Features Of The Brainstem Flashcards
Anterior Median fissure (External Medulla)
Midline prominent groove
Dividing ventral medullary evenly from left to right
Pyramids (External Medulla)
Swelling or ridge lateral to anterior median fissure
Contain axon fibers of the principal descending motor pathway
B/w motor cortex in the cerebrum and spinal cord
CORTICOSPINAL TRACT
Pyramidal decussation (External Medulla)
2/3 way down ventral medullary surface
Between the left and right pyramids
Smooth and flat
Location where the majority of the corticospinal fibers within the pyramids
Cross the midline to continue descending into the
Contralateral part of the spinal cord
Olivary Eminence (External Medulla)
Ventral medulla side
Lateral to the pyramids
Consists of underlying nucleus known as inferior olivary complex
Primary nucleus providing somatosensory inputs to cerebellar systems during the coordination of movement
Hypoglossal nerve CN XII (External Medulla)
Exits brainstem b/w pyramids and olivary eminences on each side
Motor nerve
Innervates musculature of tongue
Allows for articulatory actions and food manipulation
3 key fiber tracts to and from spinal cord in medulla
Medial lemniscus
Anterolateral tract
Corticospinal tract
Medial lemniscus (Internal Medulla)
Ribbon like
Ventral midline
Axons of contralateral neurons originating in the cuneate and gracile nuclei
Massive sensory pathway
Part of 3 neuron system transmitting tactile and proprioceptive inputs from body below neck
Axons will ascend and synapse onto the thalamus
Anterolateral tract (ALS) (Internal Medulla)
Lateral most edge of medulla
Ventral to spinal trigeminal nucleus
Transmits sensory inputs related to noxious and thermal sensations from body below neck
Corticospinal tract (Internal Medulla)
Comprises mass of pyramids on ventral and midline aspects
Descending pathway transmits motor signals from primary and premotor regions of the cerebral cortex down to LMN
Active during skilled and precision forms of motor control
Vestibular nuclei (Internal medulla)
Dorsal and lateral part of medulla
House neurons that receive input from the auditory-vestibular cranial nerve (VIII)
Shares this info with areas of CNS mediating balance, equilibrium regulation, and eye motion.
Major input source to balance control regions of the cerebellum
Cochlear nuclei (Internal medulla)
Anterior and posterior
Lateral to the position of the vestibular nuclei
Form the input location for sound transducer by the cochlea
And transmitted through the auditory never fibers of CN VIII
Trigeminal system (Pons External)
Ventral - nerve stalks
Primarily a sensory system that operates and the chief mediator
of tactile, proprioceptive, noxious, and thermal inputs
From all regions of the
Facial skin, oral mucosa, scalp, and skin of the neck
Has a small motor component that innervates the muscles of the jaw
Abducens nerve VI - external pons
Caudal border
Pair of fibers
Innervates extraocular muscles
Contributes to the eyeball motion during gaze
Facial Nerve VII - external pons
Lateral from Abducens
Contains both afferent and efferent components
Partially mediate our sens of taste
Provide full motor control to the muscles of the face
Inferior, middle, and superior cerebellar peduncle (external pons)
Fiber tracts - horizontal bands
Dorsal and lateral
Massively huge axon pathways into and out of the cerebellum
ONLY means cerebellum is connected to and communicates with the remainder of the CNS
Inferior and middle - input to cerebellum
Superior - output from cerebellum
Internal pons divided into two regions along ventral to dorsal region
Basilar pons
Pontine tegmentum
Basilar pontine (internal pons)
Composed of three elements:
1. Vertically-corticospinal/bulbar tracts
2. Horizontally fibers that constitute a good portion of the cerebellar peduncles
3. Pontine nuclei
Tegmentum (Internal pons)
Houses pontine reticular formation (houses apneustic and pneumotaxic centers)
Otherwise not uniformly structured
Facial nucleus (internal pons)
Home of all motoneurons innervating facial muscles
Axons comprise CN VII
Superior olivary nucleus (internal pons)
Ventral to facial nucleus
Key component of the central auditory pathway
Operates ad the first site of binaural sound integration
Coming from the left and right cochela
Oculomotor nerve III - external midbrain
Caudal border where pons meets midbrain - ventral side
Exits from junction
Innervates several extraocular muscles
Controlling most motion of the eyes during visual gaze and search
Constriction of pupils
Trochlear nerve IV - external midbrain
Emerge laterally from behind midbrain
Lateral and medial geniculate nucleus (External midbrain)
Superior colliculus communicates with a key realty station to the central visual processing pathway LGN
Interior colliculus communicates with MGN
MGN is auditory
LGN is vision
