Lecture 3 Flashcards
Integration, decision making, and processing of signals occurs occurs in which NS?
CNS
Signals from CNS traveling to/from targets in the periphery occurs in which NS?
PNS
Where does synapsing occur?
gray matter:
- cerebral cortex
- cortical nuclei/diencephalon (ex., thalamus)
- grey horns of spinal cord
Where can we find white matter?
- cerebral tract (Corpus callosum)
- White columns of spinal cord
- Spinal pathways
- Peripheral Nerves
What are the 3 white matter columns in the spinal cord?
- posterior column
- lateral column
- anterior column
What is the anterolateral column of the spinal column comprised of?
the lateral & anterior column
What signals is posterior column of the spinal cord associated with?
ascending sensory signals
What signals is the anterolateral column associated with?
contains both ascending sensory & descending motor
What signal is the posterior gray matter horn associated with?
sensory signals
What signal is the lateral horn of the gray matter associated with?
autonomic (unconscious) signals
What signal is the anterior gray matter horns associated with?
motor signals
Signals travelling in spinal nerves can enter enter/exit the spinal cord via connections known as __ __
nerve roots
Provides pathway for afferent/ incoming information to flow from spinal nerve into the spinal cord
dorsal root
Where does sensory information synapse with reference to the dorsal roots?
may synapse in dorsal grey horn OR ascend in white columns
Provides pathway for efferent/outgoing signals to leave spinal cord and enter spinal nerve
ventral root
Where does motor information synapse with reference to the ventral root?
may synapse in ventral grey horn or descend in white columns
Neurons will pass the signal from one cell to the next by forming a synapse between?
adjacent axon terminal and the cell body
Where do ventral and dorsal roots come together to form a spinal nerve?
Intervertebral foramen
What are nervous signals classified based on?
- direction that they flow
- type of signal that is carried
- target/effector that carries out the response
“Code” of nervous system: Conscious/voluntary motor (body movement)
GSE: general somatic efferent
“Code” of nervous system: general sensation (sensation on skin)
GSA: general somatic afferent
“Code” of nervous system: Involuntary/subconscious motor to organs/viscera (beating of heart)
GVE: general visceral efferent
“Code” of nervous system: Visceral sensation (stretch of vessel)
GVA: general visceral afferent
T/F: Each spinal nerve can carry only one code of the nervous system
False, can carry many
__ = “of the body” what you are aware of (conscious)
SOMATIC
__ = what you are not aware of (unconscious)
AUTONOMIC
Define: Decussate
when signals cross over from one side to another (left to right; or right to left). Occurs within the CNS
What pathways are always going to be ipsilateral?
Where are receptors for sensory information be located?
end of peripheral nerves within the layers of the skin
Afferent/Sensory information comes into the CNS via the?
dorsal root of the spinal nerve
Efferent/Motor signals originate in the ?
pre-central gyrus of the frontal lobe (primary motor cortex)
Which root do efferent/motor signals exit the CNS by?
ventral root
Target for motor signals are known as ?
effectors
Where do the first-order neurons travel?
in peripheral nervous system
Where do first order neurons synapse?
typically in the brainstem
Where do second and third order neurons travel?
in central nervous system
The __-order neuron is located either in the dorsal horn of the spinal cord or within the medulla oblongata and relays impulses to the thalamus
second
The __-order neuron residing in the thalamus conveys impulses to the general sensory area (postcentral gyrus) of the parietal lobe of the cerebral cortex
third
The __-order neuron resides in the dorsal root ganglion of the spinal nerve and conducts impulses from sensory receptors to the spinal cord or medulla oblongata
first
What are the major ascending, sensory tracts?
- Spinothalamic: pain and temperature
- Spinocerebellar: proprioception
- Posterior/Dorsal column: discriminative touch
- Spinotreticular tract
- Spinotectal tract
- Spinomesecephalic tract
- Spino-olivary tract
What is the pathway of the dorsal Column (Medial Lemniscus) tract?
Neuron 1: 1st order neuron
- Originates in peripheral receptor
- Travels towards CNS via spinal nerve
- Enters CNS via dorsal root of spinal nerve and does NOT synapse
- Axon continues to ascend in dorsal columns of spinal cord
- Synapses in nuclei of medulla
Neuron 2: 2nd order neuron
- Cell body originates in nucleus of medulla
- Axon decussates in medulla oblongata
- Ascends to thalamic nuclei via medial leminiscus pathway
- Synapses in thalamus
Neuron 3: 3rd order neuron
- Cell body originates in thalamus
- Axon travels from thalamus to post-central gyrus of parietal lobe
- Synapses in primary somatosensory cortex
- Sensation is interpreted
FC (lateral columns) - fasciculus cunetaus carries touch information from?
upper limb
FG (medial columns) = Fasciculus gracilis carries touch information from?
lower limb
The dorsal column is divided into lateral and medial columns what are they?
