Lecture 3 Flashcards
Where is the brainstem located?
base of the cerebral hemispheres within posterior fossa of cranial cavity
What are the main components and regions of the brainstem?
COMPONENTS
1) Cranial nerve nuclei and related structures
2) Long tracts
- Descending Motor pathways
- Ascending Somatosensory and viscerosomatic pathways
3) Cerebellar connections & circuitry
4) Reticular Formation
REGIONS
1) Midbrain
- pontomesenphalic junction
2) Pons
- pontomedullary junction
3) Medulla
What is the function of brainstem?
- carries all information between brain and rest of nervous system
- pillar for our ability to be awake, aroused, and alive
What is the function of the reticular formation?
- general arousal/awareness (keeping brain on when needed)
- Reticular Activating System (RAS) - synapses with all major ascending tracts and functions in arousal from sleep
- Motor awareness
- autonomic regulation
Where is the reticular formation found, and where does it project to?
- extends through central core of medulla, pons, and midbrain
- projects to thalamus, cerebellum, spinal cord, and optic
What are some of the major functions of the midbrain?
Major associations include vision, hearing, motor control, sleep and wake cycles, alertness, and temperature regulation
What structures or landmarks can be found on the external surface of the midbrain?
CN 3 (oculomotor) and 4 (trochlear)
What are the 3 regions of the midbrain? How are they generally defined?
1) tectum (roof) - dorsal to cerebral aqueduct
2) tegmentum - middle and biggest region of midbrain
3) Basis pedunculi - most ventral and somatotopically organized
Identify the structures in the midbrain tectum
- superior (rostral) and inferior (caudal) colliculi
What is the function of the superior colliculi and where is it found?
- visual relay station
- found in midbrain rostral tectum
What is the function of the inferior colliculi and where is it found?
- auditory relay station - signal, frequency integration, and pitch discrimination
- found in midbrain caudal tectum
Identify the structures in the midbrain tegmentum
- substantia nigra
- reticular formation
Rostral
- ventral tegmental area (VTA)
- Red nuclei
- oculomotor nuclei
Caudal
- trochlear nuclei
- superior cerebellar peduncle
- raphe nuclei
What is the function of the ventral tegmental area (VTA) and where is it found?
- largest dopamine-producing neurons in brain
- play role in reward system w/ projection to limbic system and cortex
- found in midbrain rostral tegmentum
What is the function of the red nuclei and where is it found?
- motor coordination and control for flexor muscles
- found in midbrain rostral tegmentum
What is the function of the superior cerebellar peduncle and where is it found?
- relay station to cerebellum
- found in midbrain caudal tegmentum and rostral pons
What is the function of the raphe nuclei and where is it found?
- major serotonin-producing neurons
- found in midbrain caudal tegmentum and rostral pons
What is the function of the substantia nigra and where is it found?
- part of basal ganglia - involved in movement
- major dopamine-producing and storage area
- found in midbrain tegmentum
What are the 2 dopamine production and storage portions of midbrain?
substantia nigra and ventral tegmental area (VTA)
What are the primary highways in and out of our cerebellum?
cerebellar peduncles
What is the biggest region of the midbrain?
tegmentum
Identify the structures and their function found in the midbrain basis pedunculi
- crus cerebri - Large bundles of somatotopically-organized axons containing fibers from motor pathway
What structures make up the cerebral peduncles and what do they contain?
substantia nigra and basis pedunculi - contain large descending (motor) nerve tracts
What is the periaqueductal gray? What roles is it involved with?
- gray matter surrounding cerebral aqueduct
- involved with pain modulation (primarily: inhibition), autonomic regulation, emotion
What are some of the major functions of the pons?
Associations with sleep, respiration, swallowing bladder control, and more
What structures or landmarks can be found on the external surface of the pons?
CN 5 - trigeminal nerve
Identify the structures and their function found in basilar pons.
STRUCTURES
- deep pontine nuclei - relay station between cortex and cerebellum
- descending motor pathways to spinal cord and cerebellum
FUNCTIONS
- convey information from the motor cortex to the cerebellum regarding movement of contralateral limbs
- help us match what we want to do with what we’re intending to do ex: pick up water and put to mouth
Identify the structures of the pontine tegmentum (10)
- reticular formation
- CN nuclei 5 (trigeminal), 6 (abducens), 7 (facial), 8 (vestibular)
- cerebellar peduncles (superior, middle, inferior)
- deep cerebellar nuclei
- ascending sensory pathway
- descending pathways
- trapezoid body
- locus ceruleus
- raphe nuclei
- superior olivary complex
What are the functions of the cerebellar peduncles (superior, middle, inferior)? Where are they found?
- Superior - afferent & efferent fibers between cerebellum and midbrain
- Middle - afferent fibers only, between cerebellum and pons
- Inferior - afferent and efferent fibers between cerebellum and medulla
- caudal pontine tegmentum
What is the function of deep cerebellar nuclei? Where is it found?
- Primary output target for all information coming out of the cerebellum
- caudal pontine tegmentum
What is the function of locus ceruleus? Where is it found?
- Primary site of norepinephrine production in the brain
- rostral pontine tegmentum
What is the function of raphe nuclei? Where is it found?
