brainstem and cranial nerves I Flashcards
where is the brainstem located?
between the forebrain and spinal cord
what foes the forebrain divide into?
telencephalon
diencephalon
what makes up the brainstem?
midbrain
pons
medulla
what is the oldest part of the brain evolutionarily?
brainstem
what are the functions of the midbrain?
processes visual, auditory data.
Maintains consciousness
Also reflexive somatic motor responses bc of the colliculi on top of the midbrain)
what are the functions of the pons?
relays sensory information to cerebellum and thalamus. Subconscious somatic and visceral motor centres
what are the functions of the medulla?
relays sensory information to thalamus. Contains autonomic centres for regulation of visceral function
name the main functions of the brainstem?
conduit - long tracts to or from spinal cord pass through brainstem
cranial nerve function - sensory input/motor output for the head plus parasympathetic motor output. Cranial nerves carry special senses, brainstem coordinates reflexes involving them
integration centres - relays info to cerebellum
reticular formation - interconnected nuclei throughout brainstem
what do the nuclei of reticular formation mediate?
o Autonomic control of important respiratory/cardiovascular reflexes and other behaviours e.g. swallowing, sneezing
o Somatic/autonomic modulation via descending pathways
o Important in regulation of consciousness.
what is the brainstem?
an extension and elaboration of the spinal cord
at what spinal level does the spinal cord become the brainstem?
C2
what happens to sensory and motor nuclei when they move from the spinal cord to the brainstem?
Sensory nuclei that were dorsal in the spinal cord move laterally, motor nuclei move medially
what is found in the dorsal part of the brainstem?
cranial nerve nuclei found here and sensory reflex centres
what is the name for the dorsal part of the brainstem?
tectum
what is the name for the middle part of the brainstem?
tegmentum
what does the tegmentum contain?
ascending pathways and reticular formation
what does the ventral part of the brainstem contain?
descending motor pathways e.g. corticospinal and corticobulbar tracts
where are the superior and inferior colliculus found?
in the midbrain
where is the cerebral peduncle found?
in the midbrain
what does the cerebral peduncles contain?
tracts descending from the cortex through the brainstem to the spinal cord (corticospinal).
what are the functions of the different regions of the pons?
- Superior: main output path from the cerebellum to the midbrain.
- Middle: afferent input from pontine nucleus (motor activity).
- 4th ventricle (found medially).
- Basal pons: bridge composed of transverse and descending fibres
from what surface can you see the cranial nerves?
ventral
how many cranial nerves are associated with the brainstem?
11
what cranial nerves are found in the midbrain?
II - IV
what are the main functions of the the midbrain?
auditory, visual, pupillary reflexes as well as eye movements
what cranial nerves are found in the pons?
V - VIII
what are the main functions of the pons?
mastification, eye movements, facial expression, taste, blinking, lacrimation, audition, salivation.
what cranial nerves are found in the medulla?
VIII - XII
what are the main functions of the medulla?
equilibrium, audition, deglutition, salivation, taste, respiration, circulation, Gi function, neck and shoulder movements, tongue movements, coughing, vomiting
what cranial nerves are purely sensory?
I, II and VIII
what cranial nerves are pure motor nerves?
III, IV, VI, XI, XII
what cranial nerves are mixed sensory and motor nerves?
V, VII, IX and X
what are the 3 types of motor nuclei and what do they do?
o Somatic motor nuclei project to skeletal muscle (eye muscles and tongue)
o Branchial motor nuclei project to muscles derived from branchial arches (craniofacial structures)– movement of jaws (V), facial expression (VII), motor to larynx and pharynx (X) and neck and shoulder muscles (XI)
o Visceral motor nuclei: pre-ganglionic parasympathetic fibres
what type of nucleus does the hypoglossal nerve have?
somatic motor
what does the hypoglossal nerve do?
innervates internal and external tongue muscles
what type of nucleus does the spinal accessory nerve have?
pure branchial motor
what does the spinal accessory nerve innervate?
SCM and trapezius
where does the spinal accessory nerve enter and exit the skull?
enters via foramen magnum
exits via jugular foramen
what are the motor neurons that give rise to the accessory nerve?
a separated fragment of the long column of the nucleus ambiguus. They arise from C3-C5
what nerves arise from the nucleus ambiguus?
XI and X
what does the vagus innervate?
- Branchial motor innervation of the palate, pharynx and larynx is conveyed via CN X
- Parasympathetic outflow to the heart and digestive system arises from the dorsal motor nucleus of the vagus (and parasympathetic part of n. ambiguous)
- Afferents from the lungs and gut travel in the vagus nerve mediating parasympathetic reflexes, swallowing, coughing, retching etc.
what does damage to the vagus nerve lead to?
difficulty swallowing and vocalizing – paralysis of vocal cords on the affected side
Poor secretion of gut gluids, salica, stomach acid bc of loss of parasympathetic control
is the glossopharyngeal nerve sensory or motor?
Mainly sensory BUT parasympathetic secretomotor to the parotid gland (mixed)
what are the main functions of the glossopharyngeal nerve?
o Detect taste of things in the back of the mouth – conveys to the NTS and stimulates saliva secretion
o Gag reflex – has touch fibres at the back of the mouth to trigger this
what does damage to the glossopharyngeal nerve lead to?
loss of gag reflex on affected side
what are the parts of the vestibulocochlear nerve and what do they each do?
o Cochlear – special sense of hearing
o Vestibular - perception of self motion, head position and spatial orientation relative to gravity
where does the vestibulocochlear nerve enter the brainstem?
ponto-medullary junction
what is the main function of the facial nerve?
provide motor supply to muscles of facial expression
what does the medial longitudinal fasciculus connect?
connects cranial nerve nuclei controlling eye movement and vestibular nuclei
what is internuclear opthalmoplegia?
problem with adduction in the affected eye
what causes internuclear opthalmoplegia?
o Damage can occur with stroke (unilateral) or multiple sclerosis lesion (often bilateral).
leads to damage to MLF
what does the MLF become in the spinal cord?
medial vestibulospinal tract (mVST)
what does the mVST do?
coordinates reflexive head and neck movements to keep eyes stable in space.
