Spinal cord and the Periphery

Question 1

Spinal Cord is composed of

Answer 1

Central grey matter

Peripheral white matter

Question 2

Where is the dorsal and ventral horn located in the spinal cord

Answer 2

In the grey matter

Question 3

What is the pathway of sensory fibres in the spinal cord

Answer 3

Enter through dorsal route into the dorsal horn of the grey matter

Question 4

Where is the motor neurones cells bodies located

Answer 4

In the ventral horn

Question 5

Where is the sensory neurones cell body located

Answer 5

In the dorsal root ganglia of the spinal cord

Question 6

How is the white matter arranged and what is it composed of

Answer 6

Arranged into three columns, Posterior, lateral and anterior, with each column having its various tracts

Question 7

What is function of tracts in the white matter

Answer 7

Act as pathways as axons transmit information between higher centres and the peripheral nerves

Question 8

What are ascending pathways

Answer 8

Pathways that carry sensory information to the brains cerebral cortex and cerebellum via the spinal cord

Question 9

What is the common characteristic of ascending pathways

Answer 9

3 neurones between peripheral receptor and cortex

always cross over at 2nd order neurone

Common pathway -

1st order:
From receipts travels via dorsal root ganglia and synapses in grey matter of spinal cord of nucleus medulla

2nd order:
Crosses over to contralateral side in spinal cord or medulla and synapses in nucleolus in contralateral thalamus

3rd order:
Travels to contralateral parietal cortex

• pathways may have different route to get to parietal cortex

Question 10

What are the two tracts in the ascending pathway

Answer 10

Posterior/dorsal column

Lateral spinothalmic tract

Question 11

What sensory information is the posterior/dorsal column responsible for

Answer 11

Fine touch

Vibration sense

proprioception

tactile localisation

(touch and pressure receptors located in the skin)

Question 12

What is the pathway os posterior/dorsal column

Answer 12

1st order neurones pick up sensory impulses from receptors in skin

travels into spinal cord through dorsal route

the enters posterior column of the dorsal part and travels upwards

Synapses in the medulla in the gracille and cuneate nuclei

The second neurone then crosses over to opposite side and travels up to pons via medial lemniscus

Then synapses in the VLPL nucleus in the thalamus

the 3rd order neurone then travels to post central gyrus in parietal lobe

Question 13

Why is the thalamus called the relay station

Answer 13

as is a group of nuclei that all sensory information synapse in then the thalamus modulates

Question 14

Where does the posterior dorsal column cross over

Answer 14

2nd order neurone in the gracille and cuneate nuclei in the medulla

Question 15

What sensory information is the lateral spinothalmic tract responsible for

Answer 15

Pain

Temperature

(nociceptors and thermoreceptors)

Question 16

What is the pathway of the spinothalmic tract

Answer 16

1st order neurones pick up sensory impulses nociceptor/thermoreceptor in the skin

travels into spinal cord through dorsal route and synapse and level of entry

The second order neurone then crosses over at level of entry to the lateral white matter of the spinal cord

Then synapses in the VPL nucleus of the thalamus

and 3rd order neurone travels to the post central gyrus of parietal lobe

Question 17

How does the right side of the brain process pain and temperature from the left side of the body

Answer 17

Due to 2nd order neurone crossing over at the level entry to reach the lateral coloumn in the spinal cord to so carries pain and temperature from the opposite side of the body

Question 18

Why is the dorsal column thicker than the lateral spinothalmic tract

Answer 18

Due to more sensory fibres being present

Question 19

Where does the spinothalmic tract cross

Answer 19

2nd order neurone at the spinal cord level of entry

Question 20

What is descending pathways

Answer 20

Tracts coming from cerebral cortex with motor impulses concerned with voluntary control of movement, muscle tone, reflexes and spinal autonomic function

Question 21

What is the characteristic of the descending pathway

Answer 21

Originate from cerebral cortex

Have two motor neurones in there pathway:

Upper motor neurone
- primary motor cortex –> spinal cord

Lower motor neurone
Spinal cord –> skeletal muscle

Upper motor neurone crosses to the opposite side of the bodying brainstem (pyramidal decussation in medulla)

Question 22

What is the name of the descending motor pathway

Answer 22

Pyramidal tracts:

