Lecture 10: Spinal Cord Pathways Flashcards
What 3 parts can the brain be divided into?
- Cerebrum
- Brainstem
- Cerebellum
What is included in the Brainstem?
The Midbrain, Pons and Medulla
What are the three embryological origins of the brain?
The Forebrain, Midbrain and Hindbrain
Which part of the brain originates from the Forebrain?
The Cerebrum
Which part of the brain originates from the Midbrain?
The midbrain
Which part of the brain originates from the Hindbrain?
The Pons, Medulla and Cerebellum
What is the spinal cord?
A cylindrical cable of pathways to and from brain and rest of the body
Where does the Spinal cord extend to and from?
The Base of the skull (medulla) to L1-L2 vertebrae
What are the two Plexuses of the Spinal cord?
Cervical (Brachial Plexus) and Lumbar (Lumbosacral Plexus)
What covers the Spinal Cord?
The Meninges
What is a the Central Canal?
A cerebrospinal fluid filled space that runs through the spinal cord
What are axons in the spinal cord known as?
Tracts
What is the spinal cord an extension of?
The Medulla
What is a Plexus?
When more than one nerve comes off the spinal cord and rejoins another nerve
Where does the Brachial Plexus extend?
C5 to T1
Where does the Lumbosacral Plexus serve?
The lower limbs
Which nerves are part of the lumbosacral plexus?
L1 - S4
What is the Central canal of the spinal cord continuous with?
The ventricles of the brain
How many pairs of Spinal Nerves are there?
31 Pairs
What is the name order of the nerves?
Cervical Thoracic Lumbar Sacral Coccygeal
How many Cervical nerves are there?
8
How many Thoracic Nerves are there?
12
How many Lumbar nerves are there?
5
How many Sacral Nerves are there?
5
How many Coccygeal nerves are there?
1
Where does every nerve come out in Cervical Vertebrae?
Every nerve comes off ABOVE the corresponding cervical vertebrae
Where does every nerve exit in Thoracic, Lumbar, Sacral, Coccygeal vertebrae?
Below the corresponding vertebrae
Why don’t Thoracic nerves form Plexuses?
Because the ribs are in the way
Why does the spinal cord stop at L1 and L2?
Because during fetal development each exiting nerve matched with the vertebrae but as one grows they no longer match
What is below L2 since the spinal cord ends there?
Nerve roots are there, just not spinal cord
What is the Conus Medullaris?
The tip of the spinal cord where it ends between L1 and L2
What is the tip of the spinal cord where it ends known as?
The Conus Medullaris
What sits below the Conus Medullaris?
The Cauda Equina
What is the Cauda Equina?
The nerve roots that extends from the Conus Medullaris
What sits below the Causa Equina?
The Filum Terminale
What is the Filum Terminale?
The attachment of the spinal cord to the coccyx using Pia Mater
In the spinal cord where is the Grey Matter?
On the inside
In the spinal cord where is the white matter?
On the outside
Where is the White matter in the brain?
On the inside
Where is the Grey Matter in the brain?
On the outside
Which part of the spinal cord do Sensory Neurons enter?
The Dorsal Horn
Which part of the Spinal cord do Motor Neurons enter?
The Ventral Horn
What leaves the Lateral Horn of the spinal cord?
Sympathetic nerves
When do we need a lot of Grey matter in the spinal cord?
When there’s cell bodies that need to extend their axons out to go to muscles or to come back in from the periphery
Which parts of the Spinal cord would you find a lot of the Grey matter?
The Cervical and Lumbar portion but not the thoracic because there isn’t a lot of movement
How can you tell which side of the spinal cord you are veiwing?
the Dorsal Horn always touches the outside of the spinal cord
What is a Ganglia?
A collection of cell bodies in the peripheral nervous system
Where are all Sensory neuron cell bodies found?
In the Peripheral nervous system, Dorsal Root Ganglia
What is the Dorsal Root Ganglia?
Where all cell bodies of sensory neurons are found in the PNS
Where do Motor Neurons always have their cell bodies?
In the spinal cord or the brainstem
In which nerves is the Lateral Horn found?
