NeuroAnatomy

Question 1

Meningiocele

Answer 1

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).

Question 2

Meningocele vs myelomeningocele?

Answer 2

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.

Question 3

rabies symptoms

emotional, hippocampus - 3 weeks after bite, bouts of terror and rage

how travel?

fast retrograde transport,

Answer 3

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.

Question 4

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

Answer 4

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.

Question 5

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.

Answer 5

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.

Question 6

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.

Answer 6

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.

Question 7

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.

Answer 7

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.

Question 8

axon hillock special properties?

portion of the soma from which the axon arises

Answer 8

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.

Question 9

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

Answer 9

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.

Question 10

can nerve regeneration occur in PNS? CNS?

Answer 10

PNS only

Question 11

Degenerative myocytes ?

Gower sign (a pattern of using upper extremities to rise from the ground r

Answer 11

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.

Question 12

“ragged-red” fibers in disarray with mitochondrial changes, some described as “parking-lot” inclusions because of crystalline deposits seen intracellularly.

Answer 12

Mitochondrial myopathies are debilitating and often lethal conditions that manifest with weakness and other syndromic abnormalities, based on the underlying pathologic changes.

Question 13

polymyositis, dermatomyositis.

Answer 13

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.

Question 14

chromatolysis?

Answer 14

Retrograde degeneration, proximal to the axonal injury, results in peripheral displacement of the nucleus, dissolution of Nissl bodies, and enlargement of the cell body.

Question 15

Deenervation of muscle fibers?

Answer 15

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).

Question 16

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.

Answer 16

it is formed by 3 structures: astrocyte foot processes, basement membrane, and tight junctions between nonfenestrated capillary endothelial cells.

Question 17

brain glial cells

Answer 17

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

Question 18

Intrathecal injection?

Answer 18

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.

Question 19

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

Answer 19

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).

Question 20

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.

Answer 20

Microglia are the macrophages of the central nervous system and produce the liquefactive necrosis cavities.

Question 21

mesoderm of CNS?

Answer 21

microglia and the dura mater and the connective tissue of the peripheral nervous system (endo-, peri-, and epineuria).

Question 22

endoderm?

Answer 22

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.

Question 23

Neural crest ?

Answer 23

Neural crest cells give rise to several tissues of the nervous system, including peripheral ganglia, afferent sensory nerves (dorsal root), and Schwann cells.

Question 24

The neuroectoderm

Answer 24

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.

Question 25

The surface ectoderm

Answer 25

is an embryologic structure that gives rise to the lens of the eye, epidermis, and the anterior pituitary.

Question 26

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.

Answer 26

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).

Question 27

oligodendrocytes - JC virus

Answer 27

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.

Question 28

Nodes of Ranvier voltage gated potassium channels?

Answer 28

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.

Question 29

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.

Answer 29

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).

Question 30

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

Answer 30

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).

Question 31

decreased vibratory sense in the feet. - callouses, lack of sense of vibration Diabetes

Answer 31

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.

Question 32

normal aging can cause

Answer 32

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.

Question 33

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

Answer 33

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.

Question 34

increase of extracellular K+ - hyperpolarize or depolarize?

Answer 34

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.

Question 35

Vincristine - chemotherapy med

Answer 35

Disruption of the neuronal cytoskeleton

Question 36

nerve was crushed in the distal one third of the finger. Which of the following is most likely?

Answer 36

Within a day, Schwann cells will begin to break down myelin of the axon distal to the lesion.

Question 37

Nucleus

Answer 37

= group of neuronal cell bodies united by similar functions Tract = many axons grouped together, pass from a given nucleus

Question 38

periferal nervous system includes what structures in the brain?

Answer 38

PNS includes Cranial and spinal nerves outside the CNS - one exception – optic nerve – it is very different from others, as is olfactory -

Question 39

spinal cord

Answer 39

``` 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

Question 40

CNS -

Answer 40

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

Question 41

peduncles? Cerebellum: Dorsal to the pons Attached to the the brainstem by peduncles

Answer 41

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.

Question 42

3 motor cortex areas?

Answer 42

primary (area 4) - least electrical current required premotor (dancing) suuuplementary (initiates)

Question 43

prefrontal cortex

Answer 43

psychiatrists work here judments - intellectual, emotional events

Question 44

location of frontal eye field? voluntary horizontal eye movement HY

Answer 44

middle frontal gyrus gyrus extending into the inferior frontal gyrus and immediately rostral (IN FRONT OF) to the premotor region

Question 45

ORBITAL gyrus - if you lose it - you lose your orbit - you become mean, disinhibited

Answer 45

disinhibits you - angry, aggressive orbital gyrus INHIBITS - with out it one is uninhibited - a Mean Mo Fo

Question 46

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

Answer 46

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 –

Question 47

deaf person who signs has damage in broca's error - is there ability to communicate affected?

Answer 47

Yes. comprehension intact

Question 48

Broca's speech -

Answer 48

skip words "I doctor"

Question 49

Aphasia

Answer 49

Aphasia – absence of speech – can’t name objects – Alzheimer’s can tell you how to use the object, but can’t name it.

Question 50

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

Answer 50

under temportal - disgusting area - smells, tastes, moral disgust Reception and integration of taste sensation Reception of viscerosensations Processing of pain sensations Vestibular functions

Question 51

parietal lobe - mainly sensory

Answer 51

from central sulcus extends caudally to parietal occipital sulcus – imaginary line – only visible on medial surface of hemisphere

Question 52

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

Answer 52

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).

Question 53

Parietal lobe - 3 parts

Answer 53

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

Question 54

superior - color and motor integration processes info - sends to frontal Job is to collect sensory info and pass to prefrontal cortex-

Answer 54

``` Integrates sensory and motor functions Aids in programming complex motor functions (with premotor cortex) Lesion: Apraxia (movement disorder) Sensory neglect (eg, left hemineglect) ```

Question 55

Lesions in superior parietal? Apraxia Sensory neglect = contralateral

Answer 55

Lesion: Apraxia (movement disorder) Sensory neglect (eg, left hemineglect)

Question 56

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 -

Answer 56

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.

Question 57

apraxia - can move but not do complex movements - can't hammer a nail

Answer 57

often see w/ Alzheimer's

Question 58

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

Answer 58

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

Question 59

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

Answer 59

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 –

Question 60

where is wernicke's located?

Answer 60

superior temporal gyrus + ventral parts of supramarginal and angular gyri

Question 61

so if Broca's intact and Wernicke not

Answer 61

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

Question 62

Temporal lobe 3 guri - but a fourth area inside - mainly responsible for HEARING - 3 gyru

Answer 62

Heschl gyrus (on internal aspect) Superior temporal gyrus Middle temporal gyrus Inferior temporal gyrus

Question 63

temporral lobe functions hearing (superior and Herschl) located on INSIDE see moving objects (middle) recognize faces - inferior

Answer 63

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)

Question 64

Occipital - eyes in the back of your head - visual

Answer 64

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

Question 65

medial surface of brain frontal, parietal, occipital Paracentral - controls LOWER EXTREMITIES

Answer 65

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

Question 66

occipital lobe from medial aspect Function: Visual receiving area (primary)

