Neuro Lect 1
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What are examples of different localizations of diseases in the brain?
- focal: glioblastoma multiforme
- multifocal: non-hodgkins lymphoma
- diffuse: HIV encephalitis
Nervous system function that detects internal and external stimuli that's carried to the brain and spinal cord.
Nervous system function that processes sensory information then analyzes it and makes decision on proper responses to stimuli.
Nervous system function that cause muscles and glands to contract or secrete through effectors from spinal or cranial nerves.
What does the central nervous system (brain, spinal cord) develop from?
What does the peripheral nervous system (all neural structures outside the spinal cord) develop from?
When does development of the nervous system begin during gestation? What is the process of neural tube development?
- day 18
- starts with thickening of of ectoderm (neural plate), which folds inward forming a groove (neural groove), these raised adages are called neural folds which increase in height and eventually become the neural tube
What are the three layers in the neural plate during gestation that develop into the white and gray matter as well as the lining of the central canal of the spinal cord and ventricles of the brain?
- outer (marginal layer): white matter
- middle (mantle layer): gray matter
- inner (ependymal layer): lining of central canal of spinal cord & ventricles
What dosage of folic acid is appropriate for women three months before pregnancy?
What is the mass of tissue that lies between the neural tube and skin ectoderm during gestation and what does it differentiate into?
- neural crest
- dorsal/posterior root ganglia of spinal nerves
- spinal nerves
- cranial nerve ganglia
- cranial nerves
- ANS ganglia
- adrenal medulla
When does the neural tube close during gestation and why is this a problem?
- between 18 and 26 days
- most women don't know they are pregnant until at least one week late on menses (day 21 of pregnancy)
- Note: this is why supplementation before pregnancy with 400mcg folic acid is important to avoid neural tube defects (some studies suggest 800mcg)
This congenital malformation of the CNS results from failure of the neuropore to close, therefore the brain fails to develop.
This congenital malformation of the CNS results from failure of the posterior neuropore to form. Most commonly occurs in the sacrolumbar region.
spina bifida (10% SB occulta)
This congenital malformation of the CNS results from a defect in the occipital lobe through which the meninges, cerebellar tissue and 4th ventricle may herniate.
This congenital malformation of the CNS is a cerebellomedullary malformation in which the caudal vermis, cerebellar tonsils and medulla herniate through the foramen magnum, resulting in a communicating hydrocephalus.
Arnold-Chiari syndrome (1:1000)
This congenital malformation of the CNS is a hydrocephalus resulting from failure of the foramina of Luschka and Mangendie to open. It is associated with an occipital meningocele and a genesis of the cerebellar vermis.
This congenital malformation of the CNS is most commonly caused by stenosis of the cerebral aqueduct during development. Excessive CSF accumulates in the ventricles and subarachnoid space. May result from maternal infection from either CMV or toxoplasmosis.
This congenital malformation of the CNS is the most common cause of mental retardation and includes microcephaly and congenital heart disease.
fetal ETOH syndrome
What is the most severe form of fetal ETOH syndrome?
What are the six categories of supporting nervous system cells (no electric excitability, can multiply)?
- astroglia: found in CNS, perivascular processes that cover capillaries within the brain, contribute to BBB
- microglia: found in CNS, amoeboid cells that are phagocytic
- ependymoglia: found in CNS, form epithelial lining in brain cavities esp the ventricles and spinal cord, and act as cover "tufts" of capillaries forming choroid plexuses that make CSF
- oligodendroglia: found in CNS, form myelin sheaths around central axons which produce the "white" matter
- Schwann cells: found in PNS, surrounds axons of the peripheral nerve fibers, forms a neurilemmal sheath called a Schwann sheath (myelin sheaths of PNS)
- satellite cells: found in PNS, primarily a supporting structure of the neurons within the sensory and autonomic ganglia
What are the general areas and functions included in the frontal lobe of the cerebral cortex?
- motor and premotor cortex
- frontal eye field
- Broca's speech area
- prefrontal cortex
What are the affects of destruction in the motor and premotor cortex of the frontal lobe of the cerebral cortex?
What are the affects of destruction in the frontal eye field of the frontal lobe of the cerebral cortex?
deviation of the eyes to the IPSILATERAL side
What are the affects of destruction in the anterior 2/3 of the prefrontal cortex of the cerebral cortex?
- deficits in...concentration
- abstracting ability
- problem solving
What are the affects of destruction in areas other than the anterior 2/3 of the prefrontal cortex of the cerebral cortex?
- loss of initiative
- inappropriate behavior
- gait apraxia
- sphincteric incontinence
What are the affects of destruction in the orbital portion of the prefrontal cortex of the cerebral cortex?
inappropriate social behavior (obscene language/urinating in public)
What are the general areas and functions included in the temporal lobe of the cerebral cortex?
