Ascending and Descending Pathways Flashcards
How many neurons are involved in the ascending sensory tracts?
3
How many neurons are involved in the corticospinal and corticobulbar descending motor tracts?
2
What type of fibres carry information from mechanoreceptors in the skin through the medial lemniscal pathway to the brainstem?
A-beta fibres
A-beta fibres carry sensory information from mechanoreceptors in the skin. Give examples of types of mechanoreceptors?
Meissner's corpuscle Merkel discs Hair follicle receptors Pacinian corpuscle Ruffini's endings
A-beta fibres from mechanoreceptors in the skin give of a branch to the dorsal horn before continuing through the dorsal columns to the brainstem. T/F?
True
What is the name of the nucleus at which A-beta fibres synapse with the secondary neuron in the medial lemniscal ascending pathway?
Gracile nucleus
What is the name of the nucleus in the thalamus where fibres in the dorsal column tract synapse with tertiary neurons?
VPL of thalamus
At what point in the dorsal column pathway do the fibres decussate to the contralateral side?
At the synapse between primary and secondary neurons in the brainstem
What is the name for the part of the secondary neuron in the dorsal column tract which crosses to the contralateral side of the tract?
Internal arcuate fibres
What is the role of the territory neuron in the ascending tracts?
To transmit sensory information from the thalamus, through the internal capsule, to the sensory cortex
What type of fibres make up the primary neuron of the spinothalamic ascending pathway?
A-delta and C fibres
At what level of the spinothalamic tract do neurons decussate to the contralateral side of the tract?
At the synapse between the primary and secondary neuron in the spinal cord
The secondary neuron decussates and ascends to the brainstem via which column of the spinal cord in the spinothalamic tract?
Antero-lateral column
The secondary neuron of the spinothalamic tract travels through the brainstem - what is its name at this point?
Spinal lemniscus
Which descending tracts are responsible for voluntary movement?
Corticospinal and corticobulbar tracts
At which point does the upper motor neuron of the corticobulbar tract synapse with the lower motor neuron?
Brainstem
Which descending tract is responsible for innervation of the cranial nerves?
Corticobulbar tract
Which cranial nerves have bilateral nuclei in the corticobulbar tract?
Trigeminal nerve
Facial nerve
Vagus nerve
Hypoglossal nerve
The upper motor neuron of the corticospinal tract synapses with the lower motor neuron in the medulla. What percentage of these upper motor neurons will decussate to synapse with lower motor neurons on the contralateral side of the tract?
85%
The upper motor neuron of the corticospinal tract synapses with the lower motor neuron in the medulla. What percentage of these upper motor neurons will synapse with lower motor neurons on the ipsilateral side of the tract?
15%
What is the name for the portion of the corticopsinal tract through which lower motor neurons descend on the ipsilateral side to the upper motor neuron?
Anterior corticospinal tract
What is the name for the portion of the corticopsinal tract through which lower motor neurons descend on the contralateral side to the upper motor neuron?
Lateral corticospinal tract
Through which segments of the spinal cord does the anterior corticospinal tract descend?
Cervical and mid-thoracic
The reticulospinal tract is important for the maintenance of balance. Fibres from which point in the brain innervate the extensors?
Pons
The reticulospinal tract is important for the maintenance of balance. Fibres from which point in the brain innervate the flexors?
Medulla
What is the name of the descending pathway, responsible for the maintenance of balance of posture, which originates from Dieter’s nucleus?
Ventromedial pathway
The tectospinal pathway is important for the maintenance of balance and posture. Where in the brain does this pathway orignate?
Contralateral superior colliculus
The tectospinal pathway is important for the maintenance of balance and posture. To which spinal segments does this tract project to?
Cervical
In the dorsal column pathway, what nucleus of the medulla does sensory input from the leg and lower trunk travel to?
Gracile nucleus
In the dorsal column pathway, what nucleus of the medulla does sensory input from the arm, upper trunk and neck travel to?
Cuneate nucleus
In which nucleus of the thalamus does information from the dorsal column tract synapse at?
Ventroposteriolateral Nucleus
Along which ascending tract does proprioceptive information travel?
Spinocerebellar
Information about body movements is carried in Clarke’s column through to the cerebellum through the inferior cerebellar peduncle. T/F?
True
Which cranial nerves provide innervation to the parasympathetic nervous system?
3, 7, 9 and 10
