Neuroanatomy - Ascending and Descending Pathways Flashcards
how many pairs of spinal nerves are there?
31
what are the two enlargements of the spinal cord?
cervical
lumbar
where does the spinal cord end in adults?
around the level of L1/L2
what is the name of the end of the spinal cord?
conus medullaris
what is the thin connective tissue continuation of the conus medullaris called?
the filum terminale
where is the filum terminale anchored to?
the dorsum of the coccyx
how are the spinal meninges continuous with the cranial meninges?
via the foramen magnum
what suspends the spinal cord in the spinal canal?
denticulate ligaments on the lateral aspects
what are the denticulate ligaments made of?
pia and arachnoid tissue
what extends through the centre of the spinal cord?
central canal
what happens to the central canal rostrally?
opens into the 4th ventricle
what happens to the central canal caudally?
blind ending
what is the white matter of the spinal cord divided into?
posterior, lateral and anterior columns
describe the relationship between the columns of white matter in the spinal cord
lateral and anterior are continuous
posterior is isolated by the posterior horns
what extra feature of grey matter is found at spinal segments T1-L2?
lateral horns
what do the lateral horns of T1-L2 contain?
preganglionic sympathetic neurons
what are the three major groups of vessels supplying the spinal cord?
longitudinal arteries
segmental arteries
radicular arteries
how many longitudinal arteries are there?
three - one anterior and two posterior
where do the longitudinal arteries originate?
vertebral arteries
what arteries run the length of the spinal cord?
longitudinal
what are the segmental arteries derived from?
vertebral, intercostal and lumbar arteries
where do the radicular arteries travel?
along the dorsal and ventral roots
what can embolic occlusion of any artery supplying the spinal cord result in?
areas of spinal cord infarction
how are neurone organised in the primary somatosensory cortex and what does this mean?
somatotopic
the body is mapped onto the cortex
where is the primary somatosensory cortex located?
post central gyrus of the parietal lobe
how does information travel to the primary somatosensory cortex and what is the exception?
spinal cord
information from the face and scalp
what happens to the amount of white matter as you descend the spinal cord?
proportion reduces
name two ascending tracts?
dorsal column
spinothalamic tract
what is the dorsal column called in the brainstem?
medial lemniscus system
what information is carried in the dorsal column?
fine touch
conscious proprioception
where do the fibres of the dorsal column cross over?
the medulla
what two nuclei receive the information from the dorsal column?
nucleus gracilis
nucleus cuneatus
what information does the nucleus gracilis receive from the dorsal column?
info from the lower portion of the body
what information does the nucleus cuneatus receive from the dorsal column?
information from the upper portion of the body
what happens to the dorsal column in the cervical region of the spinal cord?
develops a sulcus - forms the fasciculus gracilis and cuneatus
describe the role of the first, second and third order neurones in the dorsal column?
1 = spinal cord - ML system 2 = ML system - thalamus 3 = thalamus - primary somatosensory cortex
what information does the spinothalamic tract carry?
sensory fibres for pain, temperature and deep pressure
where do the fibres of the spinothalamic tract cross?
segmentally throughout the spinal cord
where do the first order neurones for the spinothalamic tract synapse?
immediately as they enter the spinal cord
describe the role of the first, second and third order neurones in the spinothalamic tract
1 = sensory receptor - spinal cord 2 = spinal cord - thalamus 3 = thalamus - PSC
where do the fibres in the spinothalamic tract cross over?
in the segment where it synapsed
then joins the tract
what are other possible names for the spinothalamic tract?
anterolateral tract
anterolateral system
where is the primary motor cortex located?
the precentral gyrus of the frontal lobe
what is another name for the corticospinal tract?
the pyramidal tract
what type of movement is the corticospinal tract involved in?
fine, precise movements
why is the corticospinal tract called the pyramidal tract?
forms visible ridges known as the pyramids on the anterior surface of the medulla
where do the majority of the fibres of the corticospinal tract cross?
in the caudal medulla at the decussation of the pyramids
around 85% of fibres
what do the crossed fibres of the corticospinal tract form and where do they go?
the lateral corticospinal tract
descend in the lateral column of the cord to their effector tissue
what do the uncrossed fibres of the corticospinal tract form and where do they go?
the ventral corticospinal tract
cross segmentally when they reach the appropriate spinal level and then move out of the column
where does the corticospinal tract begin?
the primary motor cortex
how does the corticospinal tract exit the brain?
passes through the internal capsule and then descends out through the brainstem
what does a CVA of the internal capsule result in?
lack of descending control of the corticospinal tract - resulting in a spastic paralysis with hyperflexion of the upper limbs
sometimes known as decorticate posturing
name three tracts that are part of the extrapyramidal system
tectospinal tract
reticulospinal tract
vestibulospinal tract
where does the input to the tectospinal tract come from?
cervical segments
what does the tectospinal tract mediate?
reflex head and neck movement due to visual stimuli
where does the tectospinal tract begin?
the midbrain
where do the fibres of the tectospinal tract cross the midline?
the midbrain
where does the tectospinal tract pass out of the spinal cord?
in the cervical region
only extends as far down as the cervical region
what forms the central core of the brainstem?
reticular formation
what is one function of the reticulospinal tract?
influences voluntary movements
where do the fibres of the reticulospinal tract originate?
in areas of the reticular formation in the pons and medulla
what movements are facilitated by reticulospinal tract fibres originating in the pons?
extensor movements
inhibits flexor movements
what movements are facilitated by reticulospinal tract fibres originating in the medulla?
flexor movements
inhibit extensor movements
what does the vestibulospinal tract provide?
excitatory input to anti-gravity extensor muscles
where do the fibres of the vestibulospinal tract originate?
vestibular nuclei of the pons and medulla
where do the fibres of the vestibulospinal tract receive input from?
the vestibular labyrinth
where do the fibres of the vestibulospinal tract cross the midline?
nowhere
