11.3 Neurology Flashcards
Where do PNS neurons originate from embryologically?
Neural crest
Where do oligodendroglia originate from embryologically?
Neuroectoderm
Where do CNS neurons originate from embryologically?
Neuroectoderm
Where do Schwann cells originate from embryologically?
Neural crest
Where do microglia originate from embryologically?
Mesoderm
Microglia, like Macrophages, originate from the Mesoderm.
Where do astrocytes originate from embryologically?
Neuroectoderm
Where do ependymal cells originate from embryologically?
Neuroectoderm
Ependymal cells make up the inner lining of ventricles, and make CSF)
What neurological structures originate from Neural crest cells?
Schwann cells
PNS neurons
What neurological structures originate from Neuroectoderm?
CNS neurons
Ependymal cells
Oligodendrocytes
Astrocytes
What neurological structures originate from Mesoderm?
Microglia
T/F Neurons do not divide in adulthood.
True. Neurons comprise the nervous system and are permanent cells, which means they don’t divide in adults.
T/F Neurons have prominent nucleoli.
True. Neurons are large cells with prominent nucleoli.
Where is nissl substance located in neurons?
Nissl substance = RER of neurons. It is located in the cell body and the dendrites, but NOT in the axons.
What is Wallerian degeneration?
Axon injury leads to neuron degeneration, which starts at the point of injury and spreads distally.
What are astrocytes and what do they do?
Star-shaped type of glial cell. Maintain the blood-brain barrier. Provide physical support and repair, K+ metabolism, and removal of excess neurotransmitters (take up glutamate and GABA). They also regulate pH/ion balance.
Cause reactive gliosis in response to injury (repair following trauma).
What is the marker for astrocytes?
GFAP.
GFAP is also the marker for glioblastoma, since astrocytes are a type of glial cell.
What is reactive gliosis?
Repair by astrocytes following a trauma.
The astrocytes proliferate and swell, leading to fibrosis. The fibrosis forms a glial scar in place of the damaged neurons.
What are microglia?
CNS phagocytes (the macrophages of the CNS).
They are mesodermal in origin (like macrophages).
They have small irregular nuclei and little cytoplasm.
When there is tsu dmg, the microglia become large ameboid phagocytic cells.
They make cytotoxins and neurotoxins like NO and glutamine which mediate inflam.
How are microglia stained?
They are not discernable in Nissl stains- use lectin to stain them brown.
What happens when microglia become infected w HIV?
They fuse to form multinucleated giant cells in the CNS.
What are oligodendroglia?
Myelinating cells of the CNS- each oligodendroglial cell myelinates up to 30 (!) CNS axons.
These are the predominant type of glial cell in white matter.
How do oligodendroglia stain?
Nissl stain: small nuclei w dark chromatin and little cytoplasm.
H&E stain: fried eggs
What cells look like fried eggs on H&E?
Oligodendroglia
Koilocytes (HPV)
Seminoma
Schwann cells
Myelinating cells of the PNS. Each schwann cell only myelinates one axon.
Promote axonal regeneration.
Derived from neural crest.
Acoustic neuroma
Type of schwannoma, usu located in the internal acoustic meatus (CN VIII)
In what disease are there bilateral acoustic schwannomas?
NF-2
What kind of cells are destroyed by MS?
Oligodendrocytes! (of the CNS)
What pathway do responses to mechanical stimuli take to get to the brain?
Mechanical stimuli –> afferent neurons in SC –> either dorsal column/medial lemniscus or in the spinothalamic tract.
What are the types of free nerve endings?
Free nerve endings are aka Ruffini endings.
A-delta: feel pain; fast myelinated fibers (fast first pain)
C - hot/cold, blunt trauma; slow unmyelinated fibers (longer lasting dull 2nd pain)
Where are free nerve endings (Ruffini endings) located, and what senses do they transmit?
All skin, epidermis, and some viscera
Transmit pain (A-delta endings ) and temp (C endings)
Where are Meissner’s corpuscles located and what senses do they transmit?
They are large, myelinated fibers located in glabrous (hairless) skin and dermis.
Transmit position sense and dynamic fine touch (manipulation). They adapt quickly.
Where are Pacinian corpuscles located and what senses do they transmit?
Large myelinated fibers- these are the ones that look like a fingerprint.
Located in deep skin layers, ligaments, and joints. Subcutaneous.
Transmit vibration and prs.
Where are Merkel’s disks located and what senses do they transmit?
Large, myelinated fibers located in hair follicles.
Transmit position sense and static touch (sharp edges, textures). They adapt slowly.
Also sense vertical indentation into skin.
