1. What is the basic difference between anatomy and physiology? (p. 2) ANSWER:
Anatomy (a-NAT-ō-mē; ana- = up; -tomy = process of cutting) is the science of structure and the relationships among structures. Physiology (fiz′-ē-OL-ō-jē; physio- = nature, -logy = study of) is the science of body functions, that is, how the body parts work.
2. Define each of the following terms: atom, molecule, cell, tissue, organ, system, and organism. (p. 6) ANSWER:
AtomUnit of matter that makes up a chemical element; consists of a nucleus (containing positively charged protons and uncharged neutrons) and negatively charged electrons that orbit the nucleus.
Molecule (MOL-e-kūl)The chemical combination of two or more atoms covalently bonded together.
CellThe basic structural and functional unit of all organisms; the smallest structure capable of performing all the activities vital to life.
TissueA group of similar cells and their intercellular substance joined together to perform a specific function.
OrganA structure composed of two or more different kinds of tissues with a specific function and usually a recognizable shape.
SystemAn association of organs that have a common function.
Organism (OR-ga-nizm)A total living form; one individual
3. How are negative and positive feedback systems similar? How are they different? (p. 9) ANSWER:
A negative feedback system reverses a change in a controlled condition. Consider one negative feedback system that helps regulate blood pressure. Blood pressure (BP) is the force exerted by blood as it presses against the walls of blood vessels. When the heart beats faster or harder, BP increases. If a stimulus causes BP (controlled condition) to rise, the following sequence of events occurs (Figure 1-3). The higher pressure is detected by baroreceptors, pressure-sensitive nerve cells located in the walls of certain blood vessels (the receptors). The baroreceptors send nerve impulses (input) to the brain (control center), which interprets the impulses and responds by sending nerve impulses (output) to the heart (the effector). Heart rate decreases, which causes BP to decrease (response). This sequence of events returns the controlled condition—blood pressure—to normal, and homeostasis is restored. This is a negative feedback system because the activity of the effector produces a result, a drop in BP, that reverses the effect of the stimulus. Negative feedback systems tend to regulate conditions in the body that are held fairly stable over long periods, such as BP, blood glucose level, and body temperature.
A positive feedback system strengthens a change in a controlled condition. Normal positive feedback systems tend to reinforce conditions that don't happen very often, such as childbirth, ovulation, and blood clotting. Because a positive feedback system continually reinforces a change in a controlled condition, it must be shut off by some event outside the system. If the action of a positive feedback system isn't stopped, it can “run away” and produce life-threatening changes in the body.
The basic difference between negative and positive feedback systems is that in negative feedback systems, the response reverses a change in a controlled condition, and in positive feedback systems, the response strengthens the change in a controlled condition.
4. Describe the anatomical position and explain why it is used. (p. 15) ANSWER:
The language of anatomy and physiology is very precise.
In the study of anatomy, descriptions of any part of the human body assume that the body is in a specific stance called the anatomical position (an′-a-TOM-i-kal). In the anatomical position, the subject stands erect facing the observer, with the head level and the eyes facing forward. The feet are flat on the floor and directed forward, and the arms are at the sides with the palms turned forward (Figure 1-4 on page 11). In the anatomical position, the body is upright....