2.1 Spinal Cord: Sensory (ascending) Pathways Flashcards
What does the sensory system use for sensing the environment
1) External- exteroreceptors
2) Internal- interoreceptors
3) Spatial orientation- proprioceptors
List external- exteroreceptors:
- Touch
* Pain - Thermal
- Vision
- audition
- olfaction
- gustation
List internal- interoreceptors:
- Visceral
- Stretch
- pH
*CO2
List Spatial orientation: proprioceptors & where they’re found on the body:
• Location: head, body, vestibular apparatus
• tactile/pressure receptors
• joints, muscle spindles (stretch)
• golgi tendon organs
• ear (hair cells)
Where do proprioceptors feed into the brain?
- somatic sensory regions
- cerebellum (unconscious propreoception)
General Somatic Sensation (GSS) aka Afferent (GSA): Types
- Modality
- Dendritic zone
Modality =
what part of the environment is being sensed?
Dendritic zone =
on or near the surface of the body
• Pain
• Temperature
• Touch
• Pressure
• Kinaesthesia, sense of motion,
• conscious proprioception
What information is received at the somatosensory Cortex?
conscious information
What is this diagram showing us?
The lower extremities are mapped at the higher part of the brain at the most dorsal aspect
The higher extremities are mapped at the lateral side of the lower cerebral hemisphere
**inverse mapping
If I’m typing / using my fingers what part of the brain is responsible?
Parietal lobe
What does the parietal lobe receive and process?
All somatosensory input ( touch, pain)
Parietal lobe =
homunculus
3 key points to remember about the somatosensory cortex?
- inverted image
- disproportionally arranged
- regular somatotopic organization
GSS species differences: disproportional homunculus examples
raccoon: large forehands
camel: large lips
naked mole rats: (blind) uses teeth to burrow
pig: large snout for rooting
What are the 3 sensory pathways /tracks?
- dorsal column
- spinothalamic tracts
- spinocervicothalamic tracts
** All merge to join medial lemniscal systems
What part of the brain does the medial lemniscal system deal with?
hindbrain
Are the tracts that go from the periphery to the higher centers
dorsal column
The dorsal column splits up the?
gracile tract into hindlimb,
The dorsal column governs the hindlimb in terms of ?
touch, pressure, kinaesthesia
The spinothalamic tract:
- dominate in humans
- important for pain sensation
- superficial “pin-prick” pain, temperature (skin, viscera)
ex: hand on oven
spinocervicothalmic tracts
- touch
- pressure
- some superficial pain (skin)
The thalamus is responsible for?
prioritizing and filtering information to the cortex
which tracy is prominent in carnivores ?
ex: cat walking on fence
spine cervical tract
Medial Lemniscal System origin, termination, & what it runs through
- Located in the medulla oblongata
- Thalamus relays information to the cerebral cortex which acts as an important filter for information (sorting office)
- Final site of perception is in general sensory cortex
Medial Lemniscal System components, do fibers decussate, & is it ipsilateral or contralateral
- Composed of bundle of heavily myelinated axons
- Decussation of fibers
- Mainly contralateral (bilateral) relay close to midline
which tracts merge to join Medial Lemniscal System
- Dorsal columns
- Spinothalamic
- spinocervicothalamic
**except joint &muscle proprioception
Spinal relay tracts are predominately utilized & merge for Medial Lemniscal System
A) Dorsal columns gracile-cuneate
B) spinocervicothalamic used more than spinothalamic
all merge to form a system except joint & muscle proprioceptio
Tracts Dorsal Columns (DC) uses
- gracile tract for hindlimb
- cuneate tract for forelimb
Ascending reticular formation spinoreticular tracts (AscRF) what does deep pain loss indicates
significant bilateral spinal cord lesion
Ascending reticular formation spinoreticular tracts (AscRF): information relay process
A) Information at Spinal cord
B) Information relayed to reticular formation
C) Information relayed to thalamus
D) Information relayed to cerebral cortex
Ascending reticular formation spinoreticular tracts (AscRF): how does the tract run in relevance to the spinal cord
Bilateral relay close to midline of body
Spinocerebellar tract (ScerbT): triggers
- Subconscious proprioception
- Used in co-ordination & finetuning motor activity
Spinocerebellar tract (ScerbT): how does the tract run in relevance to the spinal cord
- 2-neuron pathway
- Ipsilateral relay (stimulated side of body gets sent to symmetrical side of brain)
Spinocerebellar tract (ScerbT): how does the tract run in relevance to the spinal cord
- 2-neuron pathway
- Ipsilateral relay (stimulated side of body gets sent to symmetrical side of brain)
Spinocerebellar tract (ScerbT): What symptoms are expected for a clinical scenario diagnosis:
- Incoordination: Ataxia (cerebellar disturbance, afferent kinesthetic deficit)
- Vestibular: loss of balance, wide based stance
- Alcohol ‘drunken’ gait
Spinocerebellar tract (ScerbT): Conscious stimuli relay process:
A) Information at Spinal cord
B) Information sent to cerebral cortex as proprioception control center
Spinocerebellar tract (ScerbT): unconscious stimuli relay process:
A) Information at Spinal cord
B) Information sent to cerebellum as proprioception control center
Pain transmission &reception: what is the clinical significance, what does it indicate &how does the tract run in relevance to the spinal cord
- Enormous clinical significance
- Pain fibers lie throughout cord &are very resilient, indicating loss of ALL pain sensation has very poor prognostic
- 2 pathways used
Which 2 tracts are utilized for pain transmission &reception
1) Delayed, slow, or true pain sent to SRetT (spinoreticuothalamic tract)
2) Fast, initial, or pin prick pain sent to STT (spinothalamic tract)
Explain general principles of lesion localization in sensory pathways within the CNS.
- presence/ absence of sensory deficit (neurological examination) determining what lesion is
- Neuroanatomical localization of where lesion is
- etiological basis of neurological lesion for why it’s occurred
Ascending reticular formation spinoreticular tracts (AscRF): triggers
- True pain (everything other than “pin-prick”)
- In superficial & deep tissues
- All intensities (itching, aches, agony)
- Arousal
Visceral pain traits:
- Poor localization
- Can be extreme (especially distension)
- Can induce skeletal muscle spasm
Can be referred to somatic areas served by same spinal nerve (angina)
Relay information process if slow, delayed or true pain:
Relay information process if fast, initial, or pin prick pain
Nociception - key points
- conscious perception of a noxious stimulus + unpleasant emotional response
- can stimulate reflex activity or transmitted to brain via sensory pathways found on both sides of spinal cord
-hyperalgesia: tissue damage
- visceral pain
