Toxic Responses of the Nervous System

Question 1

Three basic functions of the nervous system

Answer 1

Relays information, motor functions, Integrates thought processes, learning and memory

Question 2

two fundamental anatomical divisions of the nervous system

Answer 2

central and peripheral nervous system

Question 3

It is the control center, composed of brain and spinal cord

Answer 3

Central nervous system

Question 4

T/F: the central nervous system analyzes information received from sensory receptors, and in response, it issues motor commands to control body functions

Answer 4

True

Question 5

What are the two types of nerves under the peripheral nervous system?

Answer 5

Afferent nerves and efferent nerves

Question 6

Modified T/F: Efferent nerves relays sensory information to the CNS. Afferent nerves relays motor commands from the CNS to the various muscles and glands

Answer 6

BOTH FALSE. Afferent nerves relays sensory information to the CNS. Efferent nerves relays motor commands from the CNS to the various muscles and glands

Question 7

Efferent nerves are further organized into two systems, which are:

Answer 7

Somatic nervous system and Autonomic nervous system

Question 8

Modified T/F: Somatic nervous system carries motor information to smooth muscles, cardiac muscles, and various glands. Autonomic nervous system is also known as the voluntary system, which carries motor information to the skeletal muscles.

Answer 8

BOTH FALSE. Autonomic nervous system carries motor information to smooth muscles, cardiac muscles, and various glands. Somatic nervous system is also known as the voluntary system, which carries motor information to the skeletal muscles.

Question 9

T/F: Skeletal muscles, smooth muscles, cardiac muscles, and glands are effectors

Answer 9

True

Question 10

What is the major difference between the somatic and autonomic nervous system?

Answer 10

conscious control

Question 11

The nervous system is protected from the adverse effects of many potential toxicants by an anatomical barrier between the blood and the brain, or a ____________________

Answer 11

blood-brain barrier (BBB).

Question 12

To gain entry to the nervous system, molecules must pass into the __________________ of endothelial cells of the brain rather than ________________ endothelial cells, as they do in other tissues.

Answer 12

cell membranes; between

Question 13

among the unique properties of the endothelial cells in the nervous system is the presence of __________________ between the cells, this is why molecules cannot easily penetrate between them

Answer 13

tight junctures

Question 14

T/F: the BBB contains xenobiotic transporters, which transports xenobiotics that have diffused through the endothelial cells back into the blood

Answer 14

True

Question 15

If not actively transported into the brain, the penetration of toxicants or their metabolites is largely related to their _______________.

Answer 15

lipid solubility

Question 16

The _______________, ______________, and a small number of other sites within the brain are not protected by blood-tissue barriers.

Answer 16

Spinal ganglia; autonomic ganglia

Question 17

Neurons are highly dependent on ________________ because they use the energy to maintain proper ion gradients

Answer 17

aerobic metabolism

Question 18

These lead to early signs of neuronal dysfunction

Answer 18

Cyanide and CO poisoning

Question 19

neuronal dysfunction can be a combination of direct toxic effects on neurons and secondary damage from ________________________

Answer 19

systemic hypoxia or ischemia

Question 20

It is a toxicant-induced irreversible loss of neurons, including its cytoplasmic extensions, dendrites, axons, and the myelin ensheathing the axon.

Answer 20

neuronopathy

Question 21

This is where the axon degenerates while neuronal cell body continues to survive.

Answer 21

axonopathy

Question 22

Modified T/F: Neuronopathy is characterized by loss of cell body and all of its processes with no potential for regeneration. Axonopathy includes loss of myelin surrounding the axon

Answer 22

BOTH TRUE

Question 23

This is a functional assessment where sensory-specific information on nerve conduction velocity and integrity is assessed.

Answer 23

electrophysiological tests

Question 24

This is an observation with regards to behavior. This is under functional assessments

Answer 24

Functional observational studies

Question 25

Other types of functional observational studies

Answer 25

Irwin screens, tests of motor activity, and expanded clinical observations

Question 26

Individual neurotoxic compounds typically target the _______, the _______, the myelinating cell, or the ___________________ system.

