TWO COMPONENT PARTS OF NERVOUS SYSTEM NERVOUS SYSTEM AND ITS DEFENSES
CENTRAL NERVOUS SYSTEM: brain and spinal cord Defenses of the nervous system are mainly structura
PERIPHERAL NERVOUS SYSTEM: nerves emanating • Bony casings of the brain and spinal cord protect
from the brain and spinal cord to sense organs and to them from traumatic injury
the periphery of the body
• CSF serves as a cushion against impact
IMPORTANT FUNCTIONS OF NERVOUS SYSTEM
• Blood-brain barrier
SENSORY
BLOOD BRAIN BARRIER: Cells that make up the
• Sensory receptors at the ends of peripheral nerves walls of blood vessels around the brain allow very fe
molecules to pass through
• Generate nerve impulses transmitted to the CNS
• Freer passage of ions, sugars, and other metabolite
INTEGRATIVE in other areas of the body
• Translates impulses into sensation or thought • Prohibits most microorganisms from passing
• Drives motor function into the CNS
• Drugs and antibiotics are difficult to introduce
MOTOR into the CNS when needed
• Involves muscles and glands IMMUNE PRIVILEGE OF THE CNS
BRAIN AND SPINAL CORD : A different or partial immune response when expose
MADE UP OF NEURONS SURROUNDED BY BONES to immunologic challenge
• Brain inside the skull : Functions of the CNS are vital for the life of an
organism and temporary damage from a “normal”
• Spinal cord inside the spinal column immune response could be detrimental
BRAIN SURROUNDED BY MENINGES : Cells in the CNS express lower levels of MHC
antigens
• Dura mater
: Lower quantities of complement proteins
• Arachnoid mater
SPECIALIZED IMMUNE CELLS IN THE CNS
• Pia mater
: Microglial cells display phagocytic activity
CEREBROSPINAL FLUID
: Brain macrophages exist in the CNS
• Fills the subarachnoid space
: Activity of both types of cells is less than that of
• Clear, serum-like fluid
phagocytic cells elsewhere in the body
• Provides nutrition to the CNS
NORMAL BIOTA OF THE NERVOUS SYSTEM
• Provides a liquid cushion for the brain and spinal cord
It is still believed that the CNS and PNS lack normal
MENINGITIS: Infections of the meningitis biota of any kind
STRUCTURE OF THE PERIPHERAL NERVOUS • represents a deviation from a healthy state
SYSTEM
• Certain viruses live in a dormant state in the nervou
GANGLIA: swelling in the nerve where cell bodies of system between episodes of acute disease
neurons congregate
• Example: herpes simplex viruses
NERVES: bundles of neuronal axons that receive and
• Not considered normal biota
transmit nerve signals
HUMAN MICROBIOME PROJECT
• Axons and dendrites of adjacent neurons
communicate over a synapse Information from the HMP is revealing a potential link
between the gut microbiome and the nervous system
• Neurotransmitters released from one cell act on the
next cell in the synapse Gut microbiota may induce CNS autoimmunity
,• Appear to cause changes in the brain chemistry and NEISSERIA MENINGITIDIS
behavior • Phenomenon is known as the gut-brain axis
: Gram-negative diplococci lined up side by side
: Also known as the meningococcus
: Associated with epidemic forms of meningitis
: Causes the most serious form of acute meningitis
: Responsible for 14% of all meningitis cases
MENINGITIS: Inflammation of the meninges
Anatomical syndrome:
• Different microbes cause meningitis, and produce a
similar constellation of syndromes
• Noninfectious causes of meningitis exist as well, but are
less common
: Serious forms of acute meningitis are caused by
bacteria
: Entrance into CNS is facilitated by coinfection or
previous infection with respiratory viruses
WHEN MENINGITIS IS SUSPECTED
Lumbar puncture to obtain CSF G
N MENINGITIS PATHOGENESIS AND VIRULENCE
ram stain and/or culture of CSF FACTORS
Begin treatment with broad-spectrum antibiotics with a MENINGOCOCCEMIA: • Rare, high mortality rate
shift in treatment after a diagnosis has been confirmed
