Pons Flashcards
Medial Lemniscus function:
- Carries sensory information from the dorsal column to the thalamus
o Proprioception
o Fine discriminative touch o Vibrations
Trigeminal Lemniscus function
Carries sensory information from the face to the thalamus o Pain
o Temperature
o Crude touch
o Pressure
* These sensations are picked up by CN V (trigeminal) and this tract originates when fibers divide from the spinal nucleus of CN V at a lower level in the pons
Spinal Lemniscus function
Sensory information from the ventral and lateral spinothalamic tracts in the spinal cord to the thalamus
o Pain
o Temperature
o Crude Touch
o Pressure
Lateral Lemniscus function
- Carries hearing information from the contralateral cochlea to the inferior colliculus in the midbrain
- The fibers forming it cross in the trapezoid body
Ventral Spinocerebellar Tract function
- Ascending fibers carrying proprioceptive information from muscles, tendons and ligaments to the cerebellum
o Forms from lateral white column fibers at the levels of L2 to Coccis - This is used by the cerebellum as feedback on motor movement
o Aids movement co-ordination
Rubrospinal Tract function
Brings motor information from the red nucleus in the midbrain to flexor muscles
o Primarily distal flexors of upper extremities Regulates force, velocity and direction of movement
Tectospinal Tract function
Stimuli from the tectum to muscles of the eyes, head and neck
o Superior Colliculus→ Visual stimuli o Inferior Colliculus→ Auditory stimuli
Allows rapid response of the eyes, head and neck to visual and auditory stimuli
Medial Longitudinal Fasciculus funtion
- Ascending tract that connects the Nuclei of Cranial Nerves III, IV and VI
- Co-ordinates eye movements
- Can be damaged in multiple sclerosis
Motor nucleus of CN V (trigeminal) function
- Motor supply to structures of 1st pharyngeal arch (muscles of mastication)
o Temporalis
o Masseter
o Medial pterygoid
o Lateral Pterygoid
o Suprahyoid muscles - Special Visceral Efferent Fibers
Central/Principal Pontine Nucleus of CN V (trigeminal) function:
- Receives sensory information from the face o Fine touch of whole face
o Proprioception of the jaw - General Afferent Fibers
Superior Cerebellar Peduncles function :
- Connect the midbrain to the cerebellum
- A small piece can be seen at this level of the pons
Pontine Nuclei function :
- Synapse points of corticopontine motor fibers
o Impulse descends from the motor cortex
o Synapse at pontine nuclei
o Moves to the contralateral cerebellum through the
pontocerebellar fibers and the middle cerebellar
peduncles (see diagram) - This informs the cerebellum of the motor plan
o Aids movement co-ordination
Spinal Nucleus of CN V (trigeminal) function:
Extends from lower part of the pons to the top of the spinal cord
* Receives sensory information from the ipsilateral face o Pain
o Temperature o Crude touch o Pressure
* Some fibers leave the nucleus to form the trigeminal lemniscus higher up in the pons
* Also receives sensations from the middle ear through General Somatic Afferent Fibers of CN VII (facial)
Motor Nucleus of CN VII (facial) function
- Supplies muscles of 2nd pharyngeal arch (facial expression)
o Occipitofrontalis o Orbicularis oculi o Orbicularis ori
o Buccinator
o Platysma - Special Visceral Efferent Fibers
Superior Salivatory Nucleus of CN VII (facial) function
- Parasympathetic stimulus to lacrimal, palatine and salivary glands
- General Visceral Efferent Fibers
Nucleus of Tractus Solitarius of CN VII (facial) function
- Sensory information from anterior 2/3 of tongue o Gustation (taste)
- Special Visceral Afferent Fibers
General Somatic Afferent Fibers from CN VII function
Pick up sensory information from the middle ear, external ear and tympanic membrane
They are sent to the spinal nucleus of CN V General Somatic Afferent Fibers
Dorsal + Ventral Cochlear Nuclei function
- Receive hearing information from cochlear branch of CN VIII (vestibulocochlear)
- Sends fibers through the trapezoid body to the contralateral part of the pons
- These fibers ascend as the lateral lemniscus
- Both nuclei are separated by a piece of the inferior
cerebellar peduncles
o Connect the medulla to the cerebellum
Medial Lemniscus Pathway :
Carries sensory information from the body o Proprioception
o Fine discriminative touch
o Vibrations
Fibers move up the spinal cord in ipsilateral dorsal column
Synapse at nucleus gracilis and nucleus cuneatus in the medulla
Internal arcuate fibers decussate in the medulla and ascend upwards as the medial lemniscus
Fibers synapse in the thalamus
Trigeminal Lemniscus Pathway
Carries all sensory information from the face
Fibers synapse in the spinal nuclei a. Mesencephalic nucleus
b. Principal pontine nucleus
c. Spinal nucleus
2nd order neurons ascend upwards as the trigeminal lemniscus
Fibers synapse in the thalamus
Spinal Lemniscus (spinothalamic tract)
Carries sensory information from the body o Crude touch
o Pain
o Temperature
o Pressure
Fibers synapse at the dorsal grey horn Cross over to the contralateral side
Move upwards as the ventral and lateral
spinothalamic tracts
Come together to form the spinal lemniscus Synapse at the thalamus
Ventral spinocerebellar tract
Carries proprioceptive information from muscles, tendons and ligaments
Fibers synapse at the dorsal grey horn
Cross over to the contralateral side
Move upwards as the lateral white column
Enters the cerebellum through the superior cerebellar
peduncles
Moves to the ipsilateral cerebellum behind the pons
Vestibular Pathway;
CN VIII (vestibulocochlear) carries equilibrium sensations from the inner ear to the vestibular nuclear complex
o Movements of the head and neck o Up and down movements
o Dynamic + equilibrium
Vestibular nuclear complex sends fibers to:
o Downwards to extensor muscles (vestibulospinal
tract)
Maintains posture
o To the vestigial nucleus in the cerebellum Through
the inferior cerebellar peduncles Helps maintain balance
o To contralateral CN VI (abducens) nucleus
Stimulates nuclei of CN III (oculomotor) and CN IV (trochlear) through the Medial Longitudinal
Fasciculus
Co-ordinates eye movements and keeps steady gaze when head moves
