BIO - nervous system 2.1 - 2.2

• Nervous System


  Collection of tissue and specialized cells that provide information about the environment, serve as signaling pathways, and integrate information to generate responses
• Animal Nervous Systems

  • Porifera
  • Cnidarian (Jellyfish)
  • Echinoderm (Sea star)
  • Planarian (Flatworm)
  • Annelid (Earthworm)
  • Arthropods (Insects)
  • Mollusks (Octopus)
  • Vertebrates (Human)
• Porifera(sponges)


  • Do not have a networked nervous system
  • Possess ciliated sensory cells that sense and control water flow
• Cnidarian (Jellyfish)


  • Have radial symmetry and diffuse nervous system – simplest style
  • Possess nerve nets – a mesh of interconnected neurons
• Echinoderm (Sea star)


  • Possess a nervous system that is modified from a nerve net but more evolved than cnidarians
• Planarian (Flatworm)


  • Possess cerebral ganglia – concentration of nerve cells
  • The cerebral ganglia is located at the head (the term cerebral refers to something of a brain.)
• Annelid (Earthworm)


  • Possess paired ventral nerve cords that run along the underside of their body – that originate from the cerebral ganglion
  • Ganglionic swelling of the cord is found in each body segment
  • Afferent and efferent neurons are found in lateral nerves
• Arthropods (Insects)


  • The nervous system consists of a "dorsal and a ventral, ganglionated longitudinal nerve cord from which lateral nerves extend in each segment"

  
• Mollusks (Octopus)


  • Bivalves – the nervous system is composed of three sets of ganglia
  • Gastropods – six sets of ganglia
  • Cephalopods – have the most complex nervous system
• Vertebrates (Human) Nervous System

  • Central nervous system (CNS)
  • Peripheral nervous system (PNS)

  
• Central Nervous System (CNS)


  Brain and spinal cord, main control of the body

  
• Peripheral Nervous System (PNS)

  Composed of sensory receptors that branch off the brain's spinal cord
• Nervous System Functions


  • Detecting stimuli
  • Interpreting
  • Initiating appropriate responses

  
• Peripheral Nervous System Divisions

  • Sensory (afferent) Division
  • Motor (efferent) Division

  
• Sensory (afferent) Division


  • Transmits information from the peripheral organs, through the sensory nerves, to the CNS
  • Sensory nerves arise from sensory receptors, carry messages to the CNS for processing
  • Keeps the CNS aware of the external and internal environments, including sense organs and internal receptors that monitor internal state (e.g. thirst, hunger, body position, movement, pain)

  
• Motor (efferent) Division


  • Carries impulses from the CNS to the effectors for response or action through the motor neurons
  • Response may either be in the form of somatic or autonomic responses
• Motor Division Branches


  • Somatic Division
  • Autonomic Division
• Somatic Division


  • Involves the neurons that carry impulses to the skeletal muscles
  • Regulates the activities that are under conscious control (voluntary)
• Autonomic Division


  • Also called the visceral motor system
  • Manages involuntary visceral function through the reflex action
  • Regulates all activities that are involuntary or without a conscious will (e.g. heart rate, gut peristalsis)
• Autonomic Division Branches


  • Sympathetic division
  • Parasympathetic division
• Sympathetic division


  • "Fight or flight response"
  • Controls the internal functions of the body in times of stress
  • Employs noradrenaline - that provides a lot of energy enough to carry a refrigerator in times of emergencies
  • E.g. heart rate acceleration, vasoconstriction, blood pressure rising
• Parasympathetic division


  • "Rest and digest"
  • Controls the internal functions at rest
  • Employs acetylcholine - in times of relaxation
  • E.g. heartbeat, increases the intestinal and gland activities (during digestion)