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MD4001 > Neuroanatomy Revision > Flashcards

Neuroanatomy Revision Flashcards

1
Q

Describe organisation of the spinal cord.

A

Gray Matter – H-shaped, contains neuron cell bodies
within ‘horns’
dorsal/posterior horns ➡ cell bodies of interneurons
lateral horns ➡ visceral (autonomic) motor cell bodies (T1-L2 segments)
ventral/anterior horns ➡ somatic motor cell bodies

White Matter – columns containing a number of ascending and descending tracts (axons). All tracts are paired and most decussate.
• Ventral (anterior) columns
• Lateral columns
• Dorsal (posterior) columns

Anterior Median Fissure

Posterior Median Sulcus

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2
Q

Draw a transverse section of the spinal cord.

A

Refer to slide 4.

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3
Q

Describe the organisation of spinal nerves.

A

Spinal nerves initially arise from the spinal cord as rootlets ; the rootlets converge to form two nerve roots

1) Anterior (ventral) nerve root, consisting of motor (efferent) fibers passing from nerve cell bodies in the anterior horn of spinal cord gray matter to effector organs located peripherally (sympathetic fibers of the spinal nerve may synapse in a sympathetic ganglion before becoming rami)
2) Posterior (dorsal) nerve root, consisting of sensory (afferent) fibers from cell bodies in the spinal (sensory) or posterior (dorsal) root ganglion that extend peripherally to sensory endings and centrally to the posterior horn of spinal cord gray matter.

The posterior and anterior nerve roots unite, within or just proximal to the intervertebral foramen, to form a mixed (both motor and sensory) spinal nerve, which immediately divides into two rami: a posterior (dorsal) ramus and an anterior (ventral) ramus. As branches of the mixed spinal nerve, the posterior and anterior rami carry both motor and sensory fibers, as do all their subsequent branches.

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4
Q

Draw a spinal nerve, including all different fibers, and their location in the spinal cord.

A

Refer to slide 5.

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5
Q

What is the function of ramus communicans ?

A

Communicating branch between a spinal nerve and the sympathetic trunk (includes grey and white ramus communicans)

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6
Q

How many cervical vertebrae ? How many cervical spinal nerves ? What is the anatomical relation between cervical vertebrae and cervical spinal nerves ?

A
  • 7 cervical vertebra but 8 cervical spinal nerves
  • C1 nerve
    • Passes above C1 vertebra
    • Motor only; no sensory fibres
  • C8 nerve passes between C7 and T1 vertebrae
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7
Q

What level does the spinal cord end at ?

A

Spinal cord ends between L1/2 (cauda equina, bundle of spinal nerve roots arising inferior to the L1 vertebra, that descend past the termination of the spinal cord)

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8
Q

What happens upon compression of cauda equina (below L2) ?

A

E.g. if tumour compresses cauda equina, cauda equina syndrome (“lower back pain, pain that radiates down the leg, numbness around the anus, and loss of bowel or bladder control”)

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9
Q

To what extent do the thoracic spinal nerves contribute to plexuses ?

A

T1 contributes to brachial plexus

T2 through T12 retain their segmental organisation and do not contribute to plexuses

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10
Q

Describe the general organisation of the autonomic NS in the body.

A

Distributed in whole body

Sympathetic system
• Cell bodies in lateral horn of T1-L2 segments
• Postganglionic cell bodies lie in paravertebral sympathetic ganglia
• Ganglia interconnected ➡ Sympathetic chain
• Each sympathetic trunk (chain) extends between the atlas and coccyx
• Number of paravertebral sympathetic ganglia

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11
Q

Identify the four different routes taken by sympathetic axons traveling from the CNS, to their effectors.

A
  1. Enters cervical sympathetic ganglion higher up (SYNAPSES) then post-ganglionic axons pass in GRC and join cervical spinal nerves, which then has effectors in head and neck
  2. Enters sympathetic ganglion at same level (SYNAPSES), then post-ganglionic axons (unmyelinated, grey) pass in GRC and passes back into T1-L2 spinal nerve into periphery (sweat glands, smooth muscle) OR Enters sympathetic ganglion at same level, (SYNAPSES) and leaves into its own little nerve to influence viscera at that same level.
  3. Enters sympathetic chain (WITHOUT SYNAPSING) then descend into sympathetic ganglion (SYNAPSES ) (e.g. in sacral region) then passes back into a spinal nerve and then head off down to lower limbs.
  4. Enters sympathetic chain (WITHOUT SYNAPSING) passes out the front of sympathetic chain (still as pre-ganglionic neuron) then head to pre-vertebral ganglia (through splachnic nerve) in the abdomen. (SYNAPSES) then heads out to influence the gut.
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12
Q

Identify the main receptors used in the ANS, and state whaat each is used for.

