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The Nervous System image (The Somatic Nervous System image (Somatic…

- - - - The control systems of the body are nervous and endocrine systems which receive help from special senses
        
        Like any control system, they have large, complex job that is sometimes difficult to understand; they must keep track of everything that is happening in your body; therefore, systems themselves are perhaps most complex and vital systems
        
        Book describes the nervous system as a computer
        
        Senses: keyboard, mouse, microphone, internet connetion
        
        Brain; Hard drive (long term memory), random access memory (short term memory
        
        Thinking and decision making – central processing unit
        
        Interaction with the world – the computers output via the ports, and cables to the printers, displays, speakers and so forth.
- - - - Input side of nervous system is sensory system
        
        Takes everything in and brings it to the nervous system
      - Output side of nervous system is motor system
        
        It carries out orders and tells all three muscle types and bodies glands how to respond
        
        Somatic nervous system controls skeletal muscle and mostly voluntary movements
        
        Autonomic Nervous System:
        
        Controls smooth and cardiac muscle in your organs and also several glands
        
        Is involuntary and not under conscious control
        
        Can be further divided into parasympathetic and sympathetic nervous system
        
        Real life example
        
        You park your car and get out to visit a friend; as you step on the walk a large dog bounds down starts barking and snarling at you
        
        Your sensory system gathers information including large unfriendly dog, you are far from protection of your car, and no one around for help
        
        Information goes into spinal cord and brain and you process information to make decisions; you are in danger, something must be done!
        
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- - - - Glial cells are not capable of measuring the environment, making decisions, or sending orders. What they do is support activities such as lining, and covering cavities, supporting and protecting structures
        
        CNS has four types of glial cells:
        
        Astrocytes: metabolic and structural support cells that holds neurons and blood vessels close together
        
        Microglia: remove debris and microbes
        
        Ependymal cells: cover and line cavities of nervous system (they act like epithelial cells)
        
        Oligodendrocytes: hold nerve fibers together and make lipid insulation called myelin
        
        PNS has two types of glial cells:
        
        Schwann cells: make myelin for the PNS
        
        Satellite cells: support cells
    - - Neurons are bizarre looking cells, often with many branches and even what appears to be a tail
        
        Each part of neuron has specific function:
        
        Body: cell metabolism
        
        Dendrites: receive information from the environment
        
        Axon: generates and sends signals to other cells
        
        Axon terminal: where signal leaves cell
        
        Synapse: where axon terminal and receiving cell combine
      - Neurons can be classified by how they look (structure) or what they do (function)
        
        Neurons can have one axon and one dendrite (bipolar)
        
        Neurons that have one axon and many dendrites or branches (multipolar)
        
        Neurons that have one process that splits into a central and a peripheral projection (unipolar)
        
        Input neurons are known as sensory neurons while output neurons are known as motor neurons
        
        Neurons which carry information between neurons are called interneurons (inter – between) or association neurons
      - Neurons are called excitable cells; this simply means that if cell is stimulated it can carry small electrical charge
        
        Each time charged particles flow across cell membrane, there is tiny charge generated
        
        Cells are like miniature batteries, able to generate tiny currents simply by changing permeability of their membranes
        
        A cell that is not stimulated or excited is called a resting cell; it is said to be polarized
        
        It has difference in charge across membrane, being more negative inside than outside cell
        
        When cell is stimulated, sodium gates in cell membrane spring open, allowing sodium to travel across membrane
        
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        All three muscle types are excitable cells, as are many gland cells
        
        Neurons can use their ability to generate electricity to send, receive, and interpret signals
        
        If you hit your thumb with a hammer, dendrites in thumb are stimulated by blow and sodium gates open, sodium flows into dendrites and they become depolarized; number of cells affected depend on how hard you hit your thumb
- - - - Location: just anterior to central sulcus (in frontal lobe)
      - Function: contains primary motor cortex (region that controls body movements)
      - Each portion of primary motor cortex controls specific area of body
      - This creates “map” of body on brain sometimes called motor “homunculus” (little man)
      - Body parts that perform more finely coordinated movements (like hands and lips) require larger area on “map”
    - - Premotor and prefrontal areas: areas that plan movements (before movement occurs)
      - Broca’s area: area of brain that controls movements associated with speech
    - - Location: just posterior to central sulcus in parietal lobe
      - Function: contains primary somatosensory cortex (center for processing sensory information)
      - Each portion of somatosensory cortex gets sensory input from specific area of body
      - Also creates “map” of body on brain
        
