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Lecture

NEUR 2600 Lecture Notes - Spinal Cord, Ventral Root Of Spinal Nerve, Dorsal Root Of Spinal Nerve

by

Department
Neuroscience
Course Code
NEUR 2600
Professor
Ian Whishaw

Page:
of 3
Organization (3D)
-
It's function, effects of damage, approaches to fixing that
-
Organization
1.
Function
2.
Every cell and connection in the spinal cord has a function
a.
Injury and Treatment
3.
i.
Evolved from early animals that had spinal cords of sorts
a.
Transcription factors that activate other genes that in turn produce the segments
of the body of animals - they are read off from head to tail during development
i.
Color coded diagrams in powerpoint
1)
In humans, they've duplicated with four sets of Hox Genes, similar to that of a fruit
fly
ii.
Mutations - extra set of wings, nervous system, in humans - extra finger, etc
iii.
Each segment of the spinal cord essentially runs a certain part of the body
iv.
Segments of the spinal cord
1)
Dermatones in each person are a little different
2)
Locating spinal cord injury
a)
Distinguishing real and hysterical symptoms
b)
Guidance in reattaching arms
c)
Usefulnes:
3)
Dermatones: "skin-cut"
v.
Dorsal-ventral specialization
vi.
Hox genes
b.
Segmentation
1.
Sir Charles Bell
One.
Francois Megendie
Two.
Hard to find in adult animals
First.
Cut one, don't lose the other
1.
Magendie was able to find and cut them in puppies
Second.
The dorsal roots are sensory and the ventral roots are motor
Three.
Bell-Megendie Law
i)
2 sets of fibers
a)
Ventral (inside)
a.
Motor coming from spinal cord to muscles
1)
Ventral fibers
a)
Anterior
b.
Sensory coming from skin and muscles, taking info into body (behind)
1)
Dorsal fibers
a)
Posterior
c.
Cranial nerve. 12 and most anterior spinal cord segments
a)
Brain
d.
Not only are muscles organized segmentally, so are body organs
e.
Dorsal-ventral specialization
2.
Inside = cells
i)
When you cut the vertebrae
a)
The butterfly effect
1)
Medial-lateral specialization
3.
Spinal Cord Organization
The Spinal Cord
January-18-13
11:00 AM
Brain and Behavior Page 1
Inside = cells
i)
Outside = fibers (taking information up to brain)
ii)
Organized in 9 layers - the dorsal layers are concerned with sensory
information, the ventral layers are motor
iii)
Relay body info to brain
-
Carry brain info to muscles
-
Spinal behaviors or reflexes
-
What does the spinal cord do?
The Integrative Action of the Nervous System
Described the reflexes of the spinal cord
Charles Scott Sherrington
-
Finbers entering the dorsal root bring sensory info from sensory receptors
1.
Fibers leaving ventral root carry motor information to the muscles
2.
Collateral branches of sensory neurons may cross to the other side and influence
motor neruons there
3.
White matter fiber tracts carry information to and from the brain
4.
Simplest spinal cord circuit
Patellar reflex. Medial rectus femoris
Paterllar tendon
Sesnroy receptors (muscle spindles) respond to muscle. Stretching and tell the msucle to
contract and relieve the stretch
Stretch
-
This reflex ensures that muscles in each leg make opposite contractions - relations
in order to allow stepping
Crossed extensor reflex
Stepping
-
Important for walking
The paw extends to make contract with a surface
Placing
-
Big trouble if the toe goes up, it should go down to grasp
Babinski sign
Scratch
-
Reflexes
Loss of movement and sensation
All four limbs
Quadrapalegia
Only one side affected
Hemiplegia
The lower limbs
Paraplegia
Paralysis
-
All those cells die, that's hat cut it in half
Window of a number of days
Vertebrate push against spinal cord, bruise it
It is not so much the blow but the things that happen later that result in the cord losing its
confuction function
-
12 000 new cases each year
28 years average age of injurty
77% males
50% car accidents
Struggle for people studying spinal cord injuries, because such a small number of
Yearly cost $30 000
Paraplegia
-
Spinal cord Injuries
Brain and Behavior Page 2
Struggle for people studying spinal cord injuries, because such a small number of
people compared with cancer, heart disease, etc
Age 15 - car crash, paraplegic
Wheel chaired across the world.
Rick Hansen
-
Nothing is impossible
Accident riding a horse, survived
Advocate for spinal cord research
Superman
Quadraplegia
Christopher Reeve
-
One of the simplest problems, people working on it for 100 years
-
Just a little bit of tissue, input from brain, all of the spinal cord is okay except that
-
How do you grow them back?
Stem cells, tubes, chemicals
Looking for their targets
Like plant roots looking for water
Fibers sprout but cannot find their way through the severed cord
Protein chemical that tells fibers that prevents modifications by sprouting neurons
from happening
Goldfish can reproduce these fibers and be fine if spinal cord is cut
Nogo
Black color = fibers, don't die
-
The problem of regeneration
Brain and Behavior Page 3