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MedSci142 > Lecture 2 - The Spinal Cord > Flashcards

Lecture 2 - The Spinal Cord Flashcards

1
Q

Where does the sensory cortex get an input from and what is that input called.

A

sensations from skin
to the sensory cortex in the brain
sensory input

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2
Q

How does a sensory input work?

A

sensations from the skin
31 nerve fibres go into spinal cord
spinal cord sends/conveys long nerve pathways up to the top of the spinal cord (the brain)
to the PRIMARY sensory cortex

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3
Q

Where are the spinal chord nerves placed?

A

between each of the bones of the vertebrae

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4
Q

What are the nerves coming out of the spinal cord called?

A

spinal nerves

each goes to an individual dermatome (band/region of skin)

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5
Q

How many spinal nerves are there?

A

31
(30 go to the skin)
vs only 30 dermatomes

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6
Q

How do you name spinal nerves?

A 
1-8pairs= neck/cervical s.n.
9-20 (12x)pairs= thoracic s.n.
21-25 (5x)pairs= lumbar s.n.
26-30 (5x)pairs= sacral s.n.
31 (1x)pair= around anus/coccygeal s.n.

each goes to a region of skin/dermatome

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7
Q

What is a Dermatome?

A

a region/band of skin/body an individual spinal nerve goes to
30x dermatomes
nerve innervates skin at level of dermatome
dermatome provides sensory input to the CNS via the posterior roots of a pair of spinal nerves, or via the trigeminal (V) nerve

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8
Q

How does a Dermatome work?

A

provides sensory input to the CNS via

a. the posterior roots of a pair of spinal nerves
b. trigeminal (V) nerve

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9
Q

Describe the placement of the spinal cord

A

Extends from the medulla oblongata
To the superior part of the 2nd Lumbar Vertebrae

Terminates as a comical structure called the concus medullan’s
-between the 1st and 2nd lumbar

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10
Q

Nerve motorways

A

Sensory fibres which come in through the spinal nerve
too 2x roots
-upper=dorsal/posterior/afferent root, for information coming INTO the spinal cord from peripheral receptor, sensory
-lower=ventral/anterior/efferent root= for information LEAVING the spinal cord too skeletal muscles, motor

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11
Q

What is the Concus Medullans and describe its relevance

A

termination of the spinal cord
terminates as a somical structure called the Concus Medullan’s
between the 1st and 2nd lumbar vertebrae

therefore spinal nerves from the lumbar, sacral and coccygeal (pairs #21-31) respective regions’/dermatomes do not the leave the vertebral column at the same time they exit
roots called the Caudal Equine

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12
Q

What is the Caudal Equine and describe it’s relevance

A

Roots
spinal nerves 21-31 from the - Lumbar, Sacral and Coccygeal regions’ do not leave the vertebral column at the same time they exit (due to concus medullan’s/comical structure)

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13
Q

Which root has bulge?

A

dorsal/posterior root

bulge=dorsal root ganglion

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14
Q

What happens if the Dorsal/Posterior/Afferent root was cut?

A

There would be NO information coming INTO the spinal curve from that particular dermatome
the skin will be numb

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15
Q

What is the Dorsal Root?

A

Posterior/Afferent root
contains Only SENSORY nerves
“ON ramp”
conducts impulses from Sensory Receptors –> to CNS

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16
Q

What is the Ventral Root?

A

Anterior/Efferent root
contains Only MOTOR nerves
“OFF ramp”
conducts nerve impulses from CNS –> to Efferent Organs and Cells

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17
Q

What does Myelin cover?

A

Nerve fibres

18
Q

What is Gray matter?

A

Dendrites&Cell Bodies of neurons
Unmyelinated axons and neuroglia
gray matter on each side of the spinal cord is divided into “horns”

is the inner core of the spinal cord

receives and integrates incoming/outgoing info

19
Q

What is White matter?

A

primarily of bundles of Myelinated Axons of neurons
“motorways”
travel of SENSORY INputs and MOTOR OUTputs

20
Q

What does the spinal cord consist of?

A

White matter(motorways) + Inner core of Gray matter

21
Q

Why do you not count C1?

A

C1 doesnt go to the skin

-C1 takes the VENTRAL root not the dorsal root

22
Q

What does a nerve consist of?

A

Cell body

2x Roots - Dorsal root + Ventral root

23
Q

What are Dorsal Root Ganglian Cells?

A

Enlarged cell bodies which support dorsal nerve fibres

1x process out to skin +
1x process out to DORSAL HORN/spinal chord to convey information - 2x sets of sensory fibres into the brain

24
Q

What is a Peripheral receptor?

A

Encapsulated receptor
Specialised receptor which forms a capsule around the end of nerve fibre “onion”
Discriminative Sensation-can discriminate in a precise way down to

25
Q

What is the need for Myelin?

