Spinal Cord Sensory Pathways Flashcards
Brain and spinal cord are which system? Nerves and ganglia are which system?
CNS
PNS
Ganglia is typically found in which system of PNS?
Autonomic
Where do synapses occur?
grey matter
Where is grey matter found? (3)
Cerebral cortex
Cortical nuclei/diencephalon (ex: Thalamus)
Grey horns of spinal cord
Where is white matter found?(4)
Cerebral tracts (Corpus callosum)
White columns of spinal cord
Spinal pathways (coming next week!)
Peripheral Nerves
In the spinal cord what are the 3 white matter columns?
Posterior (physically separated from the other 2)
Lateral
Anterior
What signal does the posterior column house?
ascending sensory signals
What signal does the anterolateral column house?
ascending sensory AND descending motor signals
What signal stops and synapses at the posterior gray horn?
sensory signals
What signal stops and synapses at the lateral gray horn?
autonomic (unconscious) signals
What signal stops and synapses at the anterior gray horn?
motor signals
What provides pathway for afferent/ incoming information to flow from spinal nerve into the spinal cord?
dorsal root
Sensory information may synapse in __________ OR ascend in __________.
Dorsal grey horn OR ascend in white columns
What provides pathway for efferent/outgoing signals to leave spinal cord and enter spinal nerve?
Ventral root
__________ may synapse in ventral grey horn or descend in white columns
Motor information
Neurons will pass the signal from one cell to the next by forming a synapse between _________ and _______.
adjacent axon terminal and the cell body
How many pairs of spinal
What kind of matter pathways provide a route for signals to travel between PNS and CNS?
white matter
Spinal nerves are (IPSILATERAL/ BILATERAL) and will carry signals to and from targets/receptors on the same side of the body
ipsilateral
________/_________root carries sensory/afferent information into CNS so it can ascend in the cord to reach the cortex
Posterior/Dorsal
__________/__________ root carries motor/efferent information out of CNS that has descended from the cortex to the cord
Ventral/Anterior
What contains the soma/cell bodies of incoming sensory cells?
dorsal root ganglion
Which 2 roots come together to form a spinal nerve in the intervertebral foramen?
Ventral & Dorsal
Each spinal nerve has the ability to carry (many/ just one) signal(s) into the CNS and out of the CNS
many different
Nervous signals are classified based on what 3 factors?
1.) direction that they flow
2.) type of signal that is carried
3.) target/effector that carries out the response
Somatic = ___________
Autonomic = ____________
conscious
unconscious
NS code?
1.) body movement
2.) stretch of a vessel
3.) beating of heart
4.) sensation on skin
How many could 1 spinal nerve carry?
1.) GSE ( general somatic efferent)
2.) GVA (general visceral afferent)
3.) GVE (general visceral efferent)
4.) GSA (general somatic afferent)
1 of each = 4 total
What is it called when signals cross over from one side to another? Where does this occur? How many times does this occur in pathways?
decussate, CNS, once, twice, never
** explains why right affects left and left affects right **
Where are the receptors for the sensory information located?
end of peripheral nerves within the layers of skin
Sensory information comes into the CNS via what part of the spinal nerve? And it ascends in the SC via what columns?
dorsal root
posterior, lateral, and anterior columns
Where do the majority of sensory signals synapse?
thalamus
The destination for most incoming/ascending sensory information is where?
post-central gyrus of the parietal lobe
What signals originate in the pre-central gyrus of the frontal lobe?
Efferent/Motor
What do the efferent/motor signals descend in the spinal cord via?
anterior or lateral columns
Motor signals exit the CNS via what?
ventral root of the spinal nerve
Target for motor signals are known as what?
effectors
How many neurons are in the sensory tracts? What’s the exeption?
3
spinocerebellar tract which has 2
The first-order neuron resides in what area off the spinal nerve and conducts impulses from sensory receptors to the spinal cord or medulla oblongata?
the dorsal root ganglion
The second-order neuron is located in 1 of which 2 locations and relays impulses to the thalamus?
1.) dorsal horn of the spinal cord
2.) within the medulla oblongata
The third-order neuron residing where, conveys impulses to the general sensory area (postcentral gyrus) of the parietal lobe of the cerebral cortex?
thalamus
Major ascending, sensory tracts sensations:
Spinothalamic
Spinocerebellar
Posterior/Dorsal column
Spinotreticular tract
Spinotectal tract
Spinomesecephalic tract
Spino-olivary tract
They all use what to enter the spinal cord?
