PNS Revision

Question 1

what is a collection of nerve cell bodies known as in the CNS and PNS?

Answer 1

CNS = nucleus
PNS = ganglion

Question 2

dendrites vs axon?

Answer 2

dendrites = carry info towards the cell body
axon = carries info away from the cell body, much longer

Question 3

what does an axon connect to?

Answer 3

another neuron or an effector cell

Question 4

Multipolar neuron?

Answer 4

• most common
• 2 or more dendrites
• all motor neurones of skeletal muscle and ANS
• cell body in CNS, axon in PNS

Question 5

Unipolar neuron?

Answer 5

double process (aka pseudounipolar as technically have 2 processes but connect to a single point)
involved in sensory function
cell body in PNS

Question 6

describe motor neurones?

Answer 6

efferent
impulse moves towards body wall, body cavity or organ
multipolar neuron

Question 7

describe sensory neurone?

Answer 7

afferent
impulses moves towards the brain
unipolar

Question 8

what are nerves?

Answer 8

collections of axons surrounded by connective tissue and blood vessels (called a tract in CNS)

Question 9

single modality nerve?

Answer 9

all axons in the nerve carry the same one of - somatic motor, somatic sensory, special sensory, sympathetic, parasympathetic or visceral afferent
“tracts” in CNS tend to be single modality

Question 10

mixed modality nerves?

Answer 10

somatic motor, somatic sensory and sympathetic all together in one nerve
(most nerves)

Question 11

12 cranial nerves?

Answer 11

ophthalmic
optic
oculomotor
trochlear
trigeminal
abducens
facial
vestibulocochlear
glossopharyngeal
vagus
spinal accessory
hypoglossal

Question 12

cranial nerve modalities?

Answer 12

sensory
sensory
motor
motor
both
motor
both
sensory
both
both
motor
motor

Question 13

where do the cranial nerves attach to the CNS?

Answer 13

forebrain
forebrain
midbrain
midbrain
pons
junction (P&Med)
junction (P&Med)
junction (P&Med)
medulla
medulla
spinal cord
medulla

Question 14

in which direction are the cranial nerves named?

Answer 14

anterior to posterior and medial to lateral

Question 15

what are the categories of spinal nerves?

Answer 15

8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

Question 16

where are the spinal nerves found?

Answer 16

only called a spinal nerve when in the intervertebral foramina

Question 17

what do spinal nerves connect with?

Answer 17

structures of the soma via rami

the spinal cord segment of the same number via roots and rootlets

Question 18

formation and divisions of spinal nerves?

Answer 18

anterior/posterior rootlets combine to form anterior/posterior roots
anterior/posterior roots combine to form the spinal nerve
spinal nerve then splits into anterior (large) and posterior (smaller) rami

Question 19

what does the posterior rami supply?

Answer 19

posterior body wall

Question 20

what does the anterior rami supply?

Answer 20

anterolateral body wall

Question 21

spinal nerves/rami vs roots/rootlets?

Answer 21

roots/rootlets = only have one type of modality (anterior = motor, posterior = sensory)
spinal nerves/rami = all have mixed modality (somatic motor, somatic sensory and sympathetic innervation)

Question 22

what is the dorsal root ganglion?

Answer 22

swelling in posterior root where cell bodies of primary afferent neurones are found

Question 23

each spinal nerve pair supplies a body segment with what?

Answer 23

general sensory supply to all structures
somatic motor supply to skeletal muscles
sympathetic nerve supply to the skin and to the smooth muscle of arteries

Question 24

what is a dermatome?

Answer 24

area of skin supplied with sensory innervation from a single spinal nerve which also supplies sensory innervation to deeper structures

Question 25

is there any overlap in the sensory innervation of the skin of a dermatome?

Answer 25

yes innervation of skin is from adjacent spinal nerves | therefore if a dermatome is numb, more than one spinal nerve is damaged

Question 26

what is a myotome?

Answer 26

the skeletal muscles supplied with motor innervation from a single spinal nerve may be deep to the dermatome of the same spinal nerve, but not always (T2 - T12 tend to have the same dermatome/myotome)

Question 27

give an example of different dermatome/myotome?

Answer 27

C3,4,5 dermatome = shoulder and upper arm myotome = diaphragm

Question 28

dermatome landmarks?

Answer 28

``` nipple = T4 segment umbilicus = T10 ```

Question 29

dermatomes of posterior scalp, neck and shoulder?

Answer 29

C2-4

Question 30

upper limb dermatomes?

Answer 30

C5-T1

Question 31

lower limb, gluteal region and perineum dermatomes?

Answer 31

L2-Co1

Question 32

what are nerve plexuses formed of?

Answer 32

intermingled ANTERIOR rami from a number of adjacent spinal nerves

Question 33

what makes up the cervical plexus?

Answer 33

C1-C4 | posterior scalp, neck and diaphragm

Question 34

brachial plexus?

Answer 34

C5-T1 | upper limb

Question 35

lumbar plexus?

Answer 35

L1-L4 | lower limb

Question 36

sacral plexus?

Answer 36

L5-S4 | lower limb, gluteal region and perineum

Question 37

describe sympathetic outflow?

Answer 37

originates from control centres in the brain | passes down spinal cord and exits via T1 - L2

Question 38

why can sympathetic outflow only exit via T1 - L2?

Answer 38

only they have lateral horns which contain cell bodies with presynaptic sympathetic axons

Question 39

what is sympathetic innervation? what does this mean for outflow?

Answer 39

motor innervation | means it has to come from anterior roots/rootlets

Question 40

what are the 4 possible routes of exit from the spinal cord for sympathetic outflow?

Answer 40

1. ascend and then synapse Synapse at level of entry 3. Descend then synapse 4. Pass through sympathetic trunk without synapsing to enter an abdominopelvic splanchnic nerve

Question 41

sympathetic innervation is present in all spinal nerves, true or false?

Answer 41

true | just takes different routes to get into the nerves

Question 42

paravertebral ganglia?

Answer 42

sympathetic chain

Question 43

Sympathetic outflow to the heart?

Answer 43

presynaptic axons synapse in T1 or cervical paravertebral ganglia postsynaptic axons then pass in cardiopulmonary splanchnic nerves to the SA and AV nodes in myocardium

Question 44

lungs sympathetic outflow?

Answer 44

presynaptic axons synapse in upper thoracic paravertebral ganglia postsynaptic axons pass in cardiopulmonary splanchnic nerves to the bronchiolar smooth muscle and mucous glands

Question 45

abdominopelvic organs sympathetic outflow?

Answer 45

presynaptic axons synapse in one of the prevertebral ganglia (outside of the spinal column)

Question 46

adrenal medulla sympathetic outflow?

Answer 46

presynaptic axons pass through the aorticorenal ganglion to synapse directly onto the adrenaline/noradrenaline secreting cells of the adrenal medulla

Question 47

describe parasympathetic outflow?

Answer 47

presynaptic axons leave the CNS via cranial nerves 3, 7, 9, 10 and sacral spinal nerves then travel via: - ciliary ganglion (eye) - parasympathetic ganglia in head (lacrimal/salivary glands) - vagus nerve (organs between neck and mid-gut) - sacral spinal nerves (hind-gut to perineum)

Question 48

why do symptoms occur in horners syndrome?

Answer 48

no sympathetic innervation to the dilator pupillae = miosis no innervation to LPS = droopy eyelid (ptosis) no innervation to sweat glands = reduced sweating reduced innervation to arterioles = dilation = increased warmth and redness