Answer 66

``` Anteriorly: Parietal-occipital sulcus (border with parietal lobe) Calcarine sulcus (fissure) - perpendicular to parietal-occipital sulcus, in the middle of the occipital lobe ```

Question 67

Calculine sulcus – very important area

Answer 67

– where initially all visual info comes

Question 68

Cingulate Gyrus: limbic system (a part of) above CORPUS COLOSUM quick decisions, Empathy, compassion

Answer 68

where some of your emotions are controlled

Question 69

quick fast decisions? overreaction? probably made by limbic not frontal cortex

Answer 69

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

Question 70

corpus colosum? Massive fiber pathway

Answer 70

Communication between hemispheres Massive fiber pathway – all the grey matter above the corpus - corpus callosum is the white matter – connecting everything

Question 71

Septum Pellucidum:

Answer 71

Forms medial wall of lateral ventricles 2 thin-walled membranes with cavity between them (cavity of septum pellucidum) Boundaries: Ventral: corpus callosum

Question 72

Fornix - seahorse? key role in cognition and episodic memory recall.

Answer 72

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.

Question 73

Hippocampus

Answer 73

- memory skills need to sleep to develop memory

Question 74

Amygdala

Answer 74

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.

Question 75

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 -

Answer 75

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

Question 76

inferior surface of brain structures gyrus rectus (not clear function

Answer 76

Thought to be involved in higher cortical functions (esp. personality features) lateral to this is the olfactory bulb and tract

Question 77

Olfactory bulb:

Answer 77

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)

Question 78

Occipitotemporal gyrus

Answer 78

(aka fusiform gyrus): Boundaries: Medially: collateral sulcus Laterally: inferior temporal sulcus Function: Not fully understood Thought to be involved into recognition processes

Question 79

Parahippocampal gyrus: UNCUS - HOOK - brain edema - can kill you In general – recognizes letters - Memory encoding and retrieval

Answer 79

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 -

Question 80

Uncal herniation -

Answer 80

most common place of supratentorial herniation

Question 81

Hippocampal formation and amygdala are situated deep to the cortex of the parahippocampal gyrus and uncus. seizures in temporal lobe epilepsy.

Answer 81

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.

Question 82

Lingual gyrus: LOGIC ``` Vision processing (esp. letters) Analysis of logical conditions (eg, logical order of events) ```

Answer 82

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)

Question 83

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,

Answer 83

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

Question 84

Would blood every look hyperdense on CT? YES! blood is dense - Hyperdense vs air is not dense "hypodense" infaract - lacking blood - thus darker

Answer 84

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.

Question 85

Enhanced CTs - vasculature, iodine contrast

Answer 85

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)

Question 86

3 major roles for CT - 3 H

Answer 86

hemorrage hydrocephalus herniation

Question 87

MRIs

Answer 87

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

Question 88

MRIs in many flavors - many - know T1 and T2 - time function

Answer 88

T1 - spin lattice, white (matter INSIDE) bright, CSF dark, most lesions dark T2 - spin spin = grey matter bright - CSF BRIGHT, most lesions bright

Question 89

notes re MRI

Answer 89

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)

Question 90

Coronal scans =

Answer 90

viewed as though the clinician is facing the patient.

Question 91

CT windows

Answer 91

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

Question 92

CT vs MRI

Answer 92

CT - more bone details, less tissue

Question 93

BBB - do contrasts in blood get into brain?

Answer 93

not normally, but IF BBB broken will see that in CT with contrast

Question 94

iodine as contrast?

Answer 94

Iodine is more dense than most tissue – greater attenuation Early injection – assess vessels Later injection – assess disruption of BBB Complete injection – assess perfusion

Question 95

reasons to not do CT MRI can be tough on people with Kidney problems - gadolinium reaction -

Answer 95

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

Question 96

perikaryon

Answer 96

cell body

Question 97

if dendrites don't have voltage gated channels - and can't generate action potential - how do they send the message along?

Answer 97

Receives signals from other neurons Passively integrates dendritic and somatic signals; not excitable WHAT DOES THIS MEAN? how pass it along?

Question 98

neuron soma

Answer 98

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

Question 99

Axon hillock

Answer 99

``` 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 ```

Question 100

Axon doesn't have...

Answer 100

No ribosomes (vs. dendrites)

Question 101

Nodes of Ranvier

Answer 101

are unmyelinated gaps and the only excitable region of the axon Action potentials jump from node to node through saltatory conduction

Question 102

C fibers (smallest axons)

Answer 102

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

Question 103

axon terminal contains what kind of voltage gated channels?

Answer 103

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

Question 104

boutons en passant.

Answer 104

boutons are found along the length of the axon Other axons contain swellings, or varicosities, that are not button-like but still can represent points of cell-to-cell information transfer.

Question 105

Variations on basic structure of neurons

Answer 105

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

Question 106

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.

Answer 106

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

Question 107

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

Answer 107

Two main processes extend from soma: one detects incoming signals; the other transmits information to the next neuron

Question 108

various types of multipolar neurons

Answer 108

Interneurons: multipolar neurons with short axons that project locally Projection neurons: multipolar neurons supporting elongated axons that can project great distances Upper motor neurons: project from cerebral cortex and brainstem to lower motor neurons Lower motor neurons: project to skeletal muscles Association neurons: project from one gyrus or lobe to another within the same hemisphere

Question 109

Synapse

Answer 109

a neuron may function simultaneously as presynaptic and postsynaptic element

Question 110

chemical synapses

Answer 110

Chemical synapses are unidirectional | Each synaptic vesicle contains a fixed amount of neurotransmitter (called a quantum) – release depends on Ca2+ influx

Question 111

boutons contain -

Answer 111

The bouton contains mitochondria, which supply energy for synaptic function, and also a prominent collection of vesicles, which contain the neurotransmitter that will be released into the synaptic cleft. Vesicles are often aggregated near sites on the presynaptic membrane called active sites (or zones), which are the sites of neurotransmitter release.

Question 112

adrenal medulla stimulated by

Answer 112

sympathetic preganglionic neurons.

Question 113

neurotransmitters 60 types identified so far Response is defined by the type of receptor

Answer 113

excitatory (glutamate) inhibitory - GABA

Question 114

syncytium - electric synapses gap junctions, CONNEXONS

Answer 114

Allow for large numbers of cells to act as a syncytium (eg, cardiac muscle fibers) Allow rapid communication with no synaptic delay Presynaptic and postsynaptic neurons are physically connected by gap junctions formed by connexons

Question 115

chemical vs electric synapses Chemical synapses rely on diffusion of neurochemical from presynaptic to postsynaptic membrane

Answer 115

Electrical synapses are points of physical communication between presynaptic and postsynaptic membranes that allow direct ionic current flow

Question 116

neuronal cytoskeleton

Answer 116

Microtubules Neurofilaments Actin filaments Collagen fibrils provide support extracellularly but are not part of neural cytoskeleton

Question 117

microtubules Composed of protofilaments consisting of alternating α- and β-tubulin subunits that confer polarity on tubule Stabilized by microtubule-associated proteins (MAP), including tau and MAP-2 TAU faulty processing in Alzheimer's

Answer 117

Exist in longitudinal arrays in most dendrites and axons In dendrites, both orientations are found In axons, "+" ends are away from soma Provide tracks Kinesin out toward + end, Dynein back IN - retrograde

Question 118

cancer fighting - in microtubules Targeted by chemotherapeutic agents (eg, paclitaxel, vinblastine, and vincristine)

Answer 118

Stabilized by microtubule-associated proteins (MAP), including tau and MAP-2 Abnormalities in tau protein processing: hallmark of Alzheimer disease

Question 119

neurofilaments - and diseases ALS, Parkinsons' Stabilize neuron shape Major determinant of AXONAL diameter

Answer 119

Abnormal - neurodegenerative diseases ALS and amyotrophic lateral sclerosis and Parkinson disease. Neurofilament and alpha-synuclein are major components in Lewy bodies.

Question 120

Lewy bodies

Answer 120

are abnormal aggregations of protein that develop inside nerve cells, contributing to Parkinson's disease (PD), the Lewy body dementias (Parkinson's disease dementia and dementia with Lewy bodies), and some other disorders.

Question 121

actin microfilaments

Answer 121

Comprise two strands of globular actin monomer Homologous to thin filaments of striated muscle Found near microtubules and plasma membrane and are associated with presynaptic terminals, dendritic spines, and growth cones Interact with extracellular matrix and with other cells

Question 122

Axonal transport

Answer 122

Fast anterograde transport - kinesin Component A moves membrane proteins and neurotransmitters 200 to 400 mm/day Component B moves larger elements (eg, mitochondria) 50 to 100 mm/day Slow anterog

Question 123

Slow anterograde transport Regrowth of damaged axons: depends on slow transport to supply cytoskeletal materials

Answer 123

Moves soluble proteins : Cytoskeletal proteins, neurofilament proteins, soluble NT synthesizing enzymes, and proteins not membrane-bound or within organelles) 0.2 to 8 mm/day toward terminal regions Limits damaged axon regrowth to 1 to 4 mm/day

Question 124

Retrograde axonal transport

Answer 124

Moves vesicles, membrane-bound organelles, and peripherally endocytosed growth factors back to soma Rate: 200 to 300 mm/day along microtubules using dynein motors Allows peripheral cellular components to be degraded and recycled

Question 125

Rabies, tetanus Unlike the rabies virus, which is replicated in the cell body, the tetanus toxin is diluted as it passes from cell to cell. In spite of this dilution effect, patients infected with C. tetani may have a range of neurologic deficits.

