Strategies to detect Stimuli

• Nervous System


  • Collection of tissues and specialized cells

  that provides information about the

  environment

  • Serves as signaling pathways throughout the

  body

  • Integrates information input to generate

  responses
• NERVOUS SYSTEM


  • Works with the endocrine system in

  communicating signals and regulating

  biological processes for the body to maintain

  homeostasis

  • Neural regulation is relatively more rapid

  than hormonal regulation

  • Differ in structure and complexity
• CNIDARIA (HYDRA)


  • Simplest animals with NS

  •Nerve net – interconnected neurons

  • Controls contraction and expansion of

  gastrovascular cavity
• ECHINODERM (SEA STAR)


  • Nerves

  • axons of multiple neurons bundled together in

  more complex animals than sponges

  • Channel information flow along specific routes

  thru NS

  • Sea stars – a set of radial nerves connect to

  a central nerve ring

  • Radial nerve linked to a nerve net

  • receives input from nerve net

  • Sends signals to nerve net  control muscle contraction
• BILATERAL ANIMALS


  • With more specialized NS

  • Exhibit cephalization

  • evolutionary trend

  • clustering of sensory neurons

  and interneurons at the

  anterior end of body

  • With nerves that extend

  toward the posterior end

  • For communication
• Nonsegmented worms


  • Entire NS made up of few number of cells

  • planarian (flatworms)

  • a small brain and longitudinal nerve cords  simplest clearly defined CNS

  • nematode (roundworms)

  • Caenorhabditis elegans

  • entire nervous system: constructed from only a small number of cells

  • an adult worm (hermaphrodite) has exactly 302 neurons
• • central nervous system (CNS)

  • neurons that carry out integration
• • peripheral nervous system (PNS)

  • neurons that carry information into and out of the CNS
• BILATERAL ANIMALS


  • many more neurons

  • behavior is regulated by more complicated

  brains and by ventral nerve cords containing

  ganglia

  • segmentally arranged clusters of neurons

  • act as relay points in transmitting information
• NS organization often correlates with lifestyle
• • Molluscs

  • sessile and slow-moving species (ex. clams and chitons)

  • relatively simple sense organs and little or no

  cephalization

  • active predatory molluscs (ex. octopuses and squids)

  • most sophisticated nervous systems of any invertebrate

  • large, image-forming eyes

  • brain contains millions of neurons

  • octopuses

  • can discriminate between visual patterns

  • perform complex tasks

  • Ex. unscrewing a jar to feed on its contents
• Vertebrates (ex. Salamander/humans)

  • CNS - brain and the spinal cord

  • PNS - nerves and ganglia are the key elements

  * Regional specialization is a hallmark of both systems
• • 2 main divisions:

  • Central NS (CNS)

  • Brain & spinal cord

  • Main control center of body

  • Peripheral NS (PNS)

  • Sensory receptors & all nerves that branch off

  from brain & spine
• • Sensory receptors & all nerves that branch off from brain & spine

  • Serve as communication lines transmitting information to CNS & cascade

  decision of CNS to rest of body

  • Work in both directions

  • Sensory/afferent division (L. “to carry toward”)

  • Made up of afferent neurons

  • Picks up sensory stimuli

  • Motor/efferent division (L. “to carry away”)

  • Sends direction from brain to muscles & glands
• • Somatic – voluntary responses

  • Autonomic – involuntary responses

  • Further divided into 2 sections

  • Sympathetic – puts body in alert state

  • Parasympathetic – puts body in relaxed

  state