LEC 3: The Nervous System - 08.18.2014

Question 1

Neuron

Answer 1

nerve cell, basic unit of a nervous system

Question 2

soma

Answer 2

Greek for “body”

Question 3

flow of impulse in neuron

Answer 3

impulse flows from soma of one neuron, down the axon, through boutons to muscle, gland, or another neuron

Question 4

Two (2) divisions of the nervous system

Answer 4

1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)

Question 5

What are the components of the CNS

Answer 5

1. brain
2. spinal cord

Both develop from neural tube in embryo

Question 6

What are the components of the PNS

Answer 6

All nervous structures outside of the CNS that connect CNS (brain, spinal cord) to body

• includes spinal/cranial/visceral NERVES

PNS develops from neural crest cells and as outgrowth of the CNS

Question 7

What is the position of gray matter and white matter in the brain

Answer 7

• gray matter (cell bodies) are the outer portion of brain (thinking part is outer)
• white matter (axons forming tracts/pathways) are the inner portion of the brain

Question 8

What is the position of gray matter and white matter in the spinal cord

Answer 8

• gray matter (cell bodies) are the inner portion of the spinal cord (thinking part is inner)
• white matter (axons forming tracts/pathways) are the outer portion of the spinal cord

Question 9

radicle

Answer 9

the beginning of a nerve

Question 10

tract

Answer 10

a collection of nerve cell processes (axons/fibers) found WITHIN the CNS

(gross term)

Question 11

nucleus

Answer 11

a collection of nerve cell bodies (somas) found WITHIN the CNS

(gross term, do not confuse with nucleus of a cell)

Question 12

What is the function of myelin

Answer 12

• fatty myelin (white appearance) insulates axons from communicating with neighboring axons
• myelin is itself a cell; nucleus wrapped around axon, cytoplasm (fatty) on outside

Question 13

Two (2) divisions of the PNS nervous system by function

Answer 13

1. somatic
2. visceral (autonomic)

Question 14

somatic

Answer 14

• innervates structures (skin and most skeletal muscle) derived from somites in the embryo
• mainly involved with receiving and responding to information from the external environment

Question 15

visceral (autonomic)

Answer 15

• innervates organ systems in the body and other visceral elements, such as smooth muscle and glands
• concerned mainly with detecting and responding to information from the internal environment

Question 16

PNS

Answer 16

1. spinal nerves
2. cranial nerves

Question 17

nerve

Answer 17

a collection of nerve cell processes (axons/nerve fibers) found OUTSIDE the CNS

Question 18

Describe the components of a nerve trunk

Answer 18

A. nerve trunk (visible in gross dissection)

B. epineurium (visible in gross dissection)

C. perineurium

D. endoneurium

E. fasicle (surrounded by perineurium)

F. fasiculus (bundles of nerve fibers surrounded by endoneurium)

G. nerve fibers (neuronal axon) (surrounded by myelin)

Question 19

tracts and nuclei

vs.

nerves and ganglia

Answer 19

Really another way of distinguishing CNS (tracts, nuclei) from PNS (nerves, ganglia

• nerves are similar to tracts, but found in PNS
• ganglia are similar to nuclei, but found in PNS

Question 20

nerve

Answer 20

a collection of nerve cell processes (axons/fibers) found OUTSIDE the CNS

Question 21

ganglion (ganglia)

Answer 21

a collection of nerve cell bodies (somas) found outside of the CNS

Question 22

What are X and Y in this structure

Answer 22

X. Doral root ganglion (DRG)

Y. Spinal nerve (radicle – where a nerve begins)

NB: Doral (anterior) side, so this view is actually a superior cut

Question 23

Afferent sensory axons/fibers

Answer 23

conduct impulses TOWARD the CNS in the dorsal root ganglion

Think: **Afferent = DorsAL **(toward CNS)

Question 24

Efferent motor axons/fibers

Answer 24

conduct electrical impulses AWAY from CNS in the ventral root

Think: Efferent = VEntral (away from CNS)

Question 25

What is the structure of a typical **Afferent** (sensory) axon/fiber and what does it detect

Answer 25

Bipolar, detects "touch" (e.g. pain, temperature, pressure, texture, tickle) * cell body of **Afferent** sensory axon/fiber sits in **dorsAL** root ganglion (DRG) * brings signal from "touch" toward the CNS

Question 26

dermatone

Answer 26

each **afferent** sensory axon/fiber that brings in information is limited to which **dorsal** root ganglion it can go to * skin segments related to a spinal nerve are dermatones

Question 27

What is the structure of a typical **Efferent** (motor) axon/fiber and what does it affect?