- primary auditory cortex
- Wernicke's speech area (dominant hemisphere), posterior part of superior gyrus
- Meyer's loop
- olfactory bulb, tract, primary cortex
- hippocampal cortex
- anterior temporal lobe
- inferomedial occipittemporal cotex
What are the affects of destruction in the primary auditory cortex of the temporal lobe of the cerebral cortex?
- slight loss of hearing
- *bilateral loss results in cortical deafness*
What are the affects of destruction in the Wernicke's speech area of the temporal lobe (dominant hemisphere) of the cerebral cortex?
What are the affects of destruction in the Meyer's loop of the temporal lobe of the cerebral cortex?
contralateral upper quadrantanopia (pie in the sky)
What are the affects of destruction in the olfactory bulb, tract, primary cortex of the temporal lobe of the cerebral cortex?
- ipsilateral anosmia
- Note: irritative lesion of the uncus results in olfactory and gustatory hallucinations
What are the affects of destruction in the hippocampal cortex of the temporal lobe of the cerebral cortex?
inability to consolidate short-term memory into long term memory (bilateral lesions)
What are the affects of destruction in the anterior temporal lobe of the cerebral cortex?
Kluver-Bucy syndrome (bilateral lesions)
What are the affects of destruction in the inferomedial occipittemporal cortex of the temporal lobe of the cerebral cortex?
prosopagnosia (inability to recognize once familiar faces)
Syndrome that consists of psychic blindness (visual agnosia), hyperphagia, docility, and hypersexuality.
What are the general areas and functions included in the parietal lobes of the cerebral cortex?
- sensory cortex
- superior parietal lobe
- inferior parietal lobe (dominant hemisphere)
- inferior lobe (non dominant hemisphere)
What are the affects of destruction in the sensory cortex of the parietal lobe of the cerebral cortex?
- contralateral hemihyperesthesia
What are the affects of destruction in the superior parietal lobe of the cerebral cortex?
- contralateral astereognosis
- sensory neglect
What are the affects of destruction in the inferior parietal lobe (dominant) of the cerebral cortex?
Gerstmann's syndrome (damage to angular gyrus)
What are the affects of destruction in the inferior parietal lobe (non dominant) of the cerebral cortex?
- topographic memory loss
- construction apraxia
- dressing apraxia
- contralateral sensory neglect
- contralateral hemianopia or lower quadrantanopia
This syndrome includes right and left confusion, finger agnosia, dysgraphia, dyslexia, dyscalculia, and contralateral hemianopia and lower quadrantonopia.
What are the general functions of the occipital lobe in the cerebral cortex?
- visual processing
- shape and color identification
What are the affects of destruction in the occipital lobe of the cerebral cortex?
- bilateral lesions: cortical blindness
- unilateral lesions: contralateral hemianopia of quadrantanopia
The only connection between the left and right sides of the brain, and is a common area for stroke and seizure to occur.
What is the determined by the Wada test (Amytal injected into carotid) by checking for aphasia?
- cerebral dominance
- Note: if pt becomes aphasic after sodium amobarbital injection, the anesthetic was given in the dominant hemisphere
The left brain is usually dominant and better at vocal naming. What else is it responsible for?
The right brain is usually non dominant and responsible for what?
- 3D or spatial perception
- non verbal ideation
- recognition of faces
- better at pointing to a stimulus
A disconnection syndrome that results from transection of the corpus callosum causing pts to have alexia in the left visual cortex, no access to language centers, visual problems (ball effect), and erratic behavior.
- split brain syndrome
- Note: alexia refers to symbols seen in the right visual cortex
The neurotransmitter of the PNS, NMJ, parasympathetic NS, pre and postganglionic sympathetic fibers. Also found in the neurons of the basal and visceral motor nuclei of the brain stem, spinal cord, and the basal nucleus of Meynert (Alzheimer's).
What are the catecholamine neurotransmitters?
- dopamine: decreased in parkinson's dz, increased in schizophrenia (D1 & D2 are primary receptors)
- norepinephrine: most common transmitter of postganglionic sympathetic neurons, antidepressants enhance transmission, hypothesis of mood disorders
Which dopamine receptor is post synaptic, activates cyclase and is excitatory?
Which dopamine receptor of both pre- and post synaptic, inhibit adenylate cyclase is inhibitory?
What is the catecholamine hypothesis of mood disorders?
- reduced norepi activity is related to depression
- increased norepi activity is related to manic states
What neurotransmitter is frequently targeted by antidepressants that increase it's availability by reducing uptake?
