nervous

Central Nervous System (CNS)

Composed of the brain and spinal cord, serving as the master control center of the body.

Cerebrum

The largest upper part of the brain controlling voluntary muscles, perception, and cognitive functions.

Cerebellum

The lower part of the brain controlling involuntary body movements.

Brain Stem

Connects the brain to the spinal cord, regulating functions like breathing, heart rate, and blood pressure.

cauda equina

extends from the spinal cord past the lumbar region

Meninges

Three layers of tissue surrounding the brain and spinal cord, providing support and protection.

Cerebrospinal Fluid (CSF)

Watery fluid circulating in the subarachnoid space, acting as a shock absorber and providing nutrients to nervous tissues.

Arachnoid villi or arachnoid granulations

knoblike extensions of the arachnoid mater, extend into a blood-filled cavity at the top of the cranium and return CSF to the blood

dura mater

tough fibrous sheath that provides a strong, yet flexible, covering for the soft organs of the CNS. It also provides a barrier against the spread of infections from the bones.

arachnoid mater

Deep to the dura mater. contains numerous branching fibers giving the appearance of a spider’s web

subarachnoid space

cavities between the fibers of the arachnoid mater

pia meter

The inter￾nal layer, which is pressed close to the spinal cord and brain

blood-brain barrier

tightly joined cells that prevents most microbes and large molecules in the blood

from entering the subarachnoid space. Thus, blood infections and drugs do not easily spread to the CNS

Lumbar Puncture

Medical procedure involving the removal of CSF from the subarachnoid space surrounding the cauda equina. In between L3-L4 or L4-L5

Peripheral Nervous System (PNS)

Composed of nerves transferring commands between the CNS and muscles/glands, and providing sensory information.

Sensory nerves

primarily carry signals toward the CNS

Motor nerves

carry signals from the CNS to other organs of the body

Neurons

Cells of the nervous system generating electrical signals and transmitting nerve impulses.

Neuroglia

Supportive cells providing scaffolding, insulation, and nutritive support in the nervous system.

ganglion

a collection of many neurons’ cell bodies

synapses

mediates transfer of a signal to a neighboring postsynaptic cell

synaptic cleft

an intercellular space about 40 nm wide between the axon terminal and the postsynaptic cell. It stops the transmission of electrical signals; therefore,

the signal between cells is chemical—an axon terminal releases molecules called neurotransmitters

CNS as an axenic environment

it has no normal microbiota

Neisseria meningitidis

A Gram-negative cocci bacterium causing meningococcal meningitis, with strains A, B, C, and W135 being the most common. nonmotile, diplococci (coffee beans), lipooligosaccharide, endotoxin

blebbing

most damage caused by N. meningitidis. Sheds extrusions of its outer membrane. The lipid A (endotoxin) component of LOS thereby released into the body triggers fever, vasodilation, inflamma￾tion, shock, and widespread blood clotting

bacterial meningitis

Petechiae, milky CSF, high fever, meningeal inflammation, headache, nausea, drowsiness, muscle stiffness. May kill within 6 hours of initial symptoms.

encephalitis

condition when the brain is infected causing deafness, blindness, drastic changes in the patient’s behavior, coma, or death

Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, Listeria monocytogenes, and Streptococcus agalactiae.

5 bacteria causing 90% of bacterial meningitis

Streptococcus pneumoniae

A Gram-positive coccus bacterium causing bacterial pneumonia and meningitis, with encapsulated strains being virulent. phosphorylcholine. normal throat microflora, leading cause in <5 yrs old and very old adults.

Haemophilus influenzae

A pleomorphic bacillus requiring heme and NAD+ for growth, causing meningitis and having polysaccharide capsules. obligate parasite

Listeria monocytogenes

A Gram-positive coccobacillus causing listeriosis, particularly dangerous in pregnant women, fetuses, newborns, and immunocompromised individuals. non endospore forming, contaminated food.

Streptococcus agalactiae

A normal vaginal microbiota bacterium causing bacteremia, pneumonia, and meningitis in newborns, with a protective capsule aiding in evading phagocytosis.

