Lecture 5.2 Flashcards
what is the brainstem composed of
midbrain, pons, and medulla oblongata
brainstem principal function
- regulates vital functions
- relay/conduit
- integration and regulation of sensory info (reticular formation)
- cranial nerve origin and termination
what vital functions does the brainstem regulate
cardiac activity, respiration, consciousness, sleep
how does the brainstem act as a relay/conduit
ascending and descending nerve connections to and from the motor and sensory systems of the brain pass through the brainstem
how does the brainstem integrate and regulate sensory information (reticular formation)
modulation of brain sensory input (decides what is important) and in the regulation of sleep, arousal, and sleep-wake transitions
what is the rostral limit of the brainstem
the midbrain-diencephalon junction where it meets the thalamus and hypothalamus, below the optic tracts
what is the caudal limit of the brainstem
the level of the foranum magnum and the pyramidal decussation
- everything below the decussation is the spinal cord
what are the cerebellar peduncles
superior cerebellar peduncle, middle cerebellar peduncle, inferior cerebellar peduncle
what does the superior cerebellar peduncle connect to
midbrain
what does the middle cerebellar peduncle connect to
pons (the largest)
what does the inferior cerebellar peduncle connect to
medulla (at the junction between pons and medulla)
what do the pontine nuclei contain
descending neurons from the primary motor cortex —> contralateral cerebellum
where does the posterior spinocerebellar tract originate from
the lower body
characteristics of posterior spinocerebellar decussation
stays ipsilateral
where does the cuneocerebellar tract originate from
the upper body
characteristics of cuneocerebellar decussation
stays ipsilateral
how do the uncrossed tracts of the posterior spinocerebellar tract enter the cerebellum
via the inferior cerebellar peduncles (medulla)
how do the uncrossed tracts of the cuneocerebellar tract enter the cerebellum
via the inferior cerebellar peduncles
where does the anterior spinocerebellar tract originate from
the lower body
characteristics of anterior spinocerebellar tract decussation
decussates in the spinal cord at the level of its entry but decussates again in the brainstem to return to the ipsilateral side of the brain
how does the anterior spinocerebellar tract enter the cerebellum
via the superior cerebellar peduncles (midbrain)
where are the cerebral peduncles found
ventral surface, only midbrain
where are the cerebellar peduncles found
dorsal surface, all levels of brainstem
what is the ventral surface of the midbrain formed by
cerebral peduncels
what do the cerebral peduncles do
link the brainstem to the thalamus and cortex
crus cerebri
the anterior/ventral portion of the cerebral peduncles which carries the motor tracts
what is the view of the pons on the dorsal surface obstructed by
cerebellum
what is the pons attached to the cerebellum with
middle cerebellar peduncles
where are the dorsal columns of the DCML ascending tract visible
in the caudal medulla (closest to the spinal cord)
where do the dorsal column tracts synapse
on their second order neurons in the gracile and cuneate nuclei found in the caudal medulla
what forms the medial lemniscus
the decussation of the tracts from the second order neurons of the dorsal columns
- travels through the rest of the brainstem up to the thalamus
olivary nuclei location
the prominent bulges lateral to the pyramids in the rostral medulla
- not seen in the caudal medulla
main internal components of the brainstem
- cranial nerve nuclei
- long tracts “passing through”
- cerebellar circuitry
- reticular formation
components of the midbrain
tectum, cerebral peduncles, tegmentum (present throughout entire brainstem, not just midbrain)
what does the tegmentum contain
red nucleus and substantia nigra
what is the red nucleus responsible for
controlling basic body and limb movements and fine hand movements
what is the substantia nigra responsible for
integrating voluntary movements for smooth motion
where is the red nucleus located
within the rostral midbrain in the tegmentum
what tract is the red nucleus the origin of
rubrospinal extrapyramidal descending motor tract
periaqueductal gray (PAG) location
gray matter located around the cerebral aqueduct within the tegmentum of the midbrain
what information does the PAG receive
pain and temp from the lateral spinothalamic ascending tracts
what are the neurons of the PAG excited by
endorphins and by opiate analgesics
PAG function
controlling autonomic nervous system responses to painful or threatening stimuli from the lateral spinothalamic ascending tracts
- regulates behavioral and autonomic defensive reactions
what behavioral and autonomic defensive reactions does the PAG regulate
- heart rate and blood pressure changes
- production of vocalizations
- fear and panic reactions (freezing and explosive flight behaviors)
- analgesia (pain reduction)
pontine nuclie location
ventral (“basal”) pons
what neurons does the pontine nucleus contain
neurons involved in motor activity
what information does the pontine nucleus receive
info from the ipsilateral primary motor cortex and relay that information to the contralateral cerebellum via the middle cerebellar peduncle
what forms the transverse fibers of the pons
the contralateral decussation of the axon fiber tracts from the pontine nucei
what do the connections in the pontine nucleus allow for
unconscious modification of motor actions and error correction - the process of learning motor skills
what do the pyramids contain
the pyramidal tracts descending from the motor cortex to the brainstem or spinal cord
where do the pyramidal motor fibers decussate
at the base of the pyramids in the pyramidal decussation
what do the olives do
relay sensory and motor info
- mainly involved in cerebellar motor-leaning and function
- control of movement
medulla structures
pyramids, olives, gracile and cuneate nuclei
