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a) A drawing of a neuron. The cell body contains the nucleus and has short projections called dendrite. The cell also has a long projection called an axon wrapped in a layer called the myelin sheath. The myelin sheath layer covers most of the axon but also produces uncovered spaces at set intervals; each space is called a node of Ranvier. The myelin sheath is made from oligodendrocytes. At the end of the axon is a synapse. B) Diagram of a synapse. This is the region where two neurons come together (but they do not touch). The presynaptic neuron releases neurotransmitters into the synapse space. The post synaptic neuron has receptors on which the neurotransmitters attach.
(a) A myelinated neuron is associated with oligodendrocytes. Oligodendrocytes are a type of glial cell that forms the myelin sheath in the CNS that insulates the axon so that electrochemical nerve impulses are transferred more efficiently. (b) A synapse consists of the axonal end of the presynaptic neuron (top) that releases neurotransmitters that cross the synaptic space (or cleft) and bind to receptors on dendrites of the postsynaptic neuron (bottom).
  • What cells are associated with neurons, and what is their function?
  • What is the structure and function of a synapse?

Meningitis and encephalitis

Although the skull provides the brain with an excellent defense, it can also become problematic during infections. Any swelling of the brain or meninges that results from inflammation can cause intracranial pressure, leading to severe damage of the brain tissues, which have limited space to expand within the inflexible bones of the skull. The term meningitis is used to describe an inflammation of the meninges. Typical symptoms can include severe headache, fever, photophobia (increased sensitivity to light), stiff neck, convulsions, and confusion. An inflammation of brain tissue is called encephalitis , and patients exhibit signs and symptoms similar to those of meningitis in addition to lethargy, seizures, and personality changes. When inflammation affects both the meninges and the brain tissue, the condition is called meningoencephalitis . All three forms of inflammation are serious and can lead to blindness, deafness, coma, and death.

Meningitis and encephalitis can be caused by many different types of microbial pathogens. However, these conditions can also arise from noninfectious causes such as head trauma, some cancers, and certain drugs that trigger inflammation. To determine whether the inflammation is caused by a pathogen, a lumbar puncture is performed to obtain a sample of CSF . If the CSF contains increased levels of white blood cells and abnormal glucose and protein levels, this indicates that the inflammation is a response to an infectioninflinin.

  • What are the two types of inflammation that can impact the CNS?
  • Why do both forms of inflammation have such serious consequences?

Guillain-barré syndrome

Guillain-Barré syndrome (GBS) is a rare condition that can be preceded by a viral or bacterial infection that results in an autoimmune reaction against myelinated nerve cells. The destruction of the myelin sheath around these neurons results in a loss of sensation and function. The first symptoms of this condition are tingling and weakness in the affected tissues. The symptoms intensify over a period of several weeks and can culminate in complete paralysis. Severe cases can be life-threatening. Infections by several different microbial pathogens, including Campylobacter jejuni (the most common risk factor), cytomegalovirus, Epstein-Barr virus , varicella-zoster virus, Mycoplasma pneumoniae , Yuki, Nobuhiro and Hans-Peter Hartung, “Guillain–Barré Syndrome,” New England Journal of Medicine 366, no. 24 (2012): 2294-304. and Zika virus Cao-Lormeau, Van-Mai, Alexandre Blake, Sandrine Mons, Stéphane Lastère, Claudine Roche, Jessica Vanhomwegen, Timothée Dub et al., “Guillain-Barré Syndrome Outbreak Associated with Zika Virus Infection in French Polynesia: A Case-Control Study,” The Lancet 387, no. 10027 (2016): 1531-9. have been identified as triggers for GBS. Anti-myelin antibodies from patients with GBS have been demonstrated to also recognize C. jejuni . It is possible that cross-reactive antibodies, antibodies that react with similar antigenic sites on different proteins, might be formed during an infection and may lead to this autoimmune response.

GBS is solely identified by the appearance of clinical symptoms. There are no other diagnostic tests available. Fortunately, most cases spontaneously resolve within a few months with few permanent effects, as there is no available vaccine. GBS can be treated by plasmapheresis. In this procedure, the patient’s plasma is filtered from their blood, removing autoantibodies.

Key concepts and summary

  • The nervous system consists of two subsystems: the central nervous system and peripheral nervous system .
  • The skull and three meninges (the dura mater , arachnoid mater , and pia mater ) protect the brain.
  • Tissues of the PNS and CNS are formed of cells called glial cells and neurons .
  • Since the blood-brain barrier excludes most microbes, there is no normal microbiota in the CNS.
  • Some pathogens have specific virulence factors that allow them to breach the blood-brain barrier. Inflammation of the brain or meninges caused by infection is called encephalitis or meningitis , respectively. These conditions can lead to blindness, deafness, coma, and death.

Matching

Match each strategy for microbial invasion of the CNS with its description.

___intercellular entry A. pathogen gains entry by infecting peripheral white blood cells
___transcellular entry B. pathogen bypasses the blood-brain barrier by travel along the olfactory or trigeminal cranial nerves
___leukocyte-facilitated entry C. pathogen passes through the cells of the blood-brain barrier
___nonhematogenous entry D. pathogen passes between the cells of the blood-brain barrier

D, C, A, B

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Fill in the blank

The cell body of a neuron is called the ________.

soma

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A signal is transmitted down the ________ of a nerve cell.

axon

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The ________ is filled with cerebrospinal fluid.

subarachnoid space

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The ________ ________ prevents access of microbes in the blood from gaining access to the central nervous system.

blood-brain barrier

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The ________ are a set of membranes that cover and protect the brain.

meninges

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Short answer

Briefly describe the defenses of the brain against trauma and infection.