- serotonin (5HT)
- Note: the permissive serotonin hypothesis states reduced 5HT activity creates reduced levels of catecholamines that can lead to depression and insomnia, however increased lvls of catecholamines can lead to manic states…5HT dysfunction can also lead to OCD
What are the opioid peptide neurotransmitters?
- endorphins: B-endorphin, found almost exclusively in the hypothalamus, is the most powerful analgesic known (48x more powerful than morphine)
- enkephalines: most widely distributed and abundant, highest in globes pallidus, plays a role in pain reduction
- dymophins: follow same distribution as enkephalines
What are the the non-opioid neuropeptide neurotransmitters?
- substance P: pain transmission, found in dorsal root ganglion and substantia gelanosa, in highest concentration in substantia nigra, localized with GABA, plays a role in movement disorders
- somatostatin: regulates release of GH and TSH, reduced in pts with alzheimers, increased in pts with huntingtons
What are the amino acid neurotransmitters?
- GABA: major inhibitory NT of the brain, receptors are associated with benzodiazepine binding sites, benzos enhance GABA activity
- glycine: major inhibitory NT of the spinal cord
- glutamate: major excitatory NT of the brain, transmits non-nociceptive, large, primary efferent fibers entering the spinal cord and brain, transmitter of the corticobulbar and corticospinal tracts
- aspartate: excitatory transmitter of the climbing fibers of cerebellum, plays role in long term potentiation (memory) and kindling seizure activity, may be a neurotoxin under certain conditions
Results from degeneration of dopaminergic neurons found in the pars compacta of the substantia nigra.
Results from loss of ACh and GABA containing neurons in the striatum and substantia nigra.
Results from degeneration of cortical and cholinergic neurons in the basal nucleus of Meynert, and is associated with a 60-90% loss of choline acetyltransferase in the cerebral cortex.
An autoimmune syndrome that occurs in the presence of antibodies to the nicotinic ACh receptors, and reduces the number of receptors in the neuromuscular junction which results in muscle paralysis.
What are signs and symptoms that can localize the issue to cerebral functions?
- frontal lobe dysfunction
Inability to speak, usually dominant hemisphere involvement (left).
What are the two basic forms of aphasia?
- motor/expressive (Broca's): frontal lobe, DOING
- sensory/receptive (Wernicke's): temporal lobe, SENSING
Fluency impaired language production, repetition impaired, comprehension relatively preserved but may have difficulty with more complex concepts (under the paper put pen). Associated signs include right hemiparesis, and pt being aware of the deficit/problem and frustrated by it.
- Broca's aphasia (broken thoughts)
- Note: almost all pts with speech aphasia will also have agraphia or be aphasic in their writing ability
Fluency of speech preserved, problem with language comprehension, repetition limited, comprehension impaired. Associated signs include right upper visual field defect, and pt being unaware of deficit (at least initially).
- Wernicke's aphasia (word salad)
- Note: almost all pts with speech aphasia will also have agraphia or be aphasic in their writing ability
Loss of the ability to carry out learned purposeful movements despite having the desire and physical ability to perform the movements. Focal disturbance of planning/doing (i.e., dressing), involves non dominant hemisphere (right).
Directed inattention or lack of attention paid to one hemisphere due to a focal disturbance of "sensory integration". Involves non dominant hemisphere (right) parietal lobe. Pts tend to be less or completely unaware of objects or actions on one side of the body (usually left) or may even deny the side exists.
- neglect/ left hemineglect
- Note: inability to perceive stimulus despite intact sensory pathways, is not secondary to visual or physical defects
How are mild-mod forms of neglect/ left hemineglect tested for?
- double stimulation test: touch each side independently, then dependently; (+) pt can't feel affected side
- drawing test: pt pushes everything to the right or only draw the right side of a picture
What are the subcortical centers and their structures?
- basal ganglia: caudate, putamen, globus pallidus
- diencephalon: thalamus, hypothalamus, epithalamus (pineal gland)
What subcortical center coordinates motor activity input from the cerebral cortex, thalamus, and substantia nigra? What do lesions in this area cause?
- basal ganglia
- lesions cause movement disorders, tremors, and other extrapyramidal syndromes (Parkinsons, essential tremor, Huntington's)
Major sensory relay, and play an important role in memory pathways.
Master control for ANS, and controls the pituitary functions.
What are the structures of the limbic system?
- cingulate gyrus
- midbrain raphae
- locus ceruleus
Plays a major role in emotion and memory by way of endocrine, autonomic and motor changes regulated by the hypothalamus. Given its location it is involved in cortical control over the hypothalamus.
limbic cortex (system)
Nuclei deep in the temporal lobes, plays a chief role in the memory of emotional experiences, and a central role in behavioral responses to fear. Seizures arising from this nuclei are felt as fear, and enlarged nuclei are found in autism.
