5: Spinal cord Flashcards

1
Q

Where does the spinal cord end?

A

L1-L2

Conuc medullaris= termination point of spinal cord

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2
Q

General length and width of spinal cord?

A

42cm long
14mm wide

The shorter length is due to the fact that the spinal cord stops growing at four but the spinal column keeps growing with age.

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3
Q

Conus medularis

A

spinal cord termination point L1-L2

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4
Q

Filum terminale

A

anchors spinal cord to coccyx

- stables spinal cord during movement

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5
Q

What are the 5 regions of the spinal cord.

A
Cervical 8
Thoracic 12
lumbar 5
sacral 5
coccygeal 1
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6
Q

How many vertebrae do we have?

A

31

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7
Q

What occurs in terms of nerves at T12-L2

A

the lumbar, sacral and coccyx nerves branch off. They cant do it in their bone regions as the spinal cord terminates before it reaches them.

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8
Q

Name and number of spinal nerves

A

1 spinal nerves comes off with each vertebrate but because the spinal cord terminated at L1-L2, the rest banch off early creating cauda equina

Cervical 8
Thoracic 12
lumbar 5
sacral 5
coccygeal 1
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9
Q

Cauda equina

A

lumbar, sacral and coccygeal nerve roots travel beyond the conus medullaris to reach the vertebral region from which the lumbar, sacral and coccygeal spinal nerves emerge.

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10
Q

How do peripheral nerves enter the spinal cord and become tract?

A

via dorsal and ventral routes

Dorsal=

  • first in the alphabet so up higher
  • S= sensory
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11
Q

Describe a mixed nerve

A

Can spinal nerves carry both sensory and motor axons.

Spinal cord nerves are mixed.

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12
Q

Define a ganglion

A

cluster of cell bodies

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13
Q

Explain the dorsal root ganglion

A

a cluster of cell bodies on the dorsal root (upper nerve entering spinal cord)
- the point where fist and second order neurons synapse.

Think about the fact you can see it in all diagrams so it is close to the spinal cord! remember this for you have to describe length of pre and post ganglions

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14
Q

Ventral root carrier…

A

motor axons
v= verchile motor
- motor output leaves spinal cord

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15
Q

Dorsal root carries….

A

sensory axons
- inout enter spinal cord
sensory input comes first so this is up top

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16
Q

Damage to sensory neurons in dorsal root, ganglion or spinal nerve can cause

A

loss of sensation, sharp stabbing pains or abnormal sensations such as burning, stinging, pickling or tingling.

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17
Q

Damage to Motor neurons in a ventral root or spinal nerves can result in

A

muscle weakness, loss of movement and autonomic disfunction- e.g. loss of bladder and bowel control

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18
Q

What mechanisms protect the spinal cord?

A
  • vertebral column
  • CSF (also nourishes neural tissue and removes water products)
  • spinal meningies
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19
Q

Describe the structure and function of spinal meningies

A
  • continuation of cranial meninges

- extend beyond spinal cord

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20
Q

Where is the needle of a lumbar puncture or epidural placed?

A

subarachnoid space

needle inserted between L4 and L5. At this point there is no spinal cord so the spinal nerves drift away from the needle in the CSF so there is little chance of damaging the nerves.

take some CSF for texting for bacterial infection e.g. mengitis

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21
Q

List the layers of the meninges

A
durs mata
sub dural scape  
arachnoid mater 
sub arachnoid space 
pia mater
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22
Q

Describe the epidural space

A

space between dura mater and vertebral column

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23
Q

Define denticulate ligament

A

extension of pia mater that prevents lateral (side to side) movement.

24
Q

What divides the neurons and neuroglia

A

Anterior median fissure
Front-middle-deep grove

Posterior median sulcus
Back-middle-shallow grove

25
Q

Describe the position of grey and white matter

A

grey mater= deep
white matter= superficial

opposite to the brain

26
Q

Describe grey matter

A

Composed of; cell bodies, unmyelinated axons and neuroglia

  • Vary in size as they move down the spinal column
  • Enclose central canal which is filled with CSF
27
Q

Describe the grey commissure

A

site where axons cross from one side of CNS to other

  • why right side of body goes to left side of brain

Reason for cross over= unknown

Can cross over in brain stem or in CNS/spinal cord

28
Q

Name of tiny hole in the centre of the spinal cord

A

central canal

29
Q

What are the three divisions of the grey matter

A
  1. Posterior gray horns
  2. Lateral gray horns
  3. Anterior gray horns
30
Q

Describe the positions of he areas of the grey horns.

A

Posterior gray horn
= sensory nuclei

Lateral gray horn
= autonomic nuclei

Posterior grey horn
= somatic gey horn

think about sensory coming into the posterior side through the dorsal root so it is on top.

Think motor comes through anterior ventral roots and A comes first so autonomic is on top.

