SENSORY SYSTEMS, SPINAL CORD AND BRAIN STEM Flashcards
in the CNS where do we find cell bodies and axons?
cell bodies in grey matter
axons in white matter
in the PNS where do we find cell bodies and axons?
cell bodies in ganglia
axons in nerves
what are the 4 main types of sensation?
superficial, deep, visceral and special
what is superficial sensation?
crude touch, pain, temperature and 2 point discriminative touch
what is deep sensation?
muscle and joint position sense and deep muscle pain
what is visceral sensation?
sensations arising from the viscera: hunger, nausea, visceral pain
what is special sensation?
senses: smell, vision, hearing, taste and balance
where does the length of the spinal cord run from and too?
from the foramen magnum until L1/L2
what are the 2 vertebral enlargements? why do we have them?
cervical and lumbar
due to an increased number of nerves coming out of these locations
describe the layers of the meninges?
spinal cord surrounded by Pia matter which is surrounded by the subarachnoid space and arachnoid matter which is surrounded by the dura matter which is surrounded by the epidural space and this is finally surrounded by the vertebral canal.
where do we find the cerebral spinal fluid?
what is its function?
in the sub-arachnoid space
to cushion the brain and spinal cord from trauma, to supply them with nutrients and to remove waste
what is the lumbar cistern?
the sub-arachnoid space in the low lumbar spinal canal
why are lumbar punctures done below L1/L2
as the spinal cord has ended so you can gather CSF without damaging the spinal cord
what is the conus medullaris?
the tapered lowers end of the spinal cord at L1/L2
what is the film terminali?
delicate strand of fibrous tissue in length, proceeding downward from the apex of the conus medullaris. it anchors the spinal cord at S2
what is the cauda equine?
the sack of nerve roots at the lower end of the spinal cord.
what is the central canal in the centre of grey matter?
the cerebrospinal fluid-filled space that runs through the spinal cord.
what are the lateral horns of the spinal cord?
small lateral projections of grey matter located between the dorsal and ventral horns that contain the neuronal cell bodies of the sympathetic nervous system
what is the ventral median fissure of the spinal cord?
the gap in the white matter between the right and left sides
what are the dorsal median septum and sulcus?
a dent and a septum at the back of the spinal cord that runs between the right and left sides
what is the ventral white commissure?
a collection of nerve fibers that cross the midline of the spinal cord and transmit information from or to the contralateral side of the brain. It is present throughout the length of the spinal cord and lies behind the ventral median fissure
describe how the white matter is divided into columns?
we have dorsal, ventral and lateral columns.
they all contain axon tracts related to a specific function.
what are the dorsal columns of the spinal cord?
they contain ascending sensory pathways that carry information about tactile sensations and proprioception
what do ventral columns of the spinal cord carry?
carry both ascending information about pain and temperature, and descending motor information.
what are lateral columns of the spinal cord?
travel from the cerebral cortex to contact spinal motor neurons.
what are funiculi?
bundles of axons within white matter of the spinal cord
what does ipsilateral mean?
what does contralateral mean?
ipsilateral: occurring on the same side of the body
contralateral: occurring on the opposite side of the body
what are the 2 conscious sensation spinal cord pathways called?
dorsal column pathway
spinothalamic tract
what are the 4 unconscious sensation spinal cord pathways called?
spinocerebellar tract
spinotectal tract
spinoreticular tract
spino-olivary tract
what is the spinocerebellar tract?
a spinal cord pathway for unconscious proprioception and movement coordination
what is the spinotectal tract?
a spinal cord pathway for unconsciously turning towards the source of sensory auditory and visual stimulation
what is the spinoreticular tract?
the spinal cord pathway to induce and maintain wakefulness
what is the spino-olivary tract?
the spinal cord pathway for modified cerebellar activity in response to environmental change/ reaction to pain
where is the dorsal column pathway located?
what is its function?
in the dorsal column of the spinal cord
to carry discrimitve touch. pressure, vibration and proprioception signals to the cerebral cortex
roughly describe the somatotropic arrangement of the dorsal column?
from medial to lateral; we have axons from sacrum, lumbar region, thoracic region and cervical region
describe the purpose of T6 in the dorsal column pathway?
Axons from the upper body enter at or above T6 and travel in the cuneate fasciculus. axons from the lower body enter below T6 travel in the gracile fasciculus.
describe the dorsal column pathway?
A sensory receptor in the body detects a stimulus and produce an impulse which enters the dorsal column of the spinal cord. It will enter the gracile/cuneate fasciculus in the spinal cord (depending on it relative position to T6) and then it will head to its corresponding nucleus in the medulla oblongata. Then synapses with a 2nd neurone which will travel from the nucleus in the medulla and will decussate. It will then enter the thalamus and synapse to a 3rd neurone. This then carries the sensory information from the thalamus to the somatosensory cortex in the post-central gyrus
where is the spinothalamic tract located? what are its functions?
within the ventral portion of the lateral column of the spinal cord.
it carries impulses of crude touch, pain and temperature to the somatosensory cortex
what is the function of the anterior spinothalamic tract?
it carries impulses of crude touch to the somatosensory cortex
what is the function of the lateral spinothalamic tract?
it carries impulses of pain and temperature to the somatosensory cortex
describe the somatotropic arrangement of the spinothalamic tract?
sacral is more lateral and cervical more medial.
describe the spinothalamic tract pathway?
wherThe 1st order neurone from a sensory receptor somewhere in the body enters the dorsal horn of the spinal cord and ascends 1-2 segments in the dorsolateral fasciculus. It synapses with a 2nd order neurone (by release of substance P) which then decussates and travels through the ventral white commissure and ascends in the ventrolateral fasciculus of the spinal segment up to the thalamus- via the spinothalamic tract. It synapses here with a 3rd order neurone which travels to the somatosensory cortex. This is where the perception of pain/touch/temperature can be perceived.
where does the dorsal column tract decussate?
in the medulla
where does the spinothalamic tract decussate?
in the spinal cord 2 segments higher than entry level via the anterior white commissure
what is dissociated sensory loss?
A pattern of sensory loss with selective loss of touch sensation and proprioception without loss of pain and temperature, or vice-versa.
what do brainstem lesions cause?
contralateral sensory loss
what do spinal cord lesions cause?
dissociated sensory loss
