ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Nervous System Review

Updated on April 23, 2014

Organization of the Nervous System

A Little Review:

The vertebrate nervous system consists of:

  • A brain, a spinal cord, and a set of peripheral nerves.

The central nervous system or CNS

  • Contains the brain and spinal cord.

The peripheral nervous system or PNS

  • Consists of the cranial and spinal nerves that connect the CNS to all tissues.

A neuron

  • Is an excitable cell that communicates via an axon.

A nerve

  • Is a bundle of axons that carries information.

The afferent part of the PNS

  • Carries sensory information to the CNS.

The efferent part of the PNS

  • Carries information from the CNS to muscles and glands

The Afferent Pathways

Carries information to the CNS

  • Stimuli from the sensory systems, pain and limb position move through afferent pathways.We have awareness of these stimuli. (Conscious)
  • Information such as blood pressure, deep body temperature, and blood oxygen supply are also transmitted though afferent pathways.We are not aware of this information.(Unconscious)

The Efferent Pathway

Carries information from the CNS to the muscles and glands of the body.

Efferent pathways can be divided into two divisions:

  • The voluntary division, the somatic division. Which executes conscious movements
  • The involuntary, or autonomic division. Which controls physiological functions

Additional Info:

The CNS also receives chemical information from hormones circulating in the blood, or from neurohormones released by neurons into the extracellular fluids of the brain.


The Brain: Basic Structure

The Hindbrain

Consists of the Medulla, the Pons….

  • Control physiological functions, such as breathing and swallowing.
  • All information traveling from the spinal cord must pass through the pons and medulla.

And the Cerebellum

  • Were muscle control is coordinated.

The Midbrain

Houses structures that process visual and auditory information.

Together the hindbrain and midbrain are known as the brain stem.

Note: Most sources do not include the cerebellum as part of the brain stem, but some do.

The Forebrain

Consists of the Diencephalon and the Telencephalon


Consists of the Thalamus and…

  • Final relay station for sensory information


  • Regulates physiological functions such as hunger and thirst


Cerebrum which consists of two cerebral hemispheres.

  • In humans, this is the largest brain region. It is involved in sensory perception, learning, memory, and behavior.

Limbic system

  • Primitive region involved in emotions and memory
  • Hippocampus
  • Amygdala

The Limbic System
The Limbic System | Source

The Limbic System

Structures in primitive regions of the telencephalon form the limbic system.

  • This is responsible for basic physiological drives, instincts, and emotions.

Consists of two parts:


  • Involved in fear and fear memory


  • Transfers short-term memory to long-term memory

The Cerebrum

Is the largest part of the brain in mammals.

It is separated into two hemispheres connected by the corpus callosum:

  • Cerebral hemispheres

The hemispheres are covered by a ‘sheet’ of gray matter that is convoluted to fit into the skull

-Cerebral cortex

  • It consists of Gyri: (sing. gyrus): Ridges
  • And Sulci: (sing. sulcus): Valleys

The Cerebrum Is divided into four main lobes.

  • Temporal
  • Frontal
  • Parietal
  • Occipital

Each lobe has a specific function

Brain Diagram
Brain Diagram | Source

The Temporal Lobe

Receives and processes auditory information.

Areas of the temporal lobe also involve:

  • Identification of objects
  • Object naming
  • Recognition of objects and faces.


  • Disorder of the temporal lobe that causes someone to be aware of an object or stimulus, but can not identify or name it.

The Frontal Lobe

Located in front of the central sulcus

  • Which separates the frontal and parietal lobes.

Contains the primary motor cortex.

  • The neurons in this region control muscles in specific parts of the body.
  • Areas with fine motor control have disproportionate representation. (Such as the hands and the face.)

Additional areas involve



  • Phineas Gage, a nineteenth-century railroad worker whose ‘nice guy’ personality was transformed by an explosion that blew a tamping iron through his brain

The Parietal Lobe

Located behind the central sulcus.

  • Remember this separates the frontal and parietal lobes.

Contains the primary somatosensory cortex.

  • This area receives touch and pressure information.
  • Just like the motor cortex, the whole body surface can be mapped onto the primary somatosensory cortex.
  • Areas of the body that have a high density of mechanoreceptors and are capable of making fine discrimination in touch have a large representation. (Fingers and face.)

