2/1: CNS Overview II Flashcards
What is acetylcholine involved in?
Cognitive functions, especially memory
What accounts for a majority of dementia cases?
Alzheimer’s disease
*incidence increases with age
What is alzheimers disease due to?
Neuronal accumulation of abnormal proteins (A-beta amyloid and tau -a microtubule associated protein) and neurofibrially
What are areas severly impacted by alzheimer’s diseaes?
Hippocampus and temporal lobes
What does acetylcholien cause?
Degeneration of cholinergic neurons in the nucleus basalis of meynert that project throughout the cortex
What is treatment for alzheimer’s disease?
Acetylcholinesterase inhibitors and NMDA (Glutamate receptor) antagonist
What does serotonin influence?
Sleep, cognition, sensory perception, motor activity, temperature regulation, nociception, mood, appetite, sexual behavior, and hormone secretion
It has been hypothesized that every neuron in the brain may be in ________ contact with a _______ neuron
Synaptic; serotonin
Where are raphe nuclei located?
In the midbrain (ex. nucleus raphe dorsalis), pons (ex. nucleus raphe pontis), and medulla obllongata (ex. nucleus raphe magnus)
What is the nucleus raphe magnus involved in?
Dampening ascending pain (nociceptive) signals
What are physiological processes under dopaminergic control?
Reward, emotion, cognition, memory, and motor activity
Where do neurons in the substantia nigra compacta project to?
Basal nuclei
What is the pathway the defenerates in parkinson’s disease?
Substantia Nigra compacta which causes bradykenesia
Where do neurons in the ventral tegmental area peoject to?
The nucleus accumbens and the prefrontal cortex
What is dysfunction in the ventral tegmental area associated with?
Addiction, schizophrenia and psychoses (bipolar depression) and learning deficits
What does norepinephrine impact?
All areas of the brain and facilitates excitatory synaptic transmission leading to attention (alert state) and arousal
What is it suggested that depression is related to?
Deficiency in the amount or function of cortical and limbic serotonin (5-HT), norepinephrine (NE), and dopamine (DA)
All cases of antidepressants appear to enhance?
Synaptic availability of 5-HT, norepinephrine, or dopamine
Most voluntary movements ‘initiated’ by the cerebral cortex are achieved when the cortex activates ‘patterns’ of function stored in what areas?
Lower brain areas - the brainstem, basal ganglia, and cerebellum
The motor system learns by?
Doing
The motor systems performance improves with?
Repetition - involves long-term potentiation
The brainstem along with the ____ can activate ________
Thalamus; lower motor neurons
If you want a muscle to contract you need to activate _______
Lower motor neurons
ACH binds to ________ which always causes _______
Nicotinic receptor; EPSP (contraction)
Upper motor neurons from the ______ intiate and direct sequences of _____ movement which is known as the ______ pathway
cerebral cortex; voluntary movement; pyramidal pathway
Other upper motor neurons originate in the _______________ and direct _________
Motor centers in the brainstem (extrapyramidal pathways); subconscious muscle tone, posture, balance, and orientation of the head and body
Voluntary movement is associated with what pathway?
Pyramidal pathway
Subconscious movement is associated with what pathway?
Extrapyramidal pathway
The lower motor neuron is _________ and releases ______ that binds to ________ on ___________
Cholinergic; ACH; nicotinic receptors; skeletal muscle
What does damage to the upper motor neuron cause?
Spastic paralysis on muscles on the opposite side of the body
Spastic paralysis on muscles on the opposite side of the body cause what?
Increased muscle tone, exaggeration of reflexes and pathological reflexes such as babinski reflex
What does damage to the lower motor neuron cause?
Flaccid paralysis of muscles on the same side of the body
What does Flaccid paralysis of muscles on the same side of the body mean?
There is neither voluntary nor reflex action of the muscle fibers
Flaccid paralysis is like a floppy doll compared to a barbie doll that is high tone
What are the three regions of the motor cortex?
