Unlike most other animals, sponges lack which of the following?
a. a digestive tract only
b. a symmetrical body plan only
c. tissues only
d. a digestive tract and a symmetrical body plan only
e. a digestive tract, a symmetrical body plan, and tissues
e
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Nicotine from cigarette smoke acts as a ligand and associates with specific proteins on the surface cells in the brain, causing feelings of pleasure and well-being. Below are the events that happen in the cellular response to nicotine
Place the events in the correct order to describe the five basic steps in the pathway of a signal transduction system. A. receptor binding B. receptor activation C. signal transduction D. response E. termination The opening of an ion channel as a result of nicotine association is an example of _________________. ________________ occurs when an influx of ions causes an action potential, which carries the signal to the reward areas of the brain. Nicotine interaction with the transmembrane protein that normally binds the neurotransmitter acetylcholine is an example of _________________. ________________ occurs when the signal causes release of dopamine in the brain, which causes relaxation and feelings of well-being. Rapid elimination of nicotine from the body is an example of ____________. What will be an ideal response?
A person who is infected with a potential pathogen fails to develop signs or symptoms of disease. This correlates with ________ initial microbial dose, ________ microbial lethality, and/or ________ replication rate of the pathogen.
A. low; high; low B. low; low; high C. high; low; high D. high; low; low
Calcium ions are commonly stored in the ____ of the muscle cell
a. actin b. myosin c. sarcoplasm d. sarcoplasmic reticulum e. T tubules
Each human kidney contains about a million ________, which are the tubular functional units of the kidney.
A. renal medullae B. flame cells C. nephrons D. nephridia E. ureters