Integrator of incoming novel and unpleasant stimuli. Connects with temporal lobe closely, and may predict the next event based on what has already happened.
septohippocampal area (hippocampus)
Latin for "little brain", comprises 10% of brain volume and 50% of the neurons in the CNS. Has two hemispheres with 10 individual lobes, and occupies the posterior fossa. Controls body movement.
What are the three main functions of the cerebellum? What do lesions in the cerebellum do?
- sensory perception, coordination, motor control
- lesions cause no paralysis, but instead feedback disorders which affect posture, equilibrium, and motor learning
- Note: ataxia points to overall "posterior fossa" localizer
Posterior fossa localizing condition, gross lack of coordination of motor activity.
ataxia (think about a drunk walking)
White matter tracts below the cortex going to or from the cortex in the brainstem.
Tracts responsible for movement (pyramidal-voluntary, extrapyramidal-involuntary) pass through here which also contains the RAS and controls respirations (consciousness center).
What are the three part of the brainstem?
Cylindrical mass of nerve tissue, bony vertebral column for protection, extends from the medulla to the 1st or 2nd lumbar vertebra, and is composed of gray (cell bodies) and white matter (mylenated).
Motor neurons that begin in the cortex and brainstem, travel down the spine and synapse on the anterior horn cells (long cells).
upper motor neurons
Motor neurons that begin in the anterior horn. Axons travel directly to the muscle fibers carrying information all the way to the NMJ.
lower motor neurons
Ascending or descending fibers that connect the CNS with the PNS.
spinal cord tracks
What are the spinal cord tracts and what are their general functions?
- corticospinal tract: voluntary motor activity
- spinothalamic tract: pain and temperature
- dorsal columns: light touch/vibration
Pathway that transmits voluntary movements, performs integration of complicated movements, originates in the cortex, terminates on the anterior horn cell and the majority of fibers cross in the medulla.
- corticospinal pathway (motor pathway)
- Note: descends in the corticospinal tract (pyramidal tract)
What are the two main pathways that carry sensory impulses in the spinal cord?
- dorsal columns (posterior columns): vibration, position sense, light touch
- spinothalamic tracts: pain and temperature
Pathway that carries impulses for pain and temperature, sensory fibers enter and cross the midline immediately. Fibers ascend to the thalamus on the opposite side.
- spinothalamic tract
- Note: ascends in the spinothalamic tract
Pathway that carries impulses for vibration, position sense, and light touch. Sensory impulses ascend up the same side as fibers enter the cord and cross the midline at the medulla.
Where does arterial supply to the brain come from?
- bilateral internal carotid arteries
- bilateral vertebral arteries
A defect in the anterior cerebral artery (ACA) affects what area of the brain?
lower limb area of the motor cortex
A defect in the middle cerebral artery (MCA) affects what area of the brain af what function?
- face and upper limb area of the motor cortex
- also affects the dominant language hemisphere
Occlusion of either the ____ or _____ may lead to a devastating stroke.
- anterior cerebral artery (ACA)
- middle cerebral artery (MCA)
Artery that leads to both right and left posterior cerebral artery (PCA).
Occlusion of the vertebrobasilar artery system (PCA) in the brain can lead to what kind of attacks? What results from complete occlusion?
- "drop attacks"
- Note: vertebrobasilar system affects the visual cortex, thalamus, midbrain
What are the arteries involved in "posterior circulation"?
- superior cerebellar artery (SCA)
- posterior inferior cerebellar artery (PICA)
- anterior inferior cerebellar artery (AICA)
- basilar artery
The membranes that protect the CNS.
What are the different layers of the meninges?
- dura mater: outermost layer
- arachnoid mater: lies above the subarachnoid space
- pia mater: delicate inner layer that directly covers the brain & spinal cord
Surrounds the brain and spinal cord, is clear, and colorless with few cells and little protein.
cerebrospinal fluid (CSF)
What is CSF secreted by and where is it reabsorbed?
- choroid plexus
- subarachnoid space
How is venous blood drained from the head?
- venous flow from brain goes into dural sinuses within the dura,
- then passively flows into the jugular vein
- the sinuses also have direct communication with venous drainage of the face
Division of the autonomic nervous system that regulates glands, smooth muscle, cardiac muscle and provides the fight or flight response.
- sympathetic nervous system
- Note: fibers exit the spinal cord at T1-L2
Division of the autonomic nervous system that produces a restorative, conserve energy effect.
- parasympathetic nervous system
- Note: fibers exit through CNIII, VII, IX, X and S2-S4 to gut and bladder
What provides the master control for the ANS?
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