Lecture 10 - The spinal cord & Autonomic nervous system Flashcards
What are the 3 basic components of a neuron?
Cell body
Dendrites
Axon
What makes up grey matter?
Cell bodies of neurons
What makes up white matter?
Dendrites and axons
What are ganglia?
Cell bodies of neurons
What do spinal/cranial nerves conist of?
Axons
Describe the location of the spinal cord
And is it larger or smaller than the vertebral column?
The spinal cord is a continuation of the medulla to L1/L2 level
The spinal cord is smaller than the vertebral column
What are the two enlargements of the spinal cord?
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
Why is the spinal cord smaller than the vertebral column?
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
What anchors the spinal cord to the coccyx? and describe it
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
How does the spinal cord sit in the vertebral column, and what is it attached to?
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
The dorsal horn has the cell bodies for what kind of neurons?
Somatic sensory neurons
What kind of neurons are in the ventral horn?
Somatic motor
What kind of neurons are in the lateral horn?
Visceral sensory
In the CNS and PNS, what are the 4 types of neurons and nerves?
Somatic
- motor (efferents)
- Sensory (Afferents)
Visceral
- Motor (visceral)
- Sensory (afferents)
How can you tell which is the posterior side of the spinal cord?
the two pointiest horns always point posteriorly
Label these columns
Describe the general process of how something is sensed, and how in motor action is performed in response
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.
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?
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
Describe the structure of the ermerging rootlets outwards
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.
Which ramus supplies the posterior part of the trunk? (skin, and deep muscles of back)
Posterior ramus
Which ramus forms all of the plexuses in our body?
Anterior ramus
Describe the reflex arc for the patella tendon reflex
What kind of fibres are found in peripheral nerves?
Motor fibres
Sensory fibres
Sympathetic fibres
How do sympathetic fibres use the spinal nerve to reach their targets?
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.
Where are the cell bodies for the thoracolumbar outflow located?
T1-L2 in lateral horn - they come out to form the sympathetic chain ganglia
Which nerves and cell bodies make up the craniosacral outflow?
Cranial nerves 3, 7, 9, 10
and the cell bodies in S2-S4 lateral horn
these form the parasympathetic ganglia
Where are the three places that sympathetic neurons can synapse after leaving the lateral horn of the spinal cord?
- Synapse in the sympathetic trunk ganglia (paravertebral) and travel with spinal nerve rami
- (Splanchnic nerves preganglionic nerves) Synapse in prevertebral (preaortic) ganglia and travel with arteries
- Synapse in adrenal medulla
What are the 4 pathways that a sympathetic preganglionic nerve can take from the lateral horn?
- 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
What are the hindgut and pelvic structures innervated by?
Parasympathetic nerves from S2,3 4
Which has a shorter pre-ganglionic neuron, a sympathetic nerve, or a paraympathetic nerve?
pre-gang symapthetic nerve is shorter
Compare and contrast the effects of the SNS and the PNS
Desribe dura mater
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
Describe pia mater
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)
Describe the arachnoid mater
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.
Which levels is a lumbar puncture given at?
L4/5 or L3/4
Describe the blood supply to the spinal cord
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
