Sensory Processing Pathways

Question 1

Sensation

Answer 1

process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
In short = our brain receives input from PNS.

Question 2

Sensory Pathway Nerves

Answer 2

Sensory pathways regarding bodily sensation = spinal nerves

Sensory pathways regarding head, larynx, pharynx, soft palate & tongue = cranial nerves

Both are a part of the peripheral nervous system (PNS)
The body has more sensory fibers than motor fibers

Question 3

Somasensation

Answer 3

refers to pain, temperature, touch, and proprioception arising from the body

1) PNS ascending fibers carry information (somasensation) and travel through the spinal cord, brainstem and thalamus
2) From the thalamus, it will travel to the appropriate primary cortices

Question 4

Somatic Sensation Types

Answer 4

Three categories:

1. Mechanoreception
2. Thermoreception
3. Nociception

Question 5

Somatic Receptor Types

Answer 5

Types of receptors:

1. Encapsulated endings
2. Free nerve endings
3. Expanded tip endings

Question 6

Three-Neuron Organization

Answer 6

First order: with their cell bodies in the DRG, collect sensory information from the periphery and send it the 2nd order neuron in CNS.

Second order: Can either be in the spinal cord or in the brainstem. Will send information to the __________.
take note 
Third order: From the VPL it will travel to Primary Sensory Cortex or to specific cortices

Question 7

Three-Neuron Organization

Answer 7

First order: with their cell bodies in the DRG, collect sensory information from the periphery and send it the 2nd order neuron in CNS.

Second order: Can either be in the spinal cord or in the brainstem. Will send information to the thalamus

Third order: From the VPL it will travel to Primary Sensory Cortex or to specific cortices

Question 8

Sensory Impulse Decussation

Answer 8

Once 2nd order neuron reached, impulse decussates

Above the level of decussation, the neurons in a somatosensory pathway represent the contralateral (i.e., opposite) side of the body or face.

When an afferent pathway is damaged somewhere below the site of decussation, the sensory loss will be on the side ipsilateral to the lesion (i.e., the loss is on the same side as the lesion or ipsilesional).

Question 9

Ascending Pathways

Answer 9

Can be divided into two systems:

1. Dorsal column-medial lemniscal system (Epicritic System)
2. Anterolateral System (Protopathic System)———————

Question 10

Fasciculus Gracilis:

Answer 10

discriminative touch from lower half of body

1st order = DRG at the sacral – midthoracic level, will travel ipsilateral to the Nucleus Gracillis of medulla

2nd order = at Nucleus Gracilis will cross midline. Will form medial lemniscus tract and travel up the brainstem (medulla, pons, midbrain) to enter the VPL nucleus of thalamus 

3rd order = At VPL, sensory pathway will lead to the Primary Sensory Cortex and associated areas

Question 11

Epicritic System

Answer 11

1. Ventral posterolateral nucleus (VPL)
2. Fasciculus Gracilis: transmits sensation from the lower half of the body from the sacral to midthoracic regions
3. Fasciculus Cuneatus: transmits sensation from the upper half of the body from midthoracic region and up.

Question 12

Fasciculus Cuneatus:

Answer 12

discriminative touch from upper half of body

Ist order= DRG above midthoracic level, will travel ipsilateral to the Nucleus cuneatus of Medulla

2nd order= at Nucleus Cuneatus will cross midline. Will form medial lemniscus tract and travel up the brainstem (medulla, pons, midbrain) to VPL nucleus of thalamus. 

3rd order= At VPL, Sensory pathway  Primary Sensory Cortex & associated areas.

Question 13

Lateral Spinothalmic:

Answer 13

Part of the Anterolateral (or Protopathic) System
pain and temperature

Ist order: DRG at S,L,T or C level of the spinal cord will travel to the Nucleus Proprius & Substantia gelatinosa in the dorsal horn of spinal cord

2nd order: At Nucleus Proprius and Substantia gelatinosa will cross midline to the white commissure (forming the lateral Spinothalmic tract) and will travel through brainstem to VPL of thalamus

3rd order: At VPL, fibers will travel and project into the upper 2/3 of Primary Sensory Cortex

Question 14

Ventral (or Anterior) Spinothalmic:

Answer 14

Part of the Anterolateral (or Protopathic) System
Diffuse/light touch and pressure

1st order: DRG at S, L, T, or C level of spinal cord will travel to the Nucleus Proprius & Substantia gelatinosa in the dorsal horn of spinal cord