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Describe how the blood-brain barrier is formed.

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Identify the type of cell shown, as well as the following structures: axon, dendrite, myelin sheath, soma, and synapse.

Drawing of a neuron. The large round regions with a darker purple circle is A. Short projections from A are G. A long projection from A is B. This is wrapped in structure E and has gaps labeled F. E is made from C. The end of the long projection is D.
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Questions & Answers

What are antibodies?
Happy Reply
they are immune cells that are released by immune system to fight strangers like microbes
Ahmed
a blood protien produce in response to an counteracting a specific antigen
Pooja
Why salmonella typhi is harmful protozoan?
Saily Reply
because make typhoid that is considered as a food born illness
Ahmed
Name any five modes of transmission.
Happy
what are the scientific names and common names of some microbes
Rich Reply
Staphylococcus aureus - staph Streptococcus pyogenes - strep Botulism - Clostridium botulinum Rocky Mountain spotted fever - Rickettsia rickettsii Diphtheria - Corynebacterium diphtheriae Gonorrhea - Neisseria gonorrhoeae
Tammy
what are the limitations of the Koch's postulate
Naa
how a microorganism growth.
Zubair Reply
Is foetus a parasite to his or her mother? if yes and if no ho
Mashauri Reply
y
Yusri
yes
Yashkin
yes
Zubair
yes it a parasite to the mother because it feeds on the mother for survival
Beatrice
yes
Redwan
no
Elasha
definition of a parasite: an organism that lives in or on an organism of ANOTHER species (its host) and benefits by deriving nutrients at the other's expense
Elasha
no because an organism can inky be a parasite if it causes harm to its HOST. And the fetus does not cause harm to its mother under normal conditions
aliyu
yes
Naa
what is biosensor in microbiology
Raja Reply
What are biosensor
Raja
what's are biosensor
Raja
what is microbiology defination
Rinku Reply
microbiology is the study of small or manuit organisms which cannot be seen with our nacked eyes unless with the aid of the microscope
Brandina
is the study of living organisms which are not directly visible to a direct eye but can only be seen under a microscope
Ipa
ok
Ipa
microbiology is the study of living organisms of microscopic size it is also the study of micro organisms with their form structure reproduction psychology metabolism and classification
Priyanka
what are the importances of Microbiology?
Erick Reply
don't know
SINGLE
we obtained the insulin from the bacteria. and some microorganisms are decomposer in ecosystems.
Zubair
nitrogen in the air is fixed into the soil by microbes example is nitrobactor
Matilda
yes
Zubair
how a weak immune region where microorganisms attack easily?
Zubair Reply
with examples differentiate gram positive from gram negative bacteria
Mary Reply
Differentiate gram positive from gram negative
Mary
I have no idea
Zubair
hello
Kuonain
and example of gram negative is E. coli
Pooja
gram positive stain purple when subjected to gram stain whilst gram positive bacterial has thick wall composed of peptidoglycan
Matilda
ok
Zubair
what is a process of gene expression in eukaryotes ?
Nayyab Reply
pls help us with the answer
Abdussalam
spontaneous generation means
Siddhi Reply
hiii
Siddhi
Hello
eman
So, what's next 😂
eman
I have a problem with Micro
eman
I studying things and see question Some thing else
eman
Can u help me, please
eman
What i havta do
eman
firsfall when you studying understand things...
Siddhi
good afternoon dear Friends
yaya
Greeting to everyone in here.
Manka
There is a problem. I need a diagram of a virus with it functions.
Manka
structure of bacterial
Kuyiba
gghhhh
Zubair
group plz i need help in microbio
Kuonain
it really difficult fr me
Kuonain
kashur cha kah
suhail
sorry now I read in class 8th but I can help u
Zubair
Me too. It's very difficult for me
Angela
rod shape
Priyanka
helical
Priyanka
Hello
esike
spherical
Priyanka
peomorphic
Priyanka
I am ryt or not
Priyanka
hi
suhail
hello
DIPTI
Are we together pls what's the topic for the day?
esike
what is innate
Lizzy
innate means natural
Pooja
the genetic makeup of an individual
Matilda
pls i need the common names for the following parasites..ENTEROBIUS VERMICULARIS,NECATOR AMERICANUS,ASCARIES LUMBRICOIDES,TRICHURIS TRICHIURA,TRICHOMONAS VAGINALIS,GIARDIA LAMBLIA,ENTAMOEBA HISTOLYTICA,SCHISTOSOMA MANSONI,SCHISTOSOMAHEMATOBIUM,STROGYLOIDES STERCORALIS,AND TRAPANOSOMA BRUCI GAMBIENSE
timothy
ENTEROBIUS VERMICULARIS and STROGYLOIDES STERCORALIS have the same common name which is pin worm and thread worm
Chinedu
I didn't find the common names for TRICHOMONAS VAGINALIS, GIARDIA LAMBLIA, ENTAMOEBA HISTOLYTICA, TRYPANOSOMA BRUCEI GAMBIENSE
Chinedu
NECATOR AMERICANUS - New world hookworm ASCARIS LUMBRICOIDES- Ascarid TRICHURIS TRICHIURA- Whip worm
Chinedu
Hi guys
Chinedu
Why are myeloblasts not present in the bloodstream?
Chinedu
thank u
Dasaah
is blood from capillary puncture suitable for hormonal assays
NANCY Reply
Direct this question to a hematologist for a better answer please.
LAFIA
In most cases the blood is necessary but it's limited from my own Analysis
Lee
u can do but it depends on your sampling blood its enev or not
Ali
Control indications of cipro, doxicyclin, setracyclin, cloxacyclin, erythromycin
Oslen Reply
oo
babinthe
what is sims position
babinthe Reply

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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