Neuro Anatomy 2 - Ascending and Descending Tracts Flashcards
What are the 2 enlargements of the spinal cord?
Cervical (for upper limbs)
Lumbar (for lower limbs)
Which aspects of the spinal cord do the rootlets emerge from?
Dorsal and ventral aspect
What to the rootlets emerging from the spinal cord coalesce to form?
Anterior and posterior roots
What does the anterior and posterior roots merge to form?
Spinal nerve
What does the spinal nerve branch to form?
Anterior and posterior rami
What is the name of the tapered cone-shaped structure formed where the spinal cord terminates?
Conus medullaris
What does the conus medularis continue as?
A thin connective tissue cord called the filum terminale (anchored to the dorsum of the coccyx)
At what vertebral level does the spinal cord terminate?
Approximately L1/2
What suspends the spinal cord in the spinal canal?
Denticulate ligament (ribbon of tissue on the lateral aspects of the cord)
What is the denticulate ligament formed from?
Pial and arachnoid tissue
What 3 things is the white matter of the spinal cord formed from?
Longitudinally arranged nerve axons
Glial cells
Blood vessels
What 5 things is the grey matter of the spinal cord formed from?
Neuronal soma Cell processes Synapses Glia Blood vessels
What does the central canal of the spinal cord open into rostrally?
The 4th ventricle (caudally it is blind ended)
What is another name for columns i.e. posterior/ anterior/ lateral columns of white matter of the spinal cord?
Funiculus
How do you tell the difference between the posterior and anterior horns of the spinal cord?
Posterior horns extend all the way to the margin of the spinal cord whereas the anterior horns do not
What does the horizontal part of the H of the grey matter of the spinal cord represent?
Dorsal and ventral grey commisures (surround the central canal)
What part of the grey matter of the spinal cord contains the preganglionic sympathetic neurones?
Lateral horn
Between vertebral levels are lateral horns present?
T1-L2
What are the 3 major longitudinal arteries which supply the spinal cord?
1 X anterior spinal artery
2 X posterior spinal artery
Where does the spinal arteries originate?
Vertebral arteries
What are the segmental arteries of the spinal cord derived from?
Vertebral, intercostal and lumbar arteries
What is the name for the arteries associated with the roots of the spinal cord?
Radicular arteries
What can happen if the there is embolic occlusion of any of the arteries supplying the spinal cord?
Spinal cord infarction
How is blood from the spinal cord drained?
Via longitudinal and segmental veins + venous plexus (in epidural space)
What is the name of the space between the dura and the bone in the spinal canal?
Epidural space
Is there a space between the dura and periosteum in the cranial cavity?
No
What does the epidural space in the spinal canal contain?
Adipose tissue and the anterior and posterior epidural venus plexuses
What are the 3 types of arteries that supply the spinal cord?
Longitudinal arteries
Segmental arteries
Radicular arteries
What is the cerebral cortex?
Outer layer of grey matter in the cerebrum of the brain
Location of the primary somatosensory cortex?
Postcentral gyrus in the parietal lobe
Which side of the brain is the primary somatosensory cortex for the right hand side of the body?
Left
How does the information from the periphery reach the somatosensory cortex?
They travel in the spinal cord (except for face and scalp)
How does the white matter proportion part as you descend the spinal cord?
It decreases (adding sensory fibres as we go up and losing motor fibres as we go down)
What are the 2 main ascending spinal cord tracts?
Spinothalamic tract Dorsal funiculus (column containing fasciculus gracilus and fasciculus cuneaus)
What is the name for a bundle of secondary sensory fibres in the brainstem?
Lemniscus
Fill in the gap:
Dorsal column/ ____ ____ system
Medial lemniscus
What is the dorsal column/ medial lemniscus responsible for?
Fine touch and conscious proprioception (particularly from the upper limb)
Where do fibres from the dorsal column/ medial lemniscus cross?
In the medulla
Describe the path of fine touch/ conscious proprioception sensation from the lower limb to the medulla?
Travels via fasiculus gracilis in the dorsal funicular of the spinal cord
What happens to fine touch/ conscious proprioception sensation from the lower limb in the medulla?
Synpases on the nucleus gracilis and then crosses over
How does fine touch/ conscious proprioception sensation from the lower limb travel between the medulla and primary somatosensory cortex?
Once the 2nd order neurones have crossed over, they travel in the medial lemniscus from the medulla to the pons and midbrain and then to the thalamus where they synapse before 3rd order neurones pass into the primary somatosensory cortex (lower limb area)
Describe the path of fine touch/ conscious proprioception sensation from the upper limb to the medulla?
