Chapter 11 Flashcards
Somatotopic
Information arranged similarly to the anatomic organization of the body
Low-accuracy pathway
Not organized somatotopically, not well localized
Ex. Aching pain
Projection neurons
Neurons with long axons
Bundle of axons in CNS
Tract, column, lemniscus, fascicle
Somatosensory pathways are typically named for…
The origin and termination of the tract that contains the second order neuron
3 types of pathways
Conscious relay pathways
Divergent pathways
Non-conscious relay pathways
Conscious relay pathway
Brings info about location and type of stimulation to conscious awareness in the cerebral cortex
Convey light touch, proprioception, nociception, and temperature info
Divergent pathway
Transmits info to many locations in the brainstem and cerebrum, uses pathways with varying numbers of neurons
Ex. Aching pain
Nonconscious relay pathway
Brings non conscious proprioceptive and other movement into to the cerebellum
Dorsal columns
Carry sensory information about light touch and conscious proprioception
Anterolateral columns
Carry sensory info about nociception and temperature
Conscious proprioception
Awareness of movements and of relative position of body parts
Stereognosis
The ability to integrate touch and proprioceptive info to identify an object without vision
Dorsal column medial lemniscus pathway
Pathway that conveys light touch and conscious proprioception
DCML pathway 3 neuron relay
1 order: conveys info from receptors to medulla
2 order: conveys info from medulla to thalamus
3 order: conveys info from thalamus to cerebral cortex
Fasciculus gracilis
Axons from the lower limbs and lower trunk
Fasciculus cuneatus
Axons from the upper trunk, upper limbs, and neck
Cell bodies of 2nd order neurons are located in
Nucleus gracilis or cuneatus
Primary somatosensory cortex
Receives somatotopically organized info
Discriminates size, texture, and shape of objects
Located in postcentral gyrus
Secondary somatosensory area
Analyzes info from primary somatosensory cortex and thalamus to provide stereognosis and memory of the tactile and spatial environment
Located posterior to primary somatosensory cortex
Homunculus
Surrounds the cortex
A map where each part of the body is processed
Developed by recording the response of awake individuals during surgery
Fast nociception
Initial immediate sharp sensation
Travel in conscious relay pathway, via spinothalamic pathway
within 100 milliseconds
Slow nociception
Dull, throbbing ache that is not well localized
500 milliseconds later than fast nociception
Divergent pathway via spinolimbic pathway
Fast nociception, temperature, and crude touch use a 3 neuron pathway in
The spinothalamic Tract
1 order: bring info into dorsal horn of spinal cord
2 order: crosses the midline and projects from spinal cord into thalamus
3 order: from thalamus to cerebral cortex
The first order neurons in the fast nociception pathway is
Aδ
A delta fibers
The cell body of the second order neuron is found in the
Spinothalamic tract
Superficial dorsal horn
The fast nociceptive system is also called the
Lateral nociceptive system because the spinothalamic tract ends in the lateral thalamus
Crude touch conveys
Nondiscriminative tactile information
Transmitted by C fibers
Info projects to the anterior and posterior insula
Aδ fibers
Carry impulses produced by cooling/ Cold temperature
Found in free nerve endings
Lightly myelinated fibers
C fibers
Carry info regarding heat
Itching, tickling
Very slow unmyelinated fibers
Contralateral
Opposite side
Ipsilateral
Same side
If someone breaks a bone in the hand
Divergent nociceptive pathway Causes entire hand to hurt
Medial nociception system
Divergent group of neurons
Elicits affective, motivational, withdrawal, arousal, and autonomic responses
Information is not somatotopically organized, cannot be precisely localized
The first order neuron of the slow nociceptive pathway is
Unmyelinated C fiber
Transmits information to the spinal cord
Spinomesencephallic tract
Midbrain
Transmits flow nociceptive information to the superior colliculus and the PAG
Responsible for visual reflexes
Superior colliculus plays a role in visual reflexes
PAG Activate descending tracts that modulate incoming nociceptive signals
Spinoreticular tract
Terminates in the brainstem reticular formation

Reticular formation
Neural net work in the brainstem that includes the reticular nuclei and their connections
Arousal, attention, sleep/wake cycles are modulated by the reticular formation
Axons then synapse to anterior cingulate cortex and insula
Spinolimbic tract
Transmit slow nociceptive information
Projects to the amygdala, the insular cortex, and the ventral striatum of the basal ganglia
Involved with emotions, cognition, personality, and movement
Injuries to the dorsal column medial lemniscus pathway cause
Ipsilateral loss of light touch and conscious proprioception below the level of the lesion
Injuries to the spinothalamic tract will cause
Contralateral loss of pain sensation below the level of the lesion
Antalgic
Modified gait characterized by a shortened stance phase on the affected side
After a lower limb injury
Referred pain
Perceived as coming from a site distinct from the actual site of origin
Usually pain is referred from visceral tissues to skin
Due to brain misinterpreting the source of the nociceptive information
Noxious
Harmful and/or potentially harmful
Internal arcuate fibers
Carry sensory information over the midline
Hemiplegia
Motor disruption for half the body
Half paralysis
Hemiparesis
Severe weakness on half the body
