NeuroAnatomy Flashcards
Meningiocele
A meningocele is a birth defect where there is a sac protruding from the spinal column. The sac includes spinal fluid, but does not contain neural tissue. It may be covered with skin or with meninges (the membranes that cover the central nervous system).
Meningocele vs myelomeningocele?
In meningocele, the sac may be covered by a thin layer of skin. In most cases of myelomeningocele, there is no layer of skin covering the sac and an area of abnormally developed spinal cord tissue is usually exposed.
rabies symptoms
emotional, hippocampus - 3 weeks after bite, bouts of terror and rage
how travel?
fast retrograde transport,
Several weeks later, he developed profound changes in his emotional state and suffered from bouts of terror and rage. A clinician who examined the young man suspected that the raccoon that bit him was rabid, and the rabies virus had affected his hippocampus.
different types of neurons
pseudoneurons
sense blood pressure changes - vagus(nodose) and glossophyngieal ganglia -
Pseudo-unipolar neurons in the nodose ganglion sense systemic blood pressure changes
and
Dorsal root ganglia
pseudo-unipolar neurons, a single axon arising from the cell body divides into two branches. One of the branches terminates as fine endings that serve as peripheral receptors, whereas the other branch terminates on neurons in the central nervous system (CNS).
The peripheral nerve endings of the pseudo-unipolar neurons located in the nodose (vagus nerves) and petrosal (glossopharyngeal nerves) ganglia terminate in the vascular walls of the carotid sinus and aortic arch and sense blood pressure changes. Signals received from the vascular nerve endings are transmitted to the CNS for making appropriate adjustment in the systemic blood pressure.
Other pseudo-unipolar neurons lie in the dorsal root ganglia.
Golgi neurons, multipolar?
Golgi 1 - long axon
Golgi 2 - short
A Golgi I (or Golgi type I) neuron is a neuron which has a long axon that begins in the grey matter of the central nervous system and may extend from there. It is also known as a projection neuron. They include the neurons forming peripheral nerves and long tracts of brain and spinal cord.
Golgi type I neurons have relatively long axons, whereas Golgi type II neurons have relatively short axons.
Multipolar neurons (e.g., motor neurons in the anterior horn of the spinal cord) have several dendrites and one long axon arising from the cell body.
grey matter in brain?
inside or outside?
Grey matter is mainly located on the surface of the brain - white matter buried deep. The spinal cord is arranged in the opposite way, with grey matter found deep inside its core and the insulating white matter wrapped around the outside.
Grey matter contains most of the brain’s neuronal cell bodies. The grey matter includes regions of the brain involved in muscle control, and sensory perception such as seeing and hearing, memory, emotions, speech, decision making, and self-control.
axon hillock
no Nissl - therefore -no protein synthesis
Nissl substance consists of RNA
Nissl material, is a large granular body found in body of neurons. These granules are of rough endoplasmic reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis.
The axon hillock is located at the end of the soma and controls the firing of the neuron. If the total strength of the signal exceeds the threshold limit of the axon hillock, the structure will fire a signal (known as an action potential) down the axon.
axon hillock special properties?
portion of the soma from which the axon arises
The axon hillock and initial segment have a number of specialized properties that make them capable of action potential generation, including adjacency to the axon and a much higher density of voltage-gated ion channels than is found in the rest of the cell body.
cut arm - what happens?
Small, angulated muscle fibers
denervation atrophy of skeletal muscle appears as small muscle fibers with decreased cross-sectional area, which are angulated or triangular and arranged in small groups
After transection of a peripheral nerve, degeneration of the distal nerve section begins almost immediately. Wallerian degeneration (also called anterograde degeneration) refers specifically to the process whereby nerve fibers (generally the axon) distal to the site of transection undergo swelling, appear irregularly shaped, and lose their myelin (as depicted in image A). This is due to the loss of connection with the soma, which is the source of metabolic nourishment. Retrograde degeneration, proximal to the axonal injury, results in peripheral displacement of the nucleus, dissolution of Nissl bodies, and enlargement of the cell body. This is known as the axonal reaction, or chromatolysis.
can nerve regeneration occur in PNS? CNS?