Answer 26

neuron; axon; neurotransmitter

Question 27

Modified T/F: A large number of compounds are known to result in toxic neuronopathies. All of these toxicants share certain features.

Answer 27

BOTH TRUE

Question 28

T/F: Neuropathy pathway: apoptosis or necrosis --> initial injury to neurons --> permanent loss of neurons

Answer 28

False. Initial injury to neurons --> apoptosis or necrosis --> permanent loss of neurons

Question 29

The neurotoxic effect of this neurotoxicant is the degeneration of the dorsal root ganglion cells, and axonal degeneration in the PNS

Answer 29

doxorubicin

Question 30

The neurologic finding in this neurotoxicant includes ataxia, constriction of visual fields, paresthesias in adults, and psychomotor retardation (fetal exposure)

Answer 30

methylmercury (organic mercury)

Question 31

The neurologic findings of this neurotoxicant includes tremors, and hyperexcitability in experimental animals

Answer 31

trimethyltin

Question 32

T/F: doxorubicin, which is an antimitotic in cancer chemotherapy, exerts its effects on the neurons in the PNS, particularly, the dorsal root and autonomic ganglia by intercalating with the DNA and interfering with the transcription

Answer 32

True

Question 33

This neurotoxicant targets neurons of the visual cortex; massive degeneration can lead to blindness and marked ataxia for adults

Answer 33

Methylmercury (organic mercury)

Question 34

This neurotoxicant targets irreversible limbic-cerebellar syndrome in humans and similar behavioral changes in primates

Answer 34

trimethyltin

Question 35

The children affected will usually have developmental deficits, retardation and even cognitive deficits

Answer 35

methylmercury (organic mercury)

Question 36

this neurotoxicant may be found in plasticizers, antifungal agents, or pesticides

Answer 36

trimethyltin

Question 37

The accumulation of methylmercury in the body from eating fish from bodies of water connected to chemical factories may lead to ________________

Answer 37

Minamata disease

Question 38

The cellular basis of neurotoxicity of this neurotoxicant includes loss of hippocampal neurons, and on amygdala pyriform cortex

Answer 38

Trimethyltin

Question 39

The cellular basis of neurotoxicity of methylmercury (organic mercury)

Answer 39

Neuronal degeneration in visual cortex, cerebellum, and ganglia. Spongy disruption in the cortex and cerebellum

Question 40

These are chemicals associated with neuronal injury (neuropathies)

Answer 40

doxorubicin, methylmercury (organic mercury), and trimethyltin

Question 41

primary site of axonopathies

Answer 41

axons

Question 42

These are chemicals associated with axonal injury (axonopathies)

Answer 42

acrylamide, carbon disulfide, n-hexane, B,B'-Iminodipropionitrile, and organophosphorous compounds (NTE inhibitors)

Question 43

Neurotoxicant: Acrylamide Neurologic findings: peripheral neuropathy, which is often _________ Basis: axonal degeneration where the axon terminal is affected in its _________ stages

Answer 43

sensory earliest

Question 44

Neurotoxicant: Carbon disulfide Neurologic findings: Acute ____________ and chronic _____________ Basis: axonal degeneration, early stages include _______________________

Answer 44

psychosis; peripheral neuropathy neurofilamentous swelling

Question 45

Neurotoxicant: n-Hexane Neurologic finding: peripheral neuropathy, severe cases have ________ Basis: axonal degeneration, early neurofilamentous swelling (_________ and _________)

Answer 45

spasticity PNS and spinal cord

Question 46

Neurotoxicant: B,B'-Iminodipropionitrile Neurologic finding: No data in humans; ___________________ in rats Basis: ___________ axonal swellings, degeneration of _____________ epithelial cells and _________________ cells

Answer 46

excitatory movement proximal; olfactory; vestibular hair

Question 47

Neurotoxicant: Organophosphate compounds (NTE inhibitors) Neurologic findings: acute _____________ and peripheral neuropathy Basis: Axonal degeneration