A

When going from brainstem/spinal cord to end organ, autonomic NS uses at least two neurons (pre and post-synaptic):

In both SNS and PSNS, pre-ganglionic fiber releases ACh which binds to nicotinic ACh receptor.

PSNS post-ganglionic fibers release ACh as neurotransmittter, which binds to muscarinic ACh receptor.

SNS post-ganglionic fibers release noradrenaline, which binds to adinergic receptors.

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13
Q

How many neurons are there in the somatic NS, from spinal cord, to effector organ.

A

Only one (no pre- and post- synaptic)

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14
Q

Identify the main actions of the ANS.

A

SNS:

  • Increased PB
  • Increase PR
  • Relax bronchioles
  • Dilates pupils
  • Relax uterine muscles

PSNS:
Opposite of ^
-Increase peristalsis

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15
Q

Identify examples of autonomic medications.

A
  • Atropine (cholinergic antagonist, prevents cardiac slowing, dilates bronchi)
  • Cholinergic agonists
  • Epinephrine (adrenergic agonist, used for cardiac arrest, heart block, anaphylactic shock)
  • Alpha receptor agonists and antagonists
  • Beta agonists and antagonists
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16
Q

Describe organisation of spinal cord, and the way it changes as it becomes brainstem.

A

Somatic sensory grey matter towards dorsal horn
Somatic motor grey matter towards ventral horn
Autonomic grey matter between the two (sensory more posterior)

Somatic neurons are on the ends and between these two are the visceral neurons

Most posterior: somatic sensory grey matter
Then: visceral sensory
Then: visceral motor in lateral hor
Then: somatic motor in anterior horn

When go up to brainstem, retain organisation (nuclei order remains the same), but grey matter opens up dorsally, and becomes more horizontal c.f. more vertical in the spinal cord (i.e. nuclei spread out), meaning somatic motor is medial and somatic sensory is lateral (whilst autonomic sensory and motor are in between)

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17
Q

If there is some damage to the spinal cord in the midline of spinal cord or brainstem, which kinds of neurons will be affected ?

A

Somatic motor neurons (When examining patient, notice something wrong with motor system but not sensory, probably something in the midline not in periphery of spinal cord or brainstem)

18
Q

Identify ways in which peripheral nerves may be impaired ?

A

Compression

Trauma Disease

19
Q

How can we test L3/4? L5? S1?

A

L3/4: Knee reflex
L5: None, so test it by asking patient to extent big toe against resistance
S1: Ankle reflex

20
Q

Explain the coverings of the spinal cord, including the spaces present.

A
  • Bathed in CSF
  • Covered by three layers of membranes, the meninges:
  • Dura (outermost, tough, unyielding)
  • Arachnoid mater
  • Pia mater (transparent, goes into every gyrus and sulcus, contains capillaries so nourishes CNS)

• Subarachnoid space between pia and arachnoid mater (contains CSF)
Subdural space between arachnoid and dura, subdural space
Epidural space outside the dura

21
Q

Describe the arterial supply of the spinal cord.

A

1) Paired posterior spinal arteries
• from the vertebral artery or the posterior inferior cerebellar artery

2) Single anterior spinal artery
• formed from a contributory branch from each vertebral artery

3) Aorta ➡ intercostal arteries ➡ Segmental spinal arteries (feeder arteries) ➡ radicular arteries reinforce anterior and posterior spinal arteries

4) The great anterior medullary artery of Adamkiewicz arises from the aorta in the lower thoracic or upper lumbar vertebral levels
• it may be the major source of blood to the lower two- thirds of the spinal cord

22
Q

Describe veinous drainage of the spinal cord.

A

• Internal vertebral venous plexus (Anterior and posterior)

  • Lies in the epidural/extradural space (between the dura and vertebrae)
  • Do not have valves and pressure gradients permit blood flow
  • Communicates with cranial dural venous sinuses and pelvic veins ➡ Infection and metastasis spread
23
Q

Identify possible pathologies affecting the spinal cord.

A

Disk herniation (posteriorly or postero-laterally) compressing spinal nerve roots

Osteophytes may also “poke” spinal nerve roots

24
Q

Describe the main white matter tracts in the spinal cord.

A

Columns are formed by axons with similar functions. These axons form fascicles/tracts.

DORSAL COLUMN
1) Fasciculus gracilis
Sensory (fine touch, vibration, proprioception) from ipsilateral lower limb
2) Fasciculus cuneatus
Sensory (fine touch, vibration, proprioception) from ipsilateral upper limb

LATERAL COLUMN

1) Spinocerebellar tract (proprioception from limbs to cerebellum)
2) Lateral corticospinal tract (motor to ipsilateral anterior horn (mostly limb musculature))
3) Spinothalamic tract (pain and temperature from contralateral side of the body)

VENTRAL COLUMN?
1) Anterior corticospinal (motor to ipsi- and contralateral anterior horn, mostly axial musculature)

25
Q

What is the underlying mechanisms which would allow the burn reflex response to be modified so a man can fire-walk?

