Rotation: Spinal Cord Flashcards
The axons now forming the lateral corticospinal tract will continue their caudal descent in the spinal cord until they reach their synaptic targets- a second neuron in the ______ of the spinal cord, called an alpha motorneuron.
ventral grey matter
In the caudal medulla, approximately ___% of the fibers decussate.
80
The nucleus gracilis’ axon immediately crosses the midline to ascend within the brainstem as part of a bundle called the _______.
medial lemniscus
What happens when the anterior/ventral corticospinal tract reach their intended segment of the spinal cord?
they innervate not only the ipsilateral alpha motor neuron, but they also send a branch of their axon across the midline in a white matter band called the ventral white commisure to innervate some contralateral alpha motor neurons
What is the corona radiata?
a bundle of white matter fibers extending from the cortex to the spinal cord
This is a small band of white matter near the dorsal rootlet where pain and temperature afferents travel the spinal cord.
Lissauer’s fasciculus
Alpha motor neurons located medially in the grey matter innervate _____ important for _____ and are innervated by the anterior corticiospinal pathways.
core muscles; posture
What is the connection btw the caudate and the putamen called?
the ventral striatum
The _____ splits into a medial caudate and a lateral putamen and globus pallidus- here they are part of white matter called the internal capsule.
corona radiata
How does a dissociated sensory loss, in which one side of the body below the injury lacks pain and temperature sensation, and the other lacks dorsal column sensation, occur?
a hemisection injury of the spinal cord (Brown-Sequard syndrome)
On the lateral surface of the brain, the primary motor cortex is found along the pre-central gyrus, just anterior to ______.
the central sulcus
Alpha motor neurons located laterally in the ventral grey matter innervate muscles important for _____, like the ________. These neurons are innervated by the lateral corticospinal tract.
dexterity; fingers or thumb musculature
What is upper motor neuron (UMN) syndrome?
- muscles innervated by these lower motor neurons are weak.
- There is an initial loss of reflex activity and muscle tone for a period between a few days and weeks.
- After this time, the muscle tone and reflex activity returns in an exaggerated fashion (spasticity and hyperreflexia)
On the lateral surface of the brain, the primary motor cortex is found along the ______, just anterior to the central sulcus.
pre-central gyrus
The white matter fibers traverse the diencephalon laterally and then enter the midbrain, where they form a stalk-like white matter bundle called the ______- a part of the midbrain referred to as the cerebral peduncle.
crus cerebri
The medial lemniscus will terminate on a third neuron in the pathway, located in a nucleus of the _____, called the ventral posteriolateral nucleus, or VPL.
thalamus
What is the nucleus cuneatus?
a second order neuron in a nucleus lateral to the nucleus gracilis where axons about T6 synapse
This is a second order neuron in a nucleus lateral to the nucleus gracilis where axons about T6 synapse.
the nucleus cuneatus
The white matter fibers traverse the ______ laterally and then enter the ______, where they form a stalk-like white matter bundle called the crus cerebri- referred to as the cerebral peduncle.
diencephalon; midbrain
The axons continue through the ____ then reemerge as part of a structure visible on the ventral surface of the medulla known as the pyramid.
pons
What happens to the pt with a hemisection injury of the spinal cord (Brown-Sequard syndrome)?
a dissociated sensory loss, in which one side of the body below the injury lacks pain and temperature sensation, and the other lacks dorsal column sensation
The axons now forming the lateral corticospinal tract will continue their caudal descent in the spinal cord until they reach their synaptic targets- a ______ in the ventral grey matter of the spinal cord, called ______.
second neuron; an alpha motorneuron
What does the corticospinal tract divide into?
- the anterior/ventral corticospinal tract
- the lateral corticospinal tract
Above ______, axons still enter the spinal cord at their respective segments, but then ascend in a white matter column that is just lateral to the fasciculus gracilis called the fasciculus cuneatus.
the T6 dermatome
Dx?:
- muscles innervated by these alpha motor neurons would fail to respond to commands from the UMNs, producing weakness
- in those muscles, reflexes mediated by those segments would be attenuated
- muscle tone would be decreased, producing hypotonia or flaccidity
lower motor neuron (LMN) syndrome
The principal efferent pathway from the brain to the spinal cord is the _______.
corticospinal tract
What is the column of white matter in the spinal cord called?
the lateral corticospinal tract
_______ located medially in the grey matter innervate core muscles important for posture and are innervated by the anterior corticiospinal pathways.
Alpha motor neurons
Alpha motor neurons located laterally in the ______ innervate muscles important for dexterity, like the fingers or thumb musculature. These neurons are innervated by the lateral corticospinal tract.
ventral grey matter
The Babinski reflex is a hallmark of ____ syndrome.
UMN
The axons continue through the pons then reemerge as part of a structure visible on the ventral surface of the medulla known as the ______.
pyramid
The cells in layer 5 of the primary motor cortex are especially large- because of their shape they are known as “_____”, and these particular cells are called “_____.”
pyramidal cells; Betz cells
What does the anteriorlateral system (ALS) do?
transmits pain and temperature info
These are the remaining 20% of white matter fibers that did not cross to the contralateral side.
the anterior/ventral corticospinal tract
______ located laterally in the ventral grey matter innervate muscles important for dexterity, like the fingers or thumb musculature. These neurons are innervated by the lateral corticospinal tract.