        Size of body parts on “map” is proportional to amount of sensory input provided
        
        recap: the structures in the cerebrum are responsible for conscious thought, judgment, reasoning, memory, and will power
    - - Somatic sensory association area: allows understanding and interpretation of sensory information
      - Wernicke’s area: controls understanding of speech
      - Broca’s area controls movements associated with speech
    - - Collection of white matter that connects left and right hemispheres
      - Connection allows for cross-communication between right and left sides of brain
      - Many day-to-day activities, like walking or driving, require both sides of body, and therefore both sides of brain, to be well coordinated
    - - Inferior to the cerebrum
      - Not visible from the exterior
      - Plays part in our emotional state
      - Can be divided into:
        
        Thalmus- relays and processes information going to the cerebrum
        
        Hypothalamus- regulates hormone levels, temperature, water balance, thirst, appetite, pleasure and fear, regulates the pituitary gland/controls endocrine
        
        Pineal body- responsible for melatonin
        
        Pituitary gland secretes hormones
  - - - Divided into three sections
        
        Medulla oblongata: continuous with spinal cord, responsible for impulses that control heartbeat, respirations, and blood vessel diameter. It is the reflex center for coughing, sneezing, swallowing and vomiting.
        
        Pons: just superior to medulla oblongata and it plays a role in breathing
        
        Midbrain: most superior portion of brain stem and is completely covered by cerebrum
      - The brainstem contains reticular system, diffuse network of brain stem neurons responsible for “waking up” cerebral cortex
        
        General anesthesia inhibits reticular system, causing unconsciousness
        
        Injury to reticular system can lead to coma
      - Brain stem receives sensory information and contains control systems for vital processes such as blood pressure, heart rate, and ventilation (breathing)
        
        Patients with severe brain injuries with an intact brain stem can continue in a vegetative state as long as they are supported nutritionally (Persistent Vegetative State)
  - - - Layer of gray matter surrounding white matter is called cortex
        
        In cerebrum it is called cerebral cortex
        
        In cerebellum it is called cerebellar cortex
      - There are also “islands” of grey matter deep inside brain; islands are called nuclei; examples of nuclei
        
        Basal nuclei: motor coordination system
        
        Limbic system: controls emotion, mood, and memory
      - Inside of cerebrum is a reflection of the external anatomy; lobes (frontal, parietal, temporal, and occipital) are clearly visible
      - On either side of central sulcus are two gyri
        
        Precentral gyrus anterior to central sulcus
        
        Postcentral gyrus posterior to central sulcus
        
        Responsible for conscious thought, judgment, reasoning, memory and WILL POWER
- - - - HA, fever and stiff neck
      - Viral (most)
      - Serious cases bacterial
      - Untreated leads to seizures, coma, amputations, and death
      - Spinal tap– low glucose and high white blood cell count in CSF
      - CSF show specific bacteria. In viral, genetic material from viruses will show up in fluid
      - IV antibiotics/bacterial, fluid drained from brain (Blood Brain Barrier (protection of the brain)AB hard to get through
      - Viral –bed rest, fluids and medication to relieve pain and swelling (1-2 weeks)
- - - - Common causes
        
        Vehicle accidents (most common cause)
        
        Falls
        
        Violence
        
        Sports injuries
      - Damage similar to TBI can also be caused by lack of oxygen to brain, strokes, or hemorrhorage
    - - Dizziness, confusion, headache, blurred vision, ringing of the ears, sleepiness, and mood or cognitive changes.
      - More serious symptoms
        
        Vomiting, dilated pupils, convulsions, motor deficits, slurred speech, confusion or agitation and maybe unconsciousness
        
        Pts may be in a stupor (brief periods of arousal) Coma (no consciousness, or a vegetative state (sleep and arousal but no response to environment) and then PVS
    - - There are 100 cases per 100,000 people in U.S. each year
      - 50% of accident or violence related TBIs involve alcohol
      - Riskiest ages for TBI are under age 5, 15-24 (males), over age 75
      - Types of TBI
        
        Closed: skull is not open
        
        Penetrating: skull is punctured by an object
        
        Mild concussion is a form of a brain injury
        
        Contusion- is swelling and bleeding at the site and a severe hemorrhage(hematoma) may result
    - - Like spinal cord, injured brain will self-destruct due to increased swelling and cell death caused by tissue's attempt to repair damage
        
        Pressure- brain tissue swell– no where to go (intracranial pressure)
        
