Scenario (3)brain -stroke

Question 1

Venous drainage of the brain

Answer 1

Deep veins
Superficial veins
Dursley’s venous sinuses

None have valves

Question 2

What is the function of the Ascending tracts

Answer 2

neural pathways by which sensory information from the peripheral nerves is transmitted to the cerebral cortex.

Question 3

What type of information do ascending tracts carry

Answer 3

Sensory information

1) Conscious tracts -€“ comprised of the dorsal column-medial lemniscal pathway and the anterolateral or spinothalamic system.
2) Unconscious tracts -€“ comprised of the spinocerebellar tracts.

Question 4

Name the ascending tracts

Answer 4

Dorsal Column-Medial Lemniscal Pathway

(Spinothalamic)or(Anterolateral) system

Spinocerebellar Tracts -€“ Unconscious Sensation

Question 5

Dorsal Column-Medial Lemniscal Pathway

Answer 5

Carries sensory modalities of fine touch (tactile sensation), vibration and proprioception.

> spinal cord:information travels via the dorsal (posterior) columns.

> brainstem, it is transmitted through the medial lemniscus.

First, second and third order neurones are involved in this pathway

Question 6

DC First order neurones

Answer 6

Carry sensory information= touch, proprioception or vibration from the peripheral nerves to the medulla oblongata.

X2 pathways first order neurones take:

Signals from the upper limb (T6 and above) -€“ travel in the fasciculus cuneatus (the lateral part of the dorsal column). They then synapse in the nucleus cuneatus of the medulla oblongata.

Signals from the lower limb (below T6) -€“ travel in the fasciculus gracilis (the medial part of the dorsal column). They then synapse in the nucleus gracilis of the medulla oblongata.

Question 7

DC Second order neurones

Answer 7

Begin in the cuneate nucleus or gracilis.

The fibres receive the information from the preceding neurones, and delivers it to the third order neurones in the thalamus.

Within the medulla oblongata, these fibres decussate to the other side of the CNS.

They then travel in the contralateral medial lemniscus to reach the thalamus.

Question 8

DC Third order neurones

Answer 8

Transmit the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain.

They ascend from the ventral posterolateral nucleus of the thalamus, travel through the internal capsule and terminate at the sensory cortex.

Question 9

What the 2 tracts of the anterolateral tract

Answer 9

1) Anterior spinothalamic tract -€“ carries the sensory modalities of crude touch and pressure.
2) Lateral spinothalamic tract -€“ carries the sensory modalities of pain and temperature.

Also have first,second and third order neurones

Question 10

AL First order neurones

Answer 10

Arise from the sensory receptors in the periphery.

They enter the spinal cord, ascend 1-2 vertebral levels, and synapse at the tip of the dorsal horn -€“ an area known as the substantia gelatinosa.

Question 11

AL Second order neurones

Answer 11

Carry the sensory information from the substantia gelatinosa to the thalamus.

After synapsing with the first order neurones, these fibres decussate within the spinal cord, and form two distinct tracts:

1. Crude touch and pressure fibres -€“ enter the anterior spinothalamic tract.
2. Pain and temperature fibres -€“ enter the lateral spinothalamic tract.

Functionally distinct, these tracts run alongside each other, and they can be considered as a single pathway.

Travel superiorly within the spinal cord, synapsing in the thalamus.

Question 12

AL Third order neurones

Answer 12

Carry the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain.

They ascend from the ventral posterolateral nucleus of the thalamus, travel through the internal capsule and terminate at the sensory cortex.

Question 13

Name the Spinocerebellar tracts

Answer 13

1) Posterior spinocerebellar tract -€“ Carries proprioceptive information from the lower limbs to the ipsilateral cerebellum.
2) Cuneocerebellar tract -€“ Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.
3) Anterior spinocerebellar tract -€“ Carries proprioceptive information from the lower limbs. The fibres decussate twice -€“ and so terminate in the ipsilateral cerebellum.
4) Rostral spinocerebellar tract -€“ Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.

Question 14

What does the Spinocerebellar tract transmit

Answer 14

Transmit unconscious information/ proprioception

Although we cannot physically acknowledge these signals, they help our brain co-ordinate and refine motor movements.

They transmit information from the muscles to the cerebellum.

Question 15

What does the descending tracts carry

Answer 15

Motor signals are sent from the brain to lower motor neurones.

The lower motor neurones directly innervates muscles producing movement.

Question 16

2 categories of descending tract

Origin and function

Answer 16

1)Pyramidal tracts -€“ originate in cerebral cortex, carry motor fibres to the spinal cord and brain stem.

Responsible for voluntary control of musculature of the body and face.

2)Extrapyramidal tracts -€“ originate in the brain stem, carry motor fibres to the spinal cord.

Responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion

Question 17

Do the descending tracts have synapses

What are the neurones in the descending tracts classified as

Answer 17

There are no synapses within the descending pathways.

At the termination of the descending tracts, the neurones synapse with a lower motor neurone.

Therefore: the neurones within the descending motor system= upper motor neurones.

Their cell bodies are found in the cerebral cortex or the brain stem, with their axons remaining within the CNS.

Question 18

Pyramidal tracts function and 2 categories

Answer 18

Responsible for the voluntary control of the musculature of the body and face.

1) Corticospinal tracts -€“ supplies the musculature of the body.
2) Corticobulbar tracts -€“ supplies the musculature of the head and neck.

Question 19

Corticospinal tract

Answer 19

• Begins in cerebral cortex = primary motor cortex
• Terminate spinal grey matter

75% decussate

Nerve fibres from the somatosensory area =regulate the activity of the ascending tracts.

Originate cerebral cortex, the neurones converge, and descend through the internal capsule (a white matter pathway, located between the thalamus and the basal ganglia).

Question 20

What happens in the most inferior (caudal) part of the medulla

Answer 20

Tract divides into two:

Lateral corticospinal tract
Anterior corticospinal tract

1) Lateral = desiccated mainly one that crosses
2) Anterior = ipsalateral

Question 21

Corticobulbar tract

Answer 21

Arises from the lateral aspect of the primary motor cortex.

Receive the same inputs as the corticospinal tracts.

The fibres converge and pass through the internal capsule to the brainstem.

Neurones terminate on the motor nuclei of the cranial nerves within brain stem:

synapse with lower motor neurones=carry the motor signals to the muscles of the face and neck.

Question 22

Clinical importance corticospinal tract

Answer 22

Internal capsule is susceptible to compression from haemorrhagic bleeds, known as a -€˜capsular stroke-€˜.

Could cause a lesion of the descending tracts.

Question 23

Clinical importance corticobulbar tract

Answer 23

Fibres innervate the motor neurones bilaterally.

E.g fibres from the left primary motor cortex act as upper motor neurones for the right and left trochlear nerves.

Exceptions to this rule:

Upper motor neurones for the facial nerve (CN VII) have a contralateral innervation. This only affects the muscles in the lower quadrant of the face -€“ below the eyes.

Upper motor neurons for the hypoglossal (CN XII) nerve only provide contralateral innervation

Question 24

Name the 4 extrapyramidal tracts

Answer 24

vestibulospinal

reticulospinal

rubrospinal

tectospinal

Question 25

Which of the extrapyramidal tracts corss

Answer 25

Vestibulospinal and reticulospinal tracts dont decussate=ipsilateral innervation.

Rubrospinal and tectospinal tracts decussate= contralateral innervation

Question 26

Vestibulospinal Tracts

Origin and function

Answer 26

2 vestibulospinal pathways:

medial (head and eye movements)
Lateral (powerful exciters movement)

Arise from the vestibular nuclei ( medulla oblongata) which receive input from the organs of balance.

Send balance information to the spinal cord, where it remains ipsilateral.