ENDOTOXIN ACTS AS A POTENT WBC STIMULATOR
SIGNS AND SYMPTOMS OF MENINGITIS
Endotoxin acts as a potent WBC stimulator
Meningitis has the following typical symptoms, regardless
of the cause: • Damage to blood vessels caused by cytokines released by
WBC leads to vascular collapse, hemorrhage, and crops of
• Photophobia
red or purple lesions called petechiae on the trunk and
• Headache appendages
• Painful or stiff neck N.MENINGITIDIS OXIDASE TEST
• Fever
• Increased WBC in CSF
• Certain microorganisms may cause additional
characteristic symptoms
MORE MENINGITIS DETAILS
Can manifest as acute or chronic disease:
• Some microorganisms are more likely to cause acute
meningitis, others cause chronic meningitis
In a healthy person, it is difficult for microorganisms to
gain access to the nervous system
• Successful microorganisms have specific virulence
factors
, STREPTOCOCCUS PNEUMONIAE CRYPTOCOCCUS NEOFORMANS
: Also referred to as the pneumococcus Fungus that causes chronic meningitis with a gradual
onset of symptoms
: Causes the majority of bacterial pneumonias
In AIDS patients: fast onset and acute disease
: Most frequent cause of community-acquired
meningitis Widespread in human habitats
: Does not cause petechiae Spherical to ovoid shape with a large capsule
: Most likely to occur in patients with underlying Transmitted in bird droppings
susceptibility COCCIDIOISDES: VALLEY FEVER
: Carriage rates exceed 30% in some populations Fungus with a distinctive morphology:
MORE STREPTOCOCCUS PNEUMONIAE • 25°C: moist white to brown colony with abundant,
: Small, gram-positive, flattened coccus that appears in branching, septate hyphae
endto-end pairs • 37°C to 40°C: parasitic phase, small spherule
: Distinctive appearance in a Gram stain of CSF True systemic fungal infection of high virulence
: Has a polysaccharide capsule that protects against Genetic susceptibility gives rise to more serious
phagocytosis
disease
: Produces an alpha-hemolysin and hydrogen peroxide, COCCIDOIDES TRANSMISSION AND
both of which have been shown to induce damage in EPIDEMIOLOGY
the CNS
Occurs endemically in natural reservoirs
: Two vaccines are available
C. immitis causes disease in California; C. posadasii is
HAEMOPHILUS INFLUENZAE
found in northern Mexico, Central and South America,
: Gram-negative coccobacillus and the American Southwest, especially Arizona
: Causes one of the most severe forms of meningitis in VIRAL MENINGITIS
humans
Four of five meningitis cases are caused by one of a
: Often called “Hib” because serotype B is the most wide variety of viruses
common cause of infection
Aseptic meningitis: viral meningitis is assumed when a
: Vaccination has reduced asymptomatic carriage rates patient shows symptoms of meningitis but no bacteria
and has virtually eliminated Hib in the United States or fungi are found in CSF
LISTERIA MONOCYTOGENES Majority of cases in children
: Gram-positive, ranges in morphology from 90% caused by enteroviruses
coccobacilli to long filaments in palisade formation HSV-2 is sometimes known to cause meningitis; other
: Does not produce capsules or endospores Has 1 to 4 herpesviruses (HHV-6, HHV-7, and HHV-3) and HIV
flagella can manifest as meningitis as well
: Not fastidious, resistant to cold, heat, salt, pH Generally milder than bacterial or fungal meningitis –
extremes, and bile usually resolved in 2 weeks; mortality rate is less than
1%
: Grows inside host cells, moves directly from an
infected cell to an adjacent healthy cell NEONATAL AND INFANT MENINGITIS
LISTERIOSIS Usually the result of an infection transmitted by the
mother in utero or during passage through the birth
Mild or subclinical in healthy adults canal
Causes meningitis and septicemia in the elderly, As more premature babies survive, rates of neonatal
