1. Anatomy and Physiology Flashcards
CNS/PNS origins: Neuroectoderm (gives rise to what?)
CNS neurons Ependymal cells (inner lining of ventricles, make CSF) Oligodendrocytes Astrocytes
CNS/PNS origins: Neural Crest (gives rise to what?)
Schwann cells PNS neurons
CNS/PNS origins: Mesoderm (gives rise to what?)
M icroglia, like M acrophages, originate from M esoderm
Neurons: location, division and morphology
Comprise nervous system. Permanent cells – do not divide in adulthood. Large cells w/ prominent nucleoli.
Nissl substance. What are they and were do you find them?
RER found in cell body and dendrites, but not axon of neurons.
Astrocytes. What are their functions? What happen if they are injured?
Physical support, repair, K+ metabolism, removal of excess NT. Maintenance of BBB. Reactive gliosis in response to injury.
Astrocyte marker?
GFAP
Microglia. What are they and what are their origins? Can you Nissle stain them? Morphology?
CNS phagocytes. Mesodermal origin. Not readily discernible in Nissle stains. Have small, irregular nuclei and relatively little cytoplasm.
What happens to microglia in the presence of tissue damage?
Microglia –(tissue damage)–> differentiate into large ameboid phagocytic cells
What happens to HIV-infected microglia?
HIV-infected microglia fuse to form multinucleated giant cells in the CNS
Oligodendria. What are they and what do they do? Can you nissle stain them? Morphology?
Each oligodendrocyte myelinates multiple CNS axons (up to 30 each). In Nissle stains, they appear as small nuclei with dark chromatin and little cytoplasm.
What is the predominant type of glial cell in white matter?
Oligodendrocytes.
What cells are destroyed in multiple sclerosis?
Oligodendrocytes.
What do oligodendrocytes look like on H&E?
Fried Eggs
Schwann cells. Where are they and what do they do? What are they derived from?
Each Schwann cell myelinates only 1 PNS axon. Also promote axonal regeneration. Derived from neural crest.
What are the cells that are destroyed in Guillain-Barré syndrome?
Schwann cells.
An acoustic neuroma is a type of…? Where is it located?
Acoustic neuroma is a type of Schwannoma. It is typically located in internal acoustic meatus (CN VIII)
Sensory receptors/corpuscles: Free nerve endings (C, A-delta fibers) Location? Senses?
In all skin, epidermis, some viscera. Senses pain and temperature.
Sensory receptors/corpuscles (location and senses): In all skin, epidermis, some viscera. Senses pain and temperature. Which is this?
Free nerve endings (C, A-delta fibers)
Sensory receptors/corpuscles: Meissner’s corpuscles Location? Senses?
In glabrous (hairless) skin. Senses dynamic fine touch (e.g., manipulation), adapt quickly.
Sensory receptors/corpuscles (location and senses): In glabrous (hairless) skin. Senses dynamic fine touch (e.g., manipulation), adapt quickly. Which is this?
Meissner’s corpuscles
Sensory receptors/corpuscles: Pacinian corpuscles Location? Senses?
In deep skin layers, ligaments, and joints. Sense vibration, pressure.
Sensory receptors/corpuscles (location and senses): In deep skin layers, ligaments, and joints. Sense vibration, pressure. Which is this?
Pacinian corpuscles
Sensory receptors/corpuscles: Merkel’s disks Location? Senses?
(cup-shaped, unencapsulated) In hair follicles. Sense static touch (e.g., shapes, edges, textures), adapt slowly.
Sensory receptors/corpuscles (location and senses): (cup-shaped, unencapsulated) In hair follicles. Sense static touch (e.g., shapes, edges, textures), adapt slowly. Which is this?
Merkel’s disks
Peripheral nerve layers: Endoneurium
Invests a single nerve fiber (Endo = inner)
Peripheral nerve layers: Perineurium
(P erineurium is the P ermeability barrier) Surrounds a fascicle of nerve fibers. (Peri = around) Must be rejoined in microsurgery for limb reattachment.
Peripheral nerve layers: Epineurium
Dense connective tissue that surrounds entire nerve (fasicles and blood vessels) (Epi = outer)
Neurotransmitters: NE Change in dz? Location of synthesis?
Increased in anxiety, decreased in depression. Made in the locus ceruleus.