31
Q

What occurs in posterior grey horns

A

contains cell bodies of spinal interneurons that synapse with second order neurons

32
Q

What occurs in anterior grey horns

A

contains cell bodies of lower motor neurons

33
Q

What occurs in lateral grey horns

A

contains cell bodies of preganglionic neurons

- receives autonomic motor output

34
Q

Describe white matter

A
  • superficial to grey matter
  • composed main of myelinated axons but some unmyelinated to.
  • anterior white commissure- site where axons cross

contains both ascending and desending tracts

35
Q

Wha are the subdivisions of the white matter

A
  • Posterior white columns
  • Lateral white columns
  • Anterior white columns
36
Q

Spinal cord tracts of white mater

A

conduct sensory and motor info between spinal cord and brain

ascending tracts= sensory
desending= motor

37
Q

Names often tell un info on the tract explain lateral spinothelamic tract

A

origin= spinal cord
Destination= thalamus
Tract location= laterl white column

38
Q

Explain the lateral corticospinal tract

A

location= lateral white column

output= somatic motor output that controls skeletal muscles of limbs

Lateral= limbs

39
Q

Explain the anterior corticospinal tract

A

location= anterior white columns

output= somatic motor output that controls skeletal muscles of trunk

A= axial skeleton

40
Q

What neurons are involved in somatosensory pathways

A
  • Fist order (sensory neurons) conduction sensory input from receptors to CNS
  • second order (conduct info to cerebellum or thalamus)
  • Third order (conduct info to primary somatosensory cortex)

Somatosensory pathways=
- Conduct general sensory input
- Involve 3 neurons
1 peripheral and 2 interneurons in the CNS

41
Q

What neurons are involved in general sensory input

A

1st, 2nd, 3rd

42
Q

What are the three main somatosensory pathways?

A

1- spinothalamic pathway
2- posterior column pathway
(dorsal column-medial lemniscal pathway)
3- spinocerebellar pathway

43
Q

Explain the spinothalamic pathways

A

1st order=

  • receptors to posterior grey horn
  • synapse with second order neuron at posterior grey horn

2nd order=
- conducts sensory input to the thalamus where it synapses with 3rd oder

3rd order=
- conducts sensory input to primary somatosensory cortex

44
Q

Explain the posterior column pathways

A

1st order=

  • conducting sensory info into posterior grey horns up to medulla oblongata
  • asending spinal tracts= fasciculus gracilis or fasciculus cuneatus tract
  • synapse with 2nd order neurons in medulla oblongata

2nd order

  • conducts sensory input to thalamus
  • synapse w/ 3rd order neurons in the thalamus

3rd order
= conducts sensory info to PSC

45
Q

Explain the spinocerebella cerebella pathway

A

1st order
= sensory input from proprioceptors into posterior grey horn
synapses w/ second order neruons with a sensory nucleus

2nd order
= conducts sensory imput to the cerebellum
- asending psinal cord in an anterior or posterior spinocerebellar tract

46
Q

List the two somatic motor pathways

A

lateral corticospinal
anterior cortico spinal

upper and lower motor neurons

47
Q

Explain the lateral corticospinal pathway

A

upper motor neuron=

  • conducts somatic motor output from PMC to an anterior gray horn
  • desending spinal cord in a lateral corticospinal tract
  • synapse with lower motor neurons in a motor nucleus

lower motor neuron=
- conducts somotic motor output to skeletal muscles

48
Q

Define spinal reflex arch

A

neural pathway that produces a rapid, predictable, involuntary somatic or autonomic refles response to a stimulus

  • doesn’t go to the brain
  • deep grey horn= intergration centre
49
Q

Describe somatic motor reflexes

A

reflex intergration centres within the spinal cord stimulate skeletal muscle contraction.

1- receptor
2- sensory neuron
- intergration centre in grey matter
- LMN
- skeletal muscle contration
  • can be modified by primary motor cortex
50
Q

What is somatic motor reflexes used for?

A

quick diagnosis of disorders of the nervous syetem and it can assess

  • spinal cord segment
  • lower motor neurons
  • primary motor cortex
  • corticospinal tracts
51
Q

What does damage to the posterior grey horns or ascending spinal cord tracts cause?

A

= loss of sensation

52
Q

What does damage to the anterior gray horns or corticospinal tracts cause

A

spastic (lack of control) or flaccid (reduced muscle tone) paralysis

53
Q

Damage to upper motor neuron=

A

spastic pralysis

  • loss of voluntary movement
  • refles activities intact but abnormal
54
Q

Damage to lower motor neurons=

A

flaccid paralysis

- loss of voluntary movement and reflex activities

55
Q

Transection of the cervical region=

A

quadraplegic

56
Q

Transection of the thoracic or lumbar region=

A

paralysis

57
Q

Describe spinal shock

A

transent period of complete sensory and motor loss, and a loss of rreflexes (somatic and autonomic) below the level of lesion- reflex action gradually returns