- FG (medial columns) = Fasciculus gracilis
- FC (lateral columns) = Fasciculus cuneatus
Information travelling in the fasciculus cuneatus column will synpase where?
in the “nucleus cuneatus” (NC) of the medulla
Information travelling in the fasciculus gracilis will synpase where?
“nucleus gracilis” (NG) of the medulla
What is another name for the spinothalamic tract?
dorsal column medial lemniscus tract
What is the pathway of the spinocerebellar tract?
Neuron 1: 1st order neuron
- Originates in peripheral receptor
- Travels towards CNS via nerve
- Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
- Cell body originates in dorsal grey horn
- Remains ipsilateral
- Ascends in anterolateral white column of spinal cord
- Axon ascends to the level of the cerebellum
- Synapses in cerebellar hemisphere
Which pathway only has 2 neurons?
spinocerebellar tract
Which pathways crosses TWICE?
spinocerebellar tract
What does the spinocerebellar tract transmit?
General sensation (GSA) for conscious proprioception (bodies ability to observe position in space)
What does the Dorsal Column (Medial Lemniscus) Tract transmit?
General sensation (GSA) for fine touch and discriminative touch information from receptors of the skin
Injury will always be considered ipsilateral for which tract?
spinocerebellar tract
What is the pathway of the spinothalamic tract?
Neuron 1: 1st order neuron
- Originates in peripheral receptor
- Travels towards CNS via nerve
- Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
- Cell body originates in dorsal grey horn
- Axon decussates at the level of entry
- Ascends in antero-lateral white columns of spinal cord
- Synapses in thalamus
Neuron 3: 3rd order neuron
- Cell body originates in thalamus
- Axon travels from thalamus to post-central gyrus
- Synapses in primary somatosensory cortex of parietal lobe
What does the spinothalamic tract transmit?
General sensation (GSA) for pain and temperature sensation from the body
What does neurotransmitter substance P allow us to perceive?
Pain
What is the substantia gelatinosa? and what is it involved in?
- gray matter structure of the dorsal spinal cord
- primarily involved in the transmission and modulation of pain, temperature, and touch
Assumes that pain signals must be allowed through a “gate” before they can actually make it to the brain
Gate pain theory
In order for pain signals to make it through the “gate”, __ _ is used as a neurotransmitter to stimulate the fibers that will carry the pain message from the “gate” to the brain
substance P
What are two ways the ‘gate’ can be closed in gate pain theory
1 – Stimulation of touch fibres will send an inhibitory signal to the “gate.” “Rubbing it better”, and may also be the mechanism behind such therapies as acupuncture or massage.
2 – Other areas of the CNS can send inhibitory signals to the gate, for instance, in response to meditation. This relates to “willing it away” or “mind over matter.” In this instance, the inhibitory signal is likely the release of enkephalins and endorphins that block the action of substance P.
Which column sends an inhibitory interneuron to release serotonin and block the release of substance P?
dorsal
What is the pathway of spinoreticular pathway?
Neuron 1: 1st order neuron
- Originates in peripheral receptor
- Travels towards CNS via nerve
- Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
- Cell body originates in dorsal grey horn
- Axon remains ipsilateral
- Ascends in antero-lateral white columns of spinal cord
- Synapses in medulla, pons, and midbrain
What is the spinoreticular pathway responsible for?
levels of consciousness
What is the pathway of the spinotectal pathway?
Neuron 1: 1st order neuron
- Originates in peripheral receptor
- Travels towards CNS via nerve
- Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
- Cell body originates in dorsal grey horn
- Axon cross over midline
- Ascends in antero-lateral white columns of spinal cord
- Synapses in superior colliculus of midbrain
What is the spinotectal pathway responsible for?
coordinates movements of eyes and head
“reflexive turning of head and eyes towards a point of cutaneous stimulation”
The spinomesencephalic tract is similar to which tract? Except for where it terminates, which is?
- spinoreticular tract
- midbrain’s PAG
Which tract has connections to the limbic system, so this tract is likely responsible for the fear and aversion –> reactions associated with pain.
Spinomesencephalic tract
Which tract activates the descending analgesia system that arises from the PAG?
spinomesencephalic tract
What is the pathway of the spino-olivary pathway?
Neuron 1: 1st order neuron
- Originates in peripheral receptor
- Travels towards CNS via nerve
- Axon enters dorsal root and synapses in dorsal grey horn upon entry
Neuron 2: 2nd order neuron
- Cell body originates in dorsal grey horn
- Axon cross over midline
- Ascends in antero-lateral white columns of spinal cord
- Synapses in inferior Olivary nucelus of medulla
- Neuron 3: 3rd order neuron
- Cell body originates in nucleus
- Axon cross the midline again
- Enter the cerebellum
- Synapses in cerebellum
What does the spino-olivary pathway play a role in?
control of movements of body & limbs (unconscious proprioception)
efferent/motor signals descend the spinal cord via?
anterior or lateral columns
What are the neurons in the spinocerebellar tract known as?
nucleus dorsalis (Clarke’s column)
Unconscious proprioception from the upper limb is conveyed by?