Answer 125

Rabies virus Replicates in muscle tissue (site of a bite by a rabid animal) Taken up by axon terminals Retrogradely transported to cell body From CNS transported to the salivary glands - > saliva Tetanus toxin is taken up by axon terminals Retrogradely transported to cell body Released by cell body Taken up by other neurons

Question 126

research re axonal transport? Horseradish peroxidase - retrograde Radioactively labeled aminoacids and wheat germ agglutinin (WGA-HRP) - anterograde

Answer 126

Horseradish peroxidase (HRP) or a fluorescent substance are used in research of the retrograde transport Radioactively labeled aminoacids and wheat germ agglutinin (WGA-HRP) are used in research of the anterograde transport

Question 127

Electrical Properties of Neurons

Answer 127

``` Negatively charged (proteins inside) Membrane is selectively permeable to certain ions (ion channels) Channels react to variety of stimuli ```

Question 128

glial cells - majority in CNS are glial

Answer 128

macroglia - astro, olig - neuroectoderm schwann - neural crest microglia - mesoderm ependymal - neuroectoderm ??

Question 129

astrocyte end-feet.

Answer 129

Astrocyte end-feet join together to completely line the interfaces between the CNS and other tissues. The outer surface of the brain and spinal cord, where it meets the inner surface of the pia mater (the innermost of the meningeal membranes that enclose the CNS), is covered with a coating of several layers of joined end-feet called the glia limitans (or glial limiting membrane). Similarly, every blood vessel in the CNS is jacketed by a layer of end-feet that separates it from the neural tissue.

Question 130

astrocytes GFAP MC brain tumor found in white matter, grey matter -

Answer 130

Astrocytes occur throughout the CNS. They are highly branched cells with processes that contact most of the surfaces of neuronal dendrites and cell bodies as well as some axonal surfaces and synapses.

Question 131

function of astroycytes - What DON"T they do?? LOL they don't do what the other glial cells do

Answer 131

Maintain stable brain environment, transport nutrients Buffer ions in extracellular space (pH), K+ metabolism Help remove NTs released by active neurons (esp. glutamate) Produce: IL-1, TNF-α, thrombospondins, cholesterol, LP, d-serine End-feet surround brain capillaries, take up glucose, and promote formation of blood-brain barrier During neuronal damage, can proliferate and phagocytose dying neurons, form glial scar Radial glia: guide migration of neurons, direct outgrowth of axons in the developing brain Fibrous astrocytes: found in white matter Protoplasmic astrocytes: found in gray matter Glial fibrillary acidic protein(GFAP) – marker of astrocytes

Question 132

MC brain tumor?

Answer 132

Glioblastoma multiforme: high-grade (ie, very malignant) astrocytoma; the most common primary brain tumor.

Question 133

glial scar

Answer 133

Note! When injury to the CNS results in destruction of cells, the space created by the breakdown of debris is filled by proliferation or hypertrophy (or both) of astrocytes, resulting in the formation of an astrocytic (glial) scar. That astrocytes retain the ability to proliferate in the mature brain (and thus are more susceptible to events that disrupt the control of cell division) explains why the majority of CNS tumors are of astrocytic origin.

Question 134

astrocytes can secrete

Answer 134

In disease processes, astrocytes may secrete cytokines and immune mediators such as interleukin (IL)-1, tumor necrosis factor-α, and prostaglandin. Thus astrocytes as well as microglia contribute to the regulation of inflammatory processes in the CNS. In development, astrocytes induce synapse formation through their secretion of thrombospondins. Thrombospondins are a family of extracellular matrix proteins that bind to neuronal surface molecules (calcium channel subunits, integrins, and neuroligin synaptic adhesion proteins). Other astrocyte products, such as cholesterol and lipoproteins, are also thought to enhance synaptic plasticity.

Question 135

astrocytes secrete glutamate NT - excitatory also GABA - inhibitory D-serine NMDA ATP - used w/ adenosine for sleep wake cycle ammonia enzyme produces glutamine - enzyme glutamin synthetase

Answer 135

Amino acid neurotransmitter glutamate is taken up by astrocytes and is then inactivated by the enzymatic addition of ammonia to produce glutamine (catalyzed by the enzyme glutamine synthetase). Glutamine released from astrocytes can be taken up and reconverted to glutamate in neurons. This astrocytic pathway also detoxifies ammonia in the CNS. D-serine binds to neuronal N-methyl-d-aspartate (NMDA) receptors and modulates synaptic activity. Astrocytes also release other neurotransmitters. The inhibitory neurotransmitter GABA is released from astrocyte anion channels. Its sustained mode of release causes tonic inhibition of synapses in the surrounding area. In contrast, adenosine triphosphate (ATP) is released by astrocytes in response to neuronal signaling. It is metabolized to the neurotransmitter adenosine, which is involved in cellular energy regulation and the sleep-wake cycle.

Question 136

BBB end feet - physical complex of endothelium, basal lamina, and astrocyte end-feet Water, gases, and lipid-soluble small molecules can diffuse but other substances must be carried across by transport systems, and their exchange is highly selective. This selectivity is further enhanced by a reduction in pinocytotic transport. The blood-brain barrier is of major clinical importance because it largely excludes many drugs from the CNS.

Answer 136

In the CNS, vessels are induced by the surrounding jacket of astrocyte end-feet to form extensive tight junctions, so solutes can reach the neural tissue only by passing through the endothelial cells (Figure A). The resulting restricted exchange constitutes the blood-brain barrier. In a strict sense, the blood-brain barrier is formed by the tight junctions of the endothelium. However, many people refer to the blood-brain barrier more inclusively as the physical complex of endothelium, basal lamina, and astrocyte end-feet surrounding each CNS vessel. Water, gases, and lipid-soluble small molecules can diffuse across the endothelial cells, but other substances must be carried across by transport systems, and their exchange is highly selective. This selectivity is further enhanced by a reduction in pinocytotic transport. In most tissues of the body, a high level of pinocytotic activity by endothelial cells transports solutes nonspecifically from the blood plasma to the perivascular space. In contrast, endothelial cells of capillaries in most parts of the CNS show little pinocytotic activity. The blood-brain barrier is of major clinical importance because it largely excludes many drugs from the CNS.

Question 137

oligodendrocyte myelinates | “Fried egg”

Answer 137

Oligodendroglioma: rare tumor of cortical white matter, frequently leading to seizures Destroyed in slow viral diseases, including progressive multifocal leukoencephalopathy Affected in multiple sclerosis

Question 138

acoustic neuromma?

Answer 138

Schwann cell tumor of CN VIII

Question 139

Schwann cell myelinates one segment of a single axon

Answer 139

Secrete growth factors critical to regeneration of damaged PNS axons Loss of myelin characterizes several neuropathies, including acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome) Guillain-Barré syndrome is thought to be caused by a problem with the immune system, the body's natural defence against illness and infection.

Question 140

microglia Residents - fight infection, meningitis susceptible to HIV-1 infection Toxic environment generated by dying microglia may be direct cause of CNS involvement and dementia associated with human immunodeficiency virus type 1 (HV-1) Infection HIV-infected microglia fuse to form multinucleated GIANT cells in CNS

Answer 140

Arise from monocytes derived from bone marrow (mesodermal origin) Migrate into brain during development and become resident microglia Transformed into activated microglia to phagocytose dying cells in response to damage within CNS (esp. infections, meningitis)

Question 141

microglia are versatile

Answer 141

such as viral encephalitis caused by human immuno- deficiency virus-1 (HIV-1), subacute sclerosing panencephalitis, lead encephalopathy, and neurosyphilis, microglia withdraw and reshape their processes to form long rod cells closely apposed to affected neurons. In cases of trauma or severe tissue injury, they become motile, ameboid phagocytes capable of migrating to the site of injury and proliferating. At the injury site, they phagocytose tissue debris.

Question 142

Microglial activation can be harmful.

Answer 142

