43. Brain + SC

Question 1

Grey Matter vs. White Matter

Answer 1

Grey: neuronal cell bodies, nuclei
White: myelinated axonal connections

Question 2

Function of Astrocytes, Oligodendrocytes, Microglia

What makes up the BBB?

Answer 2

Astrocytes - most numerous glial cell type, structural, role in inflammatory response, deliver nutrients + remove waste from neurons (via end feet), form BBB

Oligodendrocytes: form myelin sheaths of CNS axons (multiple segments on multiple cells - speed conduction/reduces metabolic requirements)

Microglia: CNS macrophages - involved in inflammatory process

BBB: endothelial cell with tight junctions and no fenestrations; astroglial processes further block transport

Question 3

What are Circumventricular Organs? Give examples

Answer 3

Areas of brain that lack BBB

Area Postrema: bottom of medulla - role in emesis response (detects toxins in blood)

Pineal Gland: secretes melatonin, role in circadian rhythms - sleep/wake cycle

Question 4

Main CNS excitatory NT, main CNS inhibitory NT

Answer 4

Glutamate, GABA(a)

Question 5

Dorsal Column - Medial Lemniscus Large Fiber Pathway

fx, type of fiber, decussation

Answer 5

Sensory - touch, pressure, vibration, proprioception
Aa + Ab fibers - largest/fastest
run ipsilateral in SC - decussate in Medulla
2nd order n in Gracile nucleus (medial) and Cuneate nucleus (lateral)

Question 6

Anterolateral System - Small Fiber Pathway

fx, type of fiber, decussation

Answer 6

fx: sensory - pain, temp
Ad, C fibers - smallest, slowest
run contralateral in SC - decussate within 1-3 vertebral levels of SC

Question 7

Corticospinal Tract

Fx, start, decussation, other inputs

Answer 7

fx: motor control of limbs/distal extremities
Start: precentral gyrus/primary motor cortex and out brainstem
Decussation: pyramid of medulla (ipsilateral in SC)
Inputs to rubrospinal, reticulospinal, tectospinal, vestibulospinal tract

Question 8

Brown-Sequard Syndrome

cause, effect

Answer 8

Sever half of SC

• ipsilateral loss of touch/pressure/proprioception (dorsal column)
• contralateral loss of pain/temp 1-3 segments below lesion (AL system)
• ipsilateral hemiplegia (CS tract)

Question 9

Syringomelia (Central Cord Syndrome)

cause, effect

Answer 9

Central SC swelling only disrupts anterolateral system (decussating fibers)
Bilateral 1-3 segment band of pain/temp loss