PNS only
Degenerative myocytes ?
Gower sign (a pattern of using upper extremities to rise from the ground r
duchenne’s
with interstitial fibrofatty infiltrate corresponds to Duchenne muscular dystrophy (DMD), an X-linked muscular dystrophy that is often associated with Gower sign (a pattern of using upper extremities to rise from the ground rather than lower extremities) and pseudohypertrophy of the calves.
“ragged-red” fibers in disarray with mitochondrial changes, some described as “parking-lot” inclusions because of crystalline deposits seen intracellularly.
Mitochondrial myopathies are debilitating and often lethal conditions that manifest with weakness and other syndromic abnormalities, based on the underlying pathologic changes.
polymyositis, dermatomyositis.
Transfascicular and intracellular CD8+ mediated inflammation corresponds to polymyositis, an autoimmune condition with features similar to dermatomyositis. Endomysial inflammation involving CD8+ T-lymphocytes can be seen on histologic examination.
chromatolysis?
Retrograde degeneration, proximal to the axonal injury, results in peripheral displacement of the nucleus, dissolution of Nissl bodies, and enlargement of the cell body.
Deenervation of muscle fibers?
As a result of denervation, skeletal muscles undergo atrophy. Microscopically, denervation atrophy of skeletal muscle appears as small muscle fibers with decreased cross-sectional area, which are angulated or triangular and arranged in small groups (circled in image B).
BBB?
sometimes you want a drug to get by - such as if you have ALL - boys age 2 - 5 - Acute lymphoblastic leukemia
Medications requiring adequate CNS bioavailability therefore require intrathecal delivery to achieve a therapeutic level locally. Methotrexate (along with cytarabine and prednisone) can be administered intrathecally as CNS chemopreventive therapy in patients with ALL.
it is formed by 3 structures: astrocyte foot processes, basement membrane, and tight junctions between nonfenestrated capillary endothelial cells.
brain glial cells
Ependymal cells produce CSF. neuroectoderm
Microglia are the CNS’s macrophages. - mesoderm
Oligodendrocytes myelinate CNS neurons. - neuroectoderm
Schwann cells myelinate neurons of the peripheral nervous system. neural crest
Intrathecal injection?
Intrathecal administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF) and is useful in spinal anesthesia, chemotherapy, or pain management applications.
Astrocytes - protect BBB and?
Repair
Glial scar - gliosis (walling off of absess)
GFAP - if see this - know tumor is in astrocyte -
iquefactive necrosis created by microglia
provide structural support to the brain parenchyma. Days to weeks after cerebral infarction, astrocytes are activated and extend processes to surround the area of liquefactive necrosis, forming a glial scar. This phenomenon is known as gliosis and is analogous to the role of fibroblasts in walling off an abscess. Unlike fibroblasts, however, astrocytes do not secrete collagen, and it is the cytoplasmic processes themselves that provide structural support. Astrocytes are also involved in potassium metabolism and maintain the blood-brain barrier. They are the primary repair and support cells of the central nervous system (CNS), and they stain for glial fibrillary acidic protein (GFAP).
Microglia? Mesoderm
they migrate to areas of tissue damage to help clear away dead and dying cells. They also release cytokines that stimulate the immune system to respond to the area of injury. HIV-infected microglia fuse to form multinucleated giant cells.
Microglia are the macrophages of the central nervous system and produce the liquefactive necrosis cavities.
mesoderm of CNS?
microglia and the dura mater and the connective tissue of the peripheral nervous system (endo-, peri-, and epineuria).
endoderm?
The endoderm gives rise to the epithelial lining of the gastrointestinal tract, urogenital system, and respiratory tract. The majority of the gastrointestinal system, including the pancreas and liver, is endodermal in origin.
Neural crest ?
Neural crest cells give rise to several tissues of the nervous system, including peripheral ganglia, afferent sensory nerves (dorsal root), and Schwann cells.
The neuroectoderm
gives rise to the central nervous system neurons, most of the CNS glial cells (including oligodendrocytes, astrocytes, and ependymal cells), the posterior pituitary, and the pineal gland.
