The Nervous System

Introduction:

  • the Nervous System is the most complex system in our body, it serves as the body's control and communications center
  • this system detects, interprets, and responds to changes in internal and external conditions
  • it integrates countless bits of information and generates appropriate reactions by sending electrochemical impulses through nerves to effector organs (muscles/glands)
  • two major divisions: central & peripheral nervous system
  • without the nervous system no other systems would be able to function

Central Division:

  • the "command station"
  • made up of the brain and spinal cord
  • the main function of the central nervous system is to process sensory information and determine what the appropriate reaction is
  • neurons of the central nervous system only interact with other neurons and are called interneurons
  • unlike sensory and motor neurons, interneurons both send and receive signals to and from other neurons

Peripheral Division:

  • functions to gather sensory information and to control the actions of our bodies
  • the peripheral nervous system includes two basic types of neurons: sensory & motor neurons
  • sensory neurons are neurons that collect sensory input and send it to the brain
  • motor neurons are neurons that transmit signals to responsive tissues.
  • contains two systems: somatic & autonomic, at times these two system work in opposition
Somatic
  1. The somatic system carries signals about moving the head, trunk, and limbs.
  2. Sensory axons deliver information from receptors in the skin, skeletal muscles, and tendons to the central nervous system.
  3. Motor axons deliver the commands from the brain and spinal cord to the skeletal muscles.
Autonomic
  1. provides almost every organ with a double set of nerves, the sympathetic and parasympathetic
  2. sympathetic system activates & prepares body for vigorous muscular activity, stress and emergencies
  3. parasympathetic system lowers activity, operates during normal situations, permits digestion and conservation of energy 

Neurons, Brain, & Spinal Cord:

  • neurons transmit electric signals like electric wire
  • input channels receive information from other neurons/sensory cells (these are cells that receive information from the environment)
  • neurons send messages along the axon to other neurons/ directly to muscles or glands
  • in order to transmit signals neurons must be linked to each other
  • the brain- receives, integrates, stores, and retrieves sensory information
  • the spinal cord- expressway for signals between the brain and the peripheral nervous system

The spinal cord is considered to be an "information highway", which connects the peripheral nervous system to the brain. It is protected by 31 vertebrae. At each segment of bone a pair of spinal nerves branch out. The spinal cord receives information from sensory and motor neurons. Sensory receptors send information along sensory neurons to the spinal cord. From here it is passed via interneurons to motor neurons that lead to muscles in the body. This causes movement. Sensory neurons can also send information through the spinal cord into the brain stem, to then be processed by the thalamus, the sensory switchboard of the brain (except for smell).

Spinal cord disorders can be caused by injuries, infections, a blocked blood supply, or compression by a fractured bone or tumor. The muscles can be become weak or paralyzed and sensation can be abnormal or lost. Often, in order to recover as much function as possible, rehabilitation is needed.
Disorders of the Spinal Cord include:
  • fluid-filled cavities
  • blockage of the blood supply
  • inflammation
  • tumors
  • abscesses
  • bleeding
  • vitamin b12 or copper deficiency
  • HIV
  • multiple sclerosis
  • syphilis
Symptoms
  • weakness
  • loss of sensation
  • changes in reflexes
  • loss of bladder control
  • loss of bowel control
  • erectile dysfunction
  • paralysis
  • back pain
Picture
Image Source: http://www.questgarden.com/02/58/1/051113190125/images/nueron-l.jpg http://ak.picdn.net/shutterstock/videos/5366036/preview/stock-footage-medical-animation-of-the-human-nervous-system.jpg

Diseases of the Nervous System:

Nerve Disorders
  • stroke
  • transient ischemic attack (TIA)
  • subarachnoid hemorrhage
  • subdural hemorrhage and hematoma
  • extradural hemorrhage
Functional Difficulties
  • epilepsy
  • Parkinson's disease
  • multiple sclerosis
  • amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease
  • Huntington's chorea
  • Alzheimer's disease

General Information About Nervous System Disorders

Nervous system disorders can come from abnormalities with one's nervous system, this can be brought on by: trauma, infections, degeneration, structural defects, tumors, blood flow disruption, and auto immune disorders.  These disorders usually have some of these symptoms: odd persistent headaches, loss of feeling/tingling, weakness, loss of vision, memory loss, impaired mental ability, lack of coordination, muscle rigidity, tremors & seizures, pain, muscle wasting, and slurred speech. There are also two kind of nervous system disorders when concerning the brain.  Abnormalities that come from odd development of the brain prior to birth is a neurological disorder since it concerns how you are neurologically set up, this includes disorders such as schizophrenia and the autism spectrum.  Disorders that are gained from some form of damage during life are mental disorders. This includes things such as depression.

Parkinson's Disease: A nervous system disease that causes gradual deterioration of ones motor skills (less facial expressions, slower walking, less arm movement, slurred speech, etc.) This disease usually starts with slight tremors in the hand.  The effects are gradual and worsen as they go on.  
Bell's Palsy: This causes intense amounts of facial paralysis to part of your face. The disease does not have a known cause, however there is medication to take for it and it is possible to recover from.
Cerebral Palsy: This disorder that comes from experiencing physical head trauma around and during the time of ones birth. Possible symptoms might include, limited motor skills, limited mental capabilities, abnormalities from limb contractions, epilepsy, visual impairment, squint, reduced hearing, and behavioral problems.  
Motor Neuron Disease: Deterioration of someones motor system during middle age.  It is a disease that is inherited and may affects one's spinal cord and nuclei in the brain and causes muscle weakness.
Epilepsy Seizures: General seizures: all areas of the brain are involved.
Multiple Sclerosis: Affects are commonly seen in young and middle aged adults. The disorder is brought about through damage to the coating around nerve cells, this impairs the function of the nerve. Symptoms one might experience from this are shaking limbs, involuntary eye movement, problems with pronunciation, and weakness.
Sciatica: Common condition is caused by the damaging or compressing of one's nerves or nerve roots. this form of injury can also happen very suddenly. Symptoms might include general pain felt in the back and the legs, stiffness in the back, and/or numbness and weakness in legs.
Source: https://www.youtube.com/watch?v=RlUPCNLSJIY

References:

Balingit, Angelica. “Liver: Anatomy, Definition, Symptoms, and More.” Healthline, 30 May 2018, http://www.healthline.com/human-body-maps/liver. Accessed 9 June 2022.
Hoffman, Matthew. “The Esophagus (Human Anatomy): Picture, Function, Conditions, and More.” WebMD, 10 July 2020, https://www.webmd.com/digestive-disorders/picture-of-the-esophagus. Accessed 19 November 2022.
​Hoffman, Matthew. “Liver (Anatomy): Picture, Function, Conditions, Tests, Treatments.” WebMD, 23 June 2021, http://www.webmd.com/digestive-disorders/picture-of-the-liver. Accessed 19 November 2022.
Wedro, Benjamin. “Liver Anatomy & Function Tests, Disease Symptoms & Causes.” MedicineNet, http://www.medicinenet.com/liver_anatomy_and_function/article.htm. Accessed 28 November 2021.
Paola Arias