Lecture 4: Nervous system

Question 1

Define plexus

Answer 1

A network of nerves that intermingle as they travel resulting in end fibres innervating a specific region of the body containing a mix from different spinal nerves. This means that damage to one nerve won’t necessarily mean that all neural input/output is gone

Question 2

Define ganglia

Answer 2

A group of nerve cell bodies/ cluster that occurs in the PNS, acting as an intermediate between the CNS and the PNS

Question 3

Compare myotome and dermatome

Answer 3

Myotome is the muscles innervated by a single spinal nerve. These muscles often perform a common function- ie flexion extension whereas a Dermatome is the area of skin sensed by a single spinal nerve .

Question 4

What is the general structure and purpose of the spinal column/vertebral column

Answer 4

The linked vertebra have four regions: cervical, thoracic, lumbar and sacral,
Its role is to protect the spinal cord & provide passageway for nerves,
- transmit the weight of our body to the lower limbs through the curves in different regions, which bring the weight in line with the body axis and centre of gravity.
- maintain upright position when sitting and standing

Question 5

Compare Somatic NS and AutonomicNS

Answer 5

SNS is about the voluntary control of skeletal muscle and includes the motor and sensory fibres from CNS
ANS is a division of the PNS which controls internal organs involuntarily: with 2 divisions: Parasympathetic or Sympathetic

Question 6

Describe the structure of the spinal cord as a whole

Answer 6

It starts coming out of the foramen magnum and exit the vertebra at different levels of the spinal cord either directly or in plexuses. The spinal cord proper ends at the conus medallaris at L1. The nerves that project out from this region form the Cauda equina

Question 7

Describe the segmental structure of spinal cord

Answer 7

It has a core of grey matter containing the cell bodies of neurons and white matter tracts on the outside. There is a ventral and dorsal root which will go to the exiting spinal nerves

Question 8

Dorsal or ventral, which root carries sensory information to the CNS and which motor

Answer 8

Dorsal- sensory

Ventral - motor

Question 9

How does the amount of grey matter change in the segmental structure of spinal cord as you go to areas of enlargement vs others

Answer 9

Enlargements provide neuron input to the limbs therefore have more grey matter/cell bodies compared to areas that aren’t innervating as much eg. trunk

Question 10

Describe the 3 meninges and all the layers between the spinal cord itself and the vertebral column: inside to out

Answer 10

First thin pia mater attached to spinal cord, with a subarachnoid space= where the CSF sits ontop.
Then Arachnoid mater, tiny subdural space on the underside of the Dura mater= thick tough layer to protect the spinal cord. Above the dura mater is the epidural space where there is adipose tissue which provides padding

Question 11

What is the denticulate ligament

Answer 11

It attaches the pia mater to the dura mater and supports the spinal cord

Question 12

What is the filum terminale and what are its two parts

Answer 12

An extension of the pia mater from the conus medallaris that connects the spinal cord to the coccyx, to anchor them and stop them from getting bunched in when you bend over

The meninges go until S2 and while pia mater is inside this it is the filum terminale interna. After this it is the filum terminale externa

Question 13

Compare how sympathetic nervous system info is transmitted to the body vs parasympathetic

Answer 13

Symp: In the brainstem they have nucleus but along the spinal cord they go into ganglia adjacent to the vertebra. Whereas ParasympatheticNS is mainly controlled by cranial nerves which control glands and esp cranial nerve X which goes to multiple organs

Question 14

How can dermatome be used to differentiate between peripheral nerve or spinal cord injury

Answer 14

If sensation is lost at one dermatome but still felt at dermatomes below it it is peripheral nerve injury but if no sensation below then its spinal cord injury as info can’t go past that injury to the brain. Same for myotome but its checking if can still do action

Question 15

Compare where the spinal nerves exit in relation to the vertebra for cervical vertebrae vs Lumbar and thoracic

Answer 15

8 C nerves but only 7 C vertebra so first 7 exit above the vertebra but C8 exits below C7 vertebra. Thoracic and lumbar have the spinal nerves exiting below the vertebra

Question 16

Compare cervical, thoracic and lumbar vertebrae: vertebral foramen size, vertebral body size and shape/location of articular facets

Answer 16

As you go down the spinal column the size of vertebral body increases due to more loading but the size of vertebral foramen decreases due to less spinal cord left.
C: short flat articular processes with superior facing anteriorly , inferior facing posteriorly
T: same orientation but longer articular processes that lock more
L: long articular processes that have superior facing inwards (medially) and inferior facing outwards (laterally) to lock more
As a result , as you go down spinal column loses flexibility & rotation and gains stability.

Question 17

What are some distinguishing features of cervical, thoracic and lumbar vertebrae

Answer 17

C: have prominent spinous process, have transverse foramen on either side of the vertebral body for vertebral artery to pass through to the brain.

T: have superior, transverse and inferior costal facets which articulate with the ribs curving out following the line of the transverse processes

L: articular faces in the medial/ lateral plane.

Question 18

What is the purpose of the transverse lines, superior articular process and auricular surface of the sacrum

Answer 18

Transverse lines: mark the former boundary between the 5 fused vertebrae
Superior articular processes: articulates with the last lumbar vertebrae
Auricular surface of the sacrum articulates with the pelvic girdle via the sacro iliac joint.

Question 19

What is the purpose of the sacrum

Answer 19

To protect the excretory and reproductive organs and attach the axial skeleton to the pelvic girdle.

Question 20

C1 (atlas) and C2 (axis) are atypical vertebra: what features does it have that contribute to what movements

Answer 20

C2 enables the “no” movement. It has reduced transverse processes and large flat superior articular processes. It has a ‘dens’ bump on the superior surface of its vertebral body which forms a pivot with the facet for dens on C1 vertebrae using a transverse ligament to around the front to keep it in place.

C1 enables the “yes” motion. The superior articular processes and/ facet are large and flattened to articulate with the occipital condyles of the skull.