The surface ectoderm
is an embryologic structure that gives rise to the lens of the eye, epidermis, and the anterior pituitary.
HIV and the brain
microglia - multinucleated giant cells
HIV encephalopathy is caused by infection of macrophages and microglia in the brain.
neurons themselves are rarely infected in HIV.
HIV is not known to infect oligodendrocytes.
The histologic hallmark of HIV encephalopathy is the microglial nodule,
Microglia are macrophages of the central nervous system that, like other tissue macrophages, arise from monocytes in the bone marrow and migrate to their resident tissue site. It is postulated that HIV is carried into the brain by infected monocytes. Neurons themselves are not infected by HIV, although they may be damaged by inflammatory responses to viral products. The histologic hallmark of HIV encephalopathy is the microglial nodule, largely consisting of multinucleated giant cells (indicated by the arrow in the vignette image), which are formed by the fusion of HIV-infected microglial cells (shown in this image).
oligodendrocytes - JC virus
JC virus is a human polyomavirus that infects oligodendrocytes after it becomes reactivated. JC virus is often acquired in childhood and remains latent within most adults in the kidneys and lymphoid organs. However, if the immune system becomes severely compromised, such as in late stages of AIDS, JC virus can become reactivated, resulting in progressive multifocal leukoencephalopathy (PML), which leads to lysis of oligodendrocytes. Since oligodendrocytes are the myelin-producing cells within the central nervous system, their destruction by JC virus causes an appearance of small foci of demyelination within the subcortical white matter. Seizures, ataxia, aphasia, hemiparesis, or sensory deficits are common manifestations.
Nodes of Ranvier
voltage gated potassium channels?
Nodes of Ranvier are gaps in the myelin sheath that occur along myelinated axons. In between the nodes, ionic current is conducted via the axonal cytoplasm, as resistance to current flow is lower across the cell membrane than it is across myelin.
Here the current activates voltage-gated sodium channels in the membrane, allowing ions to flow into the cytoplasm and boost the propagating depolarizing signal. The repolarization phase is facilitated by the activation of voltage-gated potassium channels, resulting in outflow of potassium. Increased capacitance and decreased resistance at the nodes of Ranvier alter the action potential and result in this “jumping” of the action potential from one node to another, known as saltatory conduction.
The nodes of Ranvier are sites of high membrane capacitance relative to the myelinated axon segments. The higher membrane capacitance facilitates rapid action potential propagation.
Guillain-Barré syndrome
Campylobacter jejuni
is a common cause of gastroenteritis, the most common pathogen associated with Guillain-Barré syndrome. Cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae, and recent immunizations are also risk factors.
Guillain-Barré syndrome is an autoimmune disease mediated by T lymphocytes that target Schwann cells
ascending paralysis and decreased deep tendon reflexes
Most cases occur 2–4 weeks after a respiratory or gastrointestinal infection.
thought to occur because of immune responses against nonself-antigens that are misdirected toward the host (molecular mimicry).
Guillain-Barré syndrome
Campylobacter jejuni
is a common cause of gastroenteritis, the most common pathogen associated with Guillain-Barré syndrome. Cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae, and recent immunizations are also risk factors.
sudden-onset paralysis, which has progressed from her legs to her arms and face. This, combined with her diminished reflexes
Guillain-Barré syndrome is an autoimmune disease mediated by T lymphocytes that target Schwann cells
ascending paralysis and decreased deep tendon reflexes
Most cases occur 2–4 weeks after a respiratory or gastrointestinal infection.
thought to occur because of immune responses against nonself-antigens that are misdirected toward the host (molecular mimicry).
decreased vibratory sense in the feet. - callouses, lack of sense of vibration
Diabetes
Pacinian corpuscles are damaged. These receptors are mainly involved in perception of pressure, coarse touch, high-frequency vibration, and tension. They are often damaged in patients with diabetic neuropathy. Pacinian corpuscles are large, ovoid receptors, 1–2 mm long × 0.1–0.7 mm in diameter, and are found primarily in deeper layers of the skin, at joint capsules, serous membranes, and mesenteries.