What are the peripheral nerve layers?
Endoneurium- single nerve fiber
Perineurium- permeability barrier, surrounds a fascicle of nerve fibers; must be rejoined in microsurgery for limb reattachment
Epineurium- dense CT that surrounds entire nerve (fascicles + blood vessels)
Which layer of the peripheral nerves is most difficult for drugs to cross?
Perineurium (permeability barrier)
What is the main excitatory NT of the brain?
Glutamine
What is the main inhibitory NT of the brain? What other AA does it come from, and what’s required to make it?
GABA
Glutamate –> GABA, and Vit B6 is required for this.
What is the main inhibitory NT of the SC?
Glycine
Where is NE made?
Locus ceruleus (mainly) also, reticular formation and solitary tract
Where is Dopamine made?
Ventral tegmentum and SNc
Where is 5-HT made?
Raphe nucleus
Where is ACh made?
Basal nucleus of Meynert
In what dz does the Basal nucleus of Meinert degenerate?
Alzheimer’s dz
Where is GABA made?
Nucleus accumbens
What are the parts of the Reticular Activating System and what does it do?
Reticular Formation Locus ceruleus Raphe Nuclei It mediates consciousness and attentiveness (Lesions to RAS cause coma)
What feelings are propagated by the:
Locus ceruleus?
Nucleus accumbens and septal nucleus?
LC- stress and panic
NA and SN- reward center, pleasure, addiction
NT chgs in anxiety
Increased NE
Decreased 5-HT
Decreased GABA
NT chgs in depression
decreased NE, decreased 5-HT
NT chgs in Huntington’s
decreased GABA
decreased ACh
How do ACh levels change in REM sleep?
They decrease
In what dz’s/states does NE increase?
Anxiety
Mania
Amphetamine/Cocaine use
How does dopamine chg in Parkinson’s?
It decreases
What 3 structures form the BBB?
- Tight jns bt non-fenestrated capillary endothelial cells
- BM
- Astrocyte processes
Other than the BBB, what other blood/structure barriers exist?
Blood-testis barrier
Maternal-fetal barrier (placenta)
What substances cross the BBB by carrier-mediated transport?
Glucose and AAs
they cross slowly!
What substances cross the BBB by diffusion?
Nonpolar/lipid-soluble substances
(they cross rapidly)
many anesthetics are lipid-soluble and therefore can cross. the more lipid soluble, the more potent.
What areas of the brain have no BBB, and what does this allow?
Area postrema- vom after chemo
OVLT- osmotic sensing
The regions just have fenestrated capillaries.
They allow molecules from the blood to affect brain fn, or oppositely, neurosecretory products to enter circulation (eg post pit –> ADH –> blood)
Where is the area postrema?
Caudal wall of 4th ventricle in medulla
When can the BBB be breached?
Brain tumor/neoplasm
Infection
Infarction
These destroy endothelial cell tight jns, which leads to vasogenic edema. (Edema can be seen on imaging.)
What are the functions of the hypothalamus?
TAN HATS: Thirst/water balance Adenohypophysis control Neurohypophysis rls's hormones from hypothal Hunger Autonomic regulation Temp regulation Sexual urges
What are the inputs to the hypothalamus?
OVLT (senses osmolarity chgs) Area postrema (responds to emetics)
What part of the hypothalamus makes ADH?
SON- supraoptic nucleus
ADH makes the kidneys absorb more water
What part of the hypothalamus makes Oxytocin?
PVN- paraventricular nucleus
Oxytocin causes smooth musc contraction in the uterus/breast
What does the lateral area of the hypothalamus do?
Causes hunger
If it’s destroyed, no hunger, so anorexia, FTT in infants.
What does the Ventromedial area of the hypothalamus do?
Causes Satiety.
Destruction, no satiety, so hyperphagia.
Destruction can be caused by craniophryngioma.
What effect does leptin have on the hypothalamus?
Leptin inhibits the lateral area (hunger)
Leptin stimulates the ventromedial area (satiety)
Easy to remember if you know that leptin comes from fat cells. Fat –> Leptin –> don’t eat more (suppress Lateral/hunger) + do feel full (stimulate Ventromedial/satiety)
What does the anterior hypothalamus do?
Cooling
pArasympathetic
it detects increased body temp
A/C = anterior cooling
What does the posterior hypothalamus do?
Heating
sympathetic
it conserves heat
What does the septal nucleus of the hypothalamus do?
Sexual urges
What does the SCN of the hypothalamus do?
Circadian rhythm
SCN is right about the optic chiasm.
What part of the hypothalamus regulates the PNS?
