D3 Introduction to nervous system

Question 1

anatomic divisions

Answer 1

• central nervous system (CNS): brain & spinal cord

- peripheral nervous system (PNS): nerves & ganglia

Question 2

functional subdivisions

Answer 2

• somatic nervous system

- autonomic nervous system

Question 3

somatic nervous system

Answer 3

• “outer shell” exposed to world
• conscious perception & control
• body wall & limbs, skeletal muscle only

Question 4

autonomic nervous system

Answer 4

• “inner guts”; internal functions
• subconscious control
• cardiac muscle, smooth muscle, glands (GI, heart, lungs, etc)

Question 5

functional classifications of neurons

Answer 5

• motor neurons

- sensory neurons

Question 6

nerve fibers

Answer 6

• long processes of neurons
• are microscopic
• bundle up to form nerves

Question 7

nerves

Answer 7

• nerve fibers & connective tissue (bundled up)
• only in the PNS
• most are mixed (sensory & motor fibers)

Question 8

ganglia

Answer 8

• collection of neuron cell bodies in the PNS

- multipolar & pseudo-unipolar neuron clusters

Question 9

origin of CNS

Answer 9

• formed form the embryonic neural tube
• cranial 2/3 of neural tube = brain
• caudal 1/3 = spinal cord
• ganglia derived from neural crest cells

Question 10

3 parts that somites differentiate into in the trunk

Answer 10

1) Dermatomes: dermis of the skin - on the back
2) Myotomes: skeletal muscles
3) Sclerotomes: bones (ribs & vertebrae)

Question 11

dermatome

Answer 11

an area of skin that is mainly supplied by a single spinal nerve

Question 12

myotome

Answer 12

group of muscles that a single spinal nerve root innervates

Question 13

sclerotome

Answer 13

area of a bone innervated from a single spinal segment

Question 14

motor neurons

Answer 14

• project from the CNS
• multipolar cells in gray matter of spinal cord
• innervate (supply) an effector (eg a muscle or gland)

Question 15

sensory neurons

Answer 15

• project to CNS
• eg dorsal root ganglion (pseudounipolar) cells
• bring information from the periphery (eg - skin) to the CNS

Question 16

gray matter in CNS

Answer 16

• contains cell bodies of neurons
• organized into clusters of cells called nuclei
• forms an “H” shape in spinal cord, w/ 2 dorsal (posterior) horns, 2 ventral (anterior horns) and sometimes little bulges in center that are 2 lateral horns

Question 17

dorsal (posterior) horn in gray matter

Answer 17

concerned w/ sensory processing

Question 18

ventral (anterior) horn in gray matter

Answer 18

provides motor output (reflex and voluntary control)

Question 19

lateral horn in gray matter

Answer 19

provides visceral motor (autonomic) output

Question 20

white matter in CNS

Answer 20

• axons wrapped by fatty myelin
• surrounds the “H-shaped” gray matter
• cell bodies of neurons absent
• contains tracts, w/ many nerve fibers

Question 21

nerves in CNS

Answer 21

• nerves are found only in the PNS

- there are NO nerves, only tracts, in the CNS

Question 22

intervertebral foramina

Answer 22

• holes formed between adjacent vertebrae

- space for spinal nerves to leave the vertebral canal

Question 23

afferent nerve fibers

Answer 23

• “affect = feeling”

- “feel” something, then carry that info (impulses) to the CNS

Question 24

efferent nerve fibers

Answer 24

• “effect = making something happen”

- carry impulses from CNS to effectors (muscles, glands, etc - structures that perform an action)

Question 25

somatic afferents

Answer 25

afferent nerve fibers that relay info from the body wall and limbs to the CNS

Question 26

somatic efferents

Answer 26

efferent nerve fibers that relay info from CNS –> the body wall and limbs

Question 27

visceral efferents

Answer 27

efferent nerve fibers that relay info from CNS –> smooth muscle, glands, and cardiac muscle

Question 28

spinal cord segments

Answer 28

8 cervical segments (C-1 to C-8)

12 thoracic segments (T-1 to T-12)

5 lumbar segments (L-1 to L-5)

5 sacral segments (S-1 to S-5)

1 coccygeal segment (Co-1)

Question 29

cauda equina

Answer 29

• called cauda equina b/c it resembles a “horse’s tail”
• bushy structure within vertebral canal formed by long dorsal and ventral roots gathered together
• dorsal and ventral roots very long below the end of the spinal cord