landmarks for rostral medulla cross section
open ventricle, pyramids, inferior olives
landmarks for mid medulla cross sections
slightly open ventricles, pyramids
landmarks for caudal medulla cross section
decussation of pyramids
landmarks for rostral pons cross section
pontine “bulge” - transverse fiber tracts, small fourth ventricle
landmarks for mid pons cross section
pontine “bulge” - transverse fibers tracts, larger fourth ventricle
landmarks for caudal pons cross section
pontine “bulge” - transverse fiber tracts, descending motor tracts to spinal cord, pontine nuclei, largest fourth ventricle
substantia nigra
basal ganglia structure that functions in reward and movement
- high levels of neuromelanin dopaminergic neurons
where is the brainstem reticular formation located
within the tegmentum of the brainstem, but has extensive and complex axonal projections to other nuclei in
tegmentum
a general area within the brainstem between the ventricular system and the ventral structures at each level
- forms the floor of the midbrain below the cerebral aqueduct
- network of neurons involved in unconscious autonomic pathways & is a motor center that relays inhibitory signals to the thalamus and basal ganglia nuclei preventing unwanted body movements
what path does the dorsal column medial lemniscus tract take
spinal cord to the cortex
what is the cuneate fasciculus responsible for
discriminative touch, joint position, vibration, stimuli from the upper body
where is the cuneate fasciculus 2nd order nucleus located
cuneate nucleus
what is the gracile fasciculus responsible for
discriminative touch, joint position, vibration, stimuli from the lower body
where are 2nd order neurons in gracile fasciculus located
gracile nucleus
where do DCML tracts decussate
in the medulla
- from the dorsal columns —> medial lemniscus —> thalamus
where do spinothalamic tracts travel through the brain
spinal cord to the cortex
what is the lateral spinothalamic tract responsible for
pain and temp
what is the anterior spinothalamic tract responsible for
light touch and pressure
where does spinothalamic tract decussation occur
spinal cord
which spinocerebellar tracts do not decussate
posterior spinocerebellar tract, cuneocerebellar tract
which spinocerebellar tract decussates twice
anterior spinocerebellar tract
what kind of information do spinocerebellar tracts carry
proprioceptive info
why are there no midbrain cross sections of spinocerebellar tracts
spinocerebellar tracts enter the cerebellum only in the medulla and pons and do not carry on up to the thalamus like the other ascending sensory tracts
what is the reticular formation
diffuse, poorly differentiated brainstem nuclei that form the central core of the brainstem
where is the reticular formation located
within the tegmentum of the brainstem but has extensive and complex axonal projections to other nuclei in the brainstem and to the cerebellum, spinal cord, and cerebrum
what does the reticular formation modulate
- pain control
- muscle tone, motor control, and spinal reflexes
- autonomic functions (respiration, blood pressure, and cardiac function)
- arousal, awareness, & attention (maintaining consciousness)
where does the reticular formation extend
through the central core of the midbrain, pons, and medulla
- receives info from sensory systems and projects to distributed areas in the cortex
what is the function of the ascending reticular activating system
arousal/consciousness; affected by general anesthesia, alcohol, tranquilizers, and sleep inducing drugs
- acts as a filter to dampen repetitive, familiar, or weak sensory input activity
what does injury to the reticular activating system result in
vegetative state
function of the descending reticular activating system neurons
coordinate movements and autonomic system functions, including the muscles that control cardiac and respiratory functions
what do disruptions of the reticular activating system result in
- coma
- schizophrenia
- ptsd
- narcolepsy
- depression
- adhd
- parkinsons
- alzheimers
- autism
what is the largest cranial nerve
trigeminal (CN5)
which root of the trigeminal nerve is largest
sensory root - branches off into 3 divisions
what does the trigeminal nerve innervate
head, face, mouth, sinuses
- muscles involved in chewing
what medical issues is trigeminal nerve related to
dental pain, headache, migraines, pathophysiology
vagus nerve function
sensory, motor, & parasympathetic branch of ANS
how does vagus nerve affect autonomic parasympathetic activity
directs to visceral targets for “rest and digest”
- slows heart rate and reduces blood pressure
- promotes digestion
how does vagus nerve control mind-body connection
- using slow breathing to slow heart rate
- gut-brain axis
- interoception
cranial nerve mnemonic
On Occasion Our Tasty Truck Acts Funny Very Good Vehicle Any How
where does olfactory nerve travel to
piriform cortex and amygdala; doesn’t enter brinastem
where does optic nerve travel to
superior colliculus and lateral geniculate nucleus
where do oculomotor and trochlear nerves travel to
specific nuclei in midbrain
where do trigeminal, abducens, facial, and vestibulocohlear nerves travel to
specific nuclei in pon
where do glossopharyngeal, vagus, accessory, and hypoglossal nerves travel to
various structures in the medulla
CN1
olfactory nerve
olfactory nerve function
smell
olfactory nerve type
sensory
CN2
optic
optic nerve type and function
sensory; vision
CN3 name and function
oculomotor; eye movement: pupil, eyelid
CN4 name and function
trochlear; eye movement: down, lateral
Cn5 name and function
trigeminal; face sensation, mastication
CN6 name and function
abducens; eye movement: lateral
CN7 name and function
vestibulocochlear; hearing and balance
CN9 name and function
glossopharyngeal; taste, swallowing, gag reflex
CN10 name and function
vagus; gag reflex, heart rate, digestion
CN11 name and function
accessory; head and shoulder movement
CN12 name and function
hypoglossal; swallowing, speech, tongue movement
