Effector cells and Support Systems

1. Effector cells and Support Systems

2. Blobfish

3. Neuromuscular junction:From motor neuron to muscle cell  Action potential reaches the synapse  Release of neurotransmitter • provokes an action potential in the muscle cell • causes that muscle to contract

4. Muscle Fibers: the unit of the muscular system Muscle fiber giant cell with many nuclei (by fusion of younger cells) has a system of protein filaments  myofibrils Each myofibril has repeating units  Sarcomeres (contractile apparatus) Sarcomeres have Myosin (thick filaments) Actin (thin filaments)

5. The sliding-filament model of muscle contraction Sarcomere Thick filaments (myosin) Thin filaments (actin) Relaxed muscle Contracting muscle Contracted muscle Sacromeres shorten, but filaments do not

6. Thick filament (myosin) The mechanism of filament sliding Myosin head (high-energy configuration) Myosin head (low-energy configuration) Thin filament (actin) ADP P ATP ATP 3 2 1 4 5 ATP binds to a myosin head, which is then released from an actin filament. The breakdown of ATP cocks the myosin head. The myosin head attaches to an actin binding site. The power stroke slides the actin (thin) filament toward the center of the sarcomere. As long as ATP is available, the process can be repeated until the muscle is fully contracted.

7. Support systems Skeletons function in support, movement and protection

8. Skeletal systems transform muscle contraction into locomotion - Muscles are connected to bones by tendons - Bones act as levers - The action of a muscle is to contract, muscles relaxation is passive - Antagonistic pairs of muscles apply opposite forces to move parts of the skeleton

9. Endoskeletons: hard supporting elements found among soft tissues Spicules in sponges Plates in echinoderms Bone and cartilage in vertebrates

10. Hydrostatic skeleton: fluid held under pressure Found in Cnidarians Nematodes (longitudinal muscles) Annelids (circular and longitudinal muscles)

11. Exoskeletons: hard, encasement deposited on an animal’s surface In mollsuks: The mantel secretes the shell As the animal grows it adds to the outer edge.

12. Exoskeletons: hard, encasement deposited on an animal’s surface In arthropods: The skeleton is secreted by the epidermis, It does not grow with the animal so it needs to be replaced to allow for growth In a process called molting or ecdysis The arthropod skeleton is jointed Muscles attach to the skeleton at the joints Allow for articulated movement

13. Endocrine System Glands that send messages via chemicals (hormones)

14. Endocrine vs. Nervous System Function: Chemical messengers: Linked: Differences: path, speed and length of response

15. Which cells are the target cells for a particular hormone? Hormone-receptor recognition is very important to regulate the body’s functions

16. Endocrine disruptors are synthetic chemicals that disrupt the endocrine system How?

18. The Hypothalamus is the master control center It controls the endocrine glands Via the anterior pituitary (AP) By producing: Releasing hormones: Stimulate release of AP hormones Inhibiting hormones: Stop release of AP hormones

19. Positive and negative feedback on hormone regulation

20. Anterior and Posterior Pituitary AP: produces tropic hormones that stimulate other endocrine glands PP: stores hormones made by the hypothalamus

22. Pancreas secretes insulin and glucagon Function: Manage blood glucose levels (BGL) Insulin  lowers BGL Glucagon  raises BGL

24. Diabetes mellitus:two different causes for high blood glucose levels

26. Hormonal regulation of molting and metamorphosis in insects Ecdysone promotes molting (ecdysis) of the larva. High levels of Juvenile Hormone Results in _________ Low levels of JH Results in __________ Possible applications of this knowledge? Fenoxycarb mimics juvenile hormone