Several mechanisms are involved in the pathophysiology of this condition. However, microvascular disease appears to be the most prominent contributor.
normal aging can cause
78 yo -gait instability, decreased speed of postural reflexes, and slowed reaction times. Vibration sensation is diminished. Six months later, he dies in an automobile accident. An autopsy reveals a loss of neurons, especially in the frontal and temporal lobes, the presence of neurofibrillary tangles, enlarged and calcified arachnoid granulations, and enlarged ventricles. Which of the following is most consistent with the history and autopsy findings?
The brain undergoes changes in gross appearance as well as cellular and molecular composition during the aging process. There is a progressive loss of neurons from the seventh decade on, with significant loss of small neurons of layers II and IV in the frontal and superior temporal regions. Neurofibrillary tangles, senile plaques, and calcified arachnoid granulations can all be seen in normal aged brain. Neurologic findings can include a decrease in the rate and strength of motor activity as well as a slowed reaction time. Vibration sensation diminishes. There appears to be a decline in cognitive function and memory, although not all elderly individuals exhibit such changes. However, many aspects of mental decline once viewed as part of normal aging are now believed to reflect underlying pathologies.
blocking potassium channels causes?
Drug A induces seizure activity in neurons. At rest, the membrane potential of these neurons is-68 mV. Application of drug A causes these neurons to depolarize to-55 mV. Which of the following is the most likely mechanism of action of this drug?
Select one:
a. Open CI- channels
b. Block Ca2+ channels
c. Block K+ channels Correct
d. Block Na+ channels
depolarization
any increase in K+ conductance serves to move the membrane potential from-68 mV to a value closer to-90 mV, and any decrease in K conductance will move membrane potential in the other direction, that is, to a value more positive than-68 mV.
increase of extracellular K+ - hyperpolarize or depolarize?
Increasing extracellular [K+] decreases the concentration gradient driving K+ out of neurons
The result is that the opposing electrical gradient for K+ at equilibrium also decreases, that is, equilibrium potential for K+ becomes less negative. The major determinate of membrane potential at rest is K+ ion flux. As equilibrium potential for K+ becomes more depolarized, resting membrane potential also becomes more depolarized.
Vincristine - chemotherapy med
Disruption of the neuronal cytoskeleton
nerve was crushed in the distal one third of the finger. Which of the following is most likely?
Within a day, Schwann cells will begin to break down myelin of the axon distal to the lesion.
Nucleus
= group of neuronal cell bodies united by similar functions
Tract = many axons grouped together, pass from a given nucleus
periferal nervous system includes what structures in the brain?
PNS includes Cranial and spinal nerves outside the CNS - one exception – optic nerve – it is very different from others, as is olfactory -
spinal cord
Spinal cord: 5 regions: Cervical cord (8 pairs of spinal nerves) Thoracic cord (12 pairs of spinal nerves) Lumbar cord (5 pairs of spinal nerves) Sacral cord (5 pairs of spinal segments)
2 enlargements of the spinal cord:
Cervical enlargement – brachial plexus
Lumbar enlargement - lumbar and sacral plexus
CNS -
Brainstem + Cerebellum + Cerebral Hemispheres
= Brain
Brainstem:
3 divisions:
Medulla (continuous with the spinal cord)
Pons (rostral to the medulla)
Midbrain (continuous with the diencephalon)
Cerebellum:
Dorsal to the pons
Attached to the the brainstem by peduncles
peduncles?
Cerebellum:
Dorsal to the pons
Attached to the the brainstem by peduncles
a large bundle of neurons that resembles a large stalk (the Latin pedunculus means “footstalk”) and stretches from the cerebrum to the pons. There are two cerebral peduncles, one on each side of the brainstem.