A

Peripheral extension of sensory nerve pick up heat, and travel to dorsal horn of spinal cord. There, first order sensory neuron synapses with second order sensory neuron

Axon of second order sensory neurons will cross midline and go to the lateral column, then join lateral spinothalamic tract
(but not synapse) and ascend to the thalamus.

In thalamus (specifically in ventral posterolateral nucleus), synapses with third order sensory neuron, which will travel to primary somatosensory cortex

Somatosensory cortex talks with motor cortex, and tells it to keep walking/stand still (to prevent reflex). Neurons in the motor cotex will then go to muscles. Alternatively, the somatosensory cortex tells the motor reflex to enact withdrawal reflex (what normally happens)

26
Q

How can we if dorsal column is working ?

A

Test JPS (exclusive to dorsal column)

27
Q

What is the significance of the anterior white commissure ?

A

Pain and temperature fibers cross. Anterior corticospinal tract fibers cross.

28
Q

Which senses join the thalamus prior to the cortex ? Which do not ?

A

All senses except olfaction go to thalamus before going to cortex. Olfaction goes to cortex first, then to the thalamus.

29
Q

Briefly describe the organisation of motor pathways.

A

• Upper motor neuron (UMN)
- Neuron bodies in the
cortex
- Most of the axons cross over in lower medulla (hence R cortex controls L side muscles)
- Descend in the lateral column as lateral corticospinal tract
- Synapse with LMN in the anterior horn

• Lower motor neuron (LMN)
- Neuron bodies in the anterior horn

30
Q

Describe the main features of Upper Motor Neuron Lesions, and Lower Motor Neuron Lesions.

A

UPPER MOTOR NEURON
• Hypertonia (spacticity)
• Hypereflexia (Typical appearance is flexed elbow, bent wrist, clenched fist)
• Abnormal reflex (Positive Babinski sign unless younger than 6 months old)
• No fasciculations
• No atrophy
• Weakness (in the distribution of hemiplagic gait with arm flexed and leg extended)

LOWER MOTOR NEURON 
• Hypotonia/Flaccidity
• Hyporeflexia/areflexia
• No Babinski reflex
• Fasciculations
• Atrophy/wasting of muscles
• Weakness (proximal AKA myopathy, distal AKA neuropathy)
31
Q

Identify and briefly describe the main components of the ventricular system.

A

4 ventricles

  • Lateral ventricles in hemisphere
  • 3rd in thalamus
  • 4th between cerebellum and brainstem

Contains CSF (produced by choroid plexus, found in all ventricles)

32
Q

Describe the path of the CSF in the brain.

A

Produced by choroid plexus in all ventricles, then passes into ventricles from one to other (from lateral ventricles to third through interventricular foramina, then to fourth through cerebral aqueduct). In fourth ventricle, passes into subarachnoid space through lateral and median apertures. From here, ascends and is absorbed by arachnoid granulations, to the dural sinuses. From here, veinous blood will go into internal jugular, and to the heart, then back in arterial blood into all ventricles’ choroid plexuses.

33
Q

Describe the pathological effect of blocking the path of CSF in the brain.

A

Increased Intracranial Pressure

34
Q

What is the function of peripheral nerves ?

A

Peripheral nerves: Link central nervous system to peripheral tissue

35
Q

What are cranial nerves ? Are they part of the PNS or CNS ?

A

“Arise in pairs from the brainstem and reach the periphery through openings in the skull. There are 12 such pairs. Hence part of peripheral NS, except optic nerve”

36
Q

Describe arterial supply of the brain.

A

4 vessels supply brain:

  • Anterior circulation: internal carotid arteries
  • Posterior circulation: vertebral arteries

Branches of these arteries will form circle of Willis, which will supply the brain.

37
Q

Describe veinous drainage of the brain.

A

Dural Sinuses (between meningeal and periostal layers of dura) into internal jugular, into heart

38
Q

Give examples of UMN lesions, and LMN lesions.

A

UMN Lesion:

  • Cerebral infraction
  • Corticospinal tract lesion

LMN Lesion:

  • Peripheral nerve lesion
  • Lesion at nerve root
39
Q

Define positive Babinski reflex.

A

“Extension of the great toe and abduction of the other toes instead of the normal flexion reflex to plantar stimulation, considered indicative of corticospinal tract involvement “

40
Q

Describe the typical pattern of weakness associated with UMN lesions.

A

Quadriplegia, hemiplegia, triplegia, paraplegia all possible

  • Arm bent and spastic/floppy hand (flexors stronger than extensors in arm)
  • Extended LLs (extensors stronger than flexors in leg), including walking on tiptoes or outside of foot on affected side

MD4001 (74 decks)

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