practical 2 sensory pathways W2 Flashcards
major sensory pathways and their functions?
dorsal columns (fasciculi gracilis and cuneatus): proprioception and discriminative touch (aka fine touch)
spinothalamic tract: pain, crude touch, temperature
difference between fine and crude touch?
fine: allows localisation of touch
crude: doesn’t allow localisation of touch
dorsal columns pathway?
->peripheral receptor
->dorsal root ganglion
->fasciculus cuneatus/gracilis
->nucleus cuneatus/gracilis (medulla)
->internal arcuate fibres (medulla)
->medial lemniscus (medulla/pons/midbrain)
->VPL thalamus
->internal capsule
->corona radiata
->post central gyrus
what does the dorsal root ganglion contain
cell bodies of sensory neurons
spinothalamic pathway?
->peripheral receptor
->DRG
->dorsal horn
->ventral white commissure
->spinothalamic tract of spinal cord
->spinal lemniscus
->VPL thalamus
->internal capsule
->corona radiata
->post central gyrus
caudal medulla features?
posterior: fasciculus gracilis lies medial to fasciculus cuneatus. deep to these lie the corresponding nuclei.
medial: internal arcuate fibres run to the medial lemniscus which lines the anterior median fissure.
anterior: pyramid
where is the medial lemniscus found in different cross sections of the brainstem
medulla: medial, stretches anterior/posterior
mid-pons: deep to pontocerebellar fibres (transverse pontine fibres). stretches medial/lateral
midbrain: lateral, in continuous line with spinal lemniscus
where is the location of the nucleus gracilis and nucleus cuneatus marked? where are these visable?
gracile and cuneate tubercles
visible on dorsal surface of medulla above fasciculus cuneatus/gracilis
how to identify the thalamus on half brains and coronal brain sections?
half brain - find 3rd ventricle, forms wall of this (visible superior)
coronal section - lateral to third ventricle, medial to internal capsule
where do neurons carrying sensory information for the head and neck synapse?
ventroposteriomedial nucleus of the thalamus (VPM nucleus)
where do neurons carrying sensory information from the rest of the body synapse?
ventroposteriolateral nucleus of the thalamus (VPL nucleus)
what areas of grey matter form the boundaries of the internal capsule?
caudate nucleus
lentiform nucleus (globus pallidus, putamen)
thalamus
what is the functional arrangement of fibres within the internal capsule?
anterior limb: fibres associated with higher functions
posterior limb: major ascending somatosensory fibres and descending motor fibres
where is the primary somatosensory cortex?
post central gyrus (gyrus immediately posterior to central sulcus)
what is the principle arterial blood supply to the sensory cortex receiving information from the lower limb?
anterior cerebral artery
what is the principle arterial blood supply to the cortex receiving information from the head?
middle cerebral artery
where are dorsal root ganglia found?
dural root sleeve in the intervertebral foramen (only visible when some bone has been cut away)
what are the large pink cells visible in a H and E stained DRG section?
cell bodies of first order sensory neurons.
what are dorsal root ganglion?
a collection of sensory neuron cell bodies outside of the CNS
features of the cervical spinal cord?
increased grey matter due to increased neuron cell bodies to provide innervation to upper limbs
large amount of white matter (increases closer to brain)
features of thoracic spinal cord?
small amount of grey matter
features of lumbar spinal cord?
increased grey matter due to increased neuron cell bodies to provide innervation to lower limbs
less white matter than cervical as further from brain
sacral spinal cord features?
very small amount of white matter as far from brain
what is a dermatome
the specific region on the surface of the body innervated by the sensory axons carried in each individual spinal nerve (and the trigeminal nerve)
body region associated with C2/3 dermatome?
posterior scalp and neck
body region associated with C6 dermatome?
anterior arm and thumb
body region associated with T4 dermatome?
ant/post thorax at level of 6th rib (approx. nipples level)
body region associated with T10 dermatome?
ant/post abdomen at level of umbilicus
body region associated with L4 dermatome?
front of knee to medial aspect of ankle/foot
what is carried in the trigeminal nerve?
sensory information for the head and neck
where is the trigeminal nerve found in the brain stem
enters brainstem at level of the pons
visible on a cross section travelling inwards, lateral to the pontocerebellar fibres.
sensory nuclei in brainstem where sensory neurons with cell bodies in the trigeminal ganglion synapse? what type of information is associated with each nucleus?
mesencephalic nucleus: proprioception
chief sensory nucleus: touch, pressure
nucleus of the spinal tract of the trigeminal: pain, temperature
trigeminothalamic fibres decussate in the brain stem and travel to the thalamus. where in the thalamus do these fibres synapse?
ventroposteriomedial nucleus of thalamus
locations of the nuclei where trigeminal ganglion nerves synapse? (brainstem)
mesencephalic nucleus: rostral
chief sensory nucleus: middle
nucleus of spinal tract of the trigeminal: caudal (lateral to dorsal columns, visible on isolated brainstem)
what information does the spinocerebellar pathway carry
control of posture
coordination of movement
where is the cell body of the first and second order neurons of the spinocerebellar pathway found?
first order: dorsal root ganglion
second order: mostly in dorsal horn of spinal cord
2 principle tracts relating to spinocerebellar pathway? do they cross?
dorsal spinocerebellar tract (does not cross, ipsilateral)
ventral spinocerebellar tract (does cross, contralateral)
where do the dorsal and and ventral spinocerebellar tracts enter the cerebellum? (describe where these are found)
dorsal: inferior cerebellar peduncle (medial to middle cerebellar peduncle)
ventral: superior cerebellar peduncle (diagonal ridge)
what type of sensory information is carried in the spinocerebellar tract
relative stretch in muscles from muscle spindles
stretch in tendons
joint receptors
pressure on skin and superficial fascia