- Major serotonin-producing neurons in the brain
- rostral pontine tegmentum, also caudal midbrain
What is the function of superior olivary complex? Where is it found?
- Contribute to both ascending and descending input for auditory function
- caudal pontine tegmentum
What is the function of trapezoid body? Where is it found?
- ascending auditory pathway - help w/ localization of sound
- caudal pontine tegmentum
What are the 2 regions of the pons? How are they generally defined?
- basilar pons - ventral
- pontine tegmentum - dorsal and majority of pons
What are some of the major functions of the medulla?
- survival center
- HR, BP, breathing, swallowing, autonomic control
What structures or landmarks can be found on the external surface of the medulla?
CN 6-12
- 6 - abducens
- 7 - facial
- 8 - vestibulocochlear
- 9 - glossopharyngeal
- 10 - Vagus
- 11 - spinal accessory
- 12 - hypoglossal
Identify the structures found in the rostral medulla (13)
- reticular formation
- ascending tracts
- medullary pyramids (major descending tracts)
- inferior cerebellar peduncle
- open medulla
- inferior olivary nuclei
- CN 8 (vestibular) nuclei
- solitary nuclei (CN 7, 9, 10)
- nuclei ambiguous (CN 9, 10, 11)
- spinal trigeminal (CN 5, 7, 9, 10)
- area postrema
- nuclei gracili
- nuclei cuneatus
What are the function of medullary pyramids and where are they found?
- descending motor fibers
- ventral medulla
What is the function of inferior cerebellar peduncle and where is it found?
- Afferent and efferent fibers between cerebellum and medulla
- rostral medulla
What is the function of open medulla and where is it found?
- ventral wall of 4th ventricle
- rostral medulla
What is the function of inferior olivary nuclei and where is it found?
- accepts motor and sensory input and projects information to contralateral cerebellar cortex
- rostral/caudal medulla
What is the function of solitary nuclei and where is it found?
- relay station for visceral and tasta afferents by CN 7, 9, 10
- critical role in reflexes controlling CV function, respiration, and GI motility
- rostral medulla
What is the function of nuclei ambiguous and where is it found?
- cell bodies of motor divisions of CN 9, 10, 11 that innervate ipsilateral muscles of jaw, mouth, and throat - swallowing, speaking, and breathing
What is the function of area postrema and where is it found?
- vomiting center
- rostral medulla (circumventricular organ - no BBB)
Identify structures found in caudal medulla (8)
- reticular formation
- ascending tracts (nuclei gracilis and cuneatus)
- medullary pyramids
- CN nuclei
- Inferior olivary nuclei
- medial lemniscus decussation
- pyramidal decussation
What is the function of nuclei gracilis and where is it found?
- ascending somatosensory pathway for lower body
- caudal medulla
What is the function of nuclei cuneatus and where is it found?
- ascending somatosensory pathway for upper body
- caudal medulla
What is the function of medial lemniscus decussation and where is it found?
- crossing medial lemniscal dorsal pathway carrying afferent somatosensory information from the body
- caudal medulla
What is the function of the pyramidal decussation and where is it found?
- crossing pyramidal tracts, descending to provide motor drive to the body
What is the major function of the spinal cord?
nerve impulse propagation
Where are considered to be the start and finish of the spinal cord?
- start - foramen magnum
- finish - conus medullaris L1-L2 intervertebral joint
What vertebra make up cauda equina? Part of CNS or PNS?
- L2-S5
- PNS
How many pairs of spinal nerves exit the spinal cord? How are they categorized?
- 31 spinal nerves
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
What are the cervical and lumbar enlargements? Where are they found?
- increased neural output to arms and legs
- cervical - C5-T1: Brachial Plexus
- Lumbar - T11-L2: lumbosacral plexus
What are the major differences between the meninges and meningeal spaces found between cranial and spinal cord meninges?
- epidural space - cushion
- dura mater - single layer, anchors peripheral nerves to spinal cord and does not attach to bony vault
- subdural space - interstitial fluid
- arachnoid mater
- subarachnoid space - CSF
- pia mater
Where can gray matter be found in the spinal cord? What are its major areas and what do they consist of?
- butterfly in middle - dorsal (sensory), ventral (motor), lateral horns, and intermediate zone (autonomic preganglionic neurons)
Where can white matter be found in the spinal cord? What are its major areas and landmarks and what do they consist of?
- ascending and descending columns (dorsal-sensory, ventral-mixed, lateral-mixed)
- dorsolateral sulcus (entrance for dorsal roots
- dorsal intermediate sulcus (splits dorsal columns)
- ventral lateral sulcus (exit for ventral roots)
- dorsal medium septum
- ventral medium
Describe the regional differences that can be seen throughout the spinal cord with regards to white and gray matter representation. What are some identifying clues that can help you determine what region you are looking at?
- white matter increases as you move lumbosacral to cervical (bottom to top)
- volume of gray mater highest in cervical and lumbar enlargements
- gray matter increases as you go down spine
- lateral horn with lots of white matter = thoracic
- big lateral horn with little white matter and lots of gray matter = sacral