The Occipital Lobe

Receives and processes visual information

Additional areas involve:

  • Making sense of the visual world
  • Translating visual experience into language


The cerebellum is important for coordination and error checking during motor, perceptual, and cognitive functions

  • It is also involved in learning and remembering motor skills

The Brain

The Spinal Cord

Its Job:

Conducts information between brain and organs.

  • Integrates information coming from PNS.
  • Responds by issuing motor commands.

The Anatomy

Gray matter

  • Is located in the center
  • Contains cell bodies of spinal neurons, dendrites and unmyelinated axons.

White matter

  • Surrounds gray matter
  • Contains myelinated axons that conduct information up and down the spinal cord.

Spinal nerves

Extend from the spinal cord at intervals.

Each one has two roots

  • Dorsal Root
  • Connecting to the dorsal horn of the gray matter
  • This is were afferent (sensory) axons enter the spinal cord.
  • Ventral Root
  • Connecting to the ventral horn.
  • This is were efferent (motor) axons leave the spinal cord

The Spinal Reflex Arc

Sometimes afferent information can convert to efferent activity without the brain.

  • This is called a spinal reflex.

A monosynaptic spinal reflex. (The simplest kind)

Involves only two neurons and one synapse

  • The knee-jerk reflex is an example

Stretch receptors send action potentials through the dorsal horn to the ventral horn

  • via sensory neuron axons.

In the grey matter the afferent (sensory) neurons synapse with efferent (motor) neurons in the ventral horn.

  • Action potentials are sent along the efferent axons to leg muscles, causing contraction.

The Spinal Cord

Information Processing: The Autonomic Nervous System (ANS)

It Controls involuntary functions

Comprised of two divisions:

Sympathetic and Parasympathetic.

  • They work in opposition to each other, one causes an increase in activity, the other a decrease.
  • They each have different neurotransmitters and anatomy

Sympathetic division is responsible for:

  • Increasing heart rate, blood pressure, and cardiac output.
  • Decreasing digestion.
  • Remember the “flight-or-fight” response?

Parasympathetic division is responsible for:

  • Decreasing the heart and blood pressure.
  • Increasing digestion


Both divisions of the autonomic nervous system are efferent pathways.

They begins with a neuron whose cell body is in the brain stem or spinal cord

  • They are called cholinergic neuron because they use acetylcholine as a neurotransmitter.
  • These cells are also called preganglionic neurons because the second neuron in the pathway with which they synapse resides in a ganglion
  • Which is a collection of neuronal cell bodies that is outside the CNS.

The second neuron is called a postganglionic neuron because its axon extends out from the ganglion.

  • The axons of the postganglionic neurons end on the cells of the target organs.

Neurotransmitter Differences

Sympathetic postganglionic neurons are noradrenergic.

  • They use norepinephrine as their neurotransmitter.

Parasympathetic postganglionic neurons are mostly cholinergic.

  • They use acetylcholine as their neurotransmitter.

Anatomical Differences

Sympathetic division:

  • Preganglionic neurons originate from the thoracic and lumbar regions of the spinal cord.
  • Most of the sympathetic ganglia are lined up on either side of the spinal cord.

Parasympathetic division:

  • Preganglionic neurons originate from the brain stem and the sacral region of the spinal cord.
  • The parasympathetic ganglia are close to the target organs


This website uses cookies

As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

Show Details
HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
LoginThis is necessary to sign in to the HubPages Service.
Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
AkismetThis is used to detect comment spam. (Privacy Policy)
HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
MavenThis supports the Maven widget and search functionality. (Privacy Policy)
Google AdSenseThis is an ad network. (Privacy Policy)
Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
Index ExchangeThis is an ad network. (Privacy Policy)
SovrnThis is an ad network. (Privacy Policy)
Facebook AdsThis is an ad network. (Privacy Policy)
Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
AppNexusThis is an ad network. (Privacy Policy)
OpenxThis is an ad network. (Privacy Policy)
Rubicon ProjectThis is an ad network. (Privacy Policy)
TripleLiftThis is an ad network. (Privacy Policy)
Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
ClickscoThis is a data management platform studying reader behavior (Privacy Policy)