Peripheral Nervous System Flashcards

1
Q

What are the basic units of the Nervous System?

A

Neurones

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2
Q

What produces the myelin sheath in the PNS?

A

Schwann cells.

(Oligodendrocytes in the CNS).

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3
Q

Describe a multipolar neuron.

A
  • 2 or more dendrites.
  • Majority of CNS neurones.
  • All the motor neurons of skeletal muscle and ANS.
  • Cell body found in the CNS.
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4
Q

Describe a unipolar neuron.

A
  • Double process.
  • Cell body found in the PNS.
  • AKA sensory / pseudounipolar.
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5
Q

Another way to describe an Efferent neuron?

A

Motor neuron.

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6
Q

The impulse of an efferent neuron moves towards?

A

The body wall, body cavity or organ.

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7
Q

The impulse of an afferent neuron moves towards?

A

The brain.

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8
Q

Another way to describe an Afferent neuron?

A

Sensory neuron.

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9
Q

What is a nerve?

A

Collection of axons surrounded by connective tissue and blood vessels.

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10
Q

Most nerves exist in which modality?

A

Mixed i.e. somatic motor, somatic sensory and sympathetic.

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11
Q

How many pairs of spinal nerves are there?

A

31 pairs.

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12
Q

Where are spinal nerves found?

A

The intervertebral foramina.

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13
Q

Spinal nerves connect structures of the soma via what?

A

Rami

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14
Q

Spinal nerves connect via rami to what?

A

Structures of the soma.

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15
Q

Spinal nerves connect with the spinal cord segment of the same number via what?

A

Roots and rootlets.

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16
Q

Spinal nerves connect via roots and rootlets to what?

A

The spinal cord segment of the same number.

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17
Q

Describe the posterior rami of spinal nerves.

A

Small and innervate the posterior body wall.

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18
Q

Describe the anterior rami of spinal nerves.

A

Large and innervate the anterolateral body wall.

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19
Q

Describe the transmission of sensory axons in relation to the spinal nerves.

A

ALL sensory axons pass from spinal nerve > posterior root > posterior rootlets > posterior horn of spinal cord.

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20
Q

Where are the cell bodies of primary afferent neurones located?

A

Dorsal root ganglion.

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21
Q

Describe the transmission of motor axons in relation to the spinal nerves.

A

ALL motor axons pass from anterior horn of spinal cord > anterior rootlets > anterior root > spinal nerve.

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22
Q

How does segmental innervation of the body wall arise?

A

Each spinal nerve supplies innervation to a unilateral area of the body.

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23
Q

Each spinal nerve pair supplies all structures in a segment of the body with what?

A
  • General sensory supply to all structures.
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24
Q

Each spinal nerve pair supplies skeletal muscles in a body segment with what?

A
  • Somatic motor supply to skeletal muscles.
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25
Q

Each spinal nerve pair supplies the skin and smooth muscles of arterioles in a body segment with what?

A
  • Sympathetic nerve supply to skin and smooth muscle of arterioles.
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26
Q

What is a dermatome?

A

Area of skin supplied with sensory innervation from a single spinal nerve.

NB there is overlap by adjacent spinal nerves.

27
Q

What is a myotome?

A

Skeletal muscles supplied with motor innervation from single spinal nerve.

NB myotome sometimes deep to dermatome of same spinal nerve, but not always e.g. diaphragm.

28
Q

Male nipple found in which dermatome?

A

T4

29
Q

Umbilicus found in which dermatome?

A

T10

30
Q

C2-C4 of the dermatome map cover which areas?

A

Posterior scalp, neck and shoulder.

31
Q

C5-T1 of the dermatome map cover which areas?

A

The upper limb.

32
Q

L2-Co1 of the dermatome map covers which areas?

A

The lower limb, gluteal region and perineum.

33
Q

What spinal nerves contribute to the cervical plexus?

A

C1-C4

34
Q

The cervical plexus (C1-C4) supplies what?

A
  • The posterior scalp.
  • Neck.
  • Diaphragm.
35
Q

What spinal nerves contribute to the brachial plexus?

A

C5-T1.