Answer 47

abdominal pain

Question 48

identify the neurotoxicant These are classified as gamma-diketones

Answer 48

n-hexane and 2-hexanone

Question 49

identify the neurotoxicant distal axonopathy; covalent cross-linking of neurofilaments which can also lead to aberrations in mood and signs of diffuse encephalopathic disease

Answer 49

Carbon disulfide (CS2)

Question 50

This syndrome is specifically for rats as there is not much record of its effect on humans. It exhibits excitement, circling, head twitching, or over-alertness which indicates that there is already degeneration of vestibular hair cells

Answer 50

Waltzing syndrome

Question 51

Identify the neurotoxicant Causes Waltzing syndrome

Answer 51

B,B'-Iminodipropionitrile (IDPN)

Question 52

identify the neurotoxicant distal axonopathy characterized by multiple axonal swellings

Answer 52

Acrylamide

Question 53

T/F: the critical difference between central nervous system and peripheral nervous system axonal degeneration, is that in PNS, it can regenerate but for central axons, they cannot regenerate

Answer 53

True

Question 54

Factors why central axons cannot regenerate

Answer 54

inhibitory factors that are secreted by oligodendrocytes, and astrocyte scarring, and glial interference

Question 55

Modified T/F: Myelin provides electrical insulation of neuronal processes. In its absence, there is slowing of conduction and aberrant conduction of impulses between adjacent processes

Answer 55

BOTH TRUE

Question 56

This myelinopathy is caused by alterations in transcript levels of myelin basic protein mRNA, where there is separation of myelin lamellae

Answer 56

Intramyelinic edema

Question 57

This myelinopathy may result from progressive intramyelinic edema or from direct toxicity to myelinating cell, where there is selective loss of myelin

Answer 57

Demyelination

Question 58

______________ in the PNS are capable of remyelinating the axon.

Answer 58

Schwann cells

Question 59

Acute, massive exposures to lead would result in severe ____________, and intramyelinic edema

Answer 59

cerebral edema

Question 60

Chronic lead intoxication usually leads to ________________, gastritis, or _________

Answer 60

peripheral neuropathy; anemia

Question 61

Examples of chemicals associated with myelinopathies

Answer 61

hexachlorophene and tellurium

Question 62

Neurotoxicant: Hexachlorophene Neurologic findings: ____________, confusion, and ___________ Basis: _________ swelling, intramyelinic edema in _____ and _____, and _____ axonal degeneration

Answer 62

irritability; seizures brain; CNS and PNS; late

Question 63

Neurotoxicant: Tellurium Neurologic finding: _____________, and hind limb paralysis in experimental animals Basis: Demyelinating neuropathy, and ________________ in experimental animals

Answer 63

hydrocephalus lipofuscinosis

Question 64

Identify the neurotoxicant When absorbed by the skin, it enters the nervous system and causes neurotoxicity by forming vacuoles that would create spongiosis in the brain

Answer 64

Hexachlorophene

Question 65

Are primary means of defense in the CNS following exposure to neurotoxicants.

Answer 65

astrocytes

Question 66

Modified T/F: Astrocytes also serves as spatial buffering system for osmotically active ions. They are also depot for metabolic processing of exogenous molecules only.

Answer 66

1st TRUE 2nd FALSE. depot for metabolic processing of endogenous molecules and xenobiotics

Question 67

This causes astrocytic swelling and morphological changes

Answer 67

ammonia

Question 68

The inhibition of neuronal glutamate precursor synthesis (changes in neurotransmitter uptake: glutamate) is a result of ...?

Answer 68

increased intracellular ammonia

Question 69

Organic nitrates, Dinitrobenzenes (DNB), and Metronidazole are classified as

Answer 69

Nitrochemicals

Question 70

This nitrochemical creates gliovascular lesions that target astrocytes in the gray matter of the brainstem and deep cerebellar roof nuclei

Answer 70

dinitrobenzenes (DNB)

Question 71

Prolonged treatment with this drug is associated with peripheral neuropathy; effects include paresthesia, headache, glossitis, urticaria or pruritus

Answer 71

metronidazole

Question 72

This is an irreversible inhibitor of astrocyte-specific enzyme glutamine synthase in which there would be a large increase of glycogen levels that would lead to swollen and damaged astrocytic mitochondria

Answer 72

Methionine sulfoximine (MSO)

Question 73

T/F: Although neurotransmitter-associated actions may be well understood for some agents, the specificity of the mechanism should not be assumed.