Increased in anxiety, decreased in depression. Made in the locus ceruleus. What NT is this?
NE
Neurotransmitters: Dopamine Change in dz? Location of synthesis?
Increased in schizophrenia, decreased in Parkinson’s. Made in the ventral tegmentum and SNc
Increased in schizophrenia, decreased in Parkinson’s. Made in the ventral tegmentum and SNc What NT is this?
Dopamine
Neurotransmitters: 5-HT Change in dz? Location of synthesis?
Decreased in anxiety, depression. Made in the raphe nucleus
Decreased in anxiety, depression. Made in the raphe nucleus What NT is this?
5-HT
Neurotransmitters: ACh Change in dz? Location of synthesis?
Decreased in Alzheimer’s, Huntington’s. Made in the basal nucleus of Meynert. Upregulated in REM sleep
Decreased in Alzheimer’s, Huntington’s. Made in the basal nucleus of Meynert. What NT is this?
ACh
Neurotransmitters: GABA Change in dz? Location of synthesis?
Decreased in anxiety, Huntington’s. Made in nucleus accumbens.
What 3 structures form the blood-brain barrier (BBB)?
1.) Tight junctions btw nonfenestrated capillary endothelial cells 2.) Basement membrane 3.) Astrocyte processes
Besides the BBB, what are 2 similar barriers?
1.) Blood-testis barrier 2.) Maternal-fetal blood barrier of placenta
What happens at the BBB w/ infarction?
Infarction destroys endothelial cell tight junctions, leading to vasogenic edema
How do glucose and amino acids cross the BBB?
Cross slowly by carrier-mediated transport mechanism.
How do nonpolar/lipid-soluble substances cross the BBB?
Cross rapidly via diffusion.
What is the function of specialized brain regions w/ fenestrated capillaries and no BBB?
Allow molecules in the blood to affect brain function (e.g., area postrema - vomiting center after chemo, OVLT - osmotic sensing) or neurosecretory products to enter circulation (e.g., neurohypophysis - ADH release)
Hypothalamus functions
The hypothalamus wears TAN HATS : T-hirst and water balance A-denohypophysis control N-eurohypophysis releases hormones from hypothalamus H-unger A-utonomic regulation T-emperature regulation S-exual urges
Inputs to the hypothalamus
OVLT (senses change in osmolarity) Area postrema (responds to emetics)
Supraoptic nucleus of the hypothalamus
Area that makes ADH.
Area that makes ADH.
Supraoptic nucleus of the hypothalamus
Paraventricular nucleus of the hypothalamus
Area that makes oxytocin.
Area that makes oxytocin.
Paraventricular nucleus of the hypothalamus
Lateral area of the hypothalamus
Controls hunger: destruction leads to anorexia. (“If you zap the lateral nucleus, you shrink laterally “) Inhibited by leptin.
Ventromedial area of the hypothalamus
Controls satiety: destruction leads to hyperphagia. (“If you zap your ventromedial nucleus, you grow ventrally and medially .”) Stimulated by leptin.
Anterior hypothalamus
Cooling (Anterior = cooling, or A/C). A nterior is pA rasympathetic.
Posterior hypothalamus
Heating (posterior = get fired up / heating). Sympathetic. If you zap your P osterior hypothalamus, you become a P oikilotherm (cold-blooded, like a snake)
Septal nucleus of the hypothalamus
area responsible for sexual urges
area responsible for sexual urges
Septal nucleus of the hypothalamus
Suprachiasmatic nucleus of the hypothalamus
Circadian rhythm. (“You need to sleep to be charismatic [chiasmatic]”).
Posterior pituitary (neurohypophysis)
Receives hypothalamic axonal projections from supraoptic (ADH) and paraventricular (oxytocin) nuclei. Oxytocin: oxys = quick; tocos = birth.
Anterior pituitary aka…?
A nterior pituitary = A denohypophysis
What is the main function of the thalamus?
Major relay for ascending sensory information that ultimately reaches the cortex.
Blood supply to the thalamus
posterior communicating, posterior cerebral, and anterior choroidal arteries.
Lateral geniculate nucleus (LGN) of thalamus
(hint: “L ateral for L ight”) area of thalamus for visual information.
area of thalamus for visual information.
