Sensory Anatomommy Flashcards
What do primary afferent axons do?
Send somatic info to brain or spinal cord
Where do primary afferent axons enter the spinal cord?
Dorsal roots
What are the diameter of the primary afferent axons correlated with?
Type of info received
What does the axon diameter determine?
Conduction velocity
Describe Type Aa/Group 1 Axons
Large diameter and myelinated
Describe Type Ab/Type 2 axons
Medium diameter and myelinated
Describe Type Ad/Type 3 axons
Small diameter and myelinated
Describe Type C/Type 4 axons
Tiny diameter and unmyelinated
Which axon is the fastest? Which is the slowest? You def know why
Type Aa fastest
Type C slowest
What are C fibers responsible for?
Mediating temperature, throbbing pain, and itch
What are Ab axons responsible for?
Conducting touch sensations
What are Aa axons responsible for?
Proprioceptors for skeletal muscle
What are Ad axons responsible for?
Pain and temperature
How many segments are in the spinal cord?
30
What are the four divisions in the spinal cord?
Cervical (C 1-8)
Thoracic (T 1-12)
Lumbar (L 1-5)
Sacral (S 1-5)
What is a dermatome?
Area of skin inner gated by the right and left dorsal roots of a spinal segments (ex. S2-S4 controls yo dick)
What are the three divisions of the spinal gray matter?
Dorsal horn, intermediate zone, and ventral horn
Ab axons enter the dorsal horn, where do the two branches go?
One synapses in the dorsal horn to 2nd order neurons (for reflexes
One ascends straight to the brain ipsilaterally (for perception)
What are the two types of skin?
Hairy and glabrous (hairless)
What are the two layers of the skin?
Epidermis (outer) and dermis (inner)
What are the functions of skin?
Protect, prevent evaporation of bodily fluids, and provides direct contact w/ the world
What does the Dorsal Column-Medial Lemniscal Pathway mediate?
Tactile sensation, vibration, and proprioception (major route for this info to cortex)
How does the dorsal column-medial lemniscal pathway work?
- 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
What does the trigeminal touch pathway mediate?
Somatosensory info in the face via trigeminal nerve (CN 5)
What does the trigeminal touch pathway innervate?
Face, mouth area, outer 2/3 of tongue, and dura
What are the 3 branches of the trigeminal touch pathway?
V1
V2
V3
How does information from the trigeminal touch pathway reach S1?
- Enters brain stem at pons
- Decussates and sends projections to VPN
- VPN sends info to S1
What are the 4 somatosensory cortexes in the parietal lobe? (Only one rlly matters)
BA1, 2, 3A, 3B (important one)
WHY is 3B the primary SMC?
- receives info from VPN
- responsive to somato stimuli
- simulation evokes somatic sensory experiences
What layer of the 3B receives thalamic input? (It’s the same as the others)
Layer IV
What is somatotopy? (Think tonotopy)
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
What happens to S1 when a limb is removed?
It USUALLY remaps and causes reorganization
What happens when you stimulate certain bodily areas more than others?
The somatic map increases size in the areas correlated with those areas to detect touch better
What are broadmann’s areas 5 and 7 responsible for?
Somatic sensation, visual stim, movement planning, and attentiveness (dw abt this too much)
What happens if you damage the Posterior Parietal Cortex (areas 5 and 7)?
Tons of neurological disorders
What is agnosia?
Inability to recognize an object even when simple sensation is normal
What is astereognosia?
Normal sense of touch but you can’t identify object from it
What is neglect syndrome?
A part of the body or visual field is ignored