Bacterial Meningitis Transmission

N. meningitidis, H. influenzae, and S. pneumoniae are inhaled from respiratory droplets; S. agalactiae is transmitted during birth; Listeria is transmitted through contaminated food.

Bacterial Meningitis Epidemiology

H. influenzae cases reduced by vaccine; S. pneumoniae and N. meningitidis are prevalent causes; S. agalactiae is a leading cause in newborns. epidemic in sub saharan africa.

diagnosis of bacterial meningitis

symptoms, lumbar puncture, serological tests

treatment for bacterial meningitis

vancomycin plus ceftriaxone, cefotaxime, meropenem, or ampicillin

spp that have bacterial meningitis vaccine (capsulated bacteria)

S. pneumoniae, H. influenzae, H. meningitidis

viral diseases of nervous system

smaller than cells, can more readily cross the blood-brain barrier, more common than bacteria

Viral Meningitis

Caused by enteroviruses, primarily attacking intestinal tract and lungs, with symptoms resembling a cold; spread through respiratory droplets and feces.

Enterovirus

viral meningitis main causative agent, +ssRNA, no envelope, spread via blood stream (viremia), kill target cells

viral meningitis epidemiology

summer & fall, respiratory droplets & feces

Viral Meningitis Diagnosis and Treatment

Diagnosed based on symptoms and absence of bacteria in CSF; no specific treatment, with recommendations for rest, fluids, and fever management.

Subacute Sclerosing Panencephalitis

A slow progressive disease of the CNS caused by measles virus.

Viral Meningitis

A milder disease compared to bacterial or fungal meningitis, primarily caused by Enteroviruses.

Enterovirus

Small, +ssRNA viruses that spread through fecal contamination and can cause viral meningitis.

Poliomyelitis

A disease caused by poliovirus, leading to asymptomatic, minor, nonparalytic, or paralytic conditions.

asymptomatic infections

accounts for 90% of cases in polio

minor polio

5% of all polio cases. nonspecific symptoms such as temporary fever, headache, malaise, and sore throat

Nonparalytic polio

results from polioviruses invading the meninges and central nervous system, producing muscle spasms and back pain in addition to the general symptoms of

minor polio. occurs in about 2% of cases.

Paralytic polio

<2% of infections. Involves viral invasion of cells of the spinal cord and the portion of the cerebrum that controls skeletal muscles, producing paralysis by limiting nerve impulse conduction. In most paralytic cases, complete recovery results after 6–24 months, but in some cases paralysis is lifelong.

bulbar poliomyelitis

the brain stem is infected, resulting in paralysis of respiratory muscles or of muscles in the limbs. In the past, iron lungs were used to help victims breathe.

postpolio syndrome

crippling deterioration in the function of polio-affected muscles that occurs in up to 80% of recovered polio patients some 30–40 years after their original bout

with poliomyelitis.

contaminated water

most common people are infected with poliovirus

spinal cord

where poliovirus travels towards to after infecting pharyngeal and intestinal cells via lymph

pakistan & nigeria

where poliovirus remains endemically

throat secretions & feces

diagnosis of polio

salk vaccine

inactivated polio vaccine, cheap, stable during transport, requires booster for lifelong immunity, requires higher community immunization rate

sabin vaccine

attenuated oral polio vaccine, lifelong immunity without booster, herd immunity, can mutate to disease causing form in immunocompromised px, less stable

Rabies

A viral disease affecting the CNS, characterized by hydrophobia and paralysis, caused by the rabies virus.

Lyssavirus

A genus of viruses including rabies virus, which is a negative, single-stranded RNA virus. family rhabdoviridae

Poliovirus

A species of Enterovirus causing poliomyelitis, primarily transmitted through contaminated water.

Postpolio Syndrome

Deterioration in polio-affected muscles occurring years after the original infection.

rhabdoviruses

have helical caspids supercoiled into cylinders which give them a striated appearance, and are surrounded by bullet-shaped envelopes with glycoprotein spikes for attachment

Rabies Virus Pathogenesis

Rabies virus attaches to skeletal muscle cells, replicates in cytoplasm, and travels to the CNS via axonal transport.

