3. Brainstem Flashcards
brainstem: overview
- bridge that connects the brain to the spinal cord
- Regulates vital functions: HR, respiration, sleep, and consciousness
- Motor & sensory info to face & head via cranial nerves
3 major divisions of brainstem
- medulla oblongata
- pons
- midbrain
where do the cranial nerves innervate?
head
neck
thorax
abdomen
how many cranial nerves as associated w/ the brainstem?
10 of the 12 cranial nerves
(the nuclei are w/in the brainstem structures)
how are the CNs numbered?
rostral to caudal
which cranial nerves as associated with MIDBRAIN?
III - oculomotor
IV - trochlear
which CNs are assoc. w/ PONS?
V - trigeminal
VI - abducens
VII - facial
VIII - vestibulocochlear
which CNs are assoc. w/ MEDULLA OBLONGATA
IX - glossopharyngeal
X - vagus
XI - accessory (spinal)
XII - hypoglossal
overview of CNs and assoc. brainstem structure
MIDBRAIN - CN 3-4
PONS - CN 5-8
MEDULLA OBLONGATA - CN 9-12
rostral/superior continuation of the spinal cord?
medulla oblongata
medulla oblongata: functions
- pathway betwee spinal cord and brain for ascending and descending fiber tracts
- reflex centers
3 reflex centers of the medulla oblongata
- Cardiovascular - regulates blood pressure
- Respiratory - regulates O2, CO2, & pH levels
- Vestibular - maintains orientation of head and body
what are the important structures and landmarks in the medulla?
- 4 - fourth ventricle/central canal
- Cranial nerves 9-12
- Olive (olivary bodies)
- Pyramids
pyramids: define/ function
- part of medulla
- paired, ventral midline bulges
- corticospinal tract: major motor tract controlling movements of the limbs and trunk, fine movements of hands and fingers
in a myelin stain, which stains a dark blue?
the fibers (axons) stain blue
in a myelin stain, what stains white?
the nuclei are light, white
olive: define, functions
- paired anterolateral bulges of the medulla
- olivary nuclei contribute to:
- perception of sound
- motor learning
- timing of movements
in a cross section, what defines the olive?
a ruffled portion of the olive can be seen
fourth ventricle & central canal
- one of the four connected fluid-filled cavities within the human brain, where CSF is produced
- characteristic diamond shape
- The fourth ventricle extends from the cerebral aqueduct (aqueduct of Sylvius) to the obex, and is filled with cerebrospinal fluid (CSF).
ventricular system (names)
ventricular system:
- left lateral ventricle
- right lateral ventricle
- third ventricle
- fourth ventricle
CSF: functions
- buoyancy
- protection
- clearing of waste
importance of buoyancy (CSF)
nervous tissue is delicate
weight of brain w/o CSF creating buoyancy would crush neurons and cut off blood supply at caudal points
importance of protection (CSF)
shock absorber during hits/jolts
importance of clearing waste (CSF)
metabolic waste products diffuse rapidly into the CSF and then REMOVED INTO THE BLOODSTREAM where it can be processed as waste and removed
open and closed medulla
(difference)
nomenclature refers to level of central canal or at level of 4th ventricle
open medulla: has 4th ventricle
closed medulla: has central canal
CN 12
(name, motor/sensory, action, clinical sign)
- hypoglossal (most caudal)
- MOTOR
- innervates muscles that control tongue movement, assoc. w/ speech and swallowing
- CC: impaired speech, swalloing, tongue will not protrude
CN 11
(name, motor/sensory, action, clinical significance)
- accessory (spinal accessory)
- MOTOR
- inn muscles that turn your head (SCM) and shrug shoulders (trapezius)
- cc: weakness in turning head/shrugging shoulders, head drift to injured side
unique aspect of cranial nerve XI (11)
does NOT originate in the cranium; rather it enters the cranium and extends up
CN 10
(name, motor/sensory, actions, clinical signs)
- vagus nerve
- MIXED (motor and sensory
- Actions
- motor: muscles of pharynx (swallowing) and larynx (speech)
- sensory: sensations of hunger./fullness, GI discomfort
- CC: hoarse voice, lack of gag reflex
CN IX
(name, motor/sensory, action, clinical significance)
- glossopharyngeal
- MIXED (motor/sensory)
- action
- motor: salivation/swallowing
- sensory: sensation to post. 1/3 of tongue (taste/touch/pressure/pain), regulation of blood pressure
- cc: loss of bitter/sour tastes; impaired swallowing
what structure is superior/rostral to the medulla,
and anterior to the cerebellum?