The Thoracic spinal nerves
How many neurons are in the Sympathetic nervous system pathway?
2 Neurons
Where does the first neuron in the Sympathetic nervous system pathway exit?
The Lateral horn
Where does the first neuron in the Sympathetic nervous pathway synapse?
The PNS
What do Dorsal and Ventral Horns lead to?
Dorsal and Ventral roots
What do Dorsal and Ventral roots join up to form after leaving the spinal cord?
A spinal nerve
What is the Dorsal Root Ganglia?
A place outside of the spinal cord where are Cell Bodies of sensory neurons are found
What kind of neurons are sensory neurons?
Pseudounipolar neurons
What type of neurons are Motor neurons?
Multipolar neurons
What is the function of the Cerebrum?
Communication between the CNS, PNS and peripheral organ systems with ascending and descending pathways that relay sensory and motor information between periphery and higher centers
What does Each sensory or motor pathway consist of?
A chain of neurons and associated nuclei or ganglia
What varies from one neuron pathway to another?
The number of neurons and synapses (inter-neuronal connections)
How many neurons are in all Conscious sensory pathways?
3
How many neurons are in motor pathways?
2
Where is the upper motor neuron in the Motor pathway locates?
In the motor cortex of the brain
Where is the lower motor neuron in the motor pathway located?
In the spinal cord
What are the 3 Main Sensory pathways?
- Dorsal Column/Medial lemniscal pathway
- Spinothalamic (anterolateral) pathway
- Spinocerebellar Pathway
What does the Dorsal Column/medial lemniscal pathway sense?
- Joint (limb) position and motion sense (proprioception)
* Light touch (discriminant, stereognosis)
What does the Spinothalamic (anterolateral) pathway sense?
Pain and Temperature
What does the Spinocerebellar Somatosensory pathway sense?
Unconscious proprioception
Which pathway detects joint (limb) position, motion sense, and light touch?
The Dorsal Column/medial lemniscal pathway
Which pathway detects pain and temperature?
The Spinothalamic (anterolateral) pathway
What does the Spinocerebellar pathway detect?
Unconscious proprioception
What is Proprioception?
The bodies ability to sense movement of the limbs
Where does the Spinothalamic pathway go?
From the Spinal cord to the thalamus
Which sensory pathways go up to the Primary Somatosensory Cortex?
The Dorsal column/medial lemniscal pathway and the Spinothalamic pathway
Where does information from the Spinocerebellar pathway go?
The Cerebellum
What does the Spinocerebellar pathway do?
Lets the cerebellum know exactly where all parts of the body are in space in order to help with movement
What causes the difference in pathways in the Dorsal Column Sensory pathways?
The different pathways needed for the upper and lower limbs
What pathway does the Lower limbs take in the Dorsal Column sensory pathway?
The Gracile Tract
Where does the nerve in the Dorsal Column pathway synapse for the first time?
The Medulla
Where does all sensation go before it goes to the Somatosensory Cortex?
The Thalamus
How many neurons are in the Dorsal Column sensory pathway?
3
What occurs in the Dorsal Column pathway?
- Light touch will stimulate a neuron
- Action potential goes up the Dorsal Column of the spinal cord through first order neuron
- Synapses at the Medulla and switches side at the Medial Lemniscus pathway to become the second order neuron
- Synapses at the ventral thalamus and goes to the primary somatosensory cortex
What occurs first the the Dorsal Column sensory pathway?
A light touch is sensed and an action potential moves up the Dorsal Column
What occurs after an action potential is sent up the Dorsal Column of the Dorsal Column sensory pathway?
The first order neuron synapses at the Medial Lemniscus of the Medulla
What occurs after the first order neuron synapse at the Medial Lemniscus of the medulla in the Dorsal Column Sensory Pathway?
The second order neuron travels up to the thalamus where it synapses and becomes the third order neuron going to the somatosensory cortex
When in the Dorsal Column sensory pathway does the neuron switch sides?
At the medulla when the first order neuron synapses with the second order neuron
What is the Dorsal Column of the Dosral Sensory Pathway divided into?
The Gracile tract and the Cuneate Tract
What parts does the Dorsal Column Pathway go synapse?
