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Nervous System (Intro (Types of neurons (Sensory (afferent) neurons,…

- - - - BRAIN
      - SPINAL CORD
    - - all of the nerves that branched out from the CNS
      - carry sensory info to CNS & send motor command to muscles & glands
      - have two:
        
        SOMATIC NS
        
        voluntary actions
        
        AUTONOMIC NS
        
        involuntary actions
        
        divided into two:
        
        Parasympathetic Division (relax)
        
        Sympathetic Division (active)
      - send info through:
        
        sensory (afferent) neurons
        
        motor (efferent) neurons
        
        then you will get Somatic NS & Autonomic NS
  - - - have a nucleus and variety of organelles
    - - portion of neuron that conveys info to another neuron @ to other cells
      - are covered in myelin sheath (m.s.)
      - m.s. bundle together to form nerve fibers
      - Neuroglia
        
        provide support & nourishment to the neurons
        
        m.s. is formed from membranes of tightly spiraled neuroglia
        
        in PNS, Schwann cells perform this function, leaving gaps nodes of Ranvier, or neurofibril nodes
    - - short, highly branched, recieve signals from sensory receptors @ other neurons & transmit them to cell body
- - - - electrical potential difference between 2 points measured in
  - - - Resting potential
        
        when a neuron not conducting an impulse
        
        -65 mV
        
        created by unequal distribution of ions
        
        more Na+ outside the axon, more K+ inside axon
      - Action potential
        
        rapid change in polarity across axonal membrane as nerve impulse occurs
      - Threshold level
        
        when the stimulus causes the axon membrane to depolarize to threshold level
        
        it occurs in all-or-none manner
      - Depolarization & Repolarisation
        
        Depolarization
        
        Sodium Gates Open
        
        membrane potential changes from -65 mV to +40 mV
        
        inside axon changes from (-) to (+)
        
        Repolarization
        
        Potassium Gates Open
        
        Action potential changes from +40 mV back to -65 mV
        
        inside axon becomes (-) again as K+ exits the axon
  - - - In myelinated axons, gated ion channels that produce action potential are conc. at the nodes of Ranvier
- - - - divided into two types:
        
        Cold detect stimulus ~<30'C
        
        Hot detect stimulus ~ >22'C
      - Peripheral thermoreceptor
        
        detect skin & visceral body temp
      - Interothermoreceptor
        
        in anterior hypothalamus
        
        detect deep brain temperature
    - - transduces chemical signal into receptor potential
      - two types:
        
        General receptor
        
        transmit info about the total solute conc. in solution
        
        e.g. osmoreceptor in mamalian brain detects blood osmolarity
        
        Specific receptor
        
        transmit info about specific molecules
        
        e.g. chemoreceptor in antennae of male silkworm
      - w/ intermediate specificity
        
        Gustatory (taste)
        
        direct chemorec.
        
        detect chemical in aqueous state
        
        Olfactory (smell)
        
        distance chemorec.
        
        detect chemical in gaseous state
    - - detects pain
        
        two types of pain signal:
        
        Fast pain: acute @ sharp pain,lasts for ~0.1s, transmitted via myelinated A delta fibers
        
        Slow pain- chronic @ burning pain, transmitted by unmyelinated C fibers
      - results in defensive reaction
      - prostaglandins- are being released from damaged tissue & Mast cell, it stimulates the naked dendrites
    - - Photo receptor
        
        detect visible light
        
        have two cell:
        
        Rod cell- sensitive to B&W vision at night
        
        Cone cell- account for colour vision in daylight
        
        human & primate: trichromatic vision
        
        other vertebrates: dichromatic vision
      - Electroreceptor
        
        detect changes in electric current
        
        observed in aquatic & amphibious animal
        
        water much better conductor
      - Electrolocation
        
        nearby object perturb the electric field
      - i.e. magnitoreception in birds
        
        Iron-containing mineral magnetite in some bird skulls
    - - includes: pressure,touch,stretch, motion & sound
      - close to skin's surface- can detect light touch
      - deep in skin layers- can detect strong pressure
      - Merkel's receptor - at dermis, sensitive to vibration & texture
        
        Meissner's corpuscle -sensitive to light touch
        
        Pacinian corpuscle - stronger pressure & vibration
        
        Ruffini's corpuscle - skin stretch, inside epidermis