Spinothalamic: A:pain and temperature P: crude touch and pressure
Spinocerebellar: proprioception (conscious)
Posterior/Dorsal column: TOUCH (discriminative)
Spinotreticular tract: fine touch and proprioception
Spinotectal tract: Pupil reaction. Head and eye movement in response to stimuli
Spinomesecephalic tract : fear and aversion related to pain
Spino-olivary tract: movement of body and limb, proprioception (unconscious/visceral)
dorsal root of the spinal nerve
Pathway of the dorsal columns?
Pathway:
1.) Neuron 1: 1st order neuron
2.) Originates in peripheral receptor
3.) Travels towards CNS via spinal nerve
4.) Enters CNS via dorsal root of spinal nerve and does NOT synapse
5.) Axon continues to ascend in dorsal columns of spinal cord
6.) Synapses in nuclei of medulla
FIRST ORDER –> SECOND ORDER
1.) Neuron 2: 2nd order neuron
2.) Cell body originates in nucleus of medulla
3.) Axon decussates (crosses) in medulla oblongata
4.) Ascends to thalamic nuclei via medial leminiscus pathway (white matter pathway)
5.) Synapses in thalamus
SECOND ORDER –> THIRD ORDER
1.) Neuron 3: 3rd order neuron
2.) Cell body originates in thalamus
3.) Axon travels from thalamus to post-central gyrus of parietal lobe
4.) Synapses in primary somatosensory cortex
5.) Sensation is interpreted
(uses white matter the whole way to travel through)
What do the dorsal columns transmit?
TOUCH SENSATION (most common)
General sensation (GSA) for fine touch and discriminative touch information from receptors of the skin
Where does the fasciculus gracilis carry touch sensation from? Lateral or medial?
Where does the fasciculus cuneatus carry touch sensation from? Lateral or medial?
lower limb (medial)
(those graceful (gracilis) lower limbs feel sensation)
upper limb (lateral)
How many fasciculus cuneatus do we have? How many fasciculus gracilis?
2
2
Which column is subdivided?
dorsal column
What changes between the 2 dorsal column subdivisions?
first order neuron and where it synapses
Dorsal Column (medial lemniscus) Pathway with the upper/lower limb options where they vary. ONLY AFFECTS 1st order neuron
Neuron 1: 1st order neuron
**1.) Originates in peripheral receptor in UPPER limb or LOWER limb
2.) Travels towards spinal cord via spinal nerve
**3.) Enters CNS via dorsal root and ascends in dorsal columns (FC or FG) of spinal cord
Synapses in one of the nuclei in medulla:
FC (lateral columns) = Fasciculus cuneatus – transmitting touch information from upper limbs
Information travelling in this column will synapse in the “nucleus cuneatus” (NC) of the medulla
FG (medial columns) = Fasciculus gracilis – transmitting touch information from lower limbs
Information travelling in this column will synapse in the “nucleus gracilis” (NG) of the medulla
What nucleus will sensory information from the upper limb synapse in? Lower limb?
upper- nucleus cuneatus of medulla
lower- nucleus gracilis of medulla
Pathway of the spinocerebellar tract:
Pathway: (nucleus dorsalis (Clarke’s column)
Neuron 1: 1st order neuron
1.) Originates in peripheral receptor
2.) Travels towards CNS via nerve
3.) Axon enters dorsal root and synapses in dorsal grey horn upon entry
SYNAPSE!! 1st order NEURON –> 2nd order NEURON
Neuron 2: 2nd order neuron
1.) Cell body originates in dorsal grey horn
2.) Remains ipsilateral
3.) Ascends in anterolateral white column of spinal cord
4.) Axon ascends to the level of the cerebellum
5.) Synapses in cerebellar hemisphere
Injury to the spinocerebellar tract will always be considered ipsilaterally/bilaterally?
ipsilaterally (because it crosses then crosses back)
What does the spinocerebellar tract transmit?
PROPRIOCEPTION (conscious): General sensation (GSA) for proprioception (bodies ability to observe position in space)
Which 2 tracts are referred to as a double crosser?
1.) spinocerebellar tract (spinoC = C = Double CROSS)
2.) spino-olivary tract (crossing through the olive grooves, eating double olives)
What pathways are in the anterolateral system?
1.) Spinothalamic tracts (lateral and anterior); for non-discriminative touch, pain, and temperature
2.) Spinoreticular tract; ends in the reticular formation of the medulla, pons, and midbrain.
