Week 1 - B - Anatomy 1 - Craig - PNS revision

Question 1

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

Answer 1

In the CNS a collection of nerve cell bodies is known as a nucleus In the PNS it is known as a ganglion

Question 2

What are the processes that extend from the cell body of a neuron and increase the surface area of the body known as?

Answer 2

These are dendrites - – they essentially make connections with surroung neurones and increase the surface area fo the cell body

Question 3

The axon coming from the cell body is wrapped in a myelin sheath What produces myelin in both the PNS and CNS? and what is the function of myelin?

Answer 3

Oligodendrocytes produce myelin in the CNS Schwann cells produce myelin in the PNS Myelin function is to increase the speed of nerve impulses along the axon

Question 4

Oligodendrocytes are one of the four types of glial cell in the CNS What are the four types and state their function?

Answer 4

Astrocyte - important for maintaining the blood brain barrier and maintaining homeostasis Oligodendrocyte - produces myelin Microglia - main immune surveillance cell and an antigen presenting cell (APC) Ependymal cells - line the ventricles ( The choroid plexus consists of modified ependymal cells)

Question 5

The two main types of neuron are multipolar and unipolar What is the difference in the structue/location of the types of neuron and their modality?

Answer 5

Multipolar - 2 or more dendritic process with cell body located in the CNS and the axons crosses into the PNS Provides motor supply to all motor neurones of ANS and skeletal muscle Unipolar - the cell body is located in PNS & axons connect to the brain ie dorsal root ganglion of spinal column is in PNS

Question 6

What is the difference between efferent and afferent?

Answer 6

Efferent - the impulses move towards body structure or organ away from the brain Afferent - the impulses move towards the brain

Question 7

Collections of axons surrounded by connective tissue and blood vessels What are these known as in the PNS?

Answer 7

These are known as tracts

Question 8

Nerves are either a single modality ie somatic motor, somatic sensory, special sensory, sympathetic, parasympathetic or visceral afferent or mixed modality Are the cranial nerves or spinal nerves all mixed modality?

Answer 8

The spinal nerves are all mixed modality

Question 9

Need to know the name modality and function of all 12 cranial nerves Firstly list all 12, their modality and their foramen

Answer 9

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Question 10

What is the function of the first two cranial nerves and where do they arise?

Answer 10

Olfactory sense of smell arising in the forebrain - can see olfactory tracts Optic is for sight arising in the forebrain

Question 11

What muscles are supplied by the oculomotor and trochlear? Where do these nerves arise?

Answer 11

Oculomtor - supplies the extra-ocular eye muscles & parasympathetics to the sphincter pupillae causing constriction of pupil Oculomotor nerve arises at the midbrain anteriorly Trochlear - supplies superior oblique muscle of eye -moves eye down& out - arises at the midbrain laterally- very thin nerve

Question 12

Trigeminal nerve provides motor supply to what and has sensory from where? Where does it arise?

Answer 12

Motor supply to the muscles of mastication Provides sensation to the face Arises at the pons - only nerve to arise at pons - big thick nerve

Question 13

What is the function of CN VI and CN VII? Where do they arise

Answer 13

Abducent nerve - innervates the lateral rectus muscle to abduct it Arises at the pontomedullary junction at the front of the pons Facial nerve - innervates muscles of facial expression& the anterior 2/3rds of the tongue with taste & parasympathetic to submandibular &sublingual salivary glands Arises at the lateral aspect of pons- pontomedullary junction

Question 14

What is the function of CN8 and where does it arise?

Answer 14

Arises at the pontomedullary junction and special sense of hearing

Question 15

What is the function of CN IX and CN X? Where do they arise?

Answer 15

Glossopharngeal - supplies motor innervtaion to pharynx and parasympathetic to parotid gland Vagus nerve provides whole of GI tract Both arise at the medulla

Question 16

Where do CN XI and CN XII arise and innervate?

Answer 16

Spinal accessory - innervates sternocleidomastoid and trapezium - arises at base of medulla Hypoglassoal innervate extrinsic tongue muscles - arises at middle of medulla

Question 17

Which cranial nerves arise in forebrain? Which arises anterior to midbrain? Which arises at pons? Whcih arise at ponto medullary junction?

Answer 17

Forebrain - olfactory and optic Midbrain anteriorly - oculomtor Pons - trigeminal Ponto-medullary junction - Facial and Vestibulocochlear

Question 18

How many spinal nerves are there and where are the spinal nerves found?

Answer 18

There are 31 spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal There are found in the intervertebral foramen

Question 19

How are the anterior and posterior rami formed?

Answer 19

Anteiro/posterior rootlets join to form troots The anterior and posterior roots then join to form a spinal nerve at the intervertebral foramen and this splits to form the anterior and posterior rami

Question 20

Once all sensory axons have reached the spinal nerve, where do they go? Where do all motor axons come from to reach the spinal nerve?

Answer 20

ALL sensory axons pass from the spinal nerve into the posterior root then into the posterior rootlets then into the posterior horn of the spinal cord ALL motor axons pass from the anterior horn of the spinal cord into the anterior rootlets then into the anterior root then into the spinal nerve

Question 21

Is the spinal nerve single or mixed modality?

