Brainstem & Thalamus Flashcards
Cranial nerves in the thalamus include…
- optic nerve (CN2)
Cranial nerves in the midbrain include…
- oculomotor (CN3)
- trochlear (CN4)
Cranial nerves in the pons include…
- trigeminal (CN5)
- abducens (CN6)
- facial (CN7)
- vestibulocochlear (CN8)
Cranial nerves in the medulla include…
- glossopharyngeal (CN9)
- vagus (CN10)
- accessory (CN11)
- hypoglossal (CN12)
Brainstem Functions
- conduit for fibers of corticospinal & corticothalamic tracts
- site of emergence for cranial nerves
- integrate nuclei for motor, respiratory, and cardiovascular control
Medulla Functions
- respiration (sensing blood acidity)
- reflexes (vomiting, coughing, sneezing, swallowing)
- contains pyramidal decussation
Olive
Located in the anterior medulla
Bulge containing nuclei for auditory processing
Pyramid
Located in the anterior medulla
Descending corticospinal tracts
Nuclei in the inferior medulla include…
- vestibular
- cochlear
- trigeminal
- olivary
- hypoglossal
- vagal
- nucleus of solitary tract (NST)
Blood Pressure Control
- baroreceptors in the carotid body sense stretch
- information is relayed along glossopharyngeal nerve to the NTS nuclei in the inferior medulla
- vagal nuclei are activated
- heart rate decreases, blood vessels dilate, sympathetic nervous system is inhibited
Respiratory Control
Controlled in the pons and medulla
Dorsal respiratory group sets breathing rhythm and muscle contraction
Pontine respiratory group sets volitional control
PreBotC sets inspiration
RTN sets expiration
Sensory paths and NMS alter rhythm in arousal states
Pons Functions
- respiration, sleep, bladder control
- sensory information (auditory & taste)
- motor control of eyes and face
- behavioral response to threats
Medial eminence
Located on the posterior pons
Midline of the fourth ventricle
Facial colliculus
Located on the posterior pons
Bulge of fibers from facial nerve wrapping around the abducens nucleus
Stria medullaris
Located on the posterior pons
Fibers marking the boundary between the medulla and the pons
Pontine reticular formation
Responsible for complex motor patterns
Integrating motor and cerebellar commands to fine tune motor patterns
Connects to medial reticulospinal tract
Medullary reticular formation
Suppression of pain
Connects to lateral reticulospinal tract
Lateral periaqueductal gray (LPAG)
Circuit to inhibit pathway that controls pain
Modulated by serotonin via raphe
Midbrain Functions
- release of dopamine (movement control and motivation)
- sleep, wake, arousal
- thermal regulation
- nuclei for auditory and visual processing
Superior colliculi
Located in midbrain
Motor control of the eyes
Inferior colliculi
Located in midbrain
Second step of auditory processing
Pineal gland
Production of melatonin during darkness
Contains pinealocytes and glial cells
Serotonin
Reward and pleasure
Dopamine
Reward prediction and seeking, motivation, and movement
Norepinephrine
Arousal and attention
Acetylcholine
Wakefulness, arousal, attention, memory, & motivation
Reticular formation
Origin of cholinergic neurons that project to thalamus (regulating attention)
Control of arousal, consciousness/awareness, attention
Has reticulothalamic and monoamine projections that are key to consciousness
Serotonergic neurons
Source: dorsal raphe, superior central nucleus
Project to: amygdala, hippocampus, medial forebrain bundle, & spinal cord
Signaling reward and pleasure
Dopaminergic neurons
Source: ventral tegmental area, substantia nigra
Project to: ventral striatum, dorsal striatum, motor cortex
Signaling reward expectation, motivation, and movement
Ventral tegmental area
Origin of dopaminergic neurons
Projects to ventral striatum via medial forebrain bundle
Signaling reward expectation & motivation
Substantia nigra
Origin of dopaminergic neurons
Projects to dorsal striatum & motor cortex
Signaling movement
Noradrenergic neurons
Source: locus coeruleus
Project to: entire brain
Signaling arousal & attention
Cholinergic neurons
Source: basal nucleus & reticular formation
Project to: cortex, thalamus
Signaling wakefulness, arousal, attention
Basal nucleus
Located in the forebrain
Origin of cholinergic neurons
Projects to the cortex & broad brain regions
Regulating wakefulness & arousal
Anterior group
Located in thalamus
Input: hippocampus, limbic
Output: cingulate cortex
Involved in memory acquisition
Ventral lateral
Located in thalamus
Input: cerebellum
Output: motor cortex
Involved in motor functions
Lateral geniculate
Located in thalamus
Input: optic nerve
Output: visual cortex
1st order visual relay
Medial geniculate
Located in thalamus
Input: auditory brainstem
Output: auditory cortex
3rd order auditory relay
Thalamic reticular
Located in thalamus
Input: -
Output: thalamic nuclei
Inhibitory gate on thalamus; interconnected with GABAergic neurons
Pulvinar
Located in thalamus
Input: somatosensory tracts
Output: all lobes of the brain
Broad brain connections
Internal capsule
Band of white matter surrounding the thalamus
All connections to/from the cortex pass through it
Connections to cortex are spatially ordered
Basic circuits of the thalamus
- relay
- associational
- intralaminar
- reticular
Relay circuit
Circuit of the thalamus
Input: sensory
Output: sensory cortex
Associational circuit
Circuit of the thalamus
Input: cortex
Output: cortex
Responsible for learning & regulation
Intralaminar circuit
Circuit of the thalamus
Input: thalamus, midbrain
Output: cortex
Reticular circuit
Circuit of the thalamus
Input: thalamus
Output: thalamus
Intrathalamic inhibition
Radiata
Dense white matter tracks that extend to the cortical lobes from the thalamus
Travel through internal capsule & corona radiata
