NEUROSCIENCE Flashcards
The axons of the neurons in the grey matter are myelinated by what type of cell?
Oligodendrocytes
Neural crest cells will become what?
The peripheral nervous system, both somatic and autonomic. Neural crest cells migrate throughout the body, becoming the ganglia of the sensory tracts as well as the autonomic ganglia.
The neural tube will become what?
The central nervous system.
What does endoderm form?
The gut tube (colon, stomach, intestines) and the lungs.
What does the ectoderm form?
Skin (epidermis), hair, nervous system (neurons, glial cells, ependymal cells).
What does the mesoderm form?
Blood vessels, bones, meninges, lymphatics, musculoskeletal system.
What do the terms rostral, caudal, ventral and dorsal mean?
Towards the head (rostral), towards the tail (caudal), belly-side (ventral), and backside (dorsal).
What is the trilaminar disc comprised of?
The trilaminar disc consists of ectoderm, endoderm, mesoderm, and the medodermal notochord. Ectoderm is the sheet of cells on top with the amnion above it. Endoderm is the sheet of cells on the bottom, with the yolk sac below it. Between ectoderm and endoderm is the sheet of mesoderm cells.
What does the mesodermal notochord become, and is its role in neurulation?
It is a tube that will, in the adult, form intervertebral discs, padding for the vertebra. Early on in neurulation, the notochord is responsible for inducing embryogenesis of the entire nervous system.
What are the support cells of dorsal root ganglia?
The support cells of dorsal root ganglia of the peripheral sensory neurons are Schwann cells that myelinate and satellite cells that nurture axons.
The axons of the neurons in the grey matter are myelinated by what type of cell?
Oligodendrocytes
From superficial to deep, what it the order of meninges?
The layers of meninges are the dura mater, the arachnoid mater, and the pia mater.
What are the support cells of the central nervous system?
Astrocytes (that keep the blood-brain barrier tight), the oligodendrocytes (that do the myelinating), the ependymal cells (that line ventricles), and the microglial cells (that act as resident macrophages)
What are Nissl bodies?
These are darkly staining structures in the cytoplasm around the nucleus, pathognomonic for a neuron’s cell body.
Name a few of the neurotransmitters.
Acetylcholine, nitric oxide, vasoactive intestinal peptide, and norepinephrine.
Neuron cell bodies are often very active in building what?
Protein; most neurotransmitters are proteins, and transmembrane proteins are required to receive or deliver a stimulus.
In general, what are the roles of astrocytes?
Astrocytes likely supply the neurons with nutrients from the bloodstream, reinforce the CNS barrier with the ependymal cells, modulate the blood-brain barrier, modulate potassium, and modulate neurotransmitters.
What is the role of ependymal cells?
Ependymal cells are the only true epithelium of the CNS and keep the CSF out of the parenchyma, and sometimes secrete CSF (choroid plexus) or reabsorb it (arachnoid granulations).
What is the role of oligodendrocytes?
Oligodendrocytes are responsible for myelinating axons in the central nervous system. Unlike the Schwann cells that myelinate the peripheral nerves, one oligodendrocyte myelinates many axons.
What is the role of microglial cells?
Microglial cells are phagocytes and antigen-presenting cells - they are the resident macrophages of the CNS.
What is the only glial or neuronal cell derived from mesoderm?
Microglial cells.
From superficial to deep, what is the order of meninges?
The layers of meninges are the dura mater, the arachnoid mater, and the pia mater.
What is cavernous sinus syndrome?
This is caused by a pituitary tumor, an ascending infection, or a thrombosis. Headache and papilledema are common problems, but there can also be symptoms such as internal strabismus (due to impairment of the oculomotor nerve), sensory loss or the lower face, and Horner’s syndrome.
The two lateral ventricles connect to the third ventricle via the ______.
Interventricular foramen (formerly foramen of Monro).
The third ventricle is connected to the fourth ventricle by the ______.
