Lecture 4 - Ascending Sensory Systems Flashcards
Somatosensory receptors have a cell body in the _____ _____ _____ (DRG), a central ______ process, and a ______ process ending in skin, muscle, or joint.
- dorsal root ganglion
- CNS
- peripheral
What are the 2 types of cutaneous receptors in the skin?
- encapsulated
- nonencapsulated
Which 3 cutaneous receptors are encapsulated?
- Pacinian corpuscle (vibration)
- Meissner’s corpuscle (touch)
- Ruffini endings (pressure)
Which 3 cutaneous receptors are non-encapsulated?
- endings around hairs (touch)
- Merkel endings (touch)
- free nerve endings (pain, temperature, itch, touch)
3 receptors in hairy skin
- endings around hairs
- Merkel endings
- free nerve endings
- all non-encapsulated
4 receptors in hairless (glabrous) skin
- Meissner’s corpuscle
- Merkel cell
- Pacinian corpuscle
- Ruffini endings
- all encapsulated except Merkel cell
Discriminative touch (two point discrimination) that is concentrated in finger tips is done by ______ _______. These receptors have fast conducting _____ fibers.
- Meissner’s corpuscle
- Aβ
Discriminative touch endings inferior to Meissner’s corpuscles are called _______ endings. These receptors have fast conducting _____ fibers. Their adaptation is _____.
- Merkel
- Aβ
- slow
Descriminative touch impulses are carried up the _____ ______ ______ ______ pathway. This pathway also enables _________ (spatial position) and vibration.
- posterior column-medial lemniscal pathway (PCML)
- proprioception
The posterior column - medial lemniscal (PCML) pathway has ____ fibers. Its decussation level is at the ______, and it relays in the lateral _______ at the ventral posterolateral nucleus (VPL). Its termination is in the ______ ______ of the cerebrum.
- Aβ
- medulla
- thalamus
- postcentral gyrus
TRUE or FALSE. Spatial resolution (location) of a stimulus is more precise when there are more receptors.
TRUE - more receptors in the fingertips than hands allow us to feel location of stimuli in fingertips more easily
Detection of vibrations, especially in the fingers and palms, is done by ______ ______. They have ___ fibers.
- Pacinian corpuscles
- Aβ
Pain, crude touch, and temperature are signaled with ____ _____ _____ in the skin.
free nerve endings
Fast pain is carried by _____ fibers, while slow pain is carried by _______ fibers.
- δ (delta)
- unmyelinated
3 general types of pathways:
- Long, _____ fibers going to thalamus, cerebellum, or brainstem nuclei
- Long, _____ fibers going from cerebral cortex or brainstem nuclei to spinal cord gray matter
- Short, _____ fibers interconnecting different spinal cord levels for reflexes
- ascending
- descending
- propriospinal
TRUE or FALSE:
Fibers from different pathways often travel together, regardless of their destination in the brain.
FALSE - different fibers do travel together, but usually only if the destination is the same
Descending tracts are located primarily in _____ ______and _____ _____ (white matter).
- anterior funiculi
- lateral funiculi
*funiculi ARE white matter tracts in spinal cord
Ascending tracts are found in ______ ________ of the spinal cord.
all funiculi (anterior, lateral, and posterior)
Propriospinal fibers surround the spinal cord _____ ____.
gray matter
The PCML conveys ______ and limb _______ information. It is an _______ tract, meaning that afferent neurons carry information towards the brain. Receptors that pick up stimuli for the PCML are mostly _________.
- touch
- position
- ascending
- mechanoreceptors
The spinal afferent cell bodies of the PCML are located in the _____ _____ ______. The fibers enter the spinal cord, and divide into _______ (directly to brainstem) and _____ divisions.
- dorsal root ganglion
- medial
- lateral
In the PCML, most fibers caudal to T6 are added to fasciculus _______. Rostral to T6, fibers begin forming fasciculus _______. They eventually syanpse in the ______ at these nuclei.
- gracilis
- cuneatus
- brainstem (medulla)
In the PCML, fibers are added from most inferior to most superior spinal levels laterally in a pattern of lamination. This means that sacral fibers for PCML, all the way up the cord, are most _____, while cervical levels are most ______.
- medial
- lateral
In the PCML, 1° fibers synapse in nucleus _______ and nucleus ________. 2° fibers decussate in the _____ _____ and form the ______ ______. 3° fibers originate in the _______ (VPL nuclei), ascend through the internal capsule, and synapse in the primary somatosensory cortex of the ________ _______.
- card layout to collectively remember important points
- gracilis
- cuneatus
- caudal medulla
- medial lemniscus
- thalamus
- postcentral gyrus
- # ° = neurons in the pathway; after each synapse, the number increases. Thus there are 3 neurons and 2 synapses in the PCML.