immunocompromised, fetuses, and neonates meningitis increase
CENTRAL NERVOUS SYSTEM: brain and spinal cord Defenses of the nervous system are mainly structura
PERIPHERAL NERVOUS SYSTEM: nerves emanating • Bony casings of the brain and spinal cord protect
from the brain and spinal cord to sense organs and to them from traumatic injury
the periphery of the body
• CSF serves as a cushion against impact
IMPORTANT FUNCTIONS OF NERVOUS SYSTEM
• Blood-brain barrier
SENSORY
BLOOD BRAIN BARRIER: Cells that make up the
• Sensory receptors at the ends of peripheral nerves walls of blood vessels around the brain allow very fe
molecules to pass through
• Generate nerve impulses transmitted to the CNS
• Freer passage of ions, sugars, and other metabolite
INTEGRATIVE in other areas of the body
• Translates impulses into sensation or thought • Prohibits most microorganisms from passing
• Drives motor function into the CNS
• Drugs and antibiotics are difficult to introduce
MOTOR into the CNS when needed
• Involves muscles and glands IMMUNE PRIVILEGE OF THE CNS
BRAIN AND SPINAL CORD : A different or partial immune response when expose
MADE UP OF NEURONS SURROUNDED BY BONES to immunologic challenge
• Brain inside the skull : Functions of the CNS are vital for the life of an
organism and temporary damage from a “normal”
• Spinal cord inside the spinal column immune response could be detrimental
BRAIN SURROUNDED BY MENINGES : Cells in the CNS express lower levels of MHC
antigens
• Dura mater
: Lower quantities of complement proteins
• Arachnoid mater
SPECIALIZED IMMUNE CELLS IN THE CNS
• Pia mater
: Microglial cells display phagocytic activity
CEREBROSPINAL FLUID
: Brain macrophages exist in the CNS
• Fills the subarachnoid space
: Activity of both types of cells is less than that of
• Clear, serum-like fluid
phagocytic cells elsewhere in the body
• Provides nutrition to the CNS
NORMAL BIOTA OF THE NERVOUS SYSTEM
• Provides a liquid cushion for the brain and spinal cord
It is still believed that the CNS and PNS lack normal
MENINGITIS: Infections of the meningitis biota of any kind
STRUCTURE OF THE PERIPHERAL NERVOUS • represents a deviation from a healthy state
SYSTEM
• Certain viruses live in a dormant state in the nervou
GANGLIA: swelling in the nerve where cell bodies of system between episodes of acute disease
neurons congregate
• Example: herpes simplex viruses
NERVES: bundles of neuronal axons that receive and
• Not considered normal biota
transmit nerve signals
HUMAN MICROBIOME PROJECT
• Axons and dendrites of adjacent neurons
communicate over a synapse Information from the HMP is revealing a potential link
between the gut microbiome and the nervous system
• Neurotransmitters released from one cell act on the
next cell in the synapse Gut microbiota may induce CNS autoimmunity
,• Appear to cause changes in the brain chemistry and NEISSERIA MENINGITIDIS
behavior • Phenomenon is known as the gut-brain axis
: Gram-negative diplococci lined up side by side
: Also known as the meningococcus
: Associated with epidemic forms of meningitis
: Causes the most serious form of acute meningitis
: Responsible for 14% of all meningitis cases
MENINGITIS: Inflammation of the meninges
Anatomical syndrome:
• Different microbes cause meningitis, and produce a
similar constellation of syndromes
• Noninfectious causes of meningitis exist as well, but are
less common
: Serious forms of acute meningitis are caused by
bacteria
: Entrance into CNS is facilitated by coinfection or
previous infection with respiratory viruses
WHEN MENINGITIS IS SUSPECTED
Lumbar puncture to obtain CSF G
N MENINGITIS PATHOGENESIS AND VIRULENCE
ram stain and/or culture of CSF FACTORS
Begin treatment with broad-spectrum antibiotics with a MENINGOCOCCEMIA: • Rare, high mortality rate
shift in treatment after a diagnosis has been confirmed