A

“Myelinated Nerve Fibre” formed by Schwann Cells wrapped around axons
Fast conducting fibre
Nerve impulses travel fast 50ms-1 b/w nodes.o.R.
Instantaneous information to brain
Saltatory transmission

26
Q

What are fibres sensitive to touch called?

A

Meissner Corpsudes

convey discriminative information skin/dermatome–> spinal cord

27
Q

What are fibres sensitive to pressure called?

A

Paciuian Corpsudes

convey discriminative information of pressure skin/dermatome–> spinal cord

28
Q

What happens when you have a sensation?

A

you can feel it in its respective area in the sensory cortex on the other side of your brain

29
Q

How is a spinal nerve organised?

A

highly organised
Sensory nerve
each spinal nerve contains 10,00 myelinated fibres from/per dermatome due to # of the spinal nerve

30
Q

Describe LMN’s

A

Lower Motor Nerves
Off Ramps
Large Cells-120microns
In Ventral Root
these axons conveys motor info out to muscles from the motor cortex which have connected to the dendrite
Terminate on Muscle Cell
Synaptic junction when reaches Skeletal muscle,
acetylcholine release–> contraction
1000s on a single muscle cell
co-ordinated contraction of skeletal muscle
Peripheral Nerve
Essential
Damage: muscle wouldn’t receive impulses, becomes Paralysed/Floppy Meat- Flaccid Paralysis

31
Q

Describe Pain and Temperature Fibres

A

Similar to spinal nerves but different in organisation
Convey sensations of Pain and Temperature
Non-encapsulated Receptor (nerve endings have no capsule around it)
Endings end in Dermis - Naked Nerve Endings
Free Nerve Endings
Sensitive to Pain Thresholds and changes in Temperature
Sensitive in a general way (smaller number of these pain and temperature fibres relative to touch and pressure fibres)
Non-discriminative Sensation- REGION- you can fell pain and temperature but you CANNOT LOCALISE it in a precise way as touch and pressure
Non-myelinated –> 1ms-1 as no nodes
ends at centrey part of spinal cord
Cell body in the Dorsal Root Ganglion Neuron

32
Q

What are some comparisons between the two sets of fibres coming in from the skin?

A

Touch and Pressure
Discriminative sensations
Heavy Myelin covering
Information passes in a Saltatory Fashion - very fast rate 50ms - due to Nodes of Ranvier
Myelin formed by Schwann Cells
End of fibres have capsule around therefore Peripheral Receptor or Encapsulated Receptor
Function: to generate nerve impulse in a discriminative sensation
Terminate in BOTH Dorsal Horn and Brain (via branching fibre)

Thinner
Non-myelinated fibres
Temperature and pain fibres
Conduct slower rate 1ms
No receptor at end - Non-Encapsulated Receptor
Naked/Free Nerve Ending
Convey Non-discriminative Information
Terminate in Dorsal Horn
33
Q

What is present in the Dorsal Root Ganglion and what is a name for them?

A

PseudoUnipolar Neurons
both the Sensory Myelinated Fibres sensitive to touch and pressure and the Naked Non-Myelinated Pain and Temperature Fibres

34
Q

What is the function of a Peripheral/Encapsulated Receptor?

A

Capsule is wrapped around like an onion
Function is to turn light touch or pressure to generate a nerve impulse and the termination of that fibre
makes the fibre VERY SENSITIVE

35
Q

How do the two sets of nerve work in a dermatome?

A

First get touch and pressure
if pressure gets intense then you get pain which is conducted by other fibres
temperature and pain is felt in a general region

36
Q

What are UMN?

A

Upper Motor Neurons
Control Movement
Start in Motor Cortex
Come down, Cross the Spinal Cord and have to get information out to Muscles under the Skin

37
Q

What would happen if the Dorsal Root was cut?

A

Numbness

No sensory information- touch&pressure, pain&temperature

38
Q

What would happen if the Ventral Root was cut?

A

Flaccid Paralysis-
Muscle doest receive nerve impulses
Floppy muscle

39
Q

What is meant by the Peripheral Nerve?

A 
Spinal Nerve branches
Goes out to particular parts of the body
Mixture of Sensory and Motor Nerves
To either Skin(Dermatomes) or Muscle
Combine to form Complex Systems
40
Q

What is difference within the 31 Spinal Nerves?

A

30 Spinal Nerves go to one Dermatome (Dorsal Root)

31 Spinal Nerves go to Muscles (Ventral Root)

41
Q

What happens if the Spinal Cord becomes compressed and cut?

A

become Paraplegic
Lower parts:
Paralysed (no muscle use)
Lose all sensation in Skin

MedSci142 (20 decks)

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