- decussate = cross the midline
Injury of the PCML results in impaired ________ and _______ tactile functions. PCML damage is tested by having a patient identify ______ of movement drawn on their skin. If PCML damage is extensive, ______ results in uncoordinated movement.
- proprioception
- discriminative
- patterns
- ataxia
TRUE or FALSE:
Damage of a single pathway in the PCML often leads to heavy loss of function.
FALSE. There are multiple alternate paths that can circumnavigate this.
TRUE or FALSE:
If the PCML is injured, recovery is possible to some degree. However, interpretation of complex (fine) stimuli will likely remain impaired.
TRUE
The pathway that conveys pain and temperature to the brain, having a final synapse in the VPL nuclei of the thalamus is the _________ pathway. Combined with other pain pathways, all of the pain paths are collectively know as the ________ pathway. Generally, this pathway has slower conduction velocity due to the use of unmyelinated ____ fibers.
- spinothalamic
- anterolateral
- C
- resides in ANTERIOR half of LATERAL funiculus (white matter of spinal cord)
In the anterolateral pathway (ALP), 1° fibers immediately synapse in the ______ _______ of the dorsal horn. 2° fibers then decussate in the ______ ______ gray matter, and travel towards the ________ portion of the spinal cord where they begin their ascent to the ________ (VPL nuclei), where they synapse again. The 3° fibers travel to many regions of the _______.
- substantia gelatinosa
- spinal cord (anterior commissure)
- anterolateral
- thalamus
- cerebrum (not just the somatosensory cortex)
Organization laterally for caudal parts to medial for rostral parts is called ________ organization.
somatotopic
TRUE or FALSE:
The ALP is diverse, going to many different regions of the brain.
TRUE
Spinothalamic fibers start in laminae __ and __ and project to the VPL nuclei of the thalamus.
- I
- V
Polysnaptic projections project to the spinoreticular fibers in the _____ ______ of the brainstem. They modulate _____ to level of pain. Polysnaptic projections work in tandem with ______________ fibers from laminae I & V.
- reticular formation
- attention
- spinomesencephalic
The autonomic response to pain is mediated by __________ fibers.
spinohypothalamic
Damage to the ALP causes loss of sensation to ____, ______, and _______ sensations.
- pain
- temperature
- itch/tickle
TRUE or FALSE:
Some tactile/pressure info is carried by the ALP, but an injury to the ALP will not affect tactile/pressure perception because most is sensed by the PCML.
TRUE
TRUE or FALSE:
A unilateral injury to the ALP will alter bowel/bladder pressure or sexual sensations.
FALSE.
These sensations are bilateral, so a unilateral injury to the ALP will not harm their perception.
Somatotopic organization stresses a point-for-point correspondence of the somatosensory cortex of the cerebrum with a given body part. The illustration of this is shown by the ______ _______.
sensory homunculus
A procedure that intentionally destroys a portion of the lateral funiculus to cut off contralateral pain sensation through the ALP is called a _______.
cordotomy
DIRECT information from the spinal cord to the cerebellum utilizes the ________ tracts.
spinocerebellar
INDIRECT information from the spinal cord to the cerebellum utilizes ______ ______ nuclei.
brainstem relay
Proprioceptive information is conveyed from the spinal cord to the cerebellum is done in the _____ ______ pathway. The first synapse is in _____’s nucleus. Fibers ascend ipsilaterally through the ______ ______, then enter the cerebellum at the ______ _______ peduncle. This pathway is responsible for ______ proprioception.
- posterior spinocerebellar
- Clarke’s
- lateral fasciculus
- inferior cerebellar
- leg
The spinocerebellar tract responsible for proprioception of the arm is the ___________ tract. This tract [does/does not] synapse at Clarke’s nucleus. Arm afferents ascend to the medulla in the ______ ______. Axons from the lateral cuneate nucleus of the medulla then enter the cerebellum via the _____ ______ peduncle.
- cuneocerebellar
- does not
- fasciculus cuneatus
- inferior cerebellar
Information from the spinal cord to the cerebellum regarding the legs and COMPLEX coordinated movement is carried in the _______ ________ tract (differs from coarse posterior spinocerebellar). This tract crosses the midline ______, so it remains ipsilateral to its starting point.
- anterior spinocerebellar
- twice
TRUE or FALSE:
The anterior and posterior spinocerebellar tracts are directly anterior/posterior to the ALP tract in the caudal medulla.
TRUE
TRUE or FALSE:
The spinocerebellar tracts are associated primarily with nociceptors.
FALSE. They’re associated with mechanoreceptors.
The somatosensory cortex is located in the ______ ____ of the ______ lobe.
- postcentral gyrus
- parietal