3 motor cortex areas?
primary (area 4) - least electrical current required
premotor (dancing)
suuuplementary (initiates)
prefrontal cortex
psychiatrists work here
judments - intellectual, emotional events
location of frontal eye field? voluntary horizontal eye movement HY
middle frontal gyrus gyrus extending into the inferior frontal gyrus and immediately rostral (IN FRONT OF) to the premotor region
ORBITAL gyrus - if you lose it - you lose your orbit - you become mean, disinhibited
disinhibits you - angry, aggressive
orbital gyrus INHIBITS - with out it one is uninhibited - a Mean Mo Fo
Broca’s speech area - Only in dominant (usually left) hemisphere
comprehension intact - hard to name objects, repeat words
Communication (speech) difficult - even gesturing or sign language
within inferior frontal gyrus
Difficulty in naming objects
Difficulty in repeating words
Comprehension is intact
– most aspects of speech – controls larynx, pharynx working together – “speech” means communication – if someone is using sign language and had never been able to speak – if he has a stroke – and trauma to Broca’s area – this person would also be affected –
deaf person who signs has damage in broca’s error - is there ability to communicate affected?
Yes. comprehension intact
Broca’s speech -
skip words “I doctor”
Aphasia
Aphasia – absence of speech – can’t name objects – Alzheimer’s can tell you how to use the object, but can’t name it.
insula - PAIN processing (not where first received), TASTE, Disgust
It tastes painfully Disgusting
Seen only when temporal lobe is pulled away
Lies within the depths of the lateral (Sylvian) sulcus
Convergence of temporal, parietal and frontal cortices
under temportal - disgusting area - smells, tastes, moral disgust
Reception and integration of taste sensation
Reception of viscerosensations
Processing of pain sensations
Vestibular functions
parietal lobe - mainly sensory
from central sulcus extends caudally to parietal occipital sulcus – imaginary line – only visible on medial surface of hemisphere
Post central gyrus - receives PAIN and TEMP sensations -
Somatotrpic organization – any person will experience sensations in a particular area -
lots of info received here – than transported to frontal cortex for analysis
Postcentral gyrus: PAIN, TEMPERATURE – receives info
Boundaries:
Anteriorly: Central Sulcus
Posteriorly: Postcentral Sulcus
Functions:
Primary receiving area for somesthetic (i.e., kinesthetic and tactile) information
Input is contralateral
Somatotopic organization (parallel to the motor cortex)
somatotopically organized /. As the stimulating electrode is moved across the precentral gyrus from dorsomedial to ventrolateral, movements are elicited progressively from the torso, arm, hand, and face (most laterally).
Parietal lobe - 3 parts
post central gyrus
Superior Parietal
Inferior Parietal 2 parts
Supramarginal gyrus:
Boundaries: superior to the posterior extent of the lateral sulcus
Angular Gyrus:
Boundaries: posterior to the supramarginal gyrus
Functions:
Input from auditory and visual cortices
Complex perceptual discriminations
superior - color and motor integration
processes info - sends to frontal
Job is to collect sensory info and pass to prefrontal cortex-
Integrates sensory and motor functions Aids in programming complex motor functions (with premotor cortex) Lesion: Apraxia (movement disorder) Sensory neglect (eg, left hemineglect)
Lesions in superior parietal?
Apraxia
Sensory neglect = contralateral
Lesion:
Apraxia (movement disorder)
Sensory neglect (eg, left hemineglect)
Sensory neglect
will show contralaterally – eg – see patient with a stroke – “someone stole my wedding ring” – show her her hand – and she says OK – I have my ring – but in a few minutes again – forgets about it – thinks it isn’t there – not that they are blind – they just don’t pay attention -
or perceptual neglect (including: auditory neglect, visual neglect and spatial neglect) is an impaired ability to perceive objects, so individuals do not attend to visual, auditory, or sensory stimuli coming from one side of the body. This may be caused by brain damage due to various causes.
apraxia - can move but not do complex movements - can’t hammer a nail
often see w/ Alzheimer’s
Inferior parietal lobe
– complex perceptual discriminations – eg – newborn baby – 7 days old – this area will react differently to music and human speech – already – only learned about these parts of the brain in the last 30 years
2 parts
Supramarginal gyrus:
Boundaries: superior to the posterior extent of the lateral sulcus
Angular Gyrus:
Boundaries: posterior to the supramarginal gyrus
Functions:
Input from auditory and visual cortices
Complex perceptual discriminations
Wernicke’s only in left hemisphere
if lesion - person won’t understand what is being said, what being asked –
Speech still fluent - but can’t understand
for understanding communication – only in left hemisphere – comprehension of spoken language and communication – if lesion - person won’t understand what is being said, what being asked –
where is wernicke’s located?
