Nervous System

• Dendrite


  Many tree-like projections from the neuron that carry messages to the cell body
• Axon


  The single long arm of the neuron that carries messages away from the cell body
• Myelin Sheath


  Insulating layer around neurons that allow nerve impulses to be transmitted quickly and efficiently
• Synapse


  Space separating two neurons
• Nerve Impulse


  1. Stimulus creates an impulse

  2. Impulse travels into the neuron on the dendrite

  3. Impulse travels out on the axon

  4. Neurotransmitter is released at the end of the axon

  5. Neurotransmitter carries the impulse across the synapse to the next dendrite
• Types of Neurons


  • Sensory Neurons
  • Motor Neurons
  • Associative (Interneurons)
• Divisions of the Nervous System

  • Central Nervous System
  • Peripheral Nervous System
  • Autonomic Nervous System
  • Somatic Nervous System
• Central Nervous System


  Made up of brain and spinal cord
• Cerebrum


  • Largest part of the brain
  • Divided into R and L hemispheres by a deep groove called the longitudinal fissure
  • Convolutions - elevated folds on the surface that increase surface area
  • Divided into four lobes: Frontal, Parietal, Occipital and Temporal
• Frontal Lobe


  Emotions, Personality, Morality, Intellect, Speech, Smell
• Parietal Lobe


  Receives and interprets nerve impulses from sensory receptors for pain, touch, heat and cold
• Occipital Lobe


  Houses the visual area, controlling eyesight
• Temporal Lobe


  Hearing, facial recognition
• Cerebral Cortex


  Controls conscious thought, judgment, memory, reasoning and willpower
• Diencephalon


  • Located between the cerebrum and midbrain
  • Two major structures: thalamus and hypothalamus
  • Vital functions of the hypothalamus: Autonomic Nervous Control, Cardiovascular Control, Temperature Control, Appetite Control, Sleep Control
• Limbic System


  • Located in the center of the brain
  • Surrounds the brain stem
  • Complex set of structures that includes the hypothalamus, hippocampus, amygdala, and several other nearby areas
  • Involved with motivation, emotion, mood and memory
• Cerebellum


  • Located behind the pons and below the cerebrum
  • Composed of two hemispheres
  • Controls all body functions related to skeletal muscles, including: Balance, Muscle Tone, Coordination of muscle movements
• Brain Stem


  • Made up of PONS, MEDULLA, and MIDBRAIN
  • Controls the flow of messages between the brain and the body
  • Controls basic body functions such as breathing, swallowing, heart rate, blood pressure, consciousness, and whether one is awake or sleepy
• Meninges


  • Three membranes that line the skull and vertebral canal and protect the brain and spinal cord
  • Dura mater: tough outermost meningeal layer that lines the skull
  • Arachnoid: middle layer of the meninges that resembles a fine cobweb
  • Pia Mater: delicate inner layer
• Cerebrospinal Fluid


  A clear, colorless fluid that acts as a shock absorber and a source of nutrients for the brain
• Choroid Plexus


  A network of blood vessels lining the cerebral ventricles that produces cerebrospinal fluid
• Spinal Cord


  • Begins at foramen magnum
  • Continues down to 2nd lumbar vertebrae
  • White and soft in spinal canal
  • Surrounded by cerebrospinal fluid
  • Functions as a reflex center and a conduction pathway to and from the brain
• Peripheral Nervous System


  • 12 pairs of cranial nerves
  • 31 pairs of spinal nerves
• Divisions of the Autonomic Nervous System

  • Sympathetic
  • Parasympathetic
• Sympathetic Nervous System


  "Fight or Flight": When body perceives danger prepares to run away or stand and fight. Heart rate increases; mouth becomes dry; pupils and bronchi dilate
• Parasympathetic Nervous System


  Counteracts the effects of the sympathetic nervous system. For example sympathetic nervous system increases heart rate and parasympathetic decreases the heart rate.
• It is through the nervous system that we communicate with the outside world
• Our brain controls our emotions, speech, hearing, vision and many other processes
• All of these processes affect our communication with others
• Alzheimer's Disease/Dementia


  • Progressive degenerative disease of the brain
  • Most common cause of dementia among people 65 years or older
  • Characterized by memory loss and diminished cognitive function
  • Tangles of fibers develop in nerve cells which interferes with brain function
  • Cause is unknown, but age is the most important risk factor
• Cerebral Palsy


  • Permanent set of motor problems diagnosed in infants and young children—thought to be due to damage to the motor cortex
  • Risk factors: low birth weight, premature birth, multiple births, infection during pregnancy, developmental abnormalities, brain hemorrhage, perinatal brain injury, and lack of oxygen
  • Symptoms vary from mild foot drag and incoordination to complete paralysis and the inability to speak
  • Some may have developmental delays, autism or seizures. Many are of normal or above normal intellect
  • Treatment includes physical therapy, occupational therapy, assistive devices and drugs to control symptoms
• Epilepsy


  • Seizure disorder
  • Seizures believed to be a result of spontaneous uncontrolled electrical activity of neurons
  • Diagnosed with EEG (electroencephalogram)
  • Two types of seizures: Grand Mal - severe, convulsive seizure; Petit Mal - milder (sometimes like someone is just staring)
  • Treatment is anticonvulsant medications
• Meningitis


  • Infection or inflammation of the meninges
  • Caused by both bacteria and viral infections
  • Symptoms - severe headache and stiff neck with pain
  • Need to seek immediate medical attention
• Multiple Sclerosis


  • Disorder in which myelin is destroyed, probably by autoimmune attack
  • The brain, spinal cord and optic nerves are often involved
  • The areas without myelin impairs or prevents conduction of nerve impulses
  • May have impairments in vision, balance, speech or movement
  • Can be relapsing-remitting with flare-ups and remissions or chronic progressive with no remissions
  • More common in women and usually diagnosed in those under 50
• Parkinson's Disease


  • Brain disorder caused by the loss of dopamine-producing neurons
  • Decrease in dopamine leads to shaking, stiffness, and difficulty with walking, balance, and coordination
  • Symptoms usually begin gradually and get worse over time
  • Later stages affect ability to chew and swallow
  • Risk factors: age, heredity, gender and exposure to toxins
• Poliomyelitis


  • Contagious viral illness that in its most severe form causes nerve injury leading to paralysis, difficulty breathing and sometimes death
  • Due to vaccination this disease is almost eradicated in the U.S.
  • Despite a worldwide effort to wipe out polio, it continues to affect people in parts of Asia and Africa
• Spinal Cord Injury


  • Damage to the spinal cord that results in a loss of function, such as mobility and/or feeling
  • Frequent causes are trauma (car accident, gunshot, falls, etc.) or disease (polio, spina bifida)
  • The level of the injury determines the extent of loss of function
  • Paraplegia: paralysis of legs and lower body
  • Quadriplegia: paralysis of all 4 limbs
• Encephalitis


  • Inflammation of the brain
  • May be caused by a virus (ex. Herpes virus, West Nile Virus)
  • Common symptoms are fever, lethargy, headache, muscle aches, and extreme fatigue
  • Symptoms may be more severe and include confusion, hallucinations, paralysis and unconsciousness
• Spinal Cord Injury

  Damage to the spinal cord that results in a loss of function, such as mobility and/or feeling
• Spinal Cord Injury


  • Frequent causes are trauma (car accident, gunshot, falls, etc.) or disease (polio, spina bifida)
  • The level of the injury determines the extent of loss of function
  • Paraplegia: paralysis of legs and lower body
  • Quadriplegia: paralysis of all 4 limbs