36
Q

The brachial plexus supplies what?

A

The upper limb.

37
Q

What spinal nerves contribute to the lumbar plexus?

A

L1-L4.

38
Q

The lumbar plexus supplies what?

A

The lower limb.

39
Q

What spinal nerves contribute to the sacral plexus?

A

L5-S4.

40
Q

The sacral plexus supplies what?

A
  • The lower limb.
  • Gluteal region.
  • Perineum.
41
Q

Where does sympathetic outflow originate from?

A

Control centres in the brain > then passes down spinal cord.

42
Q

What segments of the spinal cord have lateral horns for cell bodies?

A

T1 to L2.

43
Q

Through which root/rootlets does “presynaptic” sympathetic axons (motor innervation) pass through?

A

Anterior rootlets/roots.

44
Q

Where do presynaptic axons destined for the heart synapse?

A

T1 or cervical PARAverterbral ganglia.

45
Q

Through what do postsynaptic axons to the SA & AV nodes + the myocardium pass?

A

Cardiopulmonary splanchnic nerves.

46
Q

Where do presynaptic axons of the lungs synapse?

A

In the upper thoracic PARAvertebral ganglia.

47
Q

Where do postsynaptic axons of the lungs pass to reach the bronchiolar smooth muscle and mucous glands?

A

Cardiopulmonary splanchnic nerves.

48
Q

Presynaptic axons of the abdominopelvic organs synapse where?

A

In one of the PREvertebral ganglia.

49
Q

Give an example of a PREvertebral ganglia in which presynaptic axons of the abdominopelvic organs synapse?

A
  • Coeliac ganglion of coeliac plexus (foregut).
  • Aorticorenal ganglion (kidney).
  • Superior mesenteric ganglion of SM plexus (midgut).
  • Inferior mesenteric ganglion of IF plexus (hindgut + pelvic/perineal organs).
50
Q

Presynaptic axons of the adrenal medulla pass through the aorticorenal ganglion to synapse where?

A

Directly onto the adrenaline/noradrenaline secreting cells of the adrenal medulla.

51
Q

Presynaptic parasympathetic axons leave the CNS via which cranial nerves?

A
  • CN III.
  • CN VII.
  • CN IX.
  • CN X.
52
Q

Presynaptic parasympathetic axons leave the CNS via cranial nerves and what other nerves?

A

Sacral spinal nerves.

53
Q

Presynaptic parasympathetic axons leave the CNS and reach the eye via what?

A

The ciliary ganglion and CN III (oculomotor).

54
Q

Presynaptic parasympathetic axons leave the CNS and reach the lacrimal gland and salivary glands via what?

A

Parasympathetic ganglia in the head.

55
Q

Presynaptic parasympathetic axons leave the CNS and reach the organs of the neck, chest, and abdomen (to mid-gut) via what?

A

CN X - vagus.

56
Q

Presynaptic parasympathetic axons leave the CNS and reach the hindgut, pelvis and perineum via what?

A

Sacral spinal nerves.

57
Q

Name the ipsilateral symptoms of Horner’s Syndrome?

A
  • Miosis.
  • Ptosis.
  • Anhydrosis.
  • Increased warmth and redness.
58
Q

Impaired innervation to the head and neck of what kind is responsible for Horner’s Syndrome?

A

Impaired sympathetic innervation.

59
Q

What may cause compression of the cervical parts of the sympathetic trunk, leading to Horner’s Syndrome?

A
  • Root of neck trauma.
  • Carotid dissection.
  • Internal jugular vein engorgement.
  • Deep cervical node metastases.
  • Pancoast tumour (lung apex).
60
Q

What causes ptosis in Horner’s Syndrome?

A

A lack of sympathetic innervation of the smooth muscle within levator palpebrae superioris.

61
Q

What causes miosis in Horner’s syndrome?

A

A lack of sympathetic innervation to dilator pupillae.

62
Q

What causes a reduction in sweating in Horner’s syndrome?

A

Lack of sympathetic innervation to sweat glands of the skin.

63
Q

What causes increased warmth in Horner’s syndrome?

A

Dilation of the skin arterioles.