Chapters 14-15 Flashcards
Brainstem cont, NTs, and cerebellum
The cranial nerve nuclei are found where?
Brainstem
Many nerve tracts, including the corticospinal tract, and the pyramidal decussation, are found where?
The brainstem
What are the 4 main groups of things found in the brainstem?
1) Cranial nerve nuclei and related structures
2) Long tracts
3) Cerebellar circuitry
4) Reticular formation and related structures
Give 2 examples of long tracts found in the brainstem
1) Corticospinal tract
2) Somatosensory pathways
Give examples of things controlled by the “reticular formation and associated structures” category of brainstem structures
Brainstem nuclei and neurons that coordinate many of our vital functions such as :
1) Ex/motor control systems
2) Posture
3) Respiration
4) Cough, hiccup, sneeze, shiver
5) N/v
6) Autonomic control including HR and BP
1) What is the Medial Longitudinal Fasciculus (MLF)?
2) Fibers from what 2 nuclei ascend here?
1) Heavily myelinated pathway connecting vestibular nuclei with nuclei involved with extraocular movements.
2) Medial and superior vestibular nuclei
Fibers from the medial and superior vestibular nuclei ascend in the MLF to what 3 nuclei to mediate vestibulo-ocular reflexes?
Oculomotor (3), trochlear (4) and abducens (6) nuclei
List and describe the long tracts of the brainstem
1) Corticospinal and corticobulbar: nerves from cortex to brainstem
2) Somatosensory pathways (posterior columns): vibration, proprioception and fine touch
3) Spinothalamic tract: antero-lateral pain, temperature, and crude touch
4) Descending sympathetic pathway: runs through lateral brainstem; damage to this causes Horner’s Syndrome
What tracts are nerves that run from the cortex to the brainstem?
Corticospinal and corticobulbar
What tract is responsible for pain, temperature, and crude touch?
Spinothalamic tract (antero-lateral)
What pathway runs through lateral brainstem? What does damage to this cause?
Descending sympathetic pathway; Horner’s Syndrome
What pathways are responsible for vibration, proprioception and fine touch?
Somatosensory pathways (posterior columns)
1) What is the reticular formation?
2) What does its rostral end do?
3) What does its caudal end do?
1) Central core of nuclei that runs through the entire length of the brainstem
2) Maintain an alert conscious state.
3) Works with cranial nerve nuclei and the spinal cord to carry out motor reflex and autonomic functions
What 2 things work with the caudal end of the reticular formation?
Cranial nerve nuclei and the spinal cord
1) What is the end goal of the rostral end of the reticular formation?
2) What is the end goal of the caudal end of the reticular formation?
1) Maintain an alert conscious state.
2) Carry out motor reflex and autonomic functions
In Locked-In-Syndrome:
1) Motor function is ________
2) Sensation and cognition are ________
3) What two tracts are affected?
1) Absent
2) Intact
3) Corticospinal and corticobulbar
True or false: Locked-In-Syndrome is a type of coma
False; they’re different
1) What usually causes locked-in-syndrome?
2) Why exactly can’t they move?
1) Infarct in the ventral pons, affecting the corticospinal and corticobulbar tracts.
2) These tracts being affected means the spinal cord and cranial nerves receive no input from the cortex
Regarding locked-in-syndrome:
1) What pathways and systems are spared? What does this cause?
2) Why are eye movements spared?
3) Is it the same as a coma?
1) Sensory pathways and arousal systems in brainstem are spared, so patients are aware and able to feel, hear, and understand.
2) Their control center is in the rostral midbrain
3) No
What forms the consciousness system?
The fronto-parietal association cortex with the arousal circuits in the upper brainstem.
List the 3 processes that control the levels of consciousness and what’s involved with each
1) Alertness: normal functioning of the brainstem and arousal circuits
2) Attention: same circuits as above plus the frontoparietal association cortex
3) Awareness: a combination of multiple higher order systems from different regions of the brain into a summary of mental activity that can be remembered at a later time
1) List the 3 processes that help control the level of consciousness
2) Which of these involves a summary of mental activity that can be remembered at a later time?
1) Alertness, attention, awareness
2) Awareness
True or false: Multiple interconnected arousal systems act in parallel to maintain normal consciousness
True
Name the 5 arousal systems that maintain normal consciousness
1) Upper brainstem neurons
2) Reticular formation
3) Posterior hypothalamic neurons
4) Basal forebrain neurons
5) Neurons in the rostral and medial thalamic nuclei
What activates the 5 arousal systems that maintain normal consciousness?
Reticular formation and related structures that receive input from sensory pathways
1) What project to the reticular formation?
2) Why?
1) Numerous regions of the association cortex
2) So cognitive processes and emotions can lead to an increased level of alertness through this system.
1) What is the major excitatory neurotransmitter in the CNS?
2) What does too much of this cause?
1) Glutamate
2) Huntington’s chorea
What is referred to as “nature’s valium”? Why?