Lateral geniculate nucleus (LGN) of thalamus (hint: “L ateral for L ight”)
Medial geniculate nucleus (MGN) of the thalamus
(hint: M edial for M usic) Area of the thalamus responsible for auditory information
Area of the thalamus responsible for auditory information
Medial geniculate nucleus (MGN) of the thalamus (hint: M edial for M usic)
Ventral posterior nucleus, lateral part (VPL) – of thalamus
part of the thalamus responsible for body sensation (proprioception, pressure, pain, touch, vibration via dorsal columns, spinothalamic tract).
part of the thalamus responsible for body sensation (proprioception, pressure, pain, touch, vibration via dorsal columns, spinothalamic tract).
Ventral posterior nucleus, lateral part (VPL) – of thalamus
Ventral posterior nucleus, medial part (VPM) – of the thalamus
(hint: you put M akeup on your face, and sensory info is relayed through the VPM ) Area of thalamus responsible for facial sensation (via CN V)
Area of thalamus responsible for facial sensation (via CN V)
Ventral posterior nucleus, medial part (VPM) – of the thalamus (hint: you put M akeup on your face, and sensory info is relayed through the VPM )
Motor and sensory locations in the thalamus
Motor is anterior to sensation in the thalamus, just like the cortex.
Limbic system: Includes what? Responsible for what?
Includes cingulate gyrus, hippocampus, fornix, and mammillary bodies. Responsible for F eeding, F leeing, F ighting, F eeling, and sex (….) (The famous 5 F’s )
Input to the cerebellum
Receives contralateral cortical input via middle cerebellar peduncle and ipsilateral proprioceptive information via inferior cerebellar peduncle. Input nerves = climbing and mossy fibers.
Output from the cerebellum
Provides stimulatory feedback to contralateral cortex to modulate movement. Output nerves = Purkinje fibers output deep to nuclei of cerebellum, which in turn output to cortex via superior cerebellar peduncle.
Deep nuclei of the cerebellum
Lateral to medial: D entate, E mboliform, G lobose, F astigial (“D on’t E at G reasy F oods”)
Lateral cerebellum
area of the cerebellum responsible for voluntary movement of extremities
area of the cerebellum responsible for voluntary movement of extremities
Lateral cerebellum
Medial cerebellum
Area of cerebellum responsible for balance, truncal coordination.
Area of cerebellum responsible for balance, truncal coordination.
Medial cerebellum
Basal ganglia (overall function)
Important in voluntary movements and making postural adjustments. Receives cortical input, provides negative feedback to cortex to modulate movement.
Important in voluntary movements and making postural adjustments. Receives cortical input, provides negative feedback to cortex to modulate movement.
Basal ganglia (overall function)
Excitatory pathway of the basal ganglia
Substantia Nigra pars compacta’s (SNc’s) dopamine binds to D1 receptros in the excitatory pathway, stimulating the excitatory pathway (incr motion). Therefore, loss of dopamine in Parkinson’s inhibits the excitatory pathway (decr motion).
Cortex ->(+) Caudate/Putamen -> (-) GPi -> (-) VA/VL thalamus -> (+) Cortex
Key: Grey = stimulatory || Black = inhibitory SNc = Substantia nigra pars compacta GPe = Globus pallidus externus GPi = Globus pallidus internus STN = Subthalamaic nucleus D1 = Dopamine D1 receptor (excitatory) D2 = Dopamine D2 receptor (inhibitory)
Inhibitory pathway of the basal ganglia
SNc’s dopamine binds to D2 receptros in the inhibitory pathway, inhibiting the inhibitory pathway (incr motion). Therefore, loss of dopamine in Parkinson’s dz excites (i.e., disinhibits) the inhibitory pathway (decr motion).
Cortex -> (+) Caudate/Putamen -> (-) GPe/subthalamic nucleus -> (-) GPi -> (-) VA/VL thalamus -> (+) Cortex
Key: Grey = stimulatory || Black = inhibitory SNc = Substantia nigra pars compacta GPe = Globus pallidus externus GPi = Globus pallidus internus STN = Subthalamaic nucleus D1 = Dopamine D1 receptor (excitatory) D2 = Dopamine D2 receptor (inhibitory)
Parkinson’s disease. Clinical Presentation, Histologic findings, Drug-related
Degenerative disorder of CNS associated w/ Lewy bodies (composed of alpha-synuclein) and depigmentation of the substantia nigra pars compacta (loss of dopaminergic neurons).
