Peripheral + Autonomic Nervous System

Question 1

Define Peripheral Nervous System (PNS)

Answer 1

motor and sensory nerves extending from spinal cord

Question 2

Define Autonomic Nervous System (ANS)

Answer 2

homeostatic coordinating system
Central and peripheral components

Question 3

Spinal Cord Structure

Answer 3

Question 4

spinal cord and roots

Answer 4

Question 5

Total number of roots/levels? And their breakdown?

Answer 5

31 total
8 cervical (7 vertebrae)
12 thoracic
5 lumbar
5 sacral
1 coccygeal

Question 6

How are cervical roots named?

Answer 6

are located above (rostral to) their respectively numbered vertebare.
C1 is above the C1 vertebra
C8 is between C7 and T1

Question 7

How are the rest of the spinal cord roots named?

Answer 7

after C, all roots are exit below their respectively numbered vertebrae

Question 8

White Matter Motor

Answer 8

Anterior funiculus
– Anterior corticospinal tract (90% cross)
– Reticulospinal and vestibulospinal fibers
• Lateral funiculus
– Lateral corticospinal tract (90%, cross)
– Organization: Sacral (LE, leg) Cervical (UE, arm) as you go from Lateral Medial

Question 9

White matter sensory

Answer 9

• Posterior funiculus = “posterior (dorsal) column”
– Gracile (T7 and below) and cuneate (T6 and above) fasciculi
– Organization: Sacral Cervical as you go from Medial Lateral
• Lateral funiculus
– Anterolateral system (spinothalamic tract)
– Organization: Sacral Cervical as you go from Lateral Medial

Question 10

Grey Matter

Answer 10

• Composed of:
– neuronal cell bodies + their dendrites
– axon terminals of synapsing fibers
– glial cells
• Rexed laminae I to IX

Question 11

how is grey matter organized?

Answer 11

Posterior (dorsal) horn – laminae
I to VI
– Intermediate grey – lamina VII
– Anterior (ventral) horn – laminae
VIII to IX

Topographic
arrangement of
motor neurons in
the anterior horn

Question 12

Where are motor efferents found?

Answer 12

Cell bodies =
anterior/ventral horn
(spinal gray matter)
• Innervate
– Visceral structures (smooth
muscle, cardiac muscle,
glandular) via synapse in
autonomic ganglion -
visceral motor (VM)
– Muscle - somatic motor
(SM)

Question 13

Functional components of sensory/visceral tracts (afferents)

Answer 13

Cell bodies = posterior (dorsal)
root ganglia
• Convey sensation from:
– Body surface and
Muscle/tendon/joint - somatic
afferent (SS)
– Internal organs (smooth muscle,
cardiac muscle, glands) -
visceral afferent (VS)

Question 14

spinal reflexes require what?

Answer 14

Reflexes require:
– Sensory (afferent) fibers
– interneurons and/or motor (efferent) neurons
– target tissue, usually skeletal muscle
• Intra-segmental – relatively simple, confined to a single cord level
• Inter-segmental – more complex, involving multiple cord segments

Question 15

Muscle Stretch Reflex

Answer 15

Monosynaptic Reflex
– Requires 1 synapse in response to
stretch of a muscle spindle
– Elicited by tapping any large tendon
• Example: “knee jerk” or quadriceps
stretch reflex
– Afferent: muscle spindle + sensory
nerve (myelinated, group Ia fibers),
originate in the patellar tendon
– Efferent: Motor neurons
– Target : Quadriceps femoris

can also be reciprocally inhibited

Question 16

reciprocal inhibition of muscle stretch reflex

Answer 16

Question 17

Autonomic nervous sytem overview

Answer 17

Regulates homeostatic functions
– Involuntary, reflexive
– CNS control centers in: limbic system, hypothalamus, brainstem
– Neural control of smooth muscle, cardiac muscle, or glandular secretory cells
• regulates cardiovascular, respiratory, digestive, urinary, integumentary, and reproductive organs
•

Question 18

key difference between somatic / autonomic?