Fibres in this pathway control balance and posture by innervating the -€˜anti-gravity-€™ muscles (flexors of the arm, and extensors of the leg), via lower motor neurones.

Question 27

Reticulospinal Tracts

Origin and Function

Answer 27

2 recticulospinal tracts have differing functions:

Medial+ lateral tracts

1) Medial reticulospinal tract arises from the pons. It facilitates voluntary movements, and increases muscle tone.
2) The lateral reticulospinal tract arises from the medulla. It inhibits voluntary movements, and reduces muscle tone.
* In stroke not moderated therefore you get an exaggerated positive babiski test

Question 28

rubrospinal tract

Origin function

Answer 28

Originates from the red nucleus, midbrain structure.

As the fibres emerge, they decussate (cross over to the other side of the CNS), and descend into the spinal cord=contralateral innervation.

Thought to play a role in the fine control of hand movements

Question 29

Tectospinal Tracts

Answer 29

Begins at the superior colliculus of the midbrain.

Superior colliculus=receives input from the optic nerves. Neurones then decussate, and enter the spinal cord. Terminate at the cervical levels of the spinal cord.

Coordinates movements of the head in relation to vision stimuli.

Question 30

Define stroke

Answer 30

Stroke is an abrupt interruption of constant blood flow to the brain that causes loss of neurological function.

Ischeamic: lack of O2 caused by blood clot

Haemorrhagic: weakened blood vessels burst

Question 30

How will impaired blood supply affect function

Answer 30

Carotid/ vertebral arteries not completely blocked = small stream of blood trickles to the brain.

Reduced blood flow to the brain starves the cells of nutrients leads malfunctioning of the cells.

A part of the brain stops functioning, symptoms of a stroke occur.

Stroke = a core area where blood is almost completely cut off and the cell necrosis

ischemic penumbra= surrounds the core of dead cells. Contains cells that are impaired but not dead = idling cells

Question 30

What else can happen after a stroke

Answer 30

impairments of voluntary movement and sensation

produce abnormalities of muscle tone caused by exaggerated stretch reflexes and secondary muscle stiffness.

Question 31

Arterial supply to the brain

Answer 31

X2 pairs of vessels

1. Internal carotid arteries
2. Vertebral arteries

Question 32

Internal carotid artery origin and termination

Answer 32

Arises from common carotid artery then enters the middle fossa of cranial cavity through the carotid canal

Pathway= carotid syphon

Reaches medial aspect of the anterior clinoid process reaching surface of brain lateral to optic chiasm

Question 33

What does the internal carotid form

Answer 33

Lateral to optic chiasm divides into

Anterior + middle cerebral arteries

Question 34

Anterior cerebral artery

Answer 34

Anterior cerebellar artery passes into great longitudinal fissure between frontal lobes of cerebral hemispheres joins opposite sides= ANTERIOR COMMUNICATING ARTERY

Left and right

X1

Question 35

Medial cerebral artery

Answer 35

Largest of the cerebral arteries

Excludes blood supply to lower limb

Question 36

Posterior communicating artery

Answer 36

Passes backwards to join posterior cerebral artery forming the circle of wilis= ensures there’s enough O2 if there is a blockage

Connects internal carotid arteries and posterior cerebral arteries= circle of wilis anterior+posterior

X2

Question 37

Internal carotid vs vertebral arteries

Answer 37

Internal carotid = more anterior part of brain

Vertebral= more posterior part of brain

Question 38

Vertebral arteries

Answer 38

Arises from subclavian artery

X2 vertebral arteries unite at the junction of the medulla and pons to form midline BASILAR ARTERY

Divides in left and right

Largest branch= posterior inferior cerebellar artery= inferior part of cerebellum

Question 39

Circle of wilis

Answer 39

Encircles the optic chiasm and floor of hypothalamus, midbrain

Compensates narrowing or blockage of proximal cerebral arteries through communicating arteries

Periforating arteries= surface of brain