3.) Spinotectal tract; travels to the superior colliculus in the midbrain
4.) Spinomesencephalic or spinoperiaqueductal tract ends in the periaqueductal grey matter in the midbrain
5.) Spino-olivary tract projections to the inferior olivary nuclei in the medulla
Where does the spinoreticular tract end?
In the reticular formation of the medulla, pons, and midbrain
Where does spinotectal tract travel to?
superior colliculus
Where does the spinomesencephalic/spinoperiaqueductal tract end?
periacqueductal grey matter in the brain
Where does the spino-olivary tract project?
inferior olivary nuclei (in the medulla)
Pathway of the spinothalamic tract:
Pathway:
Neuron 1: 1st order neuron
1.) Originates in peripheral receptor
2.) Travels towards CNS via nerve
3.) Axon enters dorsal root and synapses in DORSAL GRAY HORN upon entry
Neuron 2: 2nd order neuron
1.) Cell body originates in dorsal grey horn
2.) Axon DECUSSATES at the level of entry
3.) Ascends in antero-lateral white columns of spinal cord
4.) Synapses in thalamus
Neuron 3: 3rd order neuron
1.) Cell body originates in thalamus
2.) Axon travels from thalamus to post-central gyrus
3.) Synapses in primary somatosensory cortex of parietal lobe
What does the spinothalamic tract transmit?
general sensation (GSA) for pain and temperature sensations from the body
What is the nuerotransmitter that senses pain in the first-order neuron of the spinothalamic tract (lateral)?
Substance P
In what area can Substance P be generated?
substantsia gelatinosa (lamina II)
Between which 2 synapses does substance P get released?
Between 1st order and 2nd order
Gate control theory of pain: First order neuron from a descending touch pathway can send a signal to an inhibitory interneuron that releases serotonin and blocks substance P. This is why we do what when we are first injured? What 2 pathways are at play?
Rub the site of injury
dorsal column can shut down spinothalamic
Gate control theory of pain: What is the mechanism of the descending motor pathway that reduces substance P?
Meditation, hypnosis, distraction, “willing it away” lead to a release of enkephalins and endorphins which will block substance P and “turn down” the pain
Spinoreticular pathway:
Pathway:
Neuron 1: 1st order neuron
1.) Originates in peripheral receptor
2.) Travels towards CNS via nerve
3.) Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
1.) Cell body originates in dorsal grey horn
2.) Axon remains ipsilateral
3.) Ascends in antero-lateral white columns of spinal cord
4.) Synapses in medulla and midbrain
What does the spinoreticular pathway transmit?
levels of consciousness
Does the spinoreticular pathway cross over?
no (spinoReticular R=REMAINS, does NOT cross)
Spinaltectal pathway
Pathway:
Neuron 1: 1st order neuron
1.) Originates in peripheral receptor
2.) Travels towards CNS via nerve
3.) Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
1.) Cell body originates in dorsal grey horn
2.) Axon cross over midline
3.) Ascends in antero-lateral white columns of spinal cord
4.) Synapses in SUPERIOR COLLICULUS of midbrain
What does the spinotectal pathway transmit?
coordinated movements of eyes and head
reflexive turning of head and eyes towards a point of cutaneous stimulation
Spinomesencephalic tract pathway:
Same as spinoreticular EXCEPT it terminates in the midbrain’s periaqueductal gray matter (PAG)
What is the area surrounding the cerebral aqueduct called?
periaqueductal gray matter (PAG)
What does the spinomesencephalic tract transmit? What system does it have connects to?
fear and aversion reactions associated with pain
limbic system
The spinomesencephalic tract can also help modulate pain, what is this called?
analgesic effect
Spino-olivary pathway
Pathway:
Neuron 1: 1st order neuron
1.) Originates in peripheral receptor
2.) Travels towards CNS via nerve
3.) Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
1.) Cell body originates in dorsal grey horn
2.) Axon cross over midline
3.) Ascends in antero-lateral white columns of spinal cord
4.) Synapses in inferior Olivary nucelus of medulla
5.) Neuron 3: 3rd order neuron
6.) Cell body originates in nucleus
7.) Axon cross the midline again
8.) Enter the cerebellum
9.) Synapses in CEREBELLUM
What does the spino-olivary pathway transmit?
MOVEMENT of the body and limbs
unconscious PROPRIOCEPTION (from cutaneous and proprioception organs)