Cuneocerebellar tract
Which tract conveys the impulses concerned with pain and temperature collected from the entire body (except the head region)?
lateral spinothalamic tract
Which tract conveys the impulses of non-discriminative (crude) touch?
anterior spinothalamic tract
What is the length of the spinal cord?
43-45 cnm
Where does the spinal cord start from?
medulla oblongata at level of foramen magnum
Where does the spinal cord end?
level of L1/L2 intervertebral disc
Where can the spinal cord extend in newborns?
L3 vertebra
Why is the spinal cord go to L3 vertebra in newborns?
because elongation of the spinal cord stops at the age of 4 – 5, but the growth of the vertebral column continues
Which nerves does the cervical enlargement give rise to?
nerves innervating the upper limbs
Which nerves does the lumbar (lumbosacral) enlargement give rise to?
nerves innervating the lower limbs
The spinal cord tapers down inferior to the lumbar enlargement forming the __ __.
conus medullaris
What are the two main longitudinal grooves on the surface of the spinal cord?
- ventral (anterior) median fissure
- dorsal (posterior) median sulcus
Which rootlets of the spinal nerves emerge on either side of the ventral median fissure?
- ventral (motor) rootlets
Which rootlets of the spinal nerves emerge on either side of the dorsal median sulcus?
- dorsal (sensory) rootlets
The ventral rootlets form to join which structure?
- ventral (motor) root of spinal nerves
The dorsal rootlets merge to form which structure?
- dorsal (sensory) root of spinal nerve
Each dorsal root of the spina nerve is associated with what ganglion?
dorsal root ganglion
What does the dorsal root ganglion house?
- cell bodies of sensory neurons
Each spinal nerve is formed by what union?
- union of ventral & dorsal roots
The section of the spinal cord that gives rise to a pair of spinal nerves is known as?
spinal cord segment
How many spinal cord segments are there?
31:
- 8 cervical segments, C1-C8
- 12 thoracic segments, T1-T12
- 5 lumbar segments, L1-L5
- 5 sacral segments, S1-S5
- 1 coccygeal segment, Co
Since the spinal cord ends at the level of vertebra LI-LII, the ventral and dorsal roots of the lumbar, sacral, and coccygeal spinal nerves descend to the respective foramina before emerging from the vertebral canal. What is this bundle of roots known as?
cauda equina
How many cervical spinal nerves are there?
8
What are somatic nerve plexuses formed by?
ventral rami of spinal nerve
Which spinal region does NOT have any somatic nerve plexuses?
thoracic
Why doesn’t the thoracic region have any nerve plexuses?
- because those nerves are b/w the ribs (no opportunity)
What are the nerves of the ventral ramus of the thoracic region called?
- intercostal nerves (T1)
What are the nerves of the anterior ramus of the thoracic region called?
- subcostal nerves (T12)
The gray matter of the spinal cord is shaped like the letter “H” with a __ __ __ and a __ __ __ on each side
- ventral (anterior) horn
- dorsal (posterior) horn
What are the right & left halves of the gray mater connected by?
- gray commiseure
What does the gray commissure contain?
central canal
What are lateral horns in the spinal cord present?
- T1-L1/2
- S2-S4
What do the lateral horns of T1-L1/2 segments carry?
- cell bodies of sympathetic motor neurons
What do the lateral horns of the S2-S4 segments carry?
- cell bodies of parasympathetic motor neurons
What do the ventral (anterior) contain?
- cell bodies of the motor neurons whose axons form the motor (ventral roots of spinal nerves)
What do the dorsal horns of the spinal cord contain?
- cell bodies of sensory neurons
Where do the sensory neurons in the dorsal horns receive information from?
sensory neurons residing in the dorsal root ganglia, whose axons form the dorsal root of the spinal nerves
How is the white matter of the spinal cord organized?
- ventral columns (funiculi)
- lateral (funiculi)
- dorsal (funiculi)
What do the columns of white mater in the spinal cord contain?
bundles of myelinated nerve fibres (tracts)
Small amount of white matter in front of central canal
anterior white commissure
Convey the messages from the periphery to the upper centers of the nervous system (e.g. dorsal (posterior) spinocerebellar tract, dorsal column (medial lemniscus) tract, and lateral spinothalamic tract)
ascending (sensory) tracts
Convey messages from the upper centers of the nervous system to the periphery (e.g. lateral and ventral corticospinal tracts)
Descending (motor) tracts