Alpha motor neurons
The axons now forming the _______ will continue their caudal descent in the spinal cord until they reach their synaptic targets- a second neuron in the ventral grey matter of the spinal cord, called an alpha motorneuron.
lateral corticospinal tract
What is Lissauer’s fasciculus?
a small band of white matter near the dorsal rootlet where pain and temperature afferents travel the spinal cord
What is the ventral white commissure?
a white matter band arising from the anterior/ventral corticospinal tract that crosses the midline to innervate some contralateral alpha motor neurons
The medial lemniscus will terminate on a third neuron in the pathway, located in a nucleus of the thalamus, called the ______.
ventral posteriolateral nucleus, or VPL
The white matter fibers traverse the diencephalon laterally and then enter the midbrain, where they form a stalk-like white matter bundle called the crus cerebri- a part of the midbrain referred to as the ______.
cerebral peduncle
This third order neuron in the thalamus will then innervate the ______.
primary somatosensory cortex
This somatosensory pathway discriminative touch, vibration sense, and joint position sense or proprioception.
the Dorsal (or Posterior) Column/Medial Lemniscal (DC/ML) System
What does the anterior/ventral corticospinal tract consist of?
the remaining 20% of white matter fibers that did not cross to the contralateral side
Dx?:
- muscles innervated by these lower motor neurons are weak.
- There is an initial loss of reflex activity and muscle tone for a period between a few days and weeks.
- After this time, the muscle tone and reflex activity returns in an exaggerated fashion (spasticity and hyperreflexia)
upper motor neuron (UMN) syndrome
The corona radiata splits into a medial _____ and a lateral _____ and ______- here they are part of white matter called the internal capsule.
caudate; putamen and globus pallidus
Alpha motor neurons located medially in the grey matter innervate core muscles important for posture and are innervated by _____.
the anterior corticiospinal pathways
The principal _____ pathway from the brain to the spinal cord is the corticospinal tract.
efferent
Fasciculations are a hallmark of _____ syndrome.
LMN
This is a white matter band arising from the anterior/ventral corticospinal tract that crosses the midline to innervate some contralateral alpha motor neurons.
the ventral white commissure
The nucleus gracilis’ axon immediately ______ to ascend within the brainstem as part of a bundle called the medial lemniscus.
crosses the midline
What is the internal capsule?
a bundle of white matter fibers w/I the basal ganglia that gives rise to the caudate, putamen, and globus pallidus
What would happen to the muscle and reflex if the lower motor neuron was damaged or dysfunctional?
- muscles innervated by these alpha motor neurons would fail to respond to commands from the UMNs, producing weakness
- in those muscles reflexes mediated by those segments would be attenuated
- muscle tone would be decreased, producing hypotonia or flaccidity
In the caudal medulla, approximately 80% of the fibers ______.
decussate
The axon continues to ascend all the way to the bottom of the brainstem before it forms a synapse with a second neuron in the pathway, called the _____.
the nucleus gracilis
This is dorsal gray matter in the spinal cord containing second order neurons in the pain/temperature afferent pathway.
the substantia gelatinosa
Alpha motor neurons located laterally in the ventral grey matter innervate muscles important for dexterity, like the fingers or thumb musculature. These neurons are innervated by the _______.
lateral corticospinal tract
What does the Dorsal (or Posterior) Column/Medial Lemniscal (DC/ML) System do?
transmits info about discriminative touch, vibration sense, and joint position sense or proprioception.
The ______ will terminate on a third neuron in the pathway, located in a nucleus of the thalamus, called the ventral posteriolateral nucleus, or VPL.
medial lemniscus
The cells in layer ___ of the primary motor cortex are especially large- because of their shape they are known as “pyramidal cells”, and these particular pyramidal cells are called “Betz cells.”
5
What is the 2 neuron pathway from brain to muscle?
- the Upper Motor Neuron (UMN) from brain to spinal cord
- the Lower Motor Neuron (the alpha motor neuron) from spinal cord to neuromuscular junction
Above the T6 dermatome, axons still enter the spinal cord at their respective segments, but then ascend in a white matter column that is just lateral to the fasciculus gracilis called ______.
the fasciculus cuneatus
There are two principal pathways for transmission of somatosensory information to the central nervous system: the _____ and the _____.
- the anteriorlateral system (ALS)
- the Dorsal (or Posterior) Column/Medial Lemniscal (DC/ML) System
On the lateral surface of the brain, the _____ is found along the pre-central gyrus, just anterior to the central sulcus.
primary motor cortex
This is a bundle of white matter fibers extending from the cortex to the spinal cord.
corona radiata
Name the 2 afferent/sensory pathways from the spinal cord to the brain.
- the dorsal column/medial lemniscal system (aka the posterior column/medial lemniscal system- DCML)
- the anterolateral system (aka the spinothalamic tract)
The corona radiata splits into a medial caudate and a lateral putamen and globus pallidus- here they are part of white matter called the ______.
internal capsule
The axons continue through the pons then reemerge as part of a structure visible on the ventral surface of the ______ known as the pyramid.
medulla
Why does the pyramid taper caudally?
the majority of the fibers it contains are decussating- sharply crossing over to the other side of the neural tube, and turning dorsally as they do
What is the subcentral gyrus?
connects the pre- and postcentral gyri
The alpha motorneurons send their axons out the ______ of the spinal cord where they will ultimately innervate muscle tissue.
ventral rootlets
This connects the pre- and postcentral gyri.
the subcentral gyrus
What is the major role of the corticospinal tract?
voluntary control of skeletal muscle
Once the axon enters the spinal cord via the dorsal rootlets, it will continue to ascend in a bundle of white matter called the ______.
fasciculus gracilis
This somatosensory pathway transmits pain and temperature info.
the anteriorlateral system (ALS)
What is the substantia gelatinosa?
dorsal gray matter in the spinal cord containing second order neurons in the pain/temperature afferent pathway
What is the ventral striatum?
the connection btw the caudate and the putamen