- Premotor area/cortex
- Supplementary motor area/cortex
- Primary motor area/cortex
What does the premotor cortex set?
Posture (ex: position, shoulder, and arm) at the start of planned movement
What does the premotor area determine?
The overall motor plam
Premotor = Plan
What does the primary motor cortex in the upper motor neuron activate?
Specific muscles to execute the plan
More than half of the primary motor cortex is devoted to controlling?
The muscles of the hands and muscles of speech
What is the supplementary motor cortex involved in?
Organizing or planning motor sequences
Supplementary = Sequences
What do lesions in supplementary motor cortex produce?
Awkwardness in performing complex activities and difficulty with bimanual coordination
What do axons from neurons in the supplementary and primary motor cortex make up?
The corticospinal (lateral and ventral) and corticobulbar tracts
What indiciates a cortical areas function?
Cerebral blood flow
What is the corticospinal (pyramidal) tract called?
The direct motor pathway
Fibers from the corticospinal tract originate and descend where?
motor cortex and descend through the inernal capsule of the cerebrum
In the medulla oblongata, axon bundles are known as?
Pyramids
90% of the axons decussate to the contralateral side in the medulla oblongata and these axons form?
Lateral corticospinal tract of the spinal cord
Distal muscles (hands, feet)
The 10% that do not decussate in the medulla and these axons form the?
Anterior corticospinal tract
Proximal muscles (pelvic girdle, muscles of trunk)
Anterior corticospinal tract fibers decussate where? and synapse where?
In the spinal cord; synapse with the lower motor neuron
What do both lateral corticospinal tract and anterior corticospinal tract synapse with?
The lower motor neuron’s ventral horn of the spinal cord
Where do corticobulbar tract fibers originate and terminate?
Originate: motor cortex
Terminate: nuclei in hthe brainste,
What cranial nerves receive input from the corticobulbar tract?
Oculomotor (CN III)
Trochlear (CN IV)
trigeminal (CN V)
Abducens (CN VI)
Facial (CN VII)
Glossopharyngeal (CN IX)
Vagus (CN X)
Accessory (CN XI)
Hypoglossal (CN XII)
What do corticobulbar tract fibers innervate?
Lower motor neuron that control conscious control over skeletal muscles that move the eye, jaw, face, and some muscles of the neck and pharynx
What is the innervation of corticobulbar tract msuscles?
Bilateral (except genioglossus muscle and some muscles innervated by the facial nerve)
If a cranial nerve controls skeletal muscle, then the _________ pathway is activating the LMN
Corticobulbar pathway
What pathways regulate the activity of the LMN?
Corticospinal (anterior and lateral)
Corticubulbar
What are the extrapyramidal motor tracts responsible for?
Subconscious control of skeletal muscles
What is the location of the rubrospinal tract in the UMN?
Red nucleus in midbrain
What is the site of crossover for the rubro spinal tract?
midbrain
What is the function of the rubrospinal tract?
Upper limb muscle tone and movement
What is the location of the tectospinal tract in the UMN?
Midbrain (superior and inferior colliculi)
What is the site of crossover of the tectispinal tract?
Midbrain
What is the function of the tectospinal tract?
Regulation of eye, head, neck and UL position in response to visual and auditory stimuli
What is the location of the vestibulospinal tract in the UMN?
Vestibular nucleus (pons and medulla)
What is the site of crossover in the vestibulospinal tract?
None (controls ipsilateral muscles)
What is the function of the vestibulospinal tract?
Regulation of balance and muscle tone
What is the location of the reticulospinal tract in the UMN?
Media RS (pons +)
Lateral RS (medulla -)
What is the site of crossover for the reticulospinal tract?
None (controls ipsilateral muscles)
What is the function of the reticulospinal tract?
Regulates muscles of the trunk and limbs for maintaining posture and tone in response to ongoing body movements
What is UMN activity regulated by?
