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Nervous System (Neurotransmitters and synaptic transmission…

- - - - Region of close proximity
    - - Need neurotransmitter
  - - - Neurotransmitter --> synaptic cleft -->response --> removed from the
        cleft = prevent continuous stimulation/inhibition of postsynaptic membranes
  - - - neuron receives many excitatory signals --> axon transmit a nerveimpulse
      - both inhibitory and excitatory signals, axon x threshold and x firing
- - - - chemical signal into receptor potential
      - 2 types
        
        General receptor –total solute concentration in solution
        
        Specific receptor – specific molecules
      - Gustatory (taste)
        • Eg: sweet, sour, salty, umami or bitter
      - Olfactory (smell)
        • Eg: musky, putrid, pungent, floral
    - - various forms of electromagnetic energy
        
        Photoreceptor which detect visible light
        
        animal vision
        
        nocturnal animal has rod cells photoreceptor
        
        better vision in low light but cannot differentiate colour
        
        Example
        
        gecko
        
        3 more items...
        
        Electroreceptor which detect changes in electric current
        
        Magnitoreception in bird
        
        Iron-containing
        mineral magnetite
    - - Cold detect stimulus ~ < 30 °C
        – Hot detect stimulus ~ > 22 °C
    - - Detect pain from external or internal source
      - 2 type
        
        Fast pain: acute or sharp pain lasting ~0.1 second and is
        transmitted via myelinated A delta fibers
        
        Slow pain is chronic or burning pain (few seconds to minutes) and is transmitted by unmyelinated C fibers
      - Naked dendrites of nociceptor in skin’s epidermis
        stimulated by chemical (eg: prostaglandin) released from
        damages tissue and Mast cell
    - - pressure, touch, stretch, motion & sound
        
        Example
        
        Echolocation in bat
      - Others
        
        Merkel’s receptor – vibration, texture
        • Meissner’s corpuscle – light touch
        • Pacinian corpuscle – pressure,
        vibration
        • Ruffini’s corpuscle – skin stretch
- - - - Resting potential > Threshold level > Action potential > Refractory period
  - - - allows sodium (Na+) to pass into the axon
      - allows potassium (K+) to pass out of the axon
  - - - action potential begins--> sodium channels gates open, Na+
        --> axon (−65 mV to +40 mV)
      - aka depolarization
    - - Gates of potassium channels open,K+
        <--- axon (+40 mV back to −65 mV)
      - aka repolarization
- - - - flatworm (planarian) & higher invertebrates (annelid,arthropod, mollusk)
  - - - Central nervous system (CNS)
        
        brain and spinal cord
      - Peripheral nervous system (PNS)
        
        all the nerves that branched out
        from the CNS
        
        sensory information --> the sensory (afferent) neurons & motor command --> motor (efferent) neurons
        
        motor neurons
        
        Somatic nervous system --> voluntary actions
        
        Autonomic nervous system--> involuntary actions
- - - - digestion
  - - - fight or flight
      - accelerates heartbeat