For example, in bacterial meningitis in children, as microglia phagocytose particles of bacteria killed by penicillin, they are stimulated to secrete IL-1β. IL-1β acts on endothelial cells to loosen their tight junctions, allowing leukocytes and blood plasma to enter CNS tissue, escalating the inflammation to a level that can be fatal. When researchers and physicians pre- vented this secondary inflammation by administering steroids before giving penicillin, microglial cytokine secretion was inhibited, and the survival rate for bacterial meningitis in children vastly improved.

Question 143

Ependymal Cells Choroid epithelial cells: specialized ependymal cells that produce cerebrospinal fluid (CSF) Most ependymocytes have cilia and/or microvilli at apical processes that beat to move CSF Tanycytes move selected molecules from blood to CSF

Answer 143

Ependymal cells, similar to all other neuroglia, are derived from a layer of embryonic tissue known as neuroectoderm. Ependymal cells and their epithelial derivatives of the choroid plexus have several important functions.

Question 144

Tanycytes 3rd and 4th ventricle

Answer 144

move selected molecules from blood to CSF third ventricle of the brain, and on the floor of the fourth ventricle and have processes extending deep into the hypothalamus. It is possible that their function is to transfer chemical signals from the cerebrospinal fluid to the central nervous system.

Question 145

Wallerian degeration Wallerian degeneration occurs distal to a point of severe axonal damage. C, Chromatolysis follows. D, Reinnervation of target may occur within the peripheral nervous system

Answer 145

Axonal degeneration distal to point of severe axonal damage Nerve terminal fills with clumps of neurofilaments and disrupted mitochondria Contact with postsynaptic membrane is lost, and axon segment distal to injury withdraws Glial cells invade and phagocytose debris

Question 146

A Nissl body, also known as Nissl substance - site of protein synthesis

Answer 146

and Nissl material, is a large granular body found in neurons. These granules are of rough endoplasmic reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis.

Question 147

chromatolysis Anterograde transneuronal degeneration: when a neuron dies, downstream synaptic target neurons may die Retrograde transneuronal degeneration: when a neuron dies, upstream synaptic partners may die

Answer 147

within soma: cell body swells, nucleus moves to side of soma, rough endoplasmic reticulum disintegrates Neuron may survive: if neuron successfully reinnervates or if axotomy does not damage all terminals, chromatolysis may reverse. Neuron may die: neurons without functional terminal frequently undergo apoptosis

Question 148

axonal regeneration Actively inhibited within CNS: Oligodendrocytes actively inhibit neurite outgrowth Reactive astrocytes cause glial scarring, which interferes with nerve regrowth Fewer chemotropic factors are available in CNS.

Answer 148

May occur in PNS: Growth cones sprout from proximal axon stump Schwann cells and extracellular elements of remaining distal stump produce chemotropic factors that promote axon regrowth Axons may reinnervate muscles, although target specificity may not be perfect Some functional motor control of denervated muscle returns.

Question 149

Resting membrane potential (RMP) Normally, does not change with minor perturbations, such as action potential generation RMP is determined primarily by K+ gradient

Answer 149

Steady-state membrane potential Results primarily from constant net flux of K+ ions out of the neuron and smaller net flux of Na+ into the neuron Depends on action of Na+/K+ ATPase pump that maintains both K+ and Na+ concentration gradients

Question 150

lethal injections how work?

Answer 150

Infusion of K+-based, rather than Na+-based, solutions decreases K+ gradient, causing K+ equilibrium potential and RMP to become more positive Take-home message: intravenous K+-based solutions cause cardiac fibrillation and death Eg, lethal injection with KCl depolarizes excitable cardiac tissues, causing fibrillation and death

Question 151

Graded potentials

Answer 151

Graded” = larger signal → more channels affected → larger amplitude change in membrane potential Move across membrane by electronic (passive) conduction Signal amplitude diminishes as depolarizing wave travels from the source

Question 152

Graded potentialsSubtypes

Answer 152

End-plate potentials: Occur at motor end plate when ACh is released from the nerve terminals binds with muscle receptors to open Na+/K+ channels Receptor (generator potentials): Occur at the sensory region of primary sensory neurons that are exposed to an adequate stimulus Excitatory postsynaptic potentials (EPSPs): produced at dendrites and somas in response to excitatory neurotransmitters Inhibitory postsynaptic potentials (IPSPs): are produced at dendrites and somas in response to inhibitory neurotransmitters

Question 153

Prototypical peripheral nervous system (PNS) sensory neuron

Answer 153

A, Larger or longer incoming stimulus causes larger or longer graded potential B, Larger graded potentials are coded as increased action potential frequency, whereas longer graded potentials cause a longer train of action potentials C, Action potentials carry information from the source to the terminal region without signal degradation. In PNS sensory neurons, the source is the trigger zone; in central nervous system neurons, the axon hillock is the source D, Neurotransmitter release increases as terminal depolarization increases

Question 154

Graded potentialsSummation temporal spatial - (arrive simulateneously)

Answer 154

Temporal summation occurs when a second graded potential arrives in time to build on the first, creating a larger graded potential Spatial summation occurs when two graded potentials arrive simultaneously on a region of a neuron and add together , Neuron X excites a dendrite on neuron Y two times (arrows). Graded potentials can be measured some distance away. However, because the time constant of the membrane is short, the first excitatory postsynaptic potential (EPSP) has died before the second arrives, and they do not add. B, Time constant of the membrane is longer, so the first EPSP has not died before the second arrives. The second EPSP builds on the first, causing a larger depolarization.

Question 155

action potentials All-or-none if a membrane depolarizes to threshold Actively transmitted over long distances from cell body to nerve terminal without signal degradation Refractory periods: Prevent a second action potential during the first action potential During absolute refractory period (immediately after action potential), neuron cannot produce another action potential During relative refractory period (after absolute refractory period), only a strong stimulus will induce an action potential Action potentials do not add: Information is coded in the frequency and pattern of action potentials Ion pumps maintain necessary ion gradients for generation of action potentials (eg, Na+/K+ ATPase)

Answer 155

Generated by excitable membrane, containing voltage-gated ion channels Na+ channel opening depolarizes membrane Channels respond in a probabilistic fashion to membrane potential At more depolarized membrane potentials, the probability that a given channel will be “open” is higher K+ channel opening accelerates repolarization of membrane

Question 156

myelination See info below ??? Electrical insulation surrounding axons Increases membrane resistance of axons Increased membrane resistance increases length constant, which allows current generated by action potentials to travel further Length constant allows nodes of Ranvier to be spaced far apart on an axon. Decreases membrane capacitance by increasing charge separation Decreased membrane capacitance decreases membrane time constant, allowing membrane to charge and discharge more rapidly Rapid membrane charging allows for faster conduction of action potentials

Answer 156

Most peripheral nervous system (PNS) axons of at least 1 μm diameter and most central nervous system (CNS) axons of at least 0.25 μm are myelinated.

Question 157

nodes of ranvier Demyelination (eg, from multiple sclerosis) leads to redistribution of voltage-gated channels throughout length of axon.

Answer 157

Segments of excitable membrane that interrupt myelination every 0.5 to 1.0 mm intervals Allow for saltatory ("jumping") conduction Neurons conserve energy by producing action potentials only at nodes Increases rate of action potential conduction Voltage-gated Na+ channels stabilized at nodes Voltage-gated K+ channels stabilized adjacent to nodes

Question 158

Disorders of myelination in the PNS:

Answer 158

Acute inflammatory demyelinating neuropathy (Guillain-Barré syndrome) Diabetic neuropathy Peroneal muscular atrophy (Charcot-Marie-Tooth disease)

Question 159

Guillain-Barré syndrome COMPYLOBACTER JEJUNI mimicry immune system knows they are foreign can happen in two weeks! often there was an infection a couple weeks before don't know what causes it

Answer 159

