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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 is the size of virus
Beatrice Reply
What is the difference between TVC and Bioburden test
Mohamed
?
Mohamed
structure of bacteria and 10 types
Jennifer Reply
what is accidental host?
Domingo Reply
what is endomembrane system
Ikpi Reply
what is human anatomy
Ikpi
okay. Go ahead and ask
Blessing Reply
Industrial microbiology mcq
mohamed
Okay. What's your question?
Blessing
life arises from living matter or live organism.
Swami Reply
yes
sildra
I think live matter arises from non living matter
sildra
I dont think so...can u explain with an example
Manya
living maters made by non living matters
sildra
non living matters like stones? rocks?
Manya
eno
sildra
no
sildra
then?
Manya
cells are made by C N O minerals etc
sildra
I mentioned these as non living maters
sildra
that's all
sildra
cells are made up of those things but they originate from living things..
Manya
ok
sildra
Ok..good chat:-)
Manya
where are you from
sildra
thanks
sildra
India...u?
Manya
Tamil nadu
sildra
I am from Maharashtra
Manya
what about your studies
sildra
completed bsc.. preparing for msc entrance...wbu?
Manya
same
sildra
are you microbiologist
sildra
yes i am
Manya
good
sildra
what s the scope for micro in ur state?
Manya
did you find your college to higher studies
sildra
have to give an entrance exam for every college here...so lets c
Manya
food industries, medical lab, vaccine industries ,etc
sildra
hoping for pune University...wbu?
Manya
great!
Manya
is that centeral University right
sildra
what is your namr
sildra
hello
Udhaya
Hi
Maruf
Family kindly help me with this question? 1) Shortlist the configurative measurements of the following human anatomical ranges of÷ - Blood ( haemeglobin) in both male and female - Haematocytes in both male and female - Hepatocytes in both male and female - Lymphocyte / T. Lymphocytes in both male
Gifted
My names are Gift Mwale and am a Zambian. Kindly help me with this research which goes like this... 1) Shortlist the configurative measurements of the following human anatomical ranges of ÷ - Blood ( haemeglobin) in both male and female - Hepatocytes in both male and female - Haematocytes in both
Gifted
please what is the full meaning for TCDS
UDEME
from a single cell
Freedom
tcds means transcranial direct current stimulation...in this small electric currents are given to brain( specific parts) to help increase brain performance or to help with depression.. current should be in range 0.5-2.0mA
Manya
what's underlying disease relating unsanitary diet microorganism with the highest rate of epidemology solution and efficacy leading molecules elucidated structural solutions
feven
please can anybody talk about brain tumour and its cure.
BELLO Reply
enlargement of the thyroid gland resulting in over production of hormone.
Kamal Reply
What can u say on Thyroid Cancer?
Abdulkareem
Please, talk about the thyroid cancer.
BELLO
explain the Grave's disease
John Reply
what is cell
Avi Reply
is unit of life
Kamaluddeen
Ok
mohamed
who is an industrial microbiologist
Cynthia Reply
I want to know the biochemical composition of bacteria
Josh Reply
It contains peptidoglcon, DNA nd RNA
Asiya
what are Carrier protein
Ikpi
bacteriophage disadvantage
Momina Reply
disease due to __________ abnormalities are termed primary immunodeficiencies
Tayee Reply
Some primary immunodeficiencies are due to a defect of a single cellular or humoral component of the immune system.
Prince
Examples of primary immunodeficiencies include: chronic granulomatous disease, X-linked agammaglobulinemia, selective IgA deficiency etc
Prince
thank you
Nana
explain microbial mutation
Emerald
what is mutation
Cynthia Reply
alteration in genetic makeup
UDEME

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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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