Answer 21

The spinal nerve is mixed modality as it contains sensory and motor axons

Question 22

What is the difference between a dermatome and a myotome?

Answer 22

A dermatome is the area of skin supplied with sensory innervation from a single spinal nerve A myotome is the skeletal muscle supplied with motor innervation from a single spinal nerve

Question 23

Generally speaking the myotome is deep to the dermatome of the same spinal nerve Give an example of where this is not the case?

Answer 23

The muscle fibres of the diaphragm are supplied by spinal nerves C3,4and 5 where as the dermatome supplied by these spinal nerves relates to the neck/arm

Question 24

Dermatome maps have been developed to show the segmental cutaneous innervation of the body What is the dermatomal innveration of the: Male nipple, umbilicus, thumb, middle finger, pinky?

Answer 24

Male nipple - T4 Umbilicus - T10 Thumb - C6 (and index finger) Middle finger - C7 Pinky - C8 (and ring finger)

Question 25

What is the dermatomal cutaneous innervation of the posterior scalp and shoulder?

Answer 25

C2-C4

Question 26

What is anerve plexus?

Answer 26

This is the intertwining anterior rami from adjacent spinal nerves

Question 27

What are the 4 nerve plexuses and what is there region of innervation?

Answer 27

Cervical plexus (C1-C4) - posterior scalp, nec and diaphragm Brachial plexus (C5-T1) - upper limb Lumbar plexus (L1-L4) - lower limb Sacral plexus (S2-S4) - Lower limb, gluteal region and perineum

Question 28

Peripheral cutaneous nerve innervation refers to the area of the skin which is supplied by a specific cutaneous nerve. Dermatomes are similar; however a dermatome only specifies the area served by a spinal nerve. What nerve supplies the anatomical snuffbox and which supplies the 1st web space of the feet?

Answer 28

Anatomical snuffbox = radial nerve 1st web space of feet = deep fibular nerve (L5)

Question 29

Sympathetic outflow originates from control centres in the brain What type of outflow is sympathetics referred to as and what level does it exit the spinal cord?

Answer 29

Referred to as thoracolumbar outflow and exits the spinal cord at T1 to L2 The sympathetic chain however spans the length of the vertebral column

Question 30

What segment of the spinal cord contains lateral horns and why?

Answer 30

T1 to L2 segement of the spinal cord contains lateral horns This is to store the sympathetic neurone cell bodies for sympathetic outflow

Question 31

The presynapcitc sympathetic axons leaves spinal cord in anterior rootlets and then travels via the anterioer ramus where it travels via the what to join with the paravertebral (sympathetic) ganglion?

Answer 31

Travels via the rami communicans to join with the paravertebral ganglion

Question 32

When the sympathetics is supplying the body wall, what happens to the nerve fibres now they have synapse in the paravertebral ganglion?

Answer 32

They travel back along a different rami communicans and into the posterior ganglion to supply the body wall with sympathetic innervation

Question 33

What rami communicans contains the presynaptic sympathetic fibres and which contains the postsynaptic?

Answer 33

White rami communicans allows presynaptic sympathetic fibres in to the ganglion carries from anterior ramus to ganglion Grey rami communicans allows postsynapctic sympathetic fibres to the posterior rami carries from ganglion to posterior ramus

Question 34

There are 4 exceptions to the sympathetic outflow This being sympathetic supply to the heart, lungs, abdominopelvic organs and the adrenal medulla For the heart and lungs, where to the presynaptic fibres synapse and where do the postsynaptic fibres pass into?

Answer 34

Presynaptic fibres synapse in the cervical and upper thoracic paravertebral ganglia and pass in cardiopulmonary splanchnic nerves

Question 35

Where do the abdominopelvic presynaptic axons synapse?

Answer 35

They synapse in the prevertebral ganglia therefore passing through the paravertebral ganglia

Question 36

Where do the adrenal medulla presynaptic fibres synapse?

Answer 36

They pass directly through the aorticorenal ganglion (one of the prevertebral ganglion) and synapse directly on the adrenaline/noradrenaline secreting cells of the adrenal medulla

Question 37

Presynaptic parasympathetic axons leave the CNS via: cranial nerves III, VII, IX & X sacral spinal nerves What are the four ganglion in the head?

Answer 37

CN III - ciliary ganglion for the eye CN VII - Pterygopalatine ganglion - lacrimal gland Submandibular ganglion - sublingual and submandibular glands CN IX - otic ganglion - parotid gland

Question 38

Why does the vagus nerve have such long presynaptic fibres?

Answer 38

The is because the fibres synapse almost directly onto the organs of which it supplies

Question 39

miosis ptosis reduced sweating (anhydrosis) increased warmth and redness What is this?

Answer 39

Horner's syndrome Miosis - excessive constriction of pupil Ptosis - drooping eyelid

Question 40

Why do miosis and ptosis occur in horner's syndrome?

Answer 40

Misos -constriction occurs as the parasympathetic supply to the constrictor pupillae is now unopposed by the lack of sympathetics to the dilator pupillae Ptosis - drooping of the eyelid occurs as the smooth muscle supplied by the sympathetics in the eyelid (fuses with the levator palpebrae superiorirs) doesnt have a supply and there the eyelid droops Muscle is known as the superior tarsal muscle