Most common immune-mediated disorder to affect peripheral myelin Frequent presentation: weakness ascending rapidly from legs to arms and finally to face, without sensory involvement. Progression: May be less than 2 weeks from first signs of weakness to respiratory insufficiency requiring ventilatory support

Question 160

stocking-and-glove distribution of sensory loss Diabetes mellitus: damages peripheral myelin and axons PNS

Answer 160

Some diabetic neuropathies cause peripheral demyelination May affect sensory, motor, or autonomic systems or a combination Signs: stocking-and-glove distribution of sensory loss

Question 161

Aka Charcot-Marie-Tooth disease PNS

Answer 161

Family of genetic disorders affecting peripheral myelin Progression: slow, causing muscle weakness and mild sensory loss Signs: "stork-like legs, " clumsiness, and eventual difficulty with fine motor skills

Question 162

MyelinOligodendrocytes Inflammatory progressive disorder destroying central myelin Multiple lesions disseminated in space and time, commonly periventricular (near a ventricle), viewed on magnetic resonance imaging Cause: unknown, but genetic susceptibility, autoimmunity, and viral infections have been implicated

Answer 162

Glia responsible CNS myelination One oligodendrocyte provides myelin to up to at least 40 different axons MC condition affecting central myelination = multiple sclerosis Multiple sclerosis: destroys CNS myelin, causing sensory and motor deficitsThird or fourth decade of life Incidence is slightly higher in women Blurry or sudden loss of vision: Aka optic neuritis, frequent initial finding Ataxia (the loss of full control of bodily movements). and scanning speech: cerebellar involvement Urinary incontinence, muscle weakness, and paresthesias: demyelination of long tracks Jerky eye movements: internuclear ophthalmoplegia from pontine demyelination in medial longitudinal fasciculus

Question 163

Scanning speech  and MS

Answer 163

is a type of ataxic dysarthria in which spoken words are broken up into separate syllables, often separated by a noticeable pause, and spoken with varying force.

Question 164

Electrical Synapses a connexin hemichannel, is an assembly of six proteins called connexins that form the pore for a gap junction between the cytoplasm of two adjacent cells. This channel allows for bidirectional flow of ions and signaling molecules.

Answer 164

Rapid but limited communication Membranes of the presynaptic and postsynaptic neurons contain connexons formed by specialized proteins that link across the space, separating the cells Connexons form a gap junction (aqueous pore of communicating cytoplasm) No delay and minimal modification of signal, because flow of ions between cells is direct

Question 165

Chemical synapses

Answer 165

Slower than electrical but allow for more complex signaling Use chemical molecules (neurotransmitters) for communication Release of NT from presynaptic terminal requires calcium: Calcium enters through voltage-dependent calcium channels. Presynaptic voltage-dependent Ca2+ channels open as action potentials depolarize the terminal Synaptic cleft: space between presynaptic axon terminal and postsynaptic membrane through which transmitter diffuses Postsynaptic responses depend on receptor

Question 166

Types of chemical synapses Several neurotransmitters can activate directly gated channels including glutamate, acetylcholine, y-aminobutyric acid (GABA), glycine, and serotonin Benzodiazepines: potentiate chloride conductance through GABA receptors within CNS

Answer 166

Direct gated: Binding of neurotransmitter opens or closes an ion channel within the receptor rapid change in postsynaptic membrane potential (EPSP or IPSP) Indirect gated: Binding of neurotransmitter activates second-messenger pathways Binding of neurotransmitter activates second-messenger pathways by way of guanosine triphosphate-binding (G proteins). Signal transduction pathways activated by second messengers may have multiple and lasting effects ??? Second-messenger pathways: cyclic adenosine monophosphate, phosphoinositide, and prostaglandin Nonsteroidal anti-inflammatory drugs (aspirin and indomethacin): inhibit prostaglandin formation

Question 167

Botulinum toxin inhibits muscle contraction presynaptically by decreasing the amount of ACh released into the neuromuscular junction. In contrast, curare acts post-synaptically, blocking the nicotinic ACh receptors and preventing the excitation of the muscle cell membrane. Tetrodotoxin blocks voltage-sensitive Na! channels, impacting both the initiation and the propagation of action potentials in the motor neuron. Both ACh and neostigmine stimulate muscle contraction.

Answer 167

Botulinum toxin inhibits the release of acetylcholine from a -motoneurons by blocking one of the proteins responsible for the fusion of the synaptic channel with the presynaptic membrane. Botulinum toxin also inhibits the release of acetylcholine from the neurons of the autonomic nervous system. Botulinum and tetanus toxin are released from the same class of bacteria (Clostridium ). Tetanus toxin produces an increase in skeletal muscle contraction by blocking the release of inhibitory neurotransmitter from spinal interneurons.

Question 168

What is curare used for?

Answer 168

Curare, drug belonging to the alkaloid family of organic compounds, derivatives of which are used in modern medicine primarily as skeletal muscle relaxants, being administered concomitantly with general anesthesia for certain types of surgeries, particularly those of the chest and the abdomen.

Question 169

Bradycardia - mushroom poisoning

Answer 169

slower than normal heart rate. The hearts of adults at rest usually beat between 60 and 100 times a minute. If you have bradycardia (brad-e-KAHR-dee-uh), your heart beats fewer than 60 times a minute. Bradycardia can be a serious problem if the heart doesn't pump enough oxygen-rich blood to the body.Nov 13, 2019

Question 170

Myasthenia gravis is an autoimmune disease damage receptors

Answer 170

in which antibodies damage postsynaptic nicotinic acetylcholine receptors. This damage prevents the firing of an action potential in the postsynaptic membrane. Tensilon is a readily reversible acetylcholinesterase inhibitor that increases acetylcholine levels in the neuromuscular junction, thereby increasing the strength of muscle contraction.

Question 171

botulism toxin - blocks SNARE like proteins

Answer 171

hence muscles don't fire

Question 172

Tetanus toxin blocks release of inhibitory NT

Answer 172

produces an increase in skeletal muscle contraction by blocking the release of inhibitory neurotransmitter from spinal interneurons.

Question 173

Repetitive stimulation of a skeletal muscle fiber will cause an increase in contractile strength due to an increase in which of the following? Repetitive firing increases the amount of SEC stretch by maintaining cross-bridge cycling for a longer period of time.

Answer 173

The duration of cross-bridge cycling Each time a skeletal muscle fiber is stimulated by an a motoneuron, enough Ca2+ is released from its sarcoplasmic reticulum to fully activate all the troponin within the muscle. Therefore, every cross bridge can contribute to the generation of tension. However, the transmission of force from the cross bridges to the tendon does not occur until the series elastic component (SEC) of the muscle is stretched. Repetitive firing increases the amount of SEC stretch by maintaining cross-bridge cycling for a longer period of time. Repetitive firing increases neither the concentration of Ca2+ within the myoplasm, the number of myofibrils that are activated, nor the magnitude of the end-plate potential. Because all of the cross bridges are activated each time a skeletal muscle fiber is activated, an increase in Ca2+ concentration would have no effect on muscle strength. Limitation in rising from a seated position or combing hair is suggestive of proximal muscle weakness, characteristic of dermatomyositis.

Question 174

myasthenia gravis ?? The cautious use of this test in patients with heart failure results from the possibility that the decreased breakdown of acetylcholine released by the vagus nerve could decrease heart rate to dangerously low levels. wouldn't it increase?

Answer 174

The drug used to test for myasthenia gravis is an acetylcholine esterase inhibitor such as neostigmine. The drug prevents the breakdown of acetylcholine, increasing the duration of time acetylcholine remains in the synaptic cleft. Because acetylcholine can bind to the endplate receptors for a longer time, the magnitude of the end-plate potential increases, increasing the probability of it generating an action potential. The greater the action potential force rate, the greater the source of muscle contraction. Increasing the amount of acetylcholine released by the a motoneurons, by increasing the affinity of the skeletal muscle receptors for acetylcholine or increasing the discharge rate of a motoneurons could cause a similar effect. However, none of these changes would affect heart rate. The cautious use of this test in patients with heart failure results from the possibility that the decreased breakdown of acetylcholine released by the vagus nerve could decrease heart rate to dangerously low levels.