Anterior hypothal
and preoptic nuclei, which is part of the ant hypothal
What part of the hypothalamus makes ADH to regulate water balance?
SON
What part of the hypothalamus will cause hyperthermia if destroyed?
Anterior hyperthal (and preoptic nuclei) These are responsible for cooling. So no Ant hyperthal --> no cooling --> hyperthermia
What part of the hypothalamus regulates the SNS?
Posterior hypothalamus (and lateral nuclei)
What part of the hypothal gets input from the retina?
SCN
What part of the hypothal mediates oxytocin production?
PVN
What part of the hypothal is responsible for sweating and cutaneous vasodilation in hot temps?
Anterior hypothal (and preoptic) Anterior does cooling! (A/C)
Destruction of which part of the hypothal causes neurogenic DI?
SON (bc it makes ADH)
What part of the hypothal causes eating when stimulated, and starvation when destroyed?
Lateral area (mediates hunger)
Destruction of which part of the hypothal results in inability to stay warm?
Posterior hypothal (Responsible for heating)
What part of the hypothal regulates rls of gonadotropic hormomes (LH, FSH)?
Preoptic nucleus
What part of the hypothal releases hormons affecting the ant pit?
Arcuate nucleus
What part of the hypothal is responsible for shivering and decreased cutaneous blood flow in the cold?
Posterior hypothal (and lateral nuclei) Posterior does warming- these are warming activities!
If this part of the hypothalamus is destroyed, savage behvr and obesity result.
Ventromedial area (controls satiety.) No VM --> no satiety, so hyperphagia.
From where is the posterior pit derived embryologically?
Neuroectoderm.
Post pit = NEUROhypophysis, which is from the NEUROectoderm.
What are the inputs to the posterior pit?
Receives hypothalamic axonal projections from the supraoptic nuclei (ADH) and the paraventricular nuclei (oxytocin).
It releases the hormones in response to stimuli.
What are the major parts of the thalamus?
VA VL VPL VPM Pulvinar LGN MGN Anterior nuclear group Mediodorsal nucleus
What kind of info does the thalmus receive, and where does it send the info to?
Gets ascending sensory info
Relays it to the cortex
What info comes into the VPL (and via where), and where is the info sent to?
VPL = body sensation.
The spinothalamic tract carries Pain/Temp to the VPL, and
The dorsal columns (medial lemniscus) carry Prs/Vibration/Touch/Proprioception to the VPL.
The VPL sends all of these to the primary somatosensory cortex
What info comes into the VPM (and via where), and where is the info sent to?
VPM = face sensation (put Makeup on your face- vpM) The trigeminal (CN 5) and gustatory pathway carries face sensation and taste to the VPM The VPM sends this info to the primary somatosensory cortex.
What kind of info do the ventral anterior and ventral lateral thalamic nuclei receive?
VA and VL get motor info.
Note that in the thalamus, motor (VA, VL) is anterior to sensory (VPL, VPM), just as in the cortex.
What info comes into the LGN (and via where), and where is the info sent to?
The optic nerve (CN 2) sends vision info to the LGN. (lateral = light)
The LGN then projects via optic radiations to the occipital cortex (to the calcarine sulcus- this is where the primary visual cortex is located!)
What info comes into the MGN (and via where), and where is the info sent to?
The superior olive and the inferior colliculus of tectum send auditory info to the MGN. (medial = music)
The MGN sends this info to the auditory cortex of the temporal lobe.
What is the blood supply to the thalamus?
P-Comm
PCA
ICA (anterior choroidal arteries)
What part of the thalamus communicates with the prefrontal cortex? What happens if it’s destroyed?
Mediodorsal nucleus
Memory loss if destroyed
What part of the thalamus sends info from the cerebellum (dentate nucleus) and basal ganglia to the motor cortex?
VL (ventral lateral)
What part of the thalamus sends info from the basal ganglia to the prefrontal, premotor, and orbital corticies?
VA (ventral anterior)
What part of the thalamus sends info from the mamillothalamic tract to the cingulate gyrus (part of the Papez circuit)?
Anterior nucleus
What part of the thalamus integrates visual, auditory, and somesthetic inputs?
Pulvinar
What does the cerebellum do, generally?
Integrates sensory info from both brain and SC
Coordinates smooth motor mvmts
What are the input nerves to the cerebellum?
Climbing and mossy fibers
Does the cerebellum receive ipsilateral or contralateral input? From where?
Both!
Gets contralateral cortical input (via middle cerebellar peduncle)
Gets ipsilateral proprioceptive info (from the inferior cerebellar peduncle.