Answer 73

True

Question 74

This neurotoxicant bind to nicotinic cholinergic receptor

Answer 74

nicotine

Question 75

T/F: Nicotine toxicity pathway: rapid rise after acute OD → excessive stimulation of nicotinic receptors → ganglionic paralysis (nausea, rapid heart rate, perspiration, somnolence, coma)

Answer 75

True

Question 76

Cocaine blocks ____________, _____________, and ___________ reuptake at the nerve terminal in the CNS; causes release of dopamine from storage vesicles

Answer 76

dopamine; norepinephrine; serotonin

Question 77

Modified T/F: Cerebrovascular defects, stroke, and intracranial hemorrhage are common effects of cocaine. The PRIMARY EVENT that is responsible for the addictive properties and euphoric feelings during cocaine intoxication is the blockade of the dopamine reuptake transporter (DAT)

Answer 77

BOTH TRUE

Question 78

This neurotoxicant is involved in catecholamine neurotransmission in the CNS

Answer 78

amphetamines

Question 79

This causes higher energy and sensation in adults

Answer 79

MDMA (methylenedioxymethamphetamine; ecstasy)

Question 80

The most pronounced effects of amphetamines is on __________________, but can also damage serotonin axons and axon terminals.

Answer 80

dopaminergic neurons

Question 81

These chemicals are associated with damages in the astrocytes

Answer 81

Ammonia, nitrochemicals, and methionine sulfoximine (MSO)

Question 82

These chemicals are associated with neurotransmission-associated neurotoxicity

Answer 82

Cocaine, amphetamines, and nicotines

Question 83

Neurotoxicant: amphetamine and metamphetamine Neurologic findings: tremor, restlessness (acute), __________________ and hemorrhage, and _______________ disturbances Basis: Bilateral infarcts of _______________, abnormalities in dopaminergic, serotonergic, and dopaminergic systems. Also acts at ________________ receptors in the PNS

Answer 83

cerebral infarctions; neuropsychiatric globus pallidus, adrenergic

Question 84

Neurotoxicant: Cocaine Neurologic findings: Increased risk of stroke and ______________ in chronic users, increased risk of cardiac death; movement and psychiatric abnormalities especially during ______________ Decreased ____________ in fetal exposures (newborns) Basis: Infarcts and hemorrhages, alteration in __________ dopamine neurotransmission

Answer 84

cerebral atrophy; withdrawal head circumference striatal

Question 85

Neurotoxicant: Nicotine Neurologic findings: nausea, vomiting, ____________ Basis: binds to nicotinic receptors (____________) low-dose stimulation; high-dose blocking

Answer 85

convulsions cholinergic

Question 86

Generalized depression of CNS function is produced by a variety of volatile solvents. Give examples

Answer 86

Ethanol, organics, and anesthetics

Question 87

Mechanism of generalized depression: interactions with ____________ ion channels as well as ____________ calcium channels.

Answer 87

ligand-gated; voltage-gated

Question 88

Modified T/F: Calcium is involved in motor function and control. Interactions with these compounds possibly induces NS depression

Answer 88

BOTH TRUE

Question 89

Goal for future studies of neurotoxicology: replace standard _________ assessments with high throughput in vitro assays and ___________________________ to predict adverse outcomes.

Answer 89

In vivo; Quantitative Structure-Activity Relationships (QSARs)

Question 90

T/F: The nervous system is the most complex system of the body.

Answer 90

True

Question 91

T/F: There are still many gaps in understanding how many neurotoxins act, yet research is discovering their possible effects on the body's structures and functions which may all be due to a lot of considerations.

Answer 91

True

Question 92

T/F: It is important to understand that the most potent toxins are common kitchen ingredients, with extremely minute amounts sufficient to cause death.

Answer 92

False. Most potent toxins are neurotoxins