Answer 18

The peripheral visceral motor pathway consists of 2 neurons
(rather than 1)

Question 19

Sympathetic outflow

Answer 19

Originates from T1 through L2.
– ‘Thoracolumbar’ system
– Viscerotopic organization

activation: widespread/diffuse. fight or flight

Question 20

parasympathetic outflow

Answer 20

Cranial nerves III, VII, IX, X and sacral rootsS2 to S4
– ‘Craniosacral’ system

Question 21

Answer 21

1st synapse (preganglionic neuron to postganglionic neuron) is mediated by nicotinic receptors, activated by acetylcholine.
• 2nd synapse (target of postganglionic neuron) is mediated by adrenergic receptors, activated by norepinephrine or epinepherine.
• Exception: sweat glands, which receive sympathetic innervation but have muscarinic acetylcholine receptors

Question 22

Answer 22

Question 23

digestion q

Answer 23

Basic reflexive functions:
– Secretion, absorption, and mixing and movement of
contents
– Intrinsic rhythmic activity
(interstitial cells)
– Peristaltic reflex: sensory
neurons, motor neurons, and
several types of interneurons
– CNS influence over activities via sympathetic/para-sympathetic pathways
• Enteric neurons distributed within the myenteric and sub-mucosal plexuses

Question 24

Answer 24

Example of an inter-segmental reflex
• Initiated by painful (nociceptive) input
– protect body part by removing it from source of injury
• Lightly myelinated/unmyelinated sensory fibers posterolateral tract (of Lissauer), ascend/descend spinal gray to excite:
– 1) ascending tract cells to higher centers (“OUCH!”)
– 2) interneurons activate flexor motor neurons
• Enhanced by:
– inhibition of ipsilateral extensors

Question 25

Answer 25

Withdrawal Reflex enhanced
by:
– activation of contralateral
extensors
– inhibition of contralateral
flexors
• Conveyed via interneurons
that project to the
contralateral anterior horn 
excite contralateral extensor
muscles and inhibiting
contralateral flexor muscles

Question 26

Divisions of Autonomic Nervous System

Answer 26

– Sympathetic nervous system (“fight or flight”)

-Parasympathetic nervous system (“rest and digest”)

– Enteric nervous system (circuitry in the organ; does not involve spinal cord)

Question 27

Sympathetic Nervous System

Answer 27

– global/diffuse distribution
• Body cavities: Viscera
• Body wall/limbs: skeletal muscle (blood vessels) and in the skin (blood vessels, sweat glands, and arrector pili muscles)

Question 28

Parasympathetic Nervous System

Answer 28

– targeted to head and viscera
• Generally antagonistic influences on viscera (opposite of sympathetic influence)

Question 29

Ganglia of CN III, which receives parasympathetic outflow

Answer 29

– Ciliary: CN III (oculomotor) nerve > Edinger Westphal nucleus

Question 30

Ganglia of CN VII, which receives parasympathetic outflow

Answer 30

– Pterygopalatine (sphenopalatine): CN VII (facial) nerve > Superior Salivatory/Lacrimal nucleus
– Submandibular: CN VII (facial) nerve > Superior Salivary Nucleus

Question 31

Ganglia of CN IX, which receives parasympathetic outflow

Answer 31

– Otic: CN IX (glossopharyngeal) nerve > Inferior salivatory nucleus

Question 32

Ganglia of CN X, which receives parasympathetic outflow

Answer 32

• Dorsal motor vagal nucleus/nucleus ambiguus (brainstem): Vagus (CN X)

Question 33

Ganglia of S2-S4, which receive parasympathetic outflow

Answer 33

• Sacral cord (levels S2 to S4):
– sacral parasympathetic nucleus > pelvic nerves > visceral plexus (urinary bladder, urethra, and reproductive organs)
• Activation – targeted (“rest and digest”)

Question 34

hypothalamic nuclei project directly to preganglionic
visceral motor neurons in the… (three areas)

Answer 34

dorsal vagal nucleus,
nucleus ambiguus, and intermediolateral cell column

Question 35

what anchors the dural sac to coccyx?

Answer 35

filum terminale externum

Question 36

Conus medullaris

Answer 36

(L1-2) = end of cord

Question 37

• Cauda equina

Answer 37

(L2-Coc1) = roots

Question 38

Answer 38