GABA; it’s inhibitory
1) Meds that increase GABA are used to treat what 3 things?
2) What 4 arousal systems does it inhibit to promote deep sleep?
1) Anxiety, seizures, muscle spasms
2) Serotonergic, noradrenergic, histaminergic, and cholinergic arousal systems.
What are the 3 primary functions of acetylcholine (Ach)?
1) Autonomic function
2) Stimulates receptors at NMJ to cause muscle contraction.
3) In CNS it helps with memory
What is Myasthenia gravis and what does it lead to?
An autoimmune Ab block Ach receptors on skeletal muscle, leading to weakness
1) What can dopamine cause?
2) What does it work on?
3) What can too much lead to?
4) What can too little lead to?
1) Feelings or pleasure, satisfaction and motivation.
2) Reward center.
3) Schizophrenia, increased energy/arousal, hallucinations
4) Parkinson’s Disease
1) What are the two main functions of norepinephrine?
2) What does increased amounts cause?
3) What does too little cause?
1) Used in sympathetic response and functions in attention, cognition and BP.
2) Aggression
3) Depression, inattention/ADD
1) What is also known as the “feel good” chemical?
2) Is it excitatory, inhibitory, or both?
1) Serotonin
2) Can have excitatory and inhibitory effects
1) What does serotonin function in?
2) When is it markedly decreased?
1) Psychiatric symptoms like depression, anxiety, OCD, aggressive behavior and eating disorders.
2) During sleep
1) What does increased amounts of serotonin do?
2) What can increase it?
1) Lift and brighten mood
2) Exercise and bright light
What is histamine used to regulate?
Alertness and wakefulness
1) Most histamine is found where?
2) In what?
3) What does it do here?
1) Outside of the CNS
2) Mast cells
3) Plays a role in immune responses and allergic reactions
What are antihistamine medications used for and what do they often cause?
To treat allergies; often cause drowsiness
What does REM stand for and what often happens in this stage?
Rapid eye movement; dreaming usually occurs
1) What happens during N1-3 of sleep?
2) What is the sleep cycle and how often does it happen at night?
1) Nonrapid eye movement
2) REM, N1, N2, N3; repeats many times during the night
What area of the brain is thought to contain sleep- promoting regions?
Medulla reticular formation
What produces melatonin and in what pattern?
Pineal gland in a circadian pattern
1) Define coma
2) What is it a dysfunction of?
1) Unarousable, unconsciousness with closed eyes > 1 hour
2) Upper brainstem reticular formation
True or false: Lesions of parts of the brainstem outside the upper brainstem reticular formation do not typically affect consciousness.
True
1) What can occur during coma?
2) What can cause comas?
3) What reflexes are still present?
1) Can still have vestibulo-ocular eye movements, but no purposeful movements.
2) Typically caused by catastrophic brain injury such as trauma or anoxia.
3) Brainstem reflexes (gag, corneal, v-o)
When is consciousness typically spared?
If the reticular formation is spared
1) What 3 things should you do when a patient is in a coma? (step 1)
2) What is the second step?
3) What is the third step?
4) What exam should then be done?
1) Always secure airway, ensure patient is breathing, and has normal circulatory function.
2) Establish IV access and give IV thiamine, glucose and naloxone.
3) Treat to reverse cause of coma, if known and able.
4) ** Pupils**, labs, head CT
1) Define Akinetic Mutism, Catatonia
2) Is the patient awake? Can they respond?
3) What may cause it to improve?
1) Impaired frontal lobe and dopamine function, profound deficits in response to initiation
2) Patient appears fully awake and can track with eyes, but can not typically respond to commands, though sometimes may after a long delay.
3) Dopamine agonist
Define dissociative state. What neurologically is wrong?
Non-responsiveness (but not unconscious) from severe emotional trauma, neuro exam is normal
Patients with Akinetic Mutism, Catatonia display what?
Profound deficits in response to initiation
Define brain death
Based on clinical exam: no evidence of forebrain or brainstem function; no sleep-wake cycles
Define vegetative state
Unconscious state but can have sleep-wake cycles and other responses or reflexes mediated by the brainstem; no purposeful movement or meaningful speech, though may make sounds; incontinent.
What does CNIII do? Through what pathways?
Pupillary control; parasympathetic and sympathetic pathways
1) What can CNIII palsy lead to?
2) What commonly causes CNIII palsy?
1) Dilated pupils.
2) Aneurysm of p comm artery
What is a pupillary reflex?
Constriction of pupils in response to light
List the 6 steps of the parasympathetic pupillary light reflex
1) Light enters retina
2) Hits retinal ganglion cells
3) Sends message through optic tract which crosses at the optic chiasm
4) Fibers continue to the superior colliculus
5) After synapsing there, the axons continue to the Edinger–Westphal nuclei which contains the preganglionic parasympathetic neurons
6) These parasympathetic fibers travel bilaterally via the oculomotor nerves to the ciliary ganglia in the eye and then on to the pupillary constricting muscles causing the pupils to become smaller.
