Intro to the Nervous System

7/29/2019 Intro to the Nervous System

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Chapter 10-The Nervous System


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The nervous system isneural tissue, blood, andconnective tissue.

Neural tissue has two cell

types: neurons (nervecells) and neuroglial cells.

Neurons are specializedcells that react to their

surroundings (bothphysical and chemicalchanges).

Neural Anatomy


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Nerve cells have a body:main part with nucleus,dendrites: smallprocesses off of the body

which receiveinformation, and theaxon: nerve fiber(telephone wire) that

carries information awayfrom the cell in the formof electric signals callednerve impulses.

Neural Anatomy


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Synapse: small space

between the neuron

and the cell(s) with

which it communicates. Neurotransmitters:

chemical messengers.

Neural Anatomy


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The nervous system can bedivided into two groups.

Central nervous system(CNS): brain and spinal cord.

Peripheral nervous system(PNS): cranial and spinalnerves that connect the CNS

to other body parts.

Together the CNS and thePNS provide 3 functions:sensory, integrative, and

motor functions.

Neural Anatomy


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Neural Anatomy

There are sensory receptors at the ends ofperipheral nerves. They monitor both internaland external conditions such as temperature,

light & sound, and oxygen concentrations. Sensory receptors concerts their information into

nerve impulses that they send to the CNS. Onceat the CNS, these impulses create sensations.

Then, conscious or subconscious decisions aremade and sent by nerves from the CNS toeffectors.


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Neural Anatomy

Effectors are outside the nervous system. Theyare things such as muscles, or glands that secretewhen stimulated by the CNS.

The motor portion of the PNS can be divided intotwo nervous systems.

Somatic nervous system: conscious activitiessuch as skeletal muscle contraction.

Autonomic nervous system: controlssubconscious actions of the vicera (heart, glands,etc.)


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Although they are called headaches, migraines

are responses to changes in the diameters of

blood vessels in the face, head, and neck. The

blood vessels first constrict and then dilate whichcauses head pain, nausea, and sensitivity to light.

Some migraines are genetic and some are also

caused by environmental triggers such as suddenbright light, certain foods, lack of sleep, stress,

high altitude, excess alcohol or caffeine.

Migraine Headaches


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Two major types of migraines: classic andcommon.

Classic migraines: 10-15% experience these. Theylast 4-6 hours and begin with sight loss calledaura.

Common migraines: usually lack an aura and last3-4 days!

Third, but rare type: familial hemiplegic migrain(genetic). Paralyzes one side of the body for afew hours to a few days and may cause loss ofconsciousness.

Migraine Headaches


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Millions are affected, and of those 70% arewomen. Hormones may influence thesemigraines and some suffer from menstrualmigraines every month.

Treatments: triptans (class of drug) can haltmigraines but must be taken at the beginning.They constrict blood vessels. Sometimesibuprofen is effective. Others have been

developed to prevent the frequency of migraines(used on daily basis), such as antidepressants,anticonvulsants, and hypertension drugs.

Migraine Headaches


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Neural Anatomy

The axons of the PNS aresurrounded by Schwanncells. They are sheets oflipid that tightly windaround the axons (like abandage around a finger).

The sheets of lipid aremyelin.

The gaps between each

myelin sheath of theSchwann cells are calledNodes of Ranvier.


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Myelinated axons appearwhite, and can alsoappear in the CNS. Thesemyelinated axons in thebrain is what makes upwhite matter.Unmyelinated axons inthe brain is called graymatter.

In the CNS, it is theneuroglial cell, theoligodendrite, thatproduces the myelin.

Neural Anatomy


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Multiple Sclerosis (MS)

Disorder of the CNS that affects 2.5 million

people worldwide.

The myelin sheaths become inflamed and

destroyed by an immune response, leaving

scars that block the neurons from transmitting

messages. So, the muscles that no longer

receive info from the motor neurons stopcontracting and atrophy.


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The first symptoms are usually blurred vision and

numb limbs.

Symptoms will vary based on which neurons are

affected. Some become permanently paralyzed.

Diagnosis is based on symptoms and magnetic

resonance (MR) scans.

70% of MS patients notice symptoms between20-40 years of age. Occurs more in women and

Caucasians.

Multiple Sclerosis (MS)-Symptoms


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Certain infections such as viral infections may

stimulate T cells (white blood cells) that may

cross the blood-brain barrier. The T cells may

then attack the myelin producing cells.

Drugs can manage MS, but there is no cure.

There are both short-term and long-term

remedies to combat the acute attacks as wellas to slow the progression of the disease.

Multiple Sclerosis (MS)

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Intro to the Nervous System