Question 175

The amount of force produced by a skeletal muscle can be increased by which of the following? Maximum summation is called tetanus how to increase interval between contractions?

Answer 175

Decreasing the interval between contractions When the interval between skeletal muscle contractions is small, the force produced by the two successive contractions will summate. The shorter the interval between the contractions, the greater the summation will be. Maximum summation is called tetanus. Decreasing extracellular Ca2+ will increase the excitability of skeletal muscle fibers but does not have a direct effect on contractile force. Increasing the Mg2+ concentration will decrease skeletal muscle excitability. Increasing the preload beyond 2.2 mm decreases the overlap between thick and thin filaments and therefore decreases the force of contraction. Increasing the activity of acetylcholine esterase enhances the hydrolysis of ACh and therefore decreases the likelihood that muscle contraction will be initiated.

Question 176

Which adrenergic receptor produces its stimulatory effects by the formation of inositol 1,4,5-triphosphate (IP3) and an increase in intracellular [Ca2+]? Select one: a. a1 Receptors

Answer 176

Adrenergic α1 receptors produce physiologic actions by stimulating the formation of inositol 1,4,5-triphosphate (IP3) and causing a subsequent increase in intracellular [Ca2+]. Both β1 and β2 receptors act by stimulating adenylate cyclase and increasing the production of cyclic adenosine monophosphate (cAMP). α2 Receptors inhibit adenylate cyclase and decrease cAMP levels. Muscarinic and nicotinic receptors are cholinergic.

Question 177

Pheochromocytoma Antagonist drug Phenoxybenzamine decreases blood pressure by acting as an α1 receptor antagonist, thus decreasing intracellular IP3/Ca2+.

Answer 177

is a tumor of the adrenal medulla that secretes excessive amounts of norepinephrine and epinephrine. Increased blood pressure is due to activation of α1 receptors on vascular smooth muscle and activa- tion of β1 receptors in the heart. Phenoxybenzamine decreases blood pressure by acting as an α1 receptor antagonist, thus decreasing intracellular IP3/Ca2+.

Question 178

Myasthenia gravis (MG)

Answer 178

caused mainly by antibodies against muscle nicotinic acetylcholine receptors

Question 179

What are the muscarinic effects? parasympathetic activation - so diahhrea bladder stim, pupils constrict

Answer 179

Clinical Effects on the Peripheral Nervous System Due to Excessive Stimulation of Muscarinic Receptors Bladder stimulation, sphincter relaxation. Bronchospasm. Miosis (pupillary constriction), eye pain due to ciliary spasm. Nausea, vomiting, cramps, diarrhea.

Question 180

neostigmine

Answer 180

MG drug - enhance communication between nerves and muscles. ...

Question 181

Curare

Answer 181

first paralytic used in anesthesia,

Question 182

Atropine

Answer 182

used to treat certain types of nerve agent and pesticide poisonings as well as some types of slow heart rate, and to decrease saliva production during surgery

Question 183

aspirin irreversibly inhibits both forms (but is weakly more selective for COX-1). It does so by acetylating the hydroxyl of a serine residue. Normally COX produces prostaglandins, most of which are pro-inflammatory, and thromboxanes, which promote clotting.

Answer 183

How does aspirin work as an anticoagulant? Anticoagulants such as heparin or warfarin (also called Coumadin) slow down your body's process of making clots. Antiplatelet drugs, such as aspirin, prevent blood cells called platelets from clumping together to form a clot.

Question 184

Sympathomimetic drugs (also known as adrenergic drugs and adrenergic amines)

Answer 184

are stimulant compounds which mimic the effects of endogenous agonists of the sympathetic nervous system.

Question 185

agonists - mimic NT

Answer 185

can be full or partial - binds in same place

Question 186

Receptors - where do they bind to NT?

Answer 186

on their R arm

Question 187

ACH is made how? cholineacetyltransferase CHOLenergic (AcetylCHOLINE)

Answer 187

choline + acetyl Coa AchE (esterase) degrades - removes NT (Ach) from receptor

Question 188

Where does DOPAMINE become a NT? made in brain - substantia nigra, ventral tegmental, hypothalamus

Answer 188

kidney (renal vasculature - VASODILATES), CNS, ganglia, heart also works in heart - Does dopamine increase blood pressure? Dopamine (dopamine hydrochloride) is a catecholamine drug that acts by inotropic effect on the heart muscle (causes more intense contractions) that, in turn, can raise blood pressure. At high doses, Dopamine may help correct low blood pressure due to low systemic vascular resistance.

Question 189

What triggers dopamine release?

Answer 189

It is released during pleasurable situations and stimulates one to seek out the pleasurable activity or occupation. This means food, sex, and several drugs of abuse are also stimulants of dopamine release in the brain, particularly in areas such as the nucleus accumbens and prefrontal cortex.

Question 190

Where's tyrosine (for dopamine) made?

Answer 190

dopaminergic and adrenergic neurons, adrenal medula Norephinephre made in adrenergic neurons and adrenal medulla - epinephrine made in adrenal medulla

Question 191

DOPA problems

Answer 191

Parkinons's - degeneartion of dopaminergic neurons that use the D2 receptors SCHIZOPhrenia - involves INCREASED levels of D2 receptors

Question 192

cocaine - NE re uptake

Answer 192

inhibitor

Question 193

Degradation of NE, EPH, Dopamine

Answer 193

peripheral tissues COMT presynaptic nerve terminal MAO (reuptake) some excreted in urine - VMA, HVA, normetanephrine,  metanephrine

Question 194

PHEOCHROMOCYTOMA

Answer 194

, a tumor of the adrenal medulla that secretes catecholamines (mostly NE, not Epi), urinary excretion of VMA is increased.

Question 195

Nitric oxide (NO) Arginine → citrulline + NO (NO synthase)

Answer 195

Released by vascular endothelial cells (endothelium-derived relaxation factor [EDRF]); plays an important role in blood pressure regulation by promoting vascular smooth muscle relaxation By promoting vascular smooth muscle relaxation and increasing blood flow, NO stimulates penile erection in patients with erectile dysfunction (ED). permeant gas short-acting inhibitory neurotransmitter in the gastrointestinal tract and the central nervous system. Arginine → citrulline + NO (NO synthase) NO simply diffuses from the presynaptic terminal to its target cell

Question 196

serotonin made from? into melatonin -

Answer 196

tryptophan - > serotonin -> melatonin tryptophan -> niacin -> NAD+

Question 197

lack of tryptophan - can't reabsorb neutral AA

Answer 197

Hartnup disease is a genetic disorder that reduces tryptophan absorption, leading to pellagra. Alterations in protein metabolism may also produce pellagra-like symptoms.

Question 198

other NT histamine (from histidine glycine - inhibitory - found spinal cord and brain stem - increases Cl_ conductance (like GABA)

Answer 198

found in synthesized from histidine (histidine decarboxylase) - in neurons of the hypothalamus, in nonneural tissue (mast cells of the gastrointestinal tract)

Question 199

NT Glutamate - EXCITATORY

Answer 199

four types of receptors - 3 ionotropic - including NMDA found thruout CNS, 1 metabotropic receptor

Question 200

NT GABA - inhibitory from glutamic acid KREB's cycle 2 types of receptors ionotropic and metabotropic - both hyperpolarize with Cl-

Answer 200

degraded by GABA transaminase to enter the TCA KREB’sCycle 2 types of R: GABAA - linked to a Cl− channel (ionotropic) – increases Cl− conductance - hyperpolarizes (inhibits) the postsynaptic cell GABAB - coupled via a G protein to a K+ channel (metabotropic) -  increases K+ conductance, hyperpolarizes the postsynaptic cell

Question 201

GABAa site of what drugs being used to inhibit?

Answer 201

benzodiazepines  and barbiturates  in | the CNS

Question 202

Huntington's missing? Synthesized from glutamic acid (glutamic acid decarboxylase) riad of movement disorder: chorea, (sudden uncoordinated movements) behavioral abnormalities (aggressiveness, apathy or depression), dementia. Auto Dom, chrom 4 Anticipation

Answer 202

GABA associated with GABA deficiency  in the projections from the striatum to the globus pallidus. ANTICIPATION in this disease lack of GABA-dependent inhibition of neural pathways. The mutation is on chromosome 4 and is dominant in inheritance, with 100% penetrance disorder caused by trinucleotide repeat expansions >40 CAG repeats The mutated huntingtin protein forms insoluble plaques with cross-beta structure Huntington disease manifests with the triad of movement disorder: chorea, (sudden uncoordinated movements) behavioral abnormalities (aggressiveness, apathy or depression), dementia.