superior temporal gyrus + ventral parts of supramarginal and angular gyri
so if Broca’s intact and Wernicke not
Lesion (aka Wernicke’s [sensory]) aphasia):
Impairment of speech comprehension and repetition
Speech remains fluent -> Broca’s center is intact
can’t understand what being asked
in real life, see these two together a lot - but for exams need to know diff
Temporal lobe 3 guri - but a fourth area inside - mainly responsible for HEARING - 3 gyru
Heschl gyrus (on internal aspect)
Superior temporal gyrus
Middle temporal gyrus
Inferior temporal gyrus
temporral lobe functions
hearing (superior and Herschl) located on INSIDE
see moving objects (middle)
recognize faces - inferior
Functions:
Perception of auditory signals (primary auditory cortex, superior temporal gyrus + gyri of Heschl)
Perception of moving objects in the visual field (middle temporal gyrus)
Recognition of faces (inferior temporal gyrus)
Occipital - eyes in the back of your head - visual
Interpretation of the visual information
larger portion visible from medial surface
From eye – whatever you see – travels all the way back here and then goes back to prefrontal cortex
medial surface of brain
frontal, parietal, occipital
Paracentral - controls LOWER EXTREMITIES
paracentral -
continuation of the precentral and postcentral gyri on the medial side:
controls motor and sensory innervations of the contralateral lower extremity
– normal pressure hydrocephalus – IMPORTANT this area of brain, and disease
occipital lobe from medial aspect
Function: Visual receiving area (primary)
Anteriorly: Parietal-occipital sulcus (border with parietal lobe) Calcarine sulcus (fissure) - perpendicular to parietal-occipital sulcus, in the middle of the occipital lobe
Calculine sulcus
– very important area
– where initially all visual info comes
Cingulate Gyrus: limbic system (a part of)
above CORPUS COLOSUM
quick decisions, Empathy, compassion
where some of your emotions are controlled
quick fast decisions?
overreaction?
probably made by limbic not frontal cortex
Quick decisions made mostly by limbic decisions (running away from a rabid dog) – sometimes if too much stress, etc – limbic makes decisions for you - over-reaction – probably made by limbic and not frontal cortex
corpus colosum? Massive fiber pathway
Communication between hemispheres
Massive fiber pathway – all the grey matter above the corpus - corpus callosum is the white matter – connecting everything
Septum Pellucidum:
Forms medial wall of lateral ventricles
2 thin-walled membranes with cavity between them (cavity of septum pellucidum)
Boundaries:
Ventral: corpus callosum
Fornix - seahorse?
key role in cognition and episodic memory recall.
Transmission from hippocampal formation to the septal nuclei and hypothalamus
The fornix is a white matter bundle located in the mesial aspect of the cerebral hemispheres, which connects various nodes of a limbic circuitry and is believed to play a key role in cognition and episodic memory recall.
Hippocampus
- memory skills
need to sleep to develop memory
Amygdala
emotional map of your brain – fear of heights, spiders, all in the amygdala – aversion center –
The amygdala is recognized as a component of the limbic system, and is thought to play important roles in emotion and behavior. It is best known for its role in the processing of fear,
The amygdala is an almond-shaped structure in the brain; its name comes from the Greek word for “almond”. … Each amygdala is located close to the hippocampus, in the frontal portion of the temporal lobe. Your amygdalae are essential to your ability to feel certain emotions and to perceive them in other people.
Diencephalon:
Thalamus one of main centers – collects all sorts of info – major electric substation - the only system that can bypass this ? Olfactory!