Rabies Epidemiology

A zoonotic disease primarily spread by mammals, with bats being a common source in humans.

rabies diagnosis

neurological symptoms, antibodies, postmortem tests (noflouroesence)

human diploid cell vaccine

deactivated rabies viruses cultured in human diploid cells, administered intramuscu￾larly on days 0, 3, 7, and 14 after exposure to rabies virus

rabies treatment

first is treatment of the site of infection, human rabies immunoglobulin (HRIG), and four HDCV infections

Arboviral encephalitis

A condition characterized by high fever, weakness, nausea, vomiting, headache, confusion, and coma, caused by arboviruses crossing the blood-brain barrier.

arborviral encephalitis signs & symptoms

similar to meningitis, neurological effects may be permanent

arbovirus hosts

humans, birds, horses, chimps, cats, dogs, chipmunks

Pathogens of arboviruses

Six arboviruses, including EEE, WEE, VEE, St. Louis encephalitis, West Nile encephalitis, and California encephalitis, cause most cases of viral encephalitis in Americans.

Eastern equine encephalitis (EEE), Western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE)

identified in horses, +ssRNA from family togaviridae

St. Louis encephalitis and West Nile encephalitis

+ssRNA viruses in family flaviviridae

california encephalitis

-ssRNA enveloped and segmented virus from Bunyaviridae

mosquitoes that transmit arboviruses

Female Aedes or Culex mosquitoes

horses & humans

dead end hosts for arboviruses

Arboviral encephalitis Epidemiology

in the U.S. is seasonal, with peaks corresponding to active mosquito periods, affecting individuals engaging in outdoor activities in endemic areas. children are at higher risk for WEE, VEE, and Cal ence.

Diagnosis, Treatment, and Prevention of arboviral encephalitis

observing symptoms and detecting specific arbovirus antibodies in the cerebrospinal fluid; treatment is supportive, and prevention includes limiting mosquito contact. igM is produced early in infection <8 days.

Cryptococcal meningitis

A fungal infection affecting healthy and immunocompromised individuals, characterized by headache, dizziness, nausea, vision loss, and coma, caused by Cryptococcus neoformans.

Cryptococcus neoformans

a basidiomycete yeast, has two variants infecting hosts differently, with a polysaccharide capsule resisting phagocytosis and melanin production enhancing pathogenesis.

C. neoformans var. gattii

causative agent of cryptococcal meningitis for immunocompetent px

C. neoformans var. neoformans

causative agent of cryptococcal meningitis for immunocompromised px

cryptococcal infections

starts in the lungs, spreading to the central nervous system, affecting individuals inhaling spores from bird droppings, with AIDS patients at higher risk.

fungal antigen detection in CSF

diagnosis of cryptococcal meningitis

treatment of cryptococcal meningitis

intravenous amphotericin B (toxic) and oral 5-fluorocytosine administered together for at least four weeks. lifelong oral fluconazole treatment.

Variant Creutz-Jakob Disease

vCJD is caused by abnormal prion proteins leading to brain tissue destruction, insomnia, muscle spasms, and death, with transmission through medical procedures and consumption of contaminated nerve tissue.

vCJD

insomnia, weight loss, and memory failure. They also act irrationally, lose control of their muscles, unable to speak, walk, or maintain posture. Death usually occurs within 12 months.

Diagnosis of vcjd

CNS samples confirming abnormal prion presence;

Prions

Proteinaceous infectious particles that can survive cooking, freezing, and even autoclaving.

vCJD

Variant Creutzfeldt-Jakob disease, a prion disease that can be prevented by avoiding contaminated meat.

Autoclaving

Recommended method to destroy prions, often done in a concentrated solution of sodium hydroxide.

Enzyme treatment

Approved in the EU to remove prions from the environment.

Contaminated meat

Should be avoided to prevent vCJD, especially meat cut from bones near the spinal cord and processed meats made from brains or spinal cords of infected animals.

arbovirus

viruses entering target cells via endocytosis and causing encephalitis by crossing the blood-brain barrier.

vcjd

no treatment is available, and prevention focuses on avoiding contaminated nerve tissue consumption.

Cerebrum

Higher order thinking

Diencephalon

Release, relay, regulate

Cerebellum

Coordination