Question 203

four snare proteins?

Answer 203

synaptobrevin, syntaxin and SNAP-25, synaptotagmin

Question 204

NT binds it's own receptor?

Answer 204

can trigger other events to occur inside the cell | The fo

Question 205

NT binds it's own receptor?

Answer 205

can trigger other events to occur inside the cell

Question 206

major classes of NT receptors

Answer 206

Adrenergic: α1A, α1b, α1c, α1d, α2a, α2b, α2c, α2d, β1, β2, β3 Cholinergic: Muscarinic: M1, M2, M3, M4, M5; Nicotinic: muscle, neuronal (α-bungarotoxin-insensitive), neuronal (α-bungarotoxin-sensitive) Dopaminergic: D1, D2, D3, D4, D5 GABAergic: GABAA, GABAB1a, GABAB1δ, GABAB2, GABAC Glutaminergic: NMDA, AMPA, kainate, mGluR1, mGluR2, mGluR3, mGluR4, mGluR5, mGluR6, mGluR7 Histaminergic: H1, H2, H3 Opioid: μ, δ1, δ2, κ Serotonergic: 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1E, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3, 5-HT4, 5-HT5, 5-HT6, 5-HT7 Glycinergic: Glycine

Question 207

can parasympathetic use any nt receptors other than cholinergic?

Answer 207

NO - thus always using ACH - as NT NT are ALWAYS Muscarinic

Question 208

G protein NR receptor process

Answer 208

ligand, 7 crosses, G protein - heterotrimeric -  have three different subunits: α (When bind GDP is inactive, when binds GTP – is active), β , and γ. Gi, Gs, Gq activates one of 2 enzymes - Phopholipase C OR Adenylyl cyclase (depends on type of NT receptor)

Question 209

cAMP pathway - in sympathetic can be inhib or excitatory deals with PROTEIN Phosphorylation (not calcium as in phospholipase c)

Answer 209

in parasympathetic ONLY inhibitory (decreasing protein phosphoylation)

Question 210

phopholipase C - to DAG, IP3 activates CALCIUM BINDING

Answer 210

DAG uses protein kinase C IP3 creates CA2+ rleases - ACTIVATES CALCIUM BINDING PROTEINS

Question 211

Muscle sources of energy - ATP, phosphoCREATINE, glycolysis, oxidative metabolism (carbs first 2 - 4 hours - then fats) 95% energy from this

Answer 211

ATP - lasts for 1 - 2 seconds ATP + phosphCREATINE - 5 - 8 seconds glycolosis can sustain for 1 minute

Question 212

glycolysis can occur w/o oxygen and makes MORE - 2.5

Answer 212

glycolosis of glycogen (liberates energy to create ATP from ADP via breaking down glycogen to pyruvic acid and lactic acid)

Question 213

max muscle efficiency? moderate velocity is best for efficiency

Answer 213

when veloticity is 30% of max will lose a lot to heat, friction (if contraction too rapid if no work performed - m not move but is contracting - wasting energy

Question 214

isometric - m not shorten during contraction

Answer 214

isotonic does shorten but tension remains constant

Question 215

The active length-tension relationship

Answer 215

is thought to occur as a result of the degree of overlap between the actin and myosin filaments within an individual sarcomere The length (preload) at which the fiber generates the most active tension is called the optimal length (Lo)

Question 216

The active tension

Answer 216

is maximal when there is maximal overlap of thick and thin filaments and maximal possible cross-bridges.

Question 217

The increase in the force of contraction of skeletal muscle is regulated by

Answer 217

the number of motor units recruited by the central nervous system (CNS) and by their frequency of activation

Question 218

The velocity of shortening

Answer 218

reflects the speed of cross-bridge cycling, determined by the muscle’s ATPase activity. The velocity of shortening will be maximal (Vmax) when the afterload on the muscle is zero. As the afterload on the muscle increases, the velocity will be decreased because cross-bridges can cycle less rapidly against the higher resistance.

Question 219

bradyphrenia

Answer 219

slow thinking

Question 220

bradykinesis

Answer 220

slow moving

Question 221

vermis

Answer 221

The vermis (pl: vermes) of the cerebellum is an unpaired medial structure which separates the cerebellar hemispheres. The neocerebellar posterior lobes join in the midline behind the primary fissure to separate the vermis into superior and inferior portions.

Question 222

Dandy–Walker malformation (DWM), vermis not fully form -> hydrocephalus -> 4th may see Noncommunicating hydrocephalus and spina bifida associated with Dandy-Walker malformation

Answer 222

also known as Dandy–Walker syndrome (DWS), is a rare congenital brain malformation in which the part joining the two hemispheres of the cerebellum (the cerebellar vermis) does not fully form, and the fourth ventricle and space behind the cerebellum (the posterior fossa) are enlarged .

Question 223

What are the 3 common causes of noncommunicating hydrocephalus?

Answer 223

Stenosis of the aqueduct of Sylvius, colloid cyst blocking the foramen of Monro, tumor

Question 224

fibers of corona radiata - Normal pressure hydrocephalus, in which ventricular distention stretches the fibers of the corona radiata The corona radiata is a bundle of nerve fibers located in the brain. ... The brain stem and the cerebral cortex both are involved in sensation and motor function, and the corona radiata connects both motor and sensory nerve pathways between these structures.

Answer 224

The most prominent projection fibers are the corona radiata, which radiate out from the cortex and then come together in the brain stem. The projection fibers that make up the corona radiata also radiate out of the brain stem via the internal capsule.

Question 225

A patient takes a drug that stops DNA replication by inhibiting eukaryotic topoisomerase II. What drug is this?

Answer 225

TWO SIDED - Etoposide or teniposide vs. for topoisomerase I - they are irinotecan/topotecan I CAN !

Question 226

antibiotic that inhibits DNA gyrase (prokaryotic topoisomerase II) and topoisomerase IV. Which antibiotic is this?

Answer 226

Fluoroquinolone

Question 227

Difference between polymerase i vs iii

Answer 227

DNA polymerase 3 is essential for the replication of the leading and the lagging strands whereas DNA polymerase 1 is essential for removing of the RNA primers from the fragments and replacing it with the required nucleotides. These enzymes cannot replace each other as both have different functions to be performed

Question 228

What eukaryotic enzyme is a reverse transcriptase that adds DNA to the 3' ends of chromosomes?

Answer 228

Telomerase (RNA-dependent DNA polymerase)

Question 229

5' vs 3' dna

Answer 229

The 5' and 3' mean "five prime" and "three prime", which indicate the carbon numbers in the DNA's sugar backbone. The 5' carbon has a phosphate group attached to it and the 3' carbon a hydroxyl (-OH) group. This asymmetry gives a DNA strand a "direction".

Question 230

apurinic or apyrimidinic site WITHOUT In base excision repair, what do the apurinic/apyrimidinic endonucleases do? GEL PLease They nick the 5′ end of the apurinic or apyrimidinic site

Answer 230

an AP site (apurinic/apyrimidinic site), also known as an abasic site, is a location in DNA (also in RNA but much less likely) that has neither a purine nor a pyrimidine base, either spontaneously or due to DNA damage.

Question 231

In single-strand DNA repair, in what phases of the cycle do nucleotide excision repair, base excision repair, and mismatch repair occur?

Answer 231

nucleotide G1 base excision - thru out - it's BASICally always happening miSSSSSmatch - Synthesis

Question 232

A process uses intact dsDNA as a template to repair damaged DNA without losing nucleotides. In what diseases is this repair process defective?

Answer 232

dsDNA = DOUBLE STRANDED DNA Fanconi anemia and ovarian and breast cancers with BRCA1 mutation (process is homologous recombination)

Question 233

A patient has autoantibodies against glomerular basement membrane. What type of collagen is most likely being targeted?

Answer 233

GoodPasture's type IV

Question 234

Hypersensitivity Type II

Answer 234

GoodPastures, Myathenias Gravis

Question 235

neural crest ?

Answer 235

Albinism = problem with melanocytes, deficiency in melanocytes. Defect in tyrosinase, which is unable to convert tyrosine to melanin. Ectoderm = Skin, CNS Endoderm = including gut epithelium, pancreas, liver, lungs Mesoderm = Muscle, bones, connective tissue Non-neural crest neuroectoderm = Brain and spinal cord

Question 236

motor deficits of the lower extremities

Answer 236

(spina bifida and tethered cord)

Question 237

developmental disorders, which affect the cerebral cortex and other regions of the brain

Answer 237

(meningomyelocele and anencephaly),

Question 238

enlarged cranium, cerebellar damage, headaches, vomiting, an inabilityto learn and maintain acquisition of motor skills, and lack of coordination of the trunk

Answer 238

dandy walker

Question 239

neural crest cells fail to migrate properly. will effect?

Answer 239