Answer 27

Unipolar, effects "motion" (e.g. muscle contraction, gland secretion)

Question 28

Describe the relationship between: * Dorsal root ganglion (what runs through it) * Ventral root (what runs through it) * Spinal Nerve

Answer 28

* Afferent sensory axons/fibers run through DRG, carrying "touch" information from external environment to CNS (cell body sits in DRG) * DRG = **Pure Sensory** * Efferent motor axons/fibers run through ventral root, affecting "motion" in the form of muscle contractions, gland secretions * Ventral root = **Pure Motor** * Spinal nerve contains both afferent (sensory) and efferent (motor) axons/fibers

Question 29

What are pure fiber types and what are examples

Answer 29

only one fiber type (afferent OR efferent) e.g. ROOTS of spinal nerves

Question 30

what are mixed fiber types and what are examples

Answer 30

both afferent and efferent fibers together e.g. spinal nerves and their branches

Question 31

What is the circled structure

Answer 31

Dorsal Ramus of spinal nerve (looks like a little thumb)

Question 32

What is the circled structure

Answer 32

Ventral Ramus of spinal nerve

Question 33

What are the branches off the Dorsal Ramus and Ventral Ramus called

Answer 33

Rami

Question 34

Name the labeled parts of this card and describe the orientation

Answer 34

A. Ventral Root (anterior) B. Dorsal Root Ganglion, DRG (posterior) C. Lateral cutaneous branch of Ventral Ramus D. Anterior cutaneous branch of Ventral Ramus E. Dorsal Ramus

Question 35

What does the Dorsal Ramus innervate

Answer 35

* deep back muscles * overlaying skin NB: Little thumb = deep back muscles and overlaying skin

Question 36

What does the Ventral Ramus innervate

Answer 36

* innervates everything besides the deep back muscles and overlaying skin (Dorsal Ramus) * superficial back muscles to limbs, body wall, etc.

Question 37

What is the IVF

Answer 37

Intervertebral foramen, an opening for a spinal nerve

Question 38

How many cervical vertebrae and nerves are there

Answer 38

* 7 cervical vertebrae * 8 cervical nerves NB: Up through nerve 7 are named for vertebrae below them; nerve 8 and onward are named for the vertebrae below

Question 39

At which vertebral levels does the spinal cord end

Answer 39

* L1-L2 marks vertebral end of spinal cord * spine continues to grow after birth * roots get progressively longer as you go down spinal cord to stay connected to IVF (exit door) * Cord does not get longer, roots get longer

Question 40

Name the labeled parts of this card

Answer 40

A. conus medullaris B. Cauda equina C. filum terminale (unpaired, not nervous tissue just connective tissue)

Question 41

What are the three layers of meninges (membranes that envelop the CNS), from inner to outer

Answer 41

* form a **P.A.D.** over spinal cord * Pia Mater (tender mother) * Arachnoid Mater (spider mother) * Dura Mater (hard mother)

Question 42

Name the labeled parts of this card

Answer 42

Meninges (membranes that envelop CNS) A. Pia Mater B. Arachnoid Mater C. Dura Mater P. A. D.

Question 43

What is between arachnoid mater and pia mater

Answer 43

subarachnoid space, which contains CSF ## Footnote

Question 44

Dura Mater

Answer 44

Dura Mater surrounds spinal nerve/roots, eventually becomes part of epineurium of nerves

Question 45

What is the filum terminale made of

Answer 45

Pia Mater

Question 46

Epidural space

Answer 46

outside the dura mater (extradural); location for anesthesia placement

Question 47

subarachnoid space

Answer 47

* lumbar cistern * between arachnoid and pia layers * space is LARGE around cauda equina * location for withdrawing CSF or placing spinal block anesthesia

Question 48

lumbar cistern

Answer 48

* another word for subarachnoid space * between pia and arachnoid layers * location for withdrawing CSF or placing spinal block anesthesia

Question 49

Where do you do a lumbar puncture (draw CSF) and why

Answer 49

* below L2, because that's where spinal cord ends * L3-L4 is best * subarachnoid space (lumbar cistern) is largest in region below terminal end of spinal cord * subarachnoid space surrounding cauda equina * can draw CSF without touching cord

Question 50

What are the somas and axons/fibers of the CNS called

Answer 50

nuclei and tracts

Question 51

What are the somas and axons/fibers of the PNS called

Answer 51

ganglia and nerves

Question 52

Which fibers are sensory

Answer 52

Afferent fibers

Question 53

Which fibers are motor

Answer 53

Efferent fibers

Question 54

Where are afferent fibers found

Answer 54

Doral Roots ("pure")

Question 55

Where are efferent fibers found

Answer 55

Ventral Roots ("pure")

Question 56

Find the following structures: ## Footnote 1. Dorsal Root Ganglion (DRG) 2. Ventral Root 3. Dorsal Ramus 4. Ventral Ramus

Answer 56