Lecture 10 - The spinal cord & Autonomic nervous system

Question 1

What are the 3 basic components of a neuron?

Answer 1

Cell body

Dendrites

Axon

Question 2

What makes up grey matter?

Answer 2

Cell bodies of neurons

Question 3

What makes up white matter?

Answer 3

Dendrites and axons

Question 4

What are ganglia?

Answer 4

Cell bodies of neurons

Question 5

What do spinal/cranial nerves conist of?

Answer 5

Axons

Question 6

Describe the location of the spinal cord

And is it larger or smaller than the vertebral column?

Answer 6

The spinal cord is a continuation of the medulla to L1/L2 level

The spinal cord is smaller than the vertebral column

Question 7

What are the two enlargements of the spinal cord?

Answer 7

The cervical and lumbosacral enlargement

The enlargements are due to the plexuses in these regions, the cervical plexus, and the lumbar and sacral plexus - this causes there to be more neurons in those areas, making them appear larger

Question 8

Why is the spinal cord smaller than the vertebral column?

Answer 8

As we grow the vertebral column grows at a faster rate than the spinal cord. This is when the bone goes further down, and the spinal cord stops at L1

Question 9

What anchors the spinal cord to the coccyx? and describe it

Answer 9

The filum terminale

The filum terminale comes from the conus medularis and is an extension of the pia mater which pierces through the arachnoid and dura mater to the tip of the coccyx

Question 10

How does the spinal cord sit in the vertebral column, and what is it attached to?

Answer 10

The spinal cord floats in CSF, and is attached superiorly to the brainstem (medulla), laterally to the dura mater via denticulate ligaments, and inferiorly to the coccyx via the filum terminale

Question 11

The dorsal horn has the cell bodies for what kind of neurons?

Answer 11

Somatic sensory neurons

Question 12

What kind of neurons are in the ventral horn?

Answer 12

Somatic motor

Question 13

What kind of neurons are in the lateral horn?

Answer 13

Visceral sensory

Question 14

In the CNS and PNS, what are the 4 types of neurons and nerves?

Answer 14

Somatic

- motor (efferents)

• Sensory (Afferents)

Visceral

• Motor (visceral)
• Sensory (afferents)

Question 15

How can you tell which is the posterior side of the spinal cord?

Answer 15

the two pointiest horns always point posteriorly

Question 16

Label these columns

Answer 16

Question 17

Describe the general process of how something is sensed, and how in motor action is performed in response

Answer 17

When an afferent sensory neuron comes in, the axon goes into the dorsal spinal ganglion to where the neurons cell bodies lies. This neuron then synapses with an interneuron, or a motor neuron directly, in the ventral horn.

The message is ten relayed out the ventral root of the spinal nerve.

Question 18

As we go lower in the spine, why are spinal segments no longer at the same level as their corresponding vertebrae?

And what does this discrepancy cause in relation to the lower spinal roots?

Answer 18

Due to the different growth rates of the spinal cord and the vertebral column

The lower spinal roots become increasingly oblique and emerge from their intervertebral formaen at increasing lower levels

Question 19

Describe the structure of the ermerging rootlets outwards

Answer 19

Multiple rootlets join up to form either an anterior or posterior root. These then join to form a spinal nerve, and then they divide to form an anterior and posterior ramus.

The spinal nerve sits in the intervertebral foramen.

Question 20

Which ramus supplies the posterior part of the trunk? (skin, and deep muscles of back)

Answer 20

Posterior ramus

Question 21

Which ramus forms all of the plexuses in our body?

Answer 21

Anterior ramus

Question 22

Describe the reflex arc for the patella tendon reflex

Answer 22

Question 23

What kind of fibres are found in peripheral nerves?

Answer 23

Motor fibres

Sensory fibres

Sympathetic fibres

Question 24

How do sympathetic fibres use the spinal nerve to reach their targets?

Answer 24

The pre-ganglionic symapthetic neurons come from the lateral horns of the spinal cord. Their axons come out anteriorly and latch on to the anterior root and then run along the spinal nerve until they break off to form the white ramus communicans (myelinated), and then they synapse in their respective sympathetic ganglion in the chain. The post-ganglion sympathetic neuron then leaves the sympathetic ganglion via the gray ramus communicans (gray since unmyelinated) to get back onto the spinal nerve. It then uses ethier the anterior or posterior ramus to get to its target. This allows the sympatheic neurons to get anywhere in the body.

Question 25

Where are the cell bodies for the thoracolumbar outflow located?

Answer 25

T1-L2 in lateral horn - they come out to form the sympathetic chain ganglia

Question 26

Which nerves and cell bodies make up the craniosacral outflow?

Answer 26

Cranial nerves 3, 7, 9, 10

and the cell bodies in S2-S4 lateral horn

these form the parasympathetic ganglia

Question 27

Where are the three places that sympathetic neurons can synapse after leaving the lateral horn of the spinal cord?

Answer 27

1. Synapse in the sympathetic trunk ganglia (paravertebral) and travel with spinal nerve rami
2. (Splanchnic nerves preganglionic nerves) Synapse in prevertebral (preaortic) ganglia and travel with arteries
3. Synapse in adrenal medulla

Question 28

What are the 4 pathways that a sympathetic preganglionic nerve can take from the lateral horn?

Answer 28

• They can synapse in the paravertebral sympathetic chain at the level of outflow or run up and down in the chain and synapse in any of the ganglia of the chain
• They can synapse in the sympathetic chain ganglia and leave the ganglia to innervate the thoracic and cervical viscera
• they pass through the symapthetic chain ganglia without synapsing and form splanchnic nerves - greater, lesser and least splanchnic nervres and later synapse in the prevertebral sympathetic ganglia in front of the aorta
• They can pass through the symapthetic chain without synapsing and reach the adrenal medulla where they terminate

Question 29

What are the hindgut and pelvic structures innervated by?

Answer 29

Parasympathetic nerves from S2,3 4

Question 30

Which has a shorter pre-ganglionic neuron, a sympathetic nerve, or a paraympathetic nerve?

Answer 30

pre-gang symapthetic nerve is shorter

Question 31

Compare and contrast the effects of the SNS and the PNS

Answer 31

Question 32

Desribe dura mater

Answer 32

Dura mater is a tough outer most layer of the meninges

In the vertebral canal outside the dura mater is the epidural space, which is where epidural anaethesia is given

Question 33

Describe pia mater

Answer 33

Pia mater is a thin, vascular and innermost layer. It lies of the surface of the brain and spinal cord.

It also has lateral extensions called denticulate ligaments (which fuses with arachnoid and dura mater and then attaches spinal cord laterally to vertebral canal)

Question 34

Describe the arachnoid mater

Answer 34

It is the middle layer of the meninges - it is in contact with, but not attached to the dura.

Between the arachnoid mater and the pia mater is the sub-arachnoid space, which is where CSF is contained.

Question 35

Which levels is a lumbar puncture given at?

Answer 35

L4/5 or L3/4

Question 36

Describe the blood supply to the spinal cord

Answer 36

The spinal cord is supplied by a single anterior spinal artery, and there are two posterior spinal arteries.

These arteries come from the segmental spinal arteries, which branch from the right and left posterior intercostal arteries