ENDOTOXIN ACTS AS A POTENT WBC STIMULATOR
SIGNS AND SYMPTOMS OF MENINGITIS
Endotoxin acts as a potent WBC stimulator
Meningitis has the following typical symptoms, regardless
of the cause: • Damage to blood vessels caused by cytokines released by
WBC leads to vascular collapse, hemorrhage, and crops of
• Photophobia
red or purple lesions called petechiae on the trunk and
• Headache appendages
• Painful or stiff neck N.MENINGITIDIS OXIDASE TEST
• Fever
• Increased WBC in CSF
• Certain microorganisms may cause additional
characteristic symptoms
MORE MENINGITIS DETAILS
Can manifest as acute or chronic disease:
• Some microorganisms are more likely to cause acute
meningitis, others cause chronic meningitis
In a healthy person, it is difficult for microorganisms to
gain access to the nervous system
• Successful microorganisms have specific virulence
factors
, STREPTOCOCCUS PNEUMONIAE CRYPTOCOCCUS NEOFORMANS
: Also referred to as the pneumococcus Fungus that causes chronic meningitis with a gradual
onset of symptoms
: Causes the majority of bacterial pneumonias
In AIDS patients: fast onset and acute disease
: Most frequent cause of community-acquired
meningitis Widespread in human habitats
: Does not cause petechiae Spherical to ovoid shape with a large capsule
: Most likely to occur in patients with underlying Transmitted in bird droppings
susceptibility COCCIDIOISDES: VALLEY FEVER
: Carriage rates exceed 30% in some populations Fungus with a distinctive morphology:
MORE STREPTOCOCCUS PNEUMONIAE • 25°C: moist white to brown colony with abundant,
: Small, gram-positive, flattened coccus that appears in branching, septate hyphae
endto-end pairs • 37°C to 40°C: parasitic phase, small spherule
: Distinctive appearance in a Gram stain of CSF True systemic fungal infection of high virulence
: Has a polysaccharide capsule that protects against Genetic susceptibility gives rise to more serious
phagocytosis
disease
: Produces an alpha-hemolysin and hydrogen peroxide, COCCIDOIDES TRANSMISSION AND
both of which have been shown to induce damage in EPIDEMIOLOGY
the CNS
Occurs endemically in natural reservoirs
: Two vaccines are available
C. immitis causes disease in California; C. posadasii is
HAEMOPHILUS INFLUENZAE
found in northern Mexico, Central and South America,
: Gram-negative coccobacillus and the American Southwest, especially Arizona
: Causes one of the most severe forms of meningitis in VIRAL MENINGITIS
humans
Four of five meningitis cases are caused by one of a
: Often called “Hib” because serotype B is the most wide variety of viruses
common cause of infection
Aseptic meningitis: viral meningitis is assumed when a
: Vaccination has reduced asymptomatic carriage rates patient shows symptoms of meningitis but no bacteria
and has virtually eliminated Hib in the United States or fungi are found in CSF
LISTERIA MONOCYTOGENES Majority of cases in children
: Gram-positive, ranges in morphology from 90% caused by enteroviruses
coccobacilli to long filaments in palisade formation HSV-2 is sometimes known to cause meningitis; other
: Does not produce capsules or endospores Has 1 to 4 herpesviruses (HHV-6, HHV-7, and HHV-3) and HIV
flagella can manifest as meningitis as well
: Not fastidious, resistant to cold, heat, salt, pH Generally milder than bacterial or fungal meningitis –
extremes, and bile usually resolved in 2 weeks; mortality rate is less than
1%
: Grows inside host cells, moves directly from an
infected cell to an adjacent healthy cell NEONATAL AND INFANT MENINGITIS
LISTERIOSIS Usually the result of an infection transmitted by the
mother in utero or during passage through the birth
Mild or subclinical in healthy adults canal
Causes meningitis and septicemia in the elderly, As more premature babies survive, rates of neonatal
immunocompromised, fetuses, and neonates meningitis increase
