Nervous System Pt. 4 - Spinal Cord & Intro to Spinal Nerves

Question 1

The spinal cord is an extension from what part of the brain?

Answer 1

The brainstem

Spinal cord comes from medulla oblongata out of foramen magnum

Question 2

What level of the vertebrae does the spinal cord go down to? What specific part of the vertebrae does it travel through?

Answer 2

Goes all the way down to L2 and it travels to the vertebral canal (vertebral foramen put together by vertebral bone)

Question 3

What is the spinal cord covered in?

Answer 3

Same meningial layers as the brain = dura, arachnoid and pia mater

C.S.F. in subarachnoid space.
* Even though ends at L2 the subarachnoid space exists at the level of the sacrum so C.S.F. can be found in even lower sacrum regions

Question 4

How many spinal nerves are there at each vertebral layer? How many in total?

Answer 4

1 pair of 2 spinal nerves at each vertebral layer making a total of 31 layers

Ends at L2 at a place called conus medullaris which is this cone shape that the spinal cord forms at the end

Question 5

What is the filum terminale?

Answer 5

String of pia mater reaching all the way down to the coccyx and acts like an anchor

Question 6

What is the Cauda Equina

Answer 6

Horse Tail
= Spinal nerves still exiting after the end of the spinal cord out of the foramen

Have not gotten to their destinations; swimming around in Cerebral Spinal Fluid

Question 7

What is spinal tap? What is a possible risk to it?

Answer 7

Sample of C.S.F. from the subarachnoid space and a risk is putting the needle in and possibly touching the spinal = irreparable damage

In order to get a better look, patients would tuck their knees into their chest to “enlarge” the lumbar vertebrae space

Question 8

When looking at the internal structure of a spinal cord which part does the signal travel in to and which part of it does it travel out of?

Answer 8

Signals always enter through posterior half and exit through the anterior half

Anterior is known for motor activity while posterior is dedicated to sensory activity

Question 9

What is the central canal? What does it contain that is important for the protection & nutrients of the spinal cord?

Answer 9

In the middle of the spinal cord (extends down spinal cord from 4th ventricle) & it contains C.S.F.

Also note that the meninges (subarachnoid space) outside of the spinal cord and surrounding it has C.S.F.

Question 10

Explain the Spinal Nerve Highway Analogy?

Answer 10

Essentially with a spinal nerve we have two parts which are the anterior and posterior; the anterior carries sensory signals while the posterior carries motor signals and they never interact with one another

Motor Neuron does not have to synapse like Sensory Neurons have to; they can if they want to

Question 11

What are the spinal cord vertebrae composed of?

Answer 11

Gray & White Matter
* Gray Matter is more centrally located
* White Matter (myelinated axons) are peripheral (away from the centre)

Question 12

Explain the path of a signal in the spinal cord coming in from a muscle movement.

Answer 12

1. Path of info goes into the spinal nerve which branches off and enters the ganglion (important in the posterior branch as sensory nerves have to synapse) which passes the signal/info to the second neuron (cell body of sensory neuron)
2. Second neuron travels through ganglion specifically in the posterior root and into the posterior rootlet into the spinal cord.
3. Motor neuron takes signal back to where it has to go (Anterior Rootlet => Anterior Root (ganglion) => Spinal Nerve

Anterior Rootlet & Axon of motor neuron both have to let the signal at the body of the motor neuron pass through