Somatosensory Pathyways Flashcards
The somatosensory pathways include descending or ascending pathways?
Ascending pathways
What are the two tracts that are a part of the somatosensory pathway in the rostral, caudal midbrain, middle, caudal pons, and rostral medulla?
Medial lemniscus
Spinothalamic tract
What are the tracts and nuclei that are a part of the somatosensory pathway in the caudal medulla,
Ascending pathways: Gracile tract, cuneate tract, internal arcuate fibers, medial lemniscus, spinothalamic tract
Nuclei: gracile nucleus, cuneate nucleus
What tracts are part of the ascending pathway in the cervical spinal cord?
Gracile tract
Cuneate tract
Spinothalamic tract
What is the purpose of the posterior column-medial lemniscus pathway?
Carry peripheral information to the brain
What is the definition of somatosensory?
All sensations arising from the skin, connective tissue, voluntary muscles, periosteum and teeth
What are the touch sensations?
Discriminative touch
Pressure
Vibration
Conscious proprioception
There are 3 types of discriminative touch. What are they?
Two-point discrimination: telling 2 points apart
Stereognosis: ID objects via touch only
Graphesthesia: ID writing on skin by touch only
What are pain and temperature sensations?
Pain (nociception)
Temperature
Nondiscriminative touch
What is proprioception?
Conscious and nonconscious information from structures including muscle spindles and golgi tendon organs regarding position sense and movement
Ability to consciously know where body parts are, knowing about position sense and movement
Peripheral components: some somatosensory neurons are associated with ____ while others are ___ nerve endings
Receptors
Free nerve endings
What are the three categories of somatosensory receptors?
Mechanoreceptors (tactile sensation)
Pain receptors
Thermoreceptors
The posterior column-medial lemniscus pathway conveys which sensations
Discriminative touch
Conscious proprioception
The cuneate tract of the posterior column-medial lemniscus pathway is responsible for
Upper limb
The gracile tract of the posterior column-medial lemniscus pathway is responsible for
Lower limb
Posterior column-medial lemniscus pathway: first order neurons structure locations
Cell bodies: posterior root ganglia
Central processes: gracile tract (lower limb), cuneate tract (upper limb)
Posterior column-medial lemniscus pathway: second order neurons structure locations
Cell bodies: gracile and cuneate nuclei
Axons: medial lemniscus
Posterior column-medial lemniscus pathway: third order neurons structure locations
Cell bodies: VPL nucleus of thalamus
Axons: posterior limb of internal capsule
Vascular territories of PCML pathway: Spinal cord is supplied by
Posterior spinal artery
Vascular territories of PCML pathway: Medulla is supplied by
Anterior and posterior spinal artery
Vascular territories of PCML pathway: Pons is supplied by
Paramedian artery (basilar)
Vascular territories of PCML pathway: Midbrain is supplied by
Quadrigeminal artery
Posterior cerebral artery
Spinothalamic (anterolateral) pathway conveys which sensations
Pain
Temperature
Nondiscriminative touch
Spinothalamic pathway: First order neurons structure locations
Cell bodies: posterior root ganglia
Central processes: posterior roots
Spinothalamic pathway: Second order neurons structure location
Cell bodies: posterior horn
Axons: anterior white commissure and spinothalamic tract
Spinothalamic pathway: third order neurons structure location
Cell bodies: VPL nucleus of thalamus
Axons: posterior limb of internal capsule
Vascular territories of the spinothalamic pathway: spinal cord supplied by
Anterior spinal artery
Vascular territories of the spinothalamic pathway: medulla supplied by
Vertebral artery
Vascular territories of the spinothalamic pathway: pons supplied by
ACA, long circumferential artery
Vascular territories of the spinothalamic pathway: midbrain supplied by
PCA, quadrigeminal artery
What part of the internal capsule is associated with the spinothalamic pathway
Posterior limbs
Axons from VPL of thalamus go through post limb of internal capsule to somatosensory cortex
What is the somatosensory association cortex responsible for?
Higher level processing of sensory information
Review of blood supply to cerebrum:
MCA supplies …
PCA supplies …
ACA supplies ….
MCA: lateral cerebral hemispheres
PCA: medial temporal and occipital lobes
ACA: medial frontal and parietal lobes
Posterior column-medial lemniscus pathway is …
Touch pathway
Spinothalamic pathway is ….
Pain and temperature pathway
The cranial touch pathway conveys ….
Sensation for discriminative touch and conscious proprioception
Information to the cranial touch pathway primarily comes from ….
Trigeminal nerve
The cranial touch pathway is also called the ___ pathway
Trigeminal
Cranial touch pathway: first order neurons structure location
Cell bodies: trigeminal ganglion
Central processes in trigeminal nerve
Cranial touch pathway: second order neurons structure location
Cell bodies: principal sensory trigeminal nucleus
Axons: trigeminothalamic tract
Cranial touch pathway: third order neurons structure location
Cell bodies: VPM nucleus of thalamus
Axons: posterior limb of internal capsule
What sensations are conveyed by the cranial pain and temperature pathway?
Pain
Temperature
Non discriminative touch
Damage of the cranial touch pathway at the level of the pons and above leads to
Loss of touch only
Damage at the cranial touch/pain and temp pathway below the pons leads to
Loss of pain and temp
Decussation occurs at the level of the ___ in the cranial touch and cranial pain and temp pathway
Medulla
Cranial pain and temp pathway: first order neurons structure locations
Cell bodies: trigeminal ganglion
Central processes: CN V, spinal trigeminal tract
Cranial pain and temp pathway: second order neurons location
Cell bodies: spinal trigeminal nucleus
Axons: trigeminothalmic tract
Cranial pain and temp pathway: third order neuron structure location
Cell bodies: VPM nucleus of thalamus
Axons: posterior limb of internal capsule
Where is the point of decussation of the cranial pain and temperature pathway?
Second order neuron
