Bio: The Nerves system

• There is much diversity in the cells of the body, they are not all just little circle blobs
• Parietal cells


  • Part of the digestive system
  • Can make stomach acid
• Cells in other systems do not make stomach acid
• Mast cells


  • Part of the immune system
  • Contain substances like histamine that they can release, critical for the inflammatory response
• Skeletal muscle cells/muscle fibers


  • Part of the muscular system
  • Shaped like cylinders with multiple nuclei
  • Structure includes thin and thick filaments which are essential for muscle contraction
• There are many specialized cells in the body systems, each specialized for their function
• Neuron


  A cell that is part of the nervous system, the author's favorite specialized body cell
• Central nervous system (CNS)

  Consists of the brain and spinal cord
• Peripheral nervous system (PNS)


  Consists of all other components of the nervous system, such as nerves throughout the body
• The PNS can provide sensory information for the CNS


  The CNS can process that information and act as a command center, executing motor responses or regulating body mechanisms
• Regions of the brain

  • Hindbrain
  • Midbrain
  • Forebrain
• Hindbrain


  • Includes the medulla, pons, and cerebellum
  • Medulla has functions like regulating breathing, blood pressure, and heart rate
  • Pons is involved with coordinating signals with this area to the rest of the brain
  • Cerebellum is involved in balance and movement coordination
• Midbrain


  • Involved in alertness and the sleep/wake cycle, motor activity, and more
• Brainstem


  Includes the medulla, pons, and midbrain
• Forebrain


  • Most notably includes the cerebrum, which is divided into two hemispheres
  • Cerebrum is involved in functions like speech, thinking and reasoning, sensing, emotions
• Thalamus


  Involved with sensory and motor information
• Hypothalamus


  Has major control of the endocrine system
• The myth that "humans only use 10% of their brain" is not correct
• Somatic nervous system (SNS)


  Involved with motor functions of skeletal muscle, including voluntary actions and somatic reflexes
• Autonomic nervous system (ANS)


  Involved with the internal environment, including the gastrointestinal, excretory, endocrine, and smooth/cardiac muscle systems, as well as autonomic reflexes
• Sympathetic system


  Part of the ANS, involved in the fight-or-flight response
• Parasympathetic system


  Part of the ANS, involved in "rest and digest" functions
• Neurons


  • Cell body with nucleus and organelles
  • Dendrites where signals are received
  • Axon where signals are carried away
  • Synapse where neuron communicates with another cell
• Glial cells/Glia


  • Supporting cells that help neurons connect and function
  • Maintain chemical balance and the blood-brain barrier
  • Make myelin to insulate axons
  • Produce cerebrospinal fluid
  • Have immune functions
• Resting potential


  The electrical charge of a neuron at rest, around -70 millivolts, due to the distribution of ions like sodium, potassium, and chloride
• Action potential


  1. Rapid change in the charge of the neuron along the axon, as sodium floods in and potassium channels open and close

  2. Can "jump" from node to node in myelinated neurons

  3. An all-or-nothing event, either happens or doesn't
• Neurotransmitter release


  1. Action potential signals synaptic vesicles to release neurotransmitters into the synaptic cleft

  2. Neurotransmitters bind to receptors on the next neuron, allowing the signal to continue
• There is a lot of ongoing research to help diseases and conditions of the nervous system
• There are many careers involved in neurology to explore for those interested in the nervous system
• Candidiasis/thrush


  A fungal infection caused by various Candida species, of which Candida albicans is the most common
• Candidiasis


  • Mainly affects the mucous membranes and the skin
  • Candida occurs on all surfaces of the human body and may cause an infection if it rapidly multiplies in favourable conditions
• Conditions that cause an increase in Candida


  • Warm, moist conditions - in skin folds, the mouth, vagina and the nappy area of babies
  • Excess use of antibiotics - beneficial bacteria in the alimentary canal are destroyed and Candida grows out of control
  • Weakened immune system - HIV/AIDS and cancer treatment, amongst others, break down the immune system
  • Bad diet - too many refined carbohydrates and sugar provide a food source for Candida
  • High stress levels - cortisol (a hormone) is released, which suppresses the immune system and increases sugar levels
• Symptoms of vaginal fungal infection

  • Severe itching, burning and irritation of the vagina and surrounding tissue, with a greyish-white vaginal discharge
• Symptoms of oral thrush (candidiasis in the mouth)

  • White spots with a red base on the tongue or palate, painful, affected person eats with difficulty
• Management/treatment of Candida infections

  1. Improved hygiene - prevents parts of the body from being warm and moist for long periods of time

  2. Probiotics should be taken when long-term antibiotics are used - to replenish the beneficial bacteria in the alimentary canal

  3. Balanced diet - cut out refined carbohydrates and sugar

  4. Stress levels should be controlled
• Immune response


  The way in which an organism protects itself against pathogenic viruses, bacteria, protozoa or fungi
• Types of immunity


  • Natural immunity - present at birth
  • Acquired immunity - developed through exposure to pathogens
• Natural immunity


  • Non-specific, i.e, it is not aimed directly at one specific type of pathogen, but it is able to destroy different pathogens
  • If the pathogen penetrates the first line of defence, the acquired immune response will be activated
• Immune response in plants

  • Plants only have natural immunity without white blood cells to destroy pathogens as seen in acquired immunity in animals
  • When a part of a plant is infected by pathogens, the natural immune response is activated and chemical compounds, e.g. salicylic acid, are released
  • These chemical compounds act as chemical messengers that move in the phloem throughout the plant and send signals to uninfected cells
  • The uninfected cells are stimulated to produce chemical defences that protect the uninfected cells from infection
  • In some plants a chemical reaction occurs at the site of infection to destroy the infected cells and prevent the spread of infection
• Natural immunity in humans

  • The body's first line of defence against pathogens is the external barrier that prevents harmful substances from entering the body
  • The skin is the first line of defence
  • The coughing and sneezing reflex, the washing action of tears and the mucus secreted by the respiratory tracts are all examples of natural immune responses that protect the body from the invasion of pathogens
  • If pathogens penetrate the barriers of natural immunity and infiltrate the body, the first response is usually inflammation and fever, which serves as a second line of defence