Hypothalamus – controls all glands and smooth muscles – horner’s syndrome – Pancoast tumor –
KING Of autonomic system – any lizard will function similar to humans -
Below fornix
Structures in diencephalon:
Thalamus:
Sensory, motor, autonomic and emotional information passes through thalamus (↕ )︎
Hypothalamus:
Anterior and below thalamus
Visceral functions (t0, endocrine, feeding, drinking, emotional, sexual)
Hypophysis is attached to hypothalamus
inferior surface of brain structures
gyrus rectus (not clear function
Thought to be involved in higher cortical functions (esp. personality features)
lateral to this is the olfactory bulb and tract
Olfactory bulb:
Boundaries: lateral to gyrus rectus
Function: receive information from olfactory nerve (CNI)
Olfactory tract:
Boundaries: continuation of the tract from olfactory bulb
Branches:
Lateral (-> temporal lobe and limbic system)
Medial (-> limbic structures medially and contralaterally via anterior commissure)
Occipitotemporal gyrus
(aka fusiform gyrus):
Boundaries:
Medially: collateral sulcus
Laterally: inferior temporal sulcus
Function:
Not fully understood
Thought to be involved into recognition processes
Parahippocampal gyrus:
UNCUS - HOOK - brain edema - can kill you
In general – recognizes letters -
Memory encoding and retrieval
Boundaries:
Laterally: collateral sulcus
Inferiorly: lingual gyrus
Rostral part has a bulging – uncus
UNCUS – HOOK very important – brain edema – can affect uncul herniation and kill you -
Function:
Memory encoding and retrieval
Many of these regions are highly variabile from one person to another – so hard to test on re tests – gyru take on different forms, shapes
In general – recognizes letters -
Uncal herniation -
most common place of supratentorial herniation
Hippocampal formation and amygdala are situated deep to the cortex of the parahippocampal gyrus and uncus.
seizures in temporal lobe epilepsy.
Structures in this area (on this slide) have a very low threshold for induction of seizure activity and commonly the focus of the seizures in temporal lobe epilepsy.
Lingual gyrus: LOGIC
Vision processing (esp. letters) Analysis of logical conditions (eg, logical order of events)
Boundaries:
Rostrally: parahippocampal gyrus
Laterally: collateral sulcus
Medially: isthmus of cingulate gyrus + apex of cuneus
Function:
Vision processing (esp. letters)
Analysis of logical conditions (eg, logical order of events)
CT scans - hyperdense -
very white +1000 hyperdense bone…. blood (denser - lighter)
zero - water
very black -1000 hypodense air
isodense - tissue damage, appears basically the same as the surrounding brain,
Bone in CT: greatly attenuates x-rays
high CT number (appears white)
acute subarachnoid hemorrhage in CT is hyperdense (appearance similar to bone = whiter than surrounding brain)
Air in CT poorly attenuates x-rays
has a low CT number (appears black)
Area of ischemia (low O2 supply)
Hypodense (appearance shifted toward that of air) darker than the surrounding brain
When the lesion, or tissue damage, appears basically the same as the surrounding brain, it is specified as isodense
Would blood every look hyperdense on CT? YES! blood is dense - Hyperdense
vs air is not dense “hypodense”
infaract - lacking blood - thus darker
What does infarct in the brain mean?
Infarction refers to death of tissue. A cerebral infarction, or stroke, is a brain lesion in which a cluster of brain cells die when they don’t get enough blood.
Enhanced CTs - vasculature, iodine contrast
Iodinated contrast material injected intravenously
Iodine has a large atomic number and attenuates x-rays
Followed by CT examination
Vasculature is visualized as hyperdense (white) structures
Enhances neoplasms or areas of inflammation
contrast agent leaks from the vessels into the cellular spaces
Possible only if blood-brain barrier is broken down
Tumors, inflammation show varying degrees of enhancement or hyperdensity (varying degrees of whiteness)
3 major roles for CT - 3 H
hemorrage
hydrocephalus
herniation
MRIs
When undergoing an MRI examination
the patient becomes a magnet
all the protons align along the external magnetic field and spin at an angle with a certain frequency
MRIs in many flavors - many - know T1 and T2 - time function
T1 - spin lattice, white (matter INSIDE) bright, CSF dark, most lesions dark
T2 - spin spin = grey matter bright - CSF BRIGHT, most lesions bright
notes re MRI
Note!
