Sensory Anatomommy

Question 1

What do primary afferent axons do?

Answer 1

Send somatic info to brain or spinal cord

Question 2

Where do primary afferent axons enter the spinal cord?

Answer 2

Dorsal roots

Question 3

What are the diameter of the primary afferent axons correlated with?

Answer 3

Type of info received

Question 4

What does the axon diameter determine?

Answer 4

Conduction velocity

Question 5

Describe Type Aa/Group 1 Axons

Answer 5

Large diameter and myelinated

Question 6

Describe Type Ab/Type 2 axons

Answer 6

Medium diameter and myelinated

Question 7

Describe Type Ad/Type 3 axons

Answer 7

Small diameter and myelinated

Question 8

Describe Type C/Type 4 axons

Answer 8

Tiny diameter and unmyelinated

Question 9

Which axon is the fastest? Which is the slowest? You def know why

Answer 9

Type Aa fastest
Type C slowest

Question 10

What are C fibers responsible for?

Answer 10

Mediating temperature, throbbing pain, and itch

Question 11

What are Ab axons responsible for?

Answer 11

Conducting touch sensations

Question 12

What are Aa axons responsible for?

Answer 12

Proprioceptors for skeletal muscle

Question 13

What are Ad axons responsible for?

Answer 13

Pain and temperature

Question 14

How many segments are in the spinal cord?

Answer 14

30

Question 15

What are the four divisions in the spinal cord?

Answer 15

Cervical (C 1-8)
Thoracic (T 1-12)
Lumbar (L 1-5)
Sacral (S 1-5)

Question 16

What is a dermatome?

Answer 16

Area of skin inner gated by the right and left dorsal roots of a spinal segments (ex. S2-S4 controls yo dick)

Question 17

What are the three divisions of the spinal gray matter?

Answer 17

Dorsal horn, intermediate zone, and ventral horn

Question 18

Ab axons enter the dorsal horn, where do the two branches go?

Answer 18

One synapses in the dorsal horn to 2nd order neurons (for reflexes

One ascends straight to the brain ipsilaterally (for perception)

Question 19

What are the two types of skin?

Answer 19

Hairy and glabrous (hairless)

Question 20

What are the two layers of the skin?

Answer 20

Epidermis (outer) and dermis (inner)

Question 21

What are the functions of skin?

Answer 21

Protect, prevent evaporation of bodily fluids, and provides direct contact w/ the world

Question 22

What does the Dorsal Column-Medial Lemniscal Pathway mediate?

Answer 22

Tactile sensation, vibration, and proprioception (major route for this info to cortex)

Question 23

How does the dorsal column-medial lemniscal pathway work?

Answer 23

• Ab axons enter and ascend via ipsilateral dorsal column
• Axons terminate in dorsal column nuclei in medulla
• Axons from dorsal column decussate and ascend via medial lemniscus
• Medial lemniscus axons synapse into VPN (in thalamus)
• VPN neurons send axons to S1

Question 24

What does the trigeminal touch pathway mediate?

Answer 24

Somatosensory info in the face via trigeminal nerve (CN 5)

Question 25

What does the trigeminal touch pathway innervate?

Answer 25

Face, mouth area, outer 2/3 of tongue, and dura

Question 26

What are the 3 branches of the trigeminal touch pathway?

Answer 26

V1 V2 V3

Question 27

How does information from the trigeminal touch pathway reach S1?

Answer 27

- Enters brain stem at pons - Decussates and sends projections to VPN - VPN sends info to S1

Question 28

What are the 4 somatosensory cortexes in the parietal lobe? (Only one rlly matters)

Answer 28

BA1, 2, 3A, 3B (important one)

Question 29

WHY is 3B the primary SMC?

Answer 29

- receives info from VPN - responsive to somato stimuli - simulation evokes somatic sensory experiences

Question 30

What layer of the 3B receives thalamic input? (It’s the same as the others)

Answer 30

Layer IV

Question 31

What is somatotopy? (Think tonotopy)

Answer 31

Mapping body surface sensations onto the structure of the brain, amount of cortex devoted to a body part is correlated w/ the density of sensory input received from each part

Question 32

What happens to S1 when a limb is removed?

Answer 32

It USUALLY remaps and causes reorganization

Question 33

What happens when you stimulate certain bodily areas more than others?

Answer 33

The somatic map increases size in the areas correlated with those areas to detect touch better

Question 34

What are broadmann’s areas 5 and 7 responsible for?

Answer 34

Somatic sensation, visual stim, movement planning, and attentiveness (dw abt this too much)

Question 35

What happens if you damage the Posterior Parietal Cortex (areas 5 and 7)?

Answer 35

Tons of neurological disorders

Question 36

What is agnosia?

Answer 36

Inability to recognize an object even when simple sensation is normal

Question 37

What is astereognosia?

Answer 37

Normal sense of touch but you can’t identify object from it

Question 38

What is neglect syndrome?

Answer 38

A part of the body or visual field is ignored