Basal nuclei via the thalamus
What are basal nuclei involved in?
Initiating and terminating movements
Suppressing unwatned movements
Establishing a normal level of muscle tone
What does substance nigra do?
Dopaminergic that turns up direct pathway of basal nuclei and turns down indirect pathway which increases motor activity
What is the result of direct pathway?
More activation in motor cortex
What do striatal interneurons cholinergic do?
Turn DOWN the direct pathway
Turn UP the indirect pathway
Decreased VAVL drive to cortex
LESS MOTOR ACTIVITY
What does substantia nigra dopaminergic do?
Turn UP the direct pathway
Turn DOWN the indirect pathway
INCREASED VAVL drive to cortex
MORE MOTOR ACTIVITY
What kind of disorder is parkinsons?
Hypokinetic disorder
How does parkinson’s disease occur?
Loss of dopaminergic neurons from the substantia nigra that project to the striatum where they inhibit cholinergic neurons
What are clinical manifestations of parkinsons?
Bradykinesia, cogwheel rigidity, pill rolling, tremor, shuffling gate, stooped posture, depression, dementia
When a tremor impacts the tongue and lips, what does this further impact?
Mastication, swallowing, and speech
What are common oral mangiestations?
Due to the medications for parkinsons (targeted at dopamine)
Difficulty with oral hygeine, xerostomia, burning mouht/mucositis, difficulty swallowing, drooling, and less caries/more teeth than age matched controls
What kind of disorder is huntington?
Hyperkinetic disorder
What is huntington disease?
Autosomal dominant genetic disease
Loss of GABAergic neurons, resulting in reduced inhibitory output from the striatum
What are clinical manifestations of huntington disease?
Chorea (multiple, rapid, random movements)l athetosis (slow writhing movements), personality changes, dementia
What are oral manifestations of huntington disease?
Speech difficulties, grimacing, dysphagia
Treatment can be hindered by involuntary mouth and jaw movements
Sedation may be required for treatment of some patients
What is the cerebellum involved in monitoring?
Dufferences between intended movements and movements actually performed
What commands does the cerbellum issue?
To UMN to reduce errors in movements
What does the cerebellum coordinate?
Body movements to maintain normal posture and balance
What do cerebellum diseases result in?
Alterations in gait, balance, and coordination of motor activities; NOT paralysis
What are examples of cerebellar diseases?
Dysmetria
Dysdiadochokinesia (difficulty w/ rapid alternating movements)
Where does the spinocerebellum receive input from?
Muscle spindles and golgi tendon organ (GTO) via spinocerebellar tracts
What are the functions of the spinocerebellum?
Coordination of body and limb movement, maintenance of muscle tone
What are effect of a spinocerebellum lesion?
Ataxia
Dysdiadochokinesia
Dysmetria
Intention tremor
Hypotonia
Where does the vestibulocerebellum receive input from?
Vestibular nuclei CN VIII
Superior Colliculi
Visual cortex
What is the function of the vestibulocerebellum?
Balance and eye movement
What are effect of vestibulocerebellum lesions?
Vertigo
Nystagmus
Where does the cerebrocerebellum receive input from?
Cerebral cortex and inferior olivary nucleus in medulla
What is the function of the cerebrocerebellum?
Planning and execution of movements; coordinating complex sequential movements
What are effect lesions of cerebrocerebellum?
Abnormal coordination of ipsilateral movements
Dysdiadochokinesia
Dysmetria
Intention tremor
What is the pathway starting from where you get an idea to when it becomes a movement?
What does the vestibulocerebellum receive input from?
Vestibular system
What does the vestibulocerebellum adjust the action of?
Reticulospinal and vestibulospinal pathways
What neurotransmitter is produced by nucleus basalis of meynert?
Acetylcholine
What neurotransmitter is produced by raphe nuclei?
Serotonin
What neurotransmitter is produced by substantia nigra compacta and ventral tegmental area and nucleus accumbens?
Dopamine