        Brain stem can get pressed downward from the swelling, through the foramen magnum (herniation) damaging the respiratory centers and decreasing blood flow to the brain which causes more damage
      - Acute care of head injury
        
        Immobilization of head
        
        Stabilization of cardiovascular and respiratory functions
        
        Monitoring of intracranial pressure
        
        Medication to decrease intracranial pressure
        
        Surgery to remove clots, blood or foreign objects (for example, bullet or bone fragments) from brain
        
        Then you watch for post op complications like:
        
        Hydrocephalus, infection, pain, bed sores, and MSOF
      - Approximately 40% of brain injured people, even with mild injuries, will experience post-concussion syndrome
        
        Several days or weeks after injury, patients experience dizziness, headache, memory and concentration problems, irritability, disordered sleep, and anxiety and depression; these conditions are usually temporary
  - - - Sudden severe ha, dizziness, loss of vision in one eye, aphasia, dysphagia, coma, and possible death. Paralysis, and hemiplegia can result
      - Clots major cause
      - Risk factors: smoking,1 HTN, heart disease, and family history
    - - Major stroke
      - Brain tissue dies due to insufficient blood supply
      - Symptoms largely permanent
    - - Also known as “mini-stroke”
      - Patients have stroke-like symptoms that are temporary
      - Can be precursor to major stroke
    - - Pool of blood between any of layers of meninges and skull
      - Common locations are epidural (between dura mater and skull), subdural (between dura mater and arachnoid mater) and subarachnoid (in subarachnoid space)
      - Blow to head can rupture tiny blood vessels in skull, causing them to bleed into space
      - Stoke or ruptured aneurysm (weak spot in blood vessel inside skull) can also cause hematoma
  - - - Begin gradually with mild forgetfulness
      - 2nd stage- pts increase in memory loss, have difficult time recognizing people, trouble remembering words, sleeplessness, confusion, motor problems, loss of social skills
      - 3rd stage- difficulty speaking, reading, writing, and maintaining personal hygiene
    - - Led to the four A’s: Anger, Anxiety, Aggression, and Apathy
  - - - Some cases increased pressure inside skull (and can eventually crush brain tissue)
      - Other cases may have no obvious rise in pressure (normal pressure hydrocephalus)
    - - Expansion of skull (in infants whose skulls have not fully hardened)
        
        Older children and adults size of the head does not change
      - Nausea/vomiting
      - Irritability
      - Seizures
      - Headache
      - Blurred vision
      - Balance and coordination problems
      - Sleepiness
      - Personality changes
      - Dementia
    - - CT or MRI imaging showing enlarged ventricles
      - Monitoring of intracranial pressure
    - - Can be treated with medications
      - More commonly treated with surgical placement of shunt to drain fluid to heart or abdominal cavity
  - - - Not just about spinal nerves; cranial nerves are also subject to peripheral neuropathy
      - Symptoms would be seen on face and head or in special senses (vision, hearing, taste, smell)
- - - - CSF flows into central canal of spinal cord and subarachnoid space
        
        CSF is returned to blood via special “ports” (arachnoid villi) between subarachnoid space and blood spaces in dura mater (dural sinuses)
- - - - Cranial nerves are like spinal nerves in that they are input and output pathways for brain
        
        31 pairs of spinal nerves and all are mixed nerves (sensory and motor function)
        
        There are only 12 pairs of cranial nerves, all but two of which arise from brain stem
      - Not all mixed nerves like spinal nerves; some are mainly sensory and others are mainly motor, and some are mixed nerves
      - Much more specialized than spinal nerves
      - Carry sensory and motor information for head, face, and neck, as well as visual, auditory, smell, or taste sensations
- - - - Sensory information coming into brain from dorsal column and spinothalamic tracts both provide sensory information from skin and joints to portion of cerebrum known as primary somatic sensory cortex
        
        This is located in postcentral gyrus of parietal lobe
        
        Axons transport information to specific parts of SS cortex that correspond to parts of body Neurons in SS cortex are neurons that allow you to have conscious sensation
        
        Another area of cerebral cortex that allows understanding and interpretation of somatic sensory information is located just posterior to SS cortex in parietal lobe and is known as somatic sensory association area
        
        Somatic sensory system works on kind of hierarchy, with sensory neurons in spinal cord and brain stem collecting information and passing it to areas in thalamus, cerebellum, and cerebral cortex for processing
        
        Your actual understanding of complex sensory input happens only after information is passed to somatic sensory cortex and somatic sensory association area