``` a. Chromaffin cells b. Dorsal root ganglion c. Autonomic ganglion cells d. Schwann cells ``` cells developing from the walls of the neural tube that include the alar, basal, and floor plates have no relationship with neural crest cells. The ventral horn cells are derived from the basal plate.

Question 240

Anencephaly calvaria - open skull

Answer 240

is the failure of the rostral neuropore to close, resulting in open calvaria.

Question 241

Lissencephaly

Answer 241

absence of normal cerebral convolutions and a poorly formed sylvian fissure.

Question 242

spina bifida - vitamin problem - anemia In adult = megaloblastic anemia = large immature blood cells

Answer 242

Dermatitis = pellagra B3 deficiency Night blindness = vitamin A deficiency Numbness and tingling in the extremities can be seen in B12 deficiency Poor wound healing = vitamin C

Question 243

primary vs secondary neuralation Open NTDs usually result from defective primary neurulation, whereas closed NTDs are the result of defective secondary neurulation. OPEN - a-fetoprotein UP closed - spina bifida oculta

Answer 243

In primary neurulation, the neural plate creases inward until the edges come in contact and fuse. In secondary neurulation, the tube forms by hollowing out of the interior of a solid precursor.

Question 244

drugs that inhibit folic acid valproic acid and methotrexate.

Answer 244

some medications reduce or inhibit production of folic acid, including valproic acid and methotrexate.

Question 245

The extent of neural involvement progresses with the different forms of spina bifida cystica;

Answer 245

skin sensation is usually lost from the affected region, and there is some degree of muscle paralysis, particularly with meningomyelocele and myeloschisis. Meningocele does not always cause nerve damage.

Question 246

fetal alcohol syndrome leading cause of congenital malformations in the United States.

Answer 246

are relatively small eyes with narrow, sometimes drooping eyelids and small palpebral fissures; as well as a smooth philtrum and a vermillion border on the thin upper lip. In addition limb dislocations, intellectual disability, and heart defects may occur with this syndrome.

Question 247

Syringomyelia associated with a type 1 Chiari malformation Type 1 Chiari malformation leads to a downward herniation of the cerebellar tonsils into the foramen magnum, which can manifest with headaches, as seen in this patient. Acquired causes of syringomyelia include trauma, whiplash injury in the elderly, tumor, and inflammation.

Answer 247

enlargement of the central canal of the spinal cord, most commonly occurring at C8-T1. Crossing fibers of the spinothalamic tract are damaged (causing loss of pain and temperature sensation), but dorsal column function is preserved (intact position and vibration sense).

Question 248

Communicating hydrocephalus

Answer 248

is caused by impaired absorption of cerebrospinal fluid in the absence of any flow obstruction between the ventricles and subarachnoid space. It is typically associated with malfunctioning arachnoid villi.

Question 249

Congenital aqueductal stenosis

Answer 249

is a common cause of congenital hydrocephalus, manifesting very early in life with symptoms of increased intracranial pressure, such as vomiting, altered mental status, and papilledema.

Question 250

Dandy-Walker syndrome Drugs may cause - warfarin, retinoic acid a group of malformations reflecting disruptions in the development of the brainstem and cerebellum, probably related to the migration of the hombic lip. The term is generally applied to malformations showing a triad of changes: (1) partial or complete agenesis of the cerebellar vermis, with anterior rotation; (2) dilation of the fourth ventricle; and (3) enlarged posterior fossa with superior displacement of the tentorium. Most cases are diagnosed within the first year, but less severe cases may not be recognized until childhood or, occasionally, adulthood. The correct answer is: Enlarged fourth ventricle and absent cerebellar vermis

Answer 250

is a congenital noncommunicating hydrocephalus typically associated with a cluster of abnormal findings that include abnormal formation of the cerebellar vermis.

Question 251

Lateral medullary syndrome, or Wallenberg syndrome,

Answer 251

usually occurs as a result of occlusion of one of the posteroinferiorcerebellar arteries (PICA). It manifests with loss of pain and temperature sensations over the contralateral side of the body and the ipsilateral face, along with vertigo, dysarthria, dysphagia, and Horner’s syndrome.

Question 252

Lissencephaly, should have 6 cortical layers here reduced to four

Answer 252

meaning "smooth brain, " refers to a defect in neuronal migration that yields an agyric cerebral cortex in which the normal six neocortical layers have been reduced to four, as seen in this coronal section.

Question 253

A fasciculation, or muscle twitch,

Answer 253

is a spontaneous, involuntary muscle contraction and relaxation, involving fine muscle fibers. They are common, with as much as 70% of people experiencing them. They can be benign, or associated with more serious conditions.

Question 254

Syringomyelia,

Answer 254

a cyst or cavitation of the central canal of the spinal cord forms. It is moe common at the cervical level as seen in this case, but lumbar cysts are possible. It can follow many types of injury, including those resulting from meningitis or from trauma. Many cases are associated with a congenital Chiari type I malformation, in which the inferior cerebellum becomes displaced downward. Because the cyst begins centrally, the axons of the anterior white commissure of the spinal cord are destroyed, resulting in segmental loss of pain and temperature. If the cavitation extends anterolaterally, it may destroy lower motor neurons causing the observed weakness and fasciculations.

Question 255

notocord creates? and neural ectoderm (D 18-21)

Answer 255

a PLATE - on the plate is a CREST toothpaste TUBE neural crest, neural tube

Question 256

A fetus's myelencephalon fails to develop. Communication of the brain with what more caudal structure will likely be affected?

Answer 256

The spinal cord, which is immediately caudal to the medulla (the derivative of the myelencephalon)

Question 257

To which 4 cell types does the neuroepithelia give rise?

Answer 257

CNS neurons, ependymal cells, oligodendroglia, astrocytes

Question 258

Which 2 types of cells in the nervous system are derived from the neural crest?

Answer 258

Schwann cells and peripheral nervous system neurons The peripheral nervous system (PNS), which consists of the neurons and parts of neurons found outside of the CNS, includes sensory neurons and motor neurons. Sensory neurons bring signals into the CNS, and motor neurons carry signals out of the CNS.

Question 259

A pt who recently had a stroke has reactive gliosis around the infarct. What is the embryologic origin of the cell type involved?

Answer 259

Neuroepithelia, which gives rise to astrocytes that proliferate in reactive gliosis (astrocytosis)

Question 260

Spina bifida occulta,

Answer 260

a defect in the bony vertebral column with no myelomeningocele herniation

Question 261

Symptoms of spina bifida occulta

Answer 261

``` back pain. leg weakness. pain in the back of the legs. loss of bladder or bowel control. scoliosis, or a curving of the spine. numbness in the back or legs. misshapen legs and feet. ```

Question 262

An infant has cyclopia, holoprosencephaly, and a midline proboscis. What genetic pathway causes this finding? What midline defect is associated with a mild or moderate mutation in the sonic hedgehog pathway?

Answer 262

The sonic hedgehog (SHH) signaling pathway, also associated with holoprosencephaly Cleft lip and/or palate

Question 263

An infant has a monoventricle with fused basal ganglia on MRI. What 2 syndromes are associated with these findings?

Answer 263

Trisomy 13 and fetal alcohol syndrome (this is holoprosencephaly)

Question 264

An infant with hydrocephalus and herniation of the cerebellar vermis can't move her legs. What is the most likely Dx?

Answer 264

Chiari II malformation with associated lumbosacral meningomyelocele causing weakness/sensory loss at levels below the lesion

Question 265

A newborn is diagnosed with a Dandy-Walker malformation. How do you characterize this defect? The cerebellar tentorium or tentorium cerebelli (Latin for "tent of the cerebellum") is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes.

Answer 265

The cerebellar vermis is missing which leads to cystic dilation of the 4th ventricle filling the enlarged posterior fossa The relationship of Arnold-Chiari and Dandy-Walker malformations. ✓ The posterior fossa is abnormally small in cases of Arnold-Chiari malformation because the tentorium is too low, whereas it is abnormally large in the Dandy-Walker malformation because the tentorium is too high.

Question 266

pseudo-unipolar neurons 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. and DORSAL ROOT ganglia

Answer 266

In 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

Question 267

Protein synthesis occurs

Answer 267

in the cell body, the Barr body represents an X chromosome, Nissl substance consists of RNA, and the axoplasm does not contain Nissl substance or a Golgi apparatus.

Question 268

Astrocytes - glial scar, BBB, cell structure

Answer 268

Astrocytes are a class of glial cells that 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). Here are the cells responsible for the other functions listed: