathway carry?

Answer 19

Proprioceptive sensation from upper limb (C8 and above)

Question 20

Where does the cuneocerebellar tract first neuron synapse?

Answer 20

Open medulla - accessory cuneate nucleus

Question 21

How does information enter the cerebellum from the unconscious pathways?

Answer 21

Via the inferior cerebellar peduncles

Question 22

Where does the posterior spinocerebellar pathway bring information from?

Answer 22

Lower limb (anywhere below C8)

Question 23

What are the sensory organs of the proprioceptive sensation pathways?

Answer 23

Muscle spindles and golgi tendon organs

Question 24

Name the neurons and synapses of the cuneocerebellar tract.

Answer 24

Neuron 1: Cell body in DRG superior to C8 (incoming information from muscle spindles, golgi tendon organs). Axon ascends in cuneate fasciculus (ipsilateral - same side as it entered). Synapse in lateral (aka accessory) cuneate nucleus.

Neuron 2: Cell body in lateral cuneate nucleus. Axons ascends in cuneocerebellar tracts (medial to posterior spinocerebellar tract) on the dorsolateral side of the brainstem.
Ascends to enter cerebellum via inferior cerebellar peduncle

Question 25

Describe the pathway of proprioception from the lower limb. (Posterior spinocerebellar tract)

Answer 25

Neuron 1: Cell body in DRG at C8 and below (incoming information from muscle spindles, golgi tendon organs)
Axon enters spinal cord and immediately synapses on 2nd order neurons whose cell bodies are in the Clarke’s nucleus. Synapse in Clarke’s nucleus.

Neuron 2: Cell body in Clarke’s nucleus in the dorsomedial horn of the spinal cord grey matter
Axon ascends in posterior spinocerebellar tract on the dorsolateral side of the spinal cord
Ascends and enters cerebellum via inferior cerebellar peduncle

Question 26

Where does general sensation from the body travel in the thalamus?

Answer 26

Ventral posterolateral nucleus (VPL)

Question 27

Where does general sensation from the head/face travel in the thalamus?

Answer 27

VPM - ventral posteromedial nucleus