Rare cases have been linked to exposure to MPTP, a contaminant in illicit street drugs.
(“TRaP = T remor (at rest), cogwheel Rigidity, a nd Postural instability. You are TRaPped inside your body.”)
Degenerative disorder of CNS associated w/ Lewy bodies (composed of alpha-synuclein) and depigmentation of the substantia nigra pars compacta (loss of dopaminergic neurons). Rare cases have been linked to exposure to MPTP, a contaminant in illicit street drugs. (“TRaP = T remor (at rest), cogwheel R igidity, a nd P ostural instability. You are TRaP ped inside your body.”)
Parkinson’s disease
Hemiballismus. Classic Presentation, Etiology
Sudden, wild flailing of 1 arm. Characteristic of contralateral subthalamic nucleus lesion. Loss of inhibition of thalamus through globus pallidus. (“Hemiballismus = Half ballistic – like throwing a baseball”)
Cerebral cortex: Where is the primary auditory cortex (Heschel’s gyrus)? The primary motor area? The primary sensory area? The premotor area (part of extrapyramidal circuit)?
Homonculus: What is it? What is it used for? What reaches into the Sylvian fissure? The longitudinal fissure?
Topographical representation of sensory and motor areas in the cerebral cortex. Used to localize lesion (e.g., in blood supply) leading to specific defects. For example, lower extremity deficit in sensation or movement indicates involvement of anterior cerebral artery.
Anterior cerebral artery: what areas of cortex does it supply?
Supplies anteromedial surface of brain
What normally regulates cerebral perfusion? What regulates cerebral perfusion in severe hypoxia?
Normally driven by P CO2, but also by P O2 with severe hypoxia. Therapeutic hyperventilation (decreased P CO2 helps decrease ICP in cases of acute cerebral edema (stroke, trauma)
Watershed zones of the circle of Willis
Between anterior cerebral/middle cerebral, posterior cerebral/middle cerebral arteries. Damaged in severe hypotension –< upper leg/upper arm weakness, defects in higher-order visual processing.
Berry aneurysms: Where do they occur? What is the most common complication?
Occur at the bifurcations in the circle of Willis. Most common site is bifurcation of the anterior communicating artery. Rupture (most common complication) leads to hemorrhagic stroke/subarachnoid hemorrhage.
Epidural hematoma
Rupture of middle meningeal artery (branch of maxillary artery), often secondary to fracture of temporal bone. Lucid interval. CT shows “biconvex disk” not crossing suture lines. Can cross falx, tentorium.
Subdural hematoma
Rupture of bridging veins. Venous bleeding (less pressure) with delayed onset of Sx’s. Seen in elderly individuals, alcoholics, blunt trauma, shaken baby. Crescent-shaped hemorrhage that crosses suture lines. Cannot cross falx, tentorium.
Subarachnoid hemorrhage
Rupture of aneurysm (usually berry aneurysm) or an AVM. Pts complain of “worst headache of my life.” Bloody or yellow (xanthochromic) spinal tap. 2-3 days afterward, there is a risk of vasospasm (Tx w/ Ca2+ channel blockers).
Parenchymal hematoma
Caused by HTN, amyloid angiopathy [see below], DM, and tumor. Typically occurs in basal ganglia and internal capsule.
Dural venous sinuses: Where do they run? What is the sequence?
Venous sinuses run in the dura mater where its meningeal and periosteal layers separate. Cerebral veins –> venous sinuses –> internal jugular vein
Where is CSF made? Where is reabsorbed?
CSF is made by ependymal cells lining the ventricles; it is reabsorbed by venous sinus arachnoid granulations.
Normal pressure hydrocephalus. Symptoms and Etiology.
“Wet, wobbly and wacky”. Does not result in increased subarachnoid space volume. Expansion of ventricles distorts fibers of corona radiatia and leads to clinical traid of dementia, ataxia and urinary incontinence (reversible cause of dementia in elderly).
How are the dorsal columns of the spinal cord organized?
Medially: fasciculus gracilis (lower body, extremities) Laterally: fasciculus cuneatus (upper body, extremities) (“Dorsal column is organized as you are, with hands at sides. Arms outside, legs inside.”)
