structure and function of the spinal cord

Question 1

Where does the spinal cord extend to

Answer 1

From the atlas to the L1 vertebrae and tapers to form the conus medullaris.

Question 2

Outline the anatomy of the spinal cord

Answer 2

Sits protected within the vertebral column and is surrounded by meninges: pia, arachnoid, and dura

Question 3

How many regions is the spinal cord divided into

Answer 3

cervical region (8), thoracic region(12), lumbar(5), and sacral region (5)

Question 4

What is the lumbar cistern

Answer 4

It is the space below L1 and contains the cauda equina (lumbar and sacral dorsal and ventral roots).

Question 5

What are the roles of the cervical and lumbosacral enlargement

Answer 5

Innervation to the upper and lower limbs respectively.

Question 6

What type of nerve fibres do ventral and dorsal roots contain

Answer 6

efferent and afferent nerve fibres respectively.

Question 7

Outline the internal anatomy of the spinal cord

Answer 7

Inner core, grey matter (neuronal cell bodies, H-shaped, ventral, lateral and dorsal horns)

Outer, white matter (myelinated neurons and white tracts and columns)

Question 8

Outline grey matter organisation

Answer 8

Dorsal horn- neurons recieving sensory input
lateral horn- preganglionic sympathetic neurons
ventral horn- motor neurons

Question 9

Outline white matter organisation

Answer 9

Contains tracts: long ascending tracts that carry afferent (sensory) impulses to centres in the brain

long descending tracts carry efferent (motor) impulses from centres within the brain

tracts to and from cerebral hemispheres are crossed.

Question 10

Outline the columns in white matter

Answer 10

dorsal column (contains ascending tracts)
lateral column ( contains descending and ascending tracts)
ventral column (contains mainly descending tracts)

Question 11

What are the two types of sensory information carried within the ascending tracts

Answer 11

propriceptive- info originating inside the body e.g. muscles, joints etc

exteroceptive- info originating outside the body e.g. body, temp and touch etc

Question 12

How many neurons in a tract

Answer 12

3, first order (primary sensory) neuron enters spinal cord via dorsal root.

second order neurons- ascends spinal cord or brainstem

third order neuron- projects to the cerebral cortex

Question 13

Outline the DCML pathway

Answer 13

the dorsal column-medial lemniscus pathway, carrying information conveying fine touch and vibration sense, discriminating between fine and blunt pressures.

also conveying proprioception from muscle spindles, golgi tendons and joints.

Question 14

Outside the 1st order neurons of the DCML pathway

Answer 14

first order neurons:
enter spinal cord and ascend dorsal column on the same side.

the dorsal column can be divided into the fasiculus gracilis/cuneatus. they remain uncrossed.

Question 15

Where do the first order synapse on the second order neurons and where is information carried from lower and upper limbs

Answer 15

In the medulla.
lower limb- fasciculus gracilis terminates in nucelus gracilis
upper limb- fasciculus cuneatus and terminates in nucleus cuneatus.

Question 16

Outline the second order neurons

Answer 16

They cross in the medulla and ascend to the thalamus, form medial lemniscus

Question 17

Outline third order neurons

Answer 17

project from the thalamus to somatosensory cortex.

Question 18

Outline damage to the dorsal column

Answer 18

lesion on one side of the spinal cord e.g. MS
loss of tactile discrimination and proprioception on same side.
clinical test- rombergs sign

Question 19

Outline the spinothalamic tract

Answer 19

information on pain, temp and crude touch.
first order neurons enter dorsal horn and form tract of lissauer and synapse in dorsal horn with second order neuron.

second order neurons cross in dorsal horn at each level, ascend in the anterlateral column to thalamus

third order neurons, project from thalamus to somatosensory cortex

Question 20

Outline damage to the anterolateral column

Answer 20

Lesion on one side of spinal cord- leads to loss of pain, temp and crude touch on opposite sided.

outer tract injury e.g. cord compression due to herniated disk- loss of lower limb pain first

inner tract injury- loss of upper limb pain first

Question 21

Outline spinocerebellar tracts

Answer 21

unconscious muscle proprioception- from muscle spindles, golgi tendon organs.

there are 3 main tracts, anterior, posterior and cuniocerebllar tract

terminated in the cerebellum on the same side.

Question 22

What do the descending tract control

Answer 22

control muscular activity, many descending tracts and grouped into pyramidal and extrapyramidal.

Question 23

What is the corticospinal tract

Answer 23

A pyramidal tract, great voluntary motor pathway, 2 neurons in the circuit: upper motor neurons and lower motor neurons.

Question 24

outline the pyramidal tract

Answer 24

upper motor acons pass through the pyramids of the medulla, primary motor cortex, internal capsule, cerebral peduncle, pons to pyramids of medulla.

Question 25

What are the pyramids of descussation

Answer 25

within the pyramids of the medulla, nerve fibres decussate.

Question 26

What happens if the corticospinal tract is damaged

Answer 26

motor neurone disease, degeneration of upper motor neurons, spastic paralysis, over active tendon reflexes and no significant muscle atrophy.

lower motor neurone disease is damage to lower motor neurones : flaccid paralysis, muscle atrophy and no tendon reflexes.