The Medulla and the Thalamus
Where does the Second Order neuron for the Dorsal Column pathway go?
From the medulla to the ventral thalamus
Where does the third order neuron from the Dorsal Column pathway go?
From the thalamus to the somatosensory cortex
How many neurons are involved in the Lateral Spinothalamic pathway?
3 neurons
Where does the first neuron of the Lateral Spinothalamic tract synapse?
As soon as it gets to the spinal cord
Where does the cross over occur in the Lateral Spinothalamic pathway?
When the first order neuron synapse with second order neuron in the spinal cord
Where does the Second order neuron in the Lateral Spinothalamic pathway synapse?
The spinal cord and the ventral thalamus
What tract does the second order neuron in the Spinothalamic tract to get to the thalamus?
The Lateral Spinothalamic tract
How many neurons are there in the Spinocerebellar Pathways?
2 Neurons
Where does the Spinocerebellar pathway go?
From the spinal cord to the cerebellum
When does the Spinocerebellar pathway work?
At all times
Which sensory pathways cross over?
Only the Dorsal Columnar and the Spinothalamic
What does the Second order neuron in the Spinocerebellar pathway travel up?
The Posterior Spinocerebellar tract
What are commands of the Motor systems distributed by?
The PNS
What do Somatic Motor commands cause?
Contraction of skeletal muscle
How many neurons are in Somatic motor pathways?
At least 2 neurons
Where do the upper motor neurons have their cell body?
In the Central Nervous System processing centers
Where do Lower Motor Neurons have their cell bodies?
In the ventral horn of the spinal cord or motor cranial nerve nucleus in the brainstem
Which neurons are the bosses of the Motor pathways?
The upper motor neuron because it can excite or inhibit
What would occur if there was a lesion in an upper motor neuron?
The UMN can no longer tell the LMN what to do and the LMN uncontrollably contracts
What would occur if there was a lesion in a LMN?
The LMN would be unable to contract and would be flaccid
What are the two Motor Pathways?
The Corticospinal (pyramidal) pathway and the Corticonuclear (corticobulbar) pathway
Where do the UMNs of the Cortico spinal pathway extend?
From the cerebral cortex to the spinal cord which houses the LMN
Where do the UMN extend from in the Corticonuclear (corticobulbar) pathway?
From the cerebral cortex to motor cranial nerve nuclei in the brainstem
Which muscles do LMN in the Corticospinal (pyramidal) pathway control?
Muscles of limbs and trunk
What do muscles do the LMN of the corticonuclear (corticobulbar) motor pathway control?
Muscles of the head and neck
Where does the Corticospinal pathway synapse?
In the spinal cord
Where does the Corticonuclear pathway synpase?
In the brainstem
What is another name for the UMNs of the Corticospinal pathway?
Pyramidal Neurons
Where do UMNs in the Primary Motor Cortex orginate?
- Primary motor cortex
- Premotor + supplementary motore cortex
- Primary sensory cortex
What is the Corticospinal pathway important for?
Regulating distal limb muscles and precise skilled, learned movements
Which part of the brain is the Primary Motor Cortex located?
In the frontal lobe
Where do neurons of the Corticospinal pathway travel?
From the Primary motor cortex to the internal capsule to the crus and then to the spinal cord down through the corticospinal tract
What kind of matter is the corticospinal tract made of?
White matter
What part of the midbrain does the Corticospinal pathway go through?
The Crus Cerebri
What does the Corticospinal pathways pass through in the medulla?
The pyramids
What occurs in the pyramids in the Corticospinal pathway?
Crossover of the axons
Where do axons of the corticospinal pathway go after they go through the pyramids of the medulla?
The lateral corticospinal pathway
Where do UMNs in the corticospinal tract synapse?
In the spinal cord
What are Extrapyramidal Pathways?
Subsidiary descending pathways important as back-up systems. Involved in things like posture or contraction of biceps that happen without us thinking
What do the Basal Nuclei and Cerebellum do in Motor Pathways?
Modulate and modify activity in the corticospinal tract to ensure smooth, coordinated, purposeful movement
