{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

BIO203 - Chapter 5 Summary

BIO203 - Chapter 5 Summary - CHAPTER 5 SUMMARY Evolutionary...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
CHAPTER 5 SUMMARY Evolutionary Considerations and Invertebrate Nervous Systems •The nervous system is one of the two control systems of the body, the other being the endocrine system. In general, the nervous system coordinates rapid responses, whereas the endocrine system regulates activities that require duration rather than speed. •Nervous systems have become progressively more complex during evolution, evolving from simple reflex arcs to centralized brains with distributed, hierarchical regulation. Reflex arcs (found in most animals) consist of sensors, neurons and effectors that quickly detect common disturbances and activate corrective responses. Higher levels of control include anticipation activation of reflexes and memory-enhanced responses. •Sponges have no nerves, but some respond to stimuli using electrical signals. True nervous systems probably first arose as nerve nets in cnidarians. Nerve nets have no central integrator and control relatively simple behaviors. •Simple ganglia (clusters of neurons) and nerve rings evolved for more complex behavior, appearing first in swimming cnidaria. •A true central nervous system or CNS first evolved with bilateral symmetry, as found in flatworms. •Complex nervous systems with distributed ganglia are characteristic of higher invertebrates, such as molluscs and arthropods. True brains evolved at the anterior end of advanced animals such as arthropods, cephalopods and vertebrates. Cephalopod brains are the most advanced among invertebrates, having complex structures supporting complex behaviors including learning. •Vertebrate brain size varies up to 30-fold for a given body size. Relative brain size is hypothesized to result from several factors, including a trade-off between expensive tissue (brains, digestive systems).
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
•Some nervous systems can exhibit plasticity, changing in structure with experience. The Vertebrate Nervous System v The nervous system consists of the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system, which includes the nerve fibers carrying information to (afferent division) and from (efferent division) the CNS. HThree classes of neurons—afferent neurons, efferent neurons, and interneurons—compose the excitable cells of the nervous system. Afferent neurons apprise the CNS of conditions in both the external and internal environment. Efferent neurons carry instructions from the CNS to effector
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern