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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
What is the need for Myelin?
"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
What are fibres sensitive to touch called?
Meissner Corpsudes | convey discriminative information skin/dermatome--> spinal cord
27
What are fibres sensitive to pressure called?
Paciuian Corpsudes | convey discriminative information of pressure skin/dermatome--> spinal cord
28
What happens when you have a sensation?
you can feel it in its respective area in the sensory cortex on the other side of your brain
29
How is a spinal nerve organised?
highly organised Sensory nerve each spinal nerve contains 10,00 myelinated fibres from/per dermatome due to # of the spinal nerve
30
Describe LMN's
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
Describe Pain and Temperature Fibres
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
What are some comparisons between the two sets of fibres coming in from the skin?
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
What is present in the Dorsal Root Ganglion and what is a name for them?
PseudoUnipolar Neurons both the Sensory Myelinated Fibres sensitive to touch and pressure and the Naked Non-Myelinated Pain and Temperature Fibres
34
What is the function of a Peripheral/Encapsulated Receptor?
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
How do the two sets of nerve work in a dermatome?
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
What are UMN?
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
What would happen if the Dorsal Root was cut?
Numbness | No sensory information- touch&pressure, pain&temperature
38
What would happen if the Ventral Root was cut?
Flaccid Paralysis- Muscle doest receive nerve impulses Floppy muscle
39
What is meant by the Peripheral Nerve?
``` 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
What is difference within the 31 Spinal Nerves?
30 Spinal Nerves go to one Dermatome (Dorsal Root) | 31 Spinal Nerves go to Muscles (Ventral Root)
41
What happens if the Spinal Cord becomes compressed and cut?
become Paraplegic Lower parts: Paralysed (no muscle use) Lose all sensation in Skin

MedSci142 (20 decks)

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