Acute subarachnoid hemorrhage is poorly imaged by MRI on T1-weighted images
Some MRI sequences are sensitive for detection of acute bleeding, but other factors may limit this method of examination
Special MRI techniques can also determine if a brain infarct or ischemia is acute (about 1 to 3 hours old) or subacute (about 4 hours old or more)
Coronal scans =
viewed as though the clinician is facing the patient.
CT windows
Brain window – best for visualizing the brain structures
Subdural window – density of acute blood is visualized better than the brain structures
Stroke window – poor view on peripheral structures, better white/gray matter contrast
Bone window – visualizing bones
CT vs MRI
CT - more bone details, less tissue
BBB - do contrasts in blood get into brain?
not normally, but IF BBB broken will see that in CT with contrast
iodine as contrast?
Iodine is more dense than most tissue – greater attenuation
Early injection – assess vessels
Later injection – assess disruption of BBB
Complete injection – assess perfusion
reasons to not do CT
MRI can be tough on people with Kidney problems - gadolinium reaction -
Allergic reactions:
Hives, bronchospasm, laryngospasm
Severe reactions are rare (0.004%)
Nephrotoxicity:
Acute renal failure rare
Contraindicated in diabetics, myeloma, renal failure
Incidence reduced with hydration, low-osmolality contrast
Other:
Lactic acidosis in diabetics on metformin
Pregnancy
child - not want to give radiation
perikaryon
cell body
if dendrites don’t have voltage gated channels - and can’t generate action potential - how do they send the message along?
Receives signals from other neurons
Passively integrates dendritic and somatic signals; not excitable
WHAT DOES THIS MEAN? how pass it along?
neuron soma
Contains all major types of cellular organelles
Golgi complex
Nissl substance: abundant RER and free ribosomes support remodeling (synaptic plasticity) and constant secretory function (NT release)
Dispersed nuclear chromatin, reflecting high transcriptional activity
Axon hillock
Excitable membrane (has voltage-gated Na+ channels) Particularly low threshold for action potential generation High concentration of voltage-gated Na+ channels makes hillock exquisitely sensitive to changes in membrane potential
Axon doesn’t have…
No ribosomes (vs. dendrites)
Nodes of Ranvier
are unmyelinated gaps and the only excitable region of the axon
Action potentials jump from node to node through saltatory conduction
C fibers (smallest axons)
C fibers (smallest axons) are unmyelinated
Frequently protected by “sleeves” formed by glial cells
Excitable throughout their length
Cytoskeletal elements support extended, unique morphology and demanding transport requirements
axon terminal contains what kind of voltage gated channels?
Contains voltage-gated Ca2+ channels
NO voltage-gated Na+ channels
Passive spread of depolarization from axonal action potentials opens voltage-gated Ca2+ channels
Ca2+ entry into axon terminal initiates cascade that results in neurotransmitter release
boutons en passant.
boutons are found along the length of the axon
Other axons contain swellings, orvaricosities,that are not button-like but still can represent points of cell-to-cell information transfer.
Variations on basic structure of neurons
Sensory neurons may rely on specialized elaborations or cells to transduce specific types of non-neural inputs (eg, temperature, light, vibration)
Small neurons may function without an excitable membrane
Bipolar neurons of retina rely on passive spread of electrical signals from dendrites to terminal regions
Pseudounipolar neurons: support general somatosensory input HAVE NO DENDRITES
cell bodies in dorsal root ganglia of spinal cord and trigeminal ganglion
Pseudounipolar neurons are sensory neurons that have no dendrites, the branched axon serving both functions. The peripheral branch extends from the cell body to organs in the periphery including skin, joints and muscles, and the central branch extends from the cell body to the spinal cord.
One main process extends from soma and bifurcates into peripheral and central branch; main process is formed from fusion of two processes
Primary sensory neurons in somatosensory chain, with cell bodies in dorsal root ganglia of spinal cord and trigeminal ganglion
Bipolar neurons
special senses
Do not use action potentials in retina and olfactory system because bipolar neurons are small
Use action potentials in auditory and vestibular systems, with cell bodies in inner ear and axons projecting to brainstem
Two main processes extend from soma: one detects incoming signals; the other transmits information to the next neuron