Corticospinal

Corticobullar

Question 23

What is the pathway of the corticospinal tract pathway

Answer 23

Starts in motor homunculus on primary motor cortex on opposite side

neuronal cell bodies sit in grey matter of precentral gyrus and axons radiates through white matter to posterior limb of internal capsule and into the midbrain whose internal capsule becomes cerebral peduncles and travels through the white matter of the cerebral peduncles called the crus cerebri

Then travels through pons to medulla and forms pyramidal tracts, the first order neurone crosses at the lower part of the medulla = decussation of pyramids

(most cross)

Travels in white matter of spinal cord then enter ventral horn of grey matter in spinal cord and synapses with lower motor neurone at the levels of the skeletal muscles its going to innervate

Question 24

What are the two corticospinal tracts and how are they different

Answer 24

Lateral corticospinal tract - due to fibres crossing in decussation of pyramids

anterior corticospinal tracts - due to not crossing in decussation of pyramids (only 10-15)

Question 25

What is the function of the corticobulbar tract

Answer 25

Motor pathway connecting the motor cortex in the cerebral cortex to the Medullary pyramids,

Primarily involved in carrying the motor function of the non-oculomotor cranial nerves.

Question 26

What is the pathway of the corticobulbar tract

Answer 26

Two neurone pathway identical to corticospinal tracts until crus cerebri

then the corticobulbar fibers exit at the appropriate level of the brainstem to synapse on the lower motor neurons of the cranial nerves on contralateral side

Question 27

Define reflexes

Answer 27

An immediate response brought by sensory stimulus mediated at the level of the spinal cord and doesnt go through cerebral hemisphere

Question 28

What is an example of a monosynaptic and polysynaptic reflex

Answer 28

mono - stretch reflex

poly- flexor reflex

Question 29

What occurs in a stretch reflex

Answer 29

Tendon stretches

Intrafusal muscle fibres stimulated

Sensory neurone activates

monosynaptic reflex arc causing agonist muscle stimulated to contract

additionally

Polysynaptic reflex arc to inhibitory interneurone casing reciprocal innervation of antagonist muscle to relax

Question 30

What is the importance of the stretch reflex

Answer 30

important in control of muscle tone and posture

Question 31

What occurs in flexor reflex

Answer 31

Pain stimulus

sensory neurone activates goes through polysynaptic reflex arc

causing flexion withdrawal from stimulus

and crossed extensor response to contralateral (only in weight bearing limbs)

Question 32

What motor neurone is involved in stretch and flexor reflex

what does this show

Answer 32

The lower motor neuron (LMN) as is responsible for muscle tone and reflexes

motor response can occurs can without UMN involvement

Question 33

What is the importance of the flexor reflex

Answer 33

Help protect the body from painful stimuli

Question 34

What occurs if upper motor neurone is damaged and lower motor neurone is intact on reflexes and tone

Answer 34

reflexes and tone are exaggerated

Question 35

Why do you investigate in a neurological lesion

Answer 35

Cortical problems - speech?

Motor paralysis/wekaness

• which side
• spastic/flaccid
• what happens to reflexes

Cranial nerve weakness
- same side or opposite

Sensory defects

• which side for pain and temp
• which side for touch and vibration

Question 36

What occurs in a lesion of the upper motor neurone

Answer 36

LMN works without UMN

But causes increased tone = spastic paralysis

and exaggerated reflexes = hyperflexia

Question 37

What occurs in a lesion on the lower motor neurone

Answer 37

paralysed muscle

arefexia - reflexes lost

flaccid paralysis - lack of tone

Question 38

What causes brown-sequard syndrome

Answer 38

Hernaited disc

Question 39

If a lesion occurs in the left side of the spinal cord what is the symptoms and why?

Answer 39

Left side paralysis, and loss of touch and vibration sense
( as posterior dorsal column hasn’t crossed yet)

Right sided loss of temperature and pain (as spinothalmic tract has already crossed)

Reflexes in left side exaggerated (as corticospinal tract hasn’t crossed yet)

Question 40

What is the basic autonomic efferent pathway

Answer 40

Cell body in brainstem/spinal cord
Travels are preganglionic neurone

synapses in autonomic ganglion

travels as post ganglionic neurone to target organs where it synapses again

Question 41

What is the division of the peripheral nervous system

Answer 41

Somatic

autonomic

Question 42

What is the division of the autonomic nervous system

Answer 42

Sympathetic

Parasympathetic