2nd order: At Nucleus Proprius and Substantia gelatinosa will cross midline to the ventral gray matter (forming the Ventral Spinothalmic tract), travel through brainstem and eventually reach the VPL of Thalamus

3rd order: At the thalamus, it has projections to different thalamic nuclei:
-Ventrolateral (VL), Mediodorsal (MD), Ventral Posteromedial (VPM)
and finally travel to VPL to the upper 2/3 of Primary Sensory Cortex

Question 15

Anterolateral (or Protopathic) System

Answer 15

1. Ventral (or Anterior) Spinothalmic

2. Lateral Spinothalmic

Question 16

Cranial Nerves as Sensory Pathway

Answer 16

Cranial nerves are the primary sensory pathway for:

- skin of face
- anterior portion of the scalp
- anterior 2/3 of tongue
- outer surface of eardrum

Mediates pain, temperature, touch, pressure and proprioception for the oral and cranial areas

Question 17

Sensory Nerves for Face/Head

Answer 17

Trigeminal (sensory, 3 branches), Facial (taste, ant 2/3), Vagus, Glossopharyngeal (taste, post 1/3)

Cranial nerves generally don’t deccussate (a few do, but most don’t); Spinal nerves always deccussate

Which cranial nerve is the primary sensory nerve for the face and head? Trigeminal (all braches)

Question 18

Agnosia

Answer 18

disorder of recognition caused by a cerebral injury
-thought to occur at the sensory association areas of cerebral cortex

Visual agnosia – recognize people/objects/colors by sight

Auditory agnosia – inability to comprehend speech or nonspeech sounds
A type of AA - Pure word Deafness – in the absence of aphasia; very rare

Tactile agnosia – inability to recognize objects by touch

Agnosia results from brain damage in areas involved in spatial processing, integration of visual and motor information, and attention. However, agnosia may affect a person’s ability to recognize speech or name objects and thus present with some similarities to Wernicke’s aphasia or anomia.

Question 19

Sensation Perception

Answer 19

Conscious sensation occurs in the VPL (Ventral Posterolateral Nucleus of thalamus) for body and VPN (Ventral Posteromedial Nucleus of thalamus) for face/head

The PSC denotes where in the body the sensation derives.
Pain is processed in the thalamus/limbic system

Area near the thalamus that deals with emotional processing? Limbic system (emotional pain may be a part of sensory processing)

While much of this is conscious, there are also ascending systems that convey unconscious information involved in coordination (proprioception) and brain stem reflexes that is unconscious.

Question 20

Sensory Perception Areas of Thalamus

Answer 20

VPL – sensory processing for most of the body
VPM – SP for the face
Pulvinar and LP – visual stimuli

Question 21

Pain Perception

Answer 21

Three common types of altered responses to pain: hyper, hypo, and analgesia

Analgesia -Lack of pain sensation
Hyperalgesia – increased pain or tenderness
Hypoalgesia- decreased sense of pain or tenderness

Referred Pain – often occurs with issues with the heart – pain in the arm
chart in book shows where referred pain often occurs
pain in some areas may indicate a prblm with another area of the body

Question 22

Phantom Limb

Answer 22

A phenomenon related to pain
-If a limb or substantial part of a limb is amputated, the patient may continue to have shooting pain/ tingle-feeling

2 rationales:

1) the peripheral afferent neurons continues to grow, until it reaches scar tissue where it forms a Neuroma (hypersensitive neuronal knot).
2) difficult to forget years of associated sensory processing.

Question 23

Spatial Perception

Answer 23

Proprioception – awareness of limb position in space.
It is important for development of skilled movements such as speech and writing; provides the cortex with an awareness of the spatial positioning of body parts and the body during movement

Kinesthesia – awareness of limb movement

• important for skilled movements and provides information re: direction and limb movements
• aids fine/discriminative touch analysis
• helps discriminate between two or multiple points of touch and deep pressure touch

Romberg tests; while standing with feel together, measure amount of sway w/ eyes open & close

Question 24

Mechanoreception

Answer 24

touch, pressure, vibration, and proprioception

Question 25

Thermoreception

Answer 25

cold and heat

Question 26

Nociception

Answer 26

pain

Question 27

Encapsulated endings

Answer 27

tactile (discriminative touch, vibration)

Question 28

Free nerve endings

Answer 28

pain, temperature, some tactile

Question 29

Expanded tip endings

Answer 29

tactile (touch, pressure), temperature