A light shone in 1 eye will cause _______________ of both pupils because the information crosses
constriction
List 4 causes of coma and what the pupils look like with each
1) Toxic and metabolic disorders: Normally (usually)
2) Midbrain lesion or herniation: Unilateral or bilateral “blown” pupil
3) Pontine lesion: Small, responsive to light bilaterally
4) Opiate overdose: Pinpoint pupils bilaterally
What can cause Horner’s syndrome?
Lesions anywhere along sympathetic pathway
What is the triad of Horner’s syndrome symptoms?
1) Ptosis
2) Miosis
3) Anhidrosis
1) The medullary reticular formation contains what?
2) What is the pacemaker for respirations?
3) What do the phrenic nerve efferents do?
4) Lesions in the medulla can cause what?
1) Crucial respiratory circuits
2) Pre-Botzinger Complex in medulla= pacemaker for respirations
3) Control diaphragm during inspiration
4) Respiratory arrest and death
1) What controls breathing?
2) What do these have numerous inputs to?
1) Circuits in medulla
2) To respiratory circuit, including peripheral chemoreceptors for blood O2 level and pH and stretch receptors in the lungs
1) Where is the nucleus solitarius?
2) What is it? Where does it get input from?
1) In the medulla
2) Cardiorespiratory nucleus (controls heart rate and BP); receives inputs from baroreceptors in carotid body and aortic arch via CNs 9 and 10
The _________________ system gives rise to many branches that supply the brainstem and cerebellum
vertebrobasilar
What are the 3 functional regions of the cerebellum?
1) Lateral hemispheres
2) Intermediate hemispheres
3) Vermis and flocculonodular lobes
1) What is the vermis of the cerebellum?
2) What is on either side?
1) Wormlike structure in the midline
2) Cerebellar hemispheres on each side of vermis
Cerebellar inputs come from where?
1) All areas of the cerebral cortex, multiple sensory modalities including vestibular, visual, auditory, and somatosensory systems
2) Brainstem nuclei and the spinal cord.
1) What does the cerebellum do?
2) What do lesions in it typically cause?
1) The cerebellum coordinates movements and participates in motor planning; different regions have different functions
2) Uncoordinated movements called ataxia.
What do the inferior vermis and flocculonodular lobes of the cerebellum do?
1) Regulate balance (proximal trunk muscle control)
2) Interact with vestibular circuitry (vestibulo-ocular control)
1) What do the anterior lobes of the cerebellum do?
2) What do the intermediate cerebellar regions do?
3) What do the lateral cerebellar hemispheres do?
1) Responsible for proprioception
2) Control distal limbs
3) Motor planning of distal extremities
1) Deficits in coordination occur in what direction compared to cerebellar lesions?
2) What cerebellar lesions cause ataxia of the limbs?
3) What lesions bilaterally affect the trunk muscles?
1) Ipsilateral
2) Lesions lateral to the vermis
3) Medial lesions
1) What is the cerebellum attached to? How?
2) What does it form the roof of?
1) It is attached to the dorsal pons and rostral medulla by 3 peduncles.
2) The 4th ventricle.
Name 3 ways to test cerebellar function
1) Finger-nose-finger test
2) Finger tap test
3) Heel to shin test
What do vermis or flocculonodular cerebellar lobe lesions cause?
Unsteady gait (trunk control, posture, balance)
List the 3 functional regions of the cerebellum
1) Lateral hemispheres
2) Intermediate hemispheres
3) Vermis and flocculonodular lobe
1) What are the functions of the lateral hemispheres of the cerebellum?
2) What motor pathways do they influence?
1) Motor planning for extremities
2) Lateral corticospinal tract
1) What are the functions of the intermediate hemispheres of the cerebellum?
2) What motor pathways do they influence?
1) Distal limb coordination
2) Lateral corticospinal tract and rubrospinal tract
1) What are the functions of the vermis and flocculonodular lobe of the cerebellum?
2) What motor pathways do they influence?
1) Proximal limb and trunk coordination AND balance and vestibulo-ocular reflexes
2) Proximal limb and trunk: Anterior corticospinal tract, reticulospinal tract, vestibulospinal tract, tectospinal tract
-Balance and reflexes: Medial longitudinal fasciculus
1) What part of the cerebellum is attached to the brainstem?
2) Where are the cerebellar tonsils found?
1) Ventral surface
2) Inferior surface
What is the clinical significance of the cerebellar tonsils?
Can herniate through the foramen magnum in cases of masses, brain swelling, severely elevated ICP and compress the medulla causing death from impingement of the medullary respiratory centers.
On midsagittal section, the white matter and gray matter of the cerebellum are called what?
Arbor vitae “tree of life”
The ridges of the surface of the cerebellum are called what instead of gyri?
Folia (‘leaves”)
What connect the cerebellum to the brainstem?
The peduncles: superior, middle and inferior
True or false: All the information from the body to the brain passes through the brainstem.
True
