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The Nervous System (Anatomy of Nervous System (Nerve components…

- - - - Surrounds each nerve fiber
    - - Surrounds group of nerve fibers
    - - Tough fibrous tissue; surrounds nerve
  - - - Satellite cells
        
        Structurally supportive and regulates
        
        Exchange materials in / out of neuron cell body
      - Myelination
        
        Insulates axon
        
        Mostly lipid; some protein
        
        Allows signals to travel faster
        
        Gaps called myelin sheath gaps or nodes of Ranvier
      - Schwann cells
        
        Speeds up transmission process
        
        Wrap plasma membrane around one portion of one axon
        
        Prevents electricity from jumping from one axon to another
    - - Astrocytes
        
        Most numerous
        
        Processes that contact neurons and capillaries
        
        Support neurons and maintain chemical balance
      - Microglia
        
        Phagocytes
        
        Remove microbes anf damaged nerve tissue
      - Ependymal cells
        
        Simple cuboidal / columnar epithelium
        
        Cilia keeps cerebrospinal fluid moving
        
        Lining spaces filled with cerebrospinal fluid called ventricles
      - Oligodendrocytes
        
        Primarily lipid; little protein
        
        Wrap their plasma membranes around on portion of several axon
- - - - Stimulus from environment
        
        Location: skin and special senses
    - - Stimulus from internal organs
    - - Stimulus from muscles, tendons, ligaments, and joints
        
        Neurons wrap around muscles
    - - Cold and hot sensitive receptors
    - - Sensitive to light
    - - Sensitive to chemicals
        
        e.g. air, saliva, water, chemicals in blood
    - - Dangerous pain receptors
    - - Touch, pressure, vibration, and stretch
    - - Measures blood pressure
  - - - Fibrous layer
        
        Sclera
        
        White
        
        Protective
        
        Gives shape
        
        Anchors muscle
        
        Dense connective tissue
        
        Cornea
        
        Clear
        
        Allows light into eye
        
        Involved in focusing light in retina
      - Vascular layer
        
        Choroid
        
        Blood vessels
        
        Deeply pigmented
        
        Nourishes the other layers
        
        Absorbs light (preventing scattering)
      - Inner layer
        
        Retina
        
        Photoreceptors
        
        Axons coverage form optic nerve
      - Rods
        
        Many
        
        Sensitive to light
        
        Ability to see in dim light
      - Cones
        
        Fewer
        
        Best in bright light
        
        Allows us to see in color
      - Lens
        
        Focuses light on retina
      - Iris
        
        Intrinsic muscle - sphincter
        
        Dilate and constrict
      - Optic disc
        
        Blind spot (no photoreceptors)
      - Macula lutea
        
        Precise posterior pole
      - Fovea centralis
        
        At center of macula lutea
        
        Location of clearest vision
      - Anterior segment
        
        From iris to cornea
        
        Filled with aqueous humor
      - Posterior segment
        
        From iris to posterior segment
        
        Filled with vitreous humor (clear; gel-like)
        
        Supports retina and lens (maintains normal pressure)
    - - Cornea ---> pupil ---> lens ---> posterior segment ---> retina ---> optic nerve ---> optic chiasma ---> optic tract ---> midbrain ---> thalamus ---> primary visual cortex of the occipital lobe
  - - - Roof of nasal cavity
        
        Goes through cribriform plate's holes
        
        pseudostratified columnar epithelium
    - - Olfactory receptors ---> olfactory sensory neurons in olfactory bulb ( top of cribriform plate) ---> olfactory tract
  - - - Epithelial cells - gustatory
        
        e.g. tongue, inner cheeks, posterior wall of pharynx, and epiglottis
    - - Medulla oblongata ---> thalamus ---> gustatory cortex
  - - - External ear
        
        External acoustic meatus
        
        Auricle (gathers and amplifies sound waves
      - Middle ear
        
        Tympanic membrane (ear drum)
        
        Auditory ossicles
        
        Cochlea (liquid filled)
        
        Receptor epithelium for hearing
        
        Vestibular and cochlear nerve go through internal acoustic meatus
    - - Cochlear branch on CN VIII ---> medulla oblongata ---> pons ---> midbrain ---> thalamus ---> primary auditory cortex (in temporal lobe)
- - - - Afferent (sensory)
        
        Brain and spinal cord
    - - Receive, process incoming signals, and respond
  - - - Efferent (motor)
        
        Cranial and spinal nerves
        
        Ganglia (cluster of neuron cell bodies
    - - Sends info to CNS
        
        Sensitive to stimuli
  - - - Output to skeletal muscle
    - - Input from skin, muscle (skeletal) joints, joints, and limbs
  - - - Input from ventral body cavity contents
    - - Smooth muscle
        
        Blood vessels
        
        Glands (e.g. sweat)
        
        Arretor pili muscle of skin Visceral (mainly contents of ventral body cavity)
- - - - Dendrites and axon
        
        Efferent neurons
        
        Interneurons
    - - Special sense
        
        Afferent neurons
        
        Dendrite, cell body, and axon
    - - Cell bodies in ganglia of PNS
        
        Receptive endings, peripheral process, cell body, central process, axon
  - - - Cell bodies in CNS ---> muscle and glands
    - - Cell bodies in ganglia of PNS
    - - Most numerous
        
        Between neurons in CNS