Cerebral aqueduct (formerly cerebral aqueduct of Sylvius).
Describe the flow of CSF.
CSF is generated from the choroid plexus, drained by arachnoid granulations, and contained by the ventricles (within the cranium), spinal canal (within the spine), and subarachnoid space.
What is the role of arachnoid granulations?
Arachnoid granulations take excess CSF and put it back into the systemic circulation, back into the venous blood, via the dural sinuses.
What is an obstructive (noncommunicating) hydrocephalus?
This is caused by a structural lesion that occludes the flow of CSF by blocking the passages from ventricle to ventricle. Any ventricles proximal to the obstruction are dilated which causes the CSF level to increase. This increase in CSF level leads to an increase an intracranial pressure which may lead to herniation.
What is a communicating (nonobstructive) hydrocephalus?
This is caused by impaired CSF reabsorption by arachnoid granulations. This classically occurs seconday to post-hemorrhage or post-meningitis effects on where the arachnoid granulations are. With nowhere for the CSF to go, the ventricles dilate, though unlike obstructive, in which only the proximal ventricle dilates, communicating hydrocephalus sees all ventricles dilate.
What is hydrocephalus ex vacuo?
This is caused by atrophy; progressive loss of tissue results in excess CSF to fill the cranial cavity. Hydrocephalus ex vacuo happens commonly in an elderly patient with dementia.
What is normal-pressure hydrocephalus?
This is a reversible cause of dementia where there is ventricular enlargement, but normal intracranial pressure. A patient with NPH thus does not show signs of increased ICP and will develop symptoms insidiously. Recall “wobbly, wacky, and wet,” which represents the classic symptoms of a broad-based gait, cognitive changes, and urinary incontinence.
What cranial nerves pass through the cavernous sinus?
The abducens (CN VI), oculomotor (CN III), trochlear (CN IV), and trigeminal (CN V) nerves (as two separate branches (opthalmic branch CN V/I and maxillary branch CN V/II)
What is cavernous sinus syndrome?
This is caused by a pituitary tumor, an ascending infection, or a thrombosis. Headache and papilledema are common problems, but there can also be symptoms such as internal strabismus (due to impairment of the oculomotor nerve), sensory loss or the lower face, and Horner’s syndrome.
Describe a subarachnoid hematoma.
Affected individuals complain of the “worst headache of their life.” Although it is possible to get these bleeds from trauma, we see them as being secondary to medical disease - either hypertensive emergency or a rupture of a berry aneurysm. Affected individuals are stricken by an excruciating headache that has a rapid onset and cresendos quickly (“thunderclap”).
What is Cushing’s triad?
Bradycardia, hypertension and irregular respirations (Cheyne-Stokes breathing).
What is the main sign of increased ICP?
Headache that is worse in the morning and with actions that increase ICP (cough, sneeze, and Valsalva maneuver).
Besides headaches, what are other signs of ICP?
Projectile vomiting without nausea, papilledema, seizures, and a cranial nerve VI palsy (inability to abduct an eye past midline).
What are ways to treat increased ICP?
Raising the head of the bed, hyperventilation, mannitol, craniotomy, and decompressive craniectomy.
Describe an uncal herniation.
The medial aspect of the temporal lobe (uncus) herniates under the tentorium cerebelli which causes compression of the ipsilateral oculomotor nerve (CN III) resulting in ipsilateral pupil dilation and extraocular muscle paralysis. As the herniation progresses, the uncus compresses the brainstem away from the lesion causing loss of bodily sensation on the entire ipsilateral side (hemiparesis).
Describe a tonsillar herniation.
The cerebellar tonsils herniate through the foramen magnum which pushes the contralateral medulla up against bone causing compression of the medulla. This causes respiratory and cardiovascular arrest.
Describe a central hernia.
Caused by diffuse cerebral edema (often in patients with significant trauma), the progression of expanding edema forces the top of the brainstem and posterior cerebrum through the tentorial notch. This shears blood vessels and compresses the eye nerves and nuclei bilaterally, resulting in bilateral pupil dilation and bilateral extraocular palsies.
Describe an epidural hematoma.
Most often caused by damage to the middle meningeal artery due to strong, blunt force trauma to the side of the head. The patient will have a trauma, with either a loss of consciousness or not, but after a brief lucid interval, there is a rapid progression to coma and death.
Describe a subdural hematoma.
This is a bleed below the dura mater (subdural) and above the arachnoid layer. These patients present with an insidious headache progressing to encephalopathy (often mistaken as dementia). Shearing of the bridging veins in this kind of hematoma is seen in children and the elderly.
Describe a subarachnoid hematoma.
Affected individuals complain of the “worst headache of their life.” Although it is possible to get these bleeds from trauma, we see them as being secondary to medical disease - either hypertensive emergency or a rupture of a berry aneurysm. Affected individuals are stricken by an excruciating headache that has a rapid onset and cresendos quickly (“thunderclap”).
What are the positive and negative symptoms of schizophrenia?
Positive symptoms include delusions, hallucinations, disorganized speech, and disorganized behavior. Negative symptoms include flat affect, poverty of speech, poverty of movement, anhedonia, and cognitive delay.
What are the components of the basal ganglia?
Caudate nucleus, putamen, nucleua accumbens, and globus pallidus.
What neurotransmitter activates the thalamus and therefore stimulates movement?
Dopamine
Describe the direct pathway of the basal ganglia.
The direct pathway results in the disinhibition of the thalamus, and therefore allows movement. It does so through dopamine from the substantia nigra.
Describe the indirect pathway of the basal ganglia.
The indirect pathway results in the inhibition of the thalamus through acetylcholine, which prevents movement.
What is the mesolimbic pathway?
This pathway involves connections from the ventral tegmental area to the forebrain, and plays roles in emotion and reward and is responsible for the positive symptoms of schizophrenia. If you give a patient dopamine therapy, this pathway may elicit hallucinations.
What is the mesocortical pathway?
This pathway involves connections from the ventral tegmental area to the prefrontal cortex. It plays a role in cognition, executive function, and the negative symptoms of schizophrenia.
Whare are the signs and symptoms of Parkinson’s disease.
Patients present with less movement, termed bradykinesia. Bradykinesia is characterized by the mask-like face (diminished facial expression), shuffling steps, a resting pill-rolling tremor, and cogwheel rigidity (movement is interrupted periodically: normal movement with abrupt pauses).
What causes Parkinson’s disease?
It is a degenerative disease of the nigrostriatal dopaminergic system. The patient progressively loses the substantia nigra (the dopamine machine). The progressive loss of dopamine leads to worsening symptoms since dopamine is movement and the disease claims the dopamine-secreting cells.
What is Lewy body dementia?
If a patient presents with severe dementia and progresses to Parkinonism, the diagnosis is Lewy body dementia.
What are the positive and negative symptoms of schizophrenia?
Positive symptoms include delusions, hallucinations, disorganized speech, and disorganized behavior. Negative symptoms include flat affect, poverty of speech, poverty of movement, anhedonia, and cognitive delay.
When do babies lose their primitive reflexes?
Babies have primitive reflexes when they are born that abate within the first year of life as their frontal lobe develops, and their spinal cord becomes fully myelinated.
What happens if a stroke lesioned Broca’s area?
The patient would be able to hear, understand, and formulate the thought of speaking, but then be unable to actually speak.
The anterior cerebral artery is responsible for which areas?
The feet and the legs.
The middle cerebral artery is responsible for which areas?
The face, hands, and Broca’s area.
What are the symptoms of an upper motor neuron lesion?
The patient will have increased muscle tone, hyperreflexia, and up-turning toes.
What are the symptoms of a lower motor neuron lesion?
The patient will have decreased muscle tone and hyporeflexia, and the muscle will eventually atrophy and there may be the presence of fasciculations.