the pons (“bridge”)
pons: functions
- pathways
- descending: forebrain–> medulla
- descending: forebrain –> cerebellum
- ascending: medulla –> thalamus
- respiratory centers that control rate of breathing
- eye movement, coordinated movements between head and eyes
pons: important structures and landmarks
- base vs. tegmentum
- 4th ventricle
- cerebellar peduncles
- CNs 5-8
pons is divided into 2 sections: describe
- base: descending fibers running rostrocaudally; fibers stain dark blue
- tegmentum: site of several cranial nerve nuclei and connections to the inferior and superior cerebellar peduncles
3 cerebellar peduncles, and what they connect
- Superior cerebellar peduncle: Cerebellum –> MIDBRAIN
- Middle cerebellar peduncle: Cerebellum –> PONS
- Inferior cerebellar peduncle: Cerebellum –> MEDULLA
CN 8
(name, motor/sensory, action, clinical signs)
- vestibulocochlear
- SENSORY
- hearing and balance
- CC: nerve deafness, dizziness, nausea, and impaired balance
cn 7
(name, motor/sensory, action, clinical significance)
- facial nerve
- MIXED (motor/sensory)
- actions
- motor: muscles that control facial expression, salivary & lacrimal glands
- sensory: taste to ant. 2/3 of tongue
- cc: inability to control facial expressions, sagging due to loss of tone
5 branches of facial nerve
*musc. of facial expression
“tiny zebras bit my cake!”
- temporal
- zygomatic
- buccal
- mandibular
- cervical
CN 6
(name, motor/sensory, action, clinical signs)
- abducens nerve
- MOTOR
- inn lateral rectus muscle of the eye; responsible for lateral eye movement
- cc: eye drifts medially and could cause double vision
CN 5
(name, motor/sensory, action, clinical significance)
- trigeminal nerve
- BOTH (motor/sensory)
- 3 branches
- ophthalmic (V1 - sensory)
- maxillary (V2 - sensory)
- mandibular (V3 - mixed)
- cc: impaired chewing
sensory of trigeminal nerve (CN V)
- V1 - sensation to upper face and forehead
- V2 - sensation to upper lip, incisors, canines, upper molars, & superior palate
- V3 - lower lip, chin, anterior 2/3 of tongue
CC: loss of sensation at outlined facial area
which structure is superior to the pons and connects the brainsten w/ the forebrain?
midbrain
midbrain: functions
- eye movements and pupillary ligth reflex
- auditory and visual processing
important structures and landmarks of midbrain
-
tectum vs. cerebral peduncle
- cerebral aqueduct
- inferior and superior colliculi
- substantia nigra
- red nucleus
- crus cerebri
- cranial nerves III and IV
midbrain is subdivided into:
tectum and cerebral peduncle
tectum: structure, and function
- part of midbrain
- 2 pairs of nuclei (superior and inferior colliculi)
- Superior: visual attention, tracking objects, focusing
- Inferior: relay from inner ear, reflexive response to sound
relationship between midbrain and peduncles
the midbrain superior and inferior colliculi are SUPERIOR to the cerebellar peduncles
RED NUCLEUS: function, location
- fxn: contributes to motor coordination as part of the extra-pyramidal system, w/ connections to cerebellum in humans
- found at level of superior colliculi
substantia nigra: functions; location
- functions:
- movement related to basal ganglia (parkinson’s disease)
- reward (Addiction)
- located at both level of superior & inferior colliculi
crus cerebri: define
- contains fiber tracts that run through the midbrain, including the CST (corticospinal tract)
- seen in all midbrain sections
what is seen at level of INFERIOR colliculus?
- TECTUM
- inferior colliculus
- cerebral aqueduct
- CEREBRAL PEDUNCLE
- substantia nigra
- cerebral crus
what is seen at level of SUPERIOR colliculus?
- TECTUM
- superior colliculus
- cerebral aqueduct
- CEREBRAL PEDUNCLE
- substantia nigra
- *red nucleus
- cerebral crus
CN 3
(name, motor/sensory, action, clinical signs)
- oculomotor
- MOTOR
- opening eyelid, constricting pupil, turning eye upward/inward
- cc: eye rotates laterally/downward, double vision, drooping eyelid
CN 4
(name, motor/sensory, action, clinical signs)
- trochlear
- MOTOR
- inn superior oblique muscle that controls downward and LATERAL movements of the eye
- cc: eye rotates upward and outward (superolaterally), double vision