Travels via fasiculus cuneatus in the dorsal funicular of the spinal cord
What happens to fine touch/ conscious proprioception sensation from the upper limb in the medulla?
Synpases on the nucleus cuneatus and then crosses over
How does fine touch/ conscious proprioception sensation from the lower limb travel between the medulla and primary somatosensory cortex?
Once the 2nd order neurones have crossed over, they travel via the medial lemniscus to the pons and midbrain and then to the thalamus where they synapse before 3rd order neurones pass into the primary somatosensory cortex (upper limb area)
Are the spinal tracts part of the white or grey matter?
White matter
What sensation does the spinothalamic tract carry?
Pain, temperature, deep pressure
Where do the neurones in the spinothalamic tract cross?
In the spinal cord
Describe the route of pain, temperature and deep pressure signals to the primary somatosensory cortex?
Primary neurones enter spinal cord and synapse in posterior horn on the same side
Second order neurones cross over and travel up in the spinothalamic tract on the opposite side
Second order neurones the travel in the spinal lemniscus through the medulla, pons and midbrain synapsing in the thalamus
3rd order neurones travel to the primary somatosensory area
Where is the primary motor cortex located?
Precentral gyrus in the frontal lobe
What side of the body does the right primary motor cortex control?
Left
What is the name for the model that reflects the relative space occupied on the primary motto cortex by each part of the body?
Cortical motor homunculus
What signals does the corticospinal tract carry?
Fine, precise movement, particularly of distal limb muscle e.g. digits
What is the name for the visibleridges created by the corticospinal tract on the anterior surface of the medulla?
What is therefore another name for the corticospinal tract?
Pyramids
Pyramidal tract
Where does the corticospinal tract fibres cross?
Lateral CST = in the caudal medulla (at the decussation of the pyramids)
Ventral CST = cross in the spinal cord (segmentally)
How many orders of neurones are involved in the relay of fine, precise movement (corticospinal tract)?
1
What side of the brainstem do fine, precise movement signals to the right side of the body pass down?
Left
In terms of the corticospinal tract, what can a cerebrovascular accident of the internal case cause?
A lack of descending control of the CST causing a spastic paralysis with hyeprflexion of the upper limbs (i.e. decorticate posturing)
In the lower medulla, what % of corticospinal tract fibres change side?
85% (referred to as the decussation of the pyramids)
What is the name for the motor systems outside of the pyramidal tract?
Extrapyramidal system
What segments of the spina cord does the tectospinal tract mostly input to?
Cervical segments
What does the tectospinal tract mediate?
Reflex head and neck movement due to visual stimuli
Where does the tectospinal tract cross over?
in the midbrain
How many orders of neurones do sensory tracts have?
3
How many orders of neurones do motor tracts have?
1
What forms the central core of the brainstem?
Reticular formation
Does the reticulospinal tract receive little or many inputs?
Inputs from virtually all parts of the CNS
What is the function of the reticulospinal tract?
Carries many motor signals including the influencing of voluntary movement
What are the names of the 2 reticulospinal tracts?
Medullary and pontine reticulospinal tract
Where do the fibres of the reticulospinal tract originate?
Reticular formation in pons (pontine reticulospinal tract) and medlla (medullary reticulospinal tract)
What type of movements do reticulospinal tract fibres originating in the pons facilitate and inhibit?
Facilitate extensor movements and inhibit flexor movements
what type of movements do reticulospinal tract fibres originating in the medulla facilitate and inhibit?
Facilitate flexor movements and inhibit extensor movements
What type of signal does the vestibulospinal tract carry?
Excitatory input to anti-gravity extensor muscles
Do fibres in the vestibulspinal tract cross over?
No
Where do fibres in the vestibulospinal tract originate?
In the vestibular nuclei of the pons and medulla (these in turn receive input from vestibular apparatus and cerebellum)
What symptoms can patients have if they have a lesion of the brainstem at the level of the midbrain affecting cortical control of the vestibulospinal tract?
why?
Decerebrate rigidity
Paraplegia in extension
Domination of extensor muscle tone and hyperextended spastic paralysis
What is brown-sequards syndrome caused by?
A lesion in one (lateral) half of the spinal cord
what symptoms occur with brown-sequards syndrome?
Ipsilateral paralysis, hyperreflexia and extensor plantar reflex
Ipsilateral loss of vibratory sense and proprioception with contralateral loss of